AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
230 PM PST THU FEB 22 2007
.SYNOPSIS...
A WINTER STORM WILL BRING MODERATE TO HEAVY RAIN...HEAVY SNOW...AND
GUSTY WINDS THROUGH FRIDAY. SHOWERS WILL END BY FRIDAY EVENING.
HIGH PRESSURE WILL MOVE ACROSS THE AREA SATURDAY BRINING FAIR SKIES
AND WARMER TEMPERATURES. INCREASING CLOUDS ON SUNDAY AND A COOLING
TREND ON MONDAY AS A COLD FRONT MOVES SLOWLY SOUTH THROUGH
CALIFORNIA. RAIN AND MOUNTAIN SNOW ARE POSSIBLE NEXT TUESDAY AND
WEDNESDAY AS THE FRONT MOVES ACROSS SOUTHERN CALIFORNIA.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TONIGHT THROUGH SUNDAY)...
STORM MOTION AND INTENSITY STILL ABOUT SAME AS EARLIER FORECAST.
BUMPED UP START TIME OF HEAVY PRECIPITATION ABOUT AN HOUR EARLIER
THAN MENTIONED IN EARLIER DISCUSSION. SEE AVIATION SECTION FOR
LATEST THINKING. STORM TOTAL AMOUNTS WERE INCREASED A THIRD TO A
HALF INCH FOR A SPREAD OF ONE TO TWO AND HALF INCHES FROM THE COAST
TO THE COASTAL SLOPES AND ABOUT A QUARTER INCH OVER THE DESERTS.
SNOWFALL AMOUNTS AND SNOW LEVELS REMAIN ABOUT THE SAME...STARTING
AROUND 5000 FEET THIS EVENING AND DROPPING TO 3500 FEET AFTER
FRONTAL PASSAGE. SINCE THE BULK OF THE RAINFALL IS EXPECTED TO OCCUR
WITH THE FRONT THERE IS A CRITICAL PERIOD THIS EVENING WHEN
EXCESSIVE RUNOFF AND HIGH RAINFALL RATES COULD OCCUR ON LOWER
SLOPES/FOOTHILLS AND OVER RECENT BURN AREAS...PARTICULARLY THE
SAWTOOTH-MILLARD... ESPERANZA... AND HORSE FIRE AREAS...SO A FLASH
FLOOD WATCH WAS ISSUED FOR THE MOUNTAINS AND ADJACENT INLAND VALLEY
AREAS. THE FRONT SHOULD PUSH EAST OF THE SAN DIEGO COUNTY MOUNTAINS
AROUND MIDNIGHT BUT CARRIED THE WATCH UNTIL 0400 PST TO MESH WITH
NEXT FORECAST PACKAGE. THE UPPER TROUGH AXIS IS EXPECTED TO BE EAST
OF SAN DIEGO COUNTY BY 0700 PST FRIDAY...BUT INSTABILITY/UPSLOPE
FLOW AND ISLAND EFFECT EXPECTED TO CONTINUE TO GENERATE SHOWERS INTO
FRIDAY EVENING. EARLY FRIDAY MORNING THROUGH MIDDAY FRIDAY IS THE
MOST LIKELY PERIOD THAT THE LOWER SLOPES/FOOTHILLS/HIGH DESERT
FLOORS WILL SEE SNOWFALL. MAY STILL NEED A SNOW/BLOWING SNOW
ADVISORY FOR HIGH DESERTS DURING THIS PERIOD...BUT WILL LET
EVENING/MIDNIGHT SHIFT MAKE THE DECISION. HIGH PRESSURE RIDGE
BUILDING FRIDAY NIGHT AND SATURDAY BUT DRYING AND WARMING TREND
EXPECTED TO BE SHORT LIVED AS RIDGE AXIS IS ALREADY MOVING EAST BY
SATURDAY AFTERNOON AND NEAR ZONAL FLOW BECOMES ESTABLISHED LATE
SUNDAY/MONDAY.
&&
.LONG TERM (MONDAY THROUGH WEDNESDAY)...
A BROAD TROUGH WILL BE OVER NORTH AMERICA WITH STRONG ZONAL FLOW
BETWEEN 30-40N LATITUDE FROM 140W LONGITUDE TO THE ATLANTIC COAST.
CONFIDENCE IN MODEL TIMING ON EMBEDDED SHORT WAVES IS VERY LOW AND
FULLY EXPECT TO SEE MAJOR CHANGES FROM RUN TO RUN. BEST FORECAST FOR
NOW IS CLOUDY AND COOL WITH CHANCE OF PRECIPITATION.
&&
.AVIATION...
222000Z...LATE MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER HAD
DEEPENED TO 6000 FEET ACROSS MOST OF THE AREA FROM THIS MORNING WITH
AN EXTENSIVE STRATOCU LAYER COVERING MOST OF THE AREA FROM THE
MOUNTAINS TO THE COAST.
A COLD FRONT EXTENDING SOUTH FROM NEAR POINT CONCEPTION AT THIS TIME
WAS MOVING EAST AT ABOUT 25 KTS. THE LEADING EDGE IS EXPECTED TO
REACH VICINITY OF KSNA BY 00Z AND KSAN BY 02Z. UPSTREAM METARS STILL
INDICATE CLOUD BASES ASSOCIATED WITH THE FRONT SHOULD REMAIN IN THE
MVFR CATEGORY ALTHOUGH LOCAL IFR CONDITIONS ARE POSSIBLE WITH THE
HEAVIER SHOWERS. RADAR INDICATES THE HEAVIEST PRECIPITATION IS FROM
THE MID PART OF THE FRONTAL BAND TO THE TRAILING EDGE. EXPECT THE
TRAILING EDGE TO PASS THROUGH 3 TO 4 HOURS BEHIND THE LEADING EDGE.
BEHIND THE FRONT...AN UNSTABLE AIR MASS WILL CONTINUE BROKEN CU AND
TCU AND SHOWERS. BASES AROUND 2000 TO 2500 FEET MSL WITH TOPS TO
10000 FEET EXCEPT ISOLATED TOPS TO 15000 FEET FOR LATE TONIGHT INTO
FRIDAY MORNING. MOST AREAS WEST OF THE MOUNTAINS SHOULD BEGIN TO
SCATTER OUT DURING THE AFTERNOON ON FRIDAY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM PST FRIDAY FOR
COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 12 PM PST FRIDAY
FOR RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY
MOUNTAINS-SAN DIEGO COUNTY MOUNTAINS.
WIND ADVISORY UNTIL 10 PM PST FRIDAY FOR APPLE AND LUCERNE
VALLEYS.
SNOW AND BLOWING SNOW ADVISORY FROM 6 PM THIS EVENING TO 12 PM
PST FRIDAY FOR SANTA ANA MOUNTAINS AND FOOTHILLS.
FLASH FLOOD WATCH LOWER SLOPES/RECENT BURN AREAS INLAND EMPIRE-
SAN DIEGO COUNTY VALLEYS-RIVERSIDE COUNTY MOUNTAINS-
SAN BERNARDINO COUNTY MOUNTAINS-SAN DIEGO COUNTY MOUNTAINS
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 6 PM THIS EVENING TO 10 PM
PST FRIDAY FOR COASTAL WATERS FROM SAN MATEO POINT TO THE
MEXICAN BORDER AND OUT 30 NM-WATERS FROM SAN MATEO POINT TO
THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN
CLEMENTE ISLAND.
&&
$$
PUBLIC/FIRE WEATHER...BALFOUR
AVIATION/MARINE.......HORTON
SHORT TERM/WARNINGS...MACKECHNIE/PURPURA
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
420 AM PST WED FEB 21 2007
.SYNOPSIS...
RESIDUAL MOISTURE AND A WEAK COASTAL EDDY WILL CAUSE A FEW CLOUDS
AND PATCHY FOG WEST OF THE MOUNTAINS EARLY THIS MORNING...OTHERWISE
FAIR UNDER WEAKENING HIGH PRESSURE. A STORM APPROACHING FROM THE
NORTHWEST WILL LIKELY BRING RAIN AND MOUNTAIN SNOW LATE THURSDAY
INTO FRIDAY WITH GUSTY WINDS IN THE MOUNTAINS AND DESERTS. SNOW
LEVELS MAY LOWER ENOUGH TO BRING SNOW TO THE HIGH DESERT LATE
THURSDAY NIGHT THROUGH FRIDAY MORNING. FAIR AND WARMER NEXT
WEEKEND...THEN MORE CLOUDS AND COOLING EARLY NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY THROUGH FRIDAY)...
FAIR AND DRY TODAY UNDER WEAKENING HIGH PRESSURE. WEAK COASTAL EDDY
MAY BRING SOME PATCHY STRATUS TO AREAS NEAR THE COAST THIS MORNING
WITH RESIDUAL LOWER LEVEL MOISTURE BRINGING PATCHY RADIATIONAL FOG
TO THE VALLEYS THIS THIS MORNING. OTHERWISE SKIES WILL BE MOSTLY
CLEAR TODAY.
STORM SYSTEM DEVELOPING OVER THE EASTERN PACIFIC IS MOVING STEADILY
EASTWARD AND IS HANDLED SIMILARLY BY THE MODELS. ONSET OF
PRECIPITATION MAY HOLD OFF UNTIL LATE IN THE DAY THURSDAY FOR
NORTHWEST SECTIONS WITH THE COLD FRONT SWEEPING QUICKLY EASTWARD
ACROSS SOUTHWEST CALIFORNIA EARLY THURSDAY EVENING. THIS WILL BRING
A PERIOD OF MODERATE PRECIPITATION TO MOST AREAS ALONG AND WEST OF
THE MOUNTAINS ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS. SHOWERS
AND A SLIGHT CHANCE OF THUNDERSTORMS WILL LINGER THROUGH FRIDAY
MORNING...DECREASING FRIDAY AFTERNOON AND ENDING FRIDAY EVENING.
SNOW LEVEL WILL START OUT ABOVE 7000 FEET...BUT LOWER TO 5000 FEET
THURSDAY EVENING AND TO AROUND 3500 FEET BY FRIDAY MORNING. WINDS IN
THE MOUNTAINS AND UPPER DESERTS WILL INCREASE TO NEAR ADVISORY
STRENGTH FROM THURSDAY AFTERNOON THROUGH FRIDAY MORNING.
BELOW THE SNOW LEVEL...RAINFALL OF ONE THIRD TO TWO THIRDS INCHES IS
EXPECTED AT THE COAST TO AROUND 2 INCHES ON SOUTHWEST FACING COASTAL
SLOPES BELOW 6000 FEET. LOCALLY GREATER AMOUNTS ARE POSSIBLE. HIGHER
ELEVATIONS MAY RECEIVE FROM A FEW INCHES TO AS MUCH AS TWO FEET OF
SNOWFALL...MOSTLY ABOVE 5000 FEET WITH LIGHTER ACCUMULATIONS DOWN TO
3500 TO 4000 FEET. HIGH DESERT AREAS MAY SEE LOCAL SNOW
ACCUMULATIONS OF A FEW INCHES LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING. THE LOWERING OF THE SNOW LEVEL TO 3500 TO 4000 FEET MAY
IMPACT TRAVEL THROUGH THE CAJON PASS LATE THURSDAY NIGHT THROUGH
FRIDAY MORNING.
&&
.LONG TERM (SATURDAY THROUGH TUESDAY)...
ECWMF WEAKLY PREFERRED. NORTHWEST TO WEST NORTHWEST FLOW PATTERN
WILL BRING DRYING AND MINOR WARMING FOR THE WEEKEND WITH LOCALLY
GUSTY NORTHWEST TO NORTH WINDS IN THE MOUNTAINS AND DESERTS AT
TIMES. FOR TUESDAY AND WEDNESDAY...AS SHOWN BY DGEX/ECMWF...A WEAK
WEATHER SYSTEM MAY DEVELOP OFF THE COAST AND MOVE INLAND ACROSS
CALIFORNIA BRINGING A SLIGHT CHANCE OF PRECIPITATION TO SOUTHWEST
CALIFORNIA AS WELL AS SOME COOLING WITH GUSTY WINDS IN THE MOUNTAINS
AND DESERTS. HOWEVER...INCREASING SPREAD IN THE MODEL FORECASTS
AFTER FRIDAY MAKES THIS A LOWER CONFIDENCE FORECAST.
&&
.AVIATION...
210920Z...LATE EVENING ACARS SOUNDINGS INDICATED THE MARINE LAYER
WAS STILL DISRUPTED OVER THE AREA BUT A WEAK INVERSION WAS APPARENT
AROUND 1500 FEET MSL WITH ANOTHER AROUND 4500 FEET MSL. SCATTERED TO
LOCALLY BROKEN STRATOCU WILL CONTINUE THROUGH MID MORNING WITH BASES
AROUND 1500 TO 2000 FEET MSL. LOCAL LIFR CONDITIONS ARE EXPECTED IN
THE INLAND VALLEY AREAS WITH DENSE FOG UNTIL AN HOUR OR TWO AFTER
SUNRISE. VFR CONDITIONS SHOULD PREVAIL DURING THE AFTERNOON. BROKEN
TO OVERCAST STRATOCU WITH BASES AROUND 2000 FEET MSL ARE EXPECTED TO
MOVE BACK OVER THE COASTAL AIRPORTS LATE THIS EVENING AND OVERNIGHT
TONIGHT.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...MARTIN
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS LINCOLN IL
1020 AM CST WED FEB 21 2007
.DISCUSSION...
ZONE UPDATE ALREADY SENT OUT TO LET FOG ADVISORY GO AT 10 AM. VSBYS
ACRS THE AREA HAVE COME UP DRAMATICALLY OVER THE PAST COUPLE OF
HOURS WITH LOCATIONS EAST OF INTERSTATE 57 SLOW TO IMPROVE. RANTOUL
OVER THE PAST HALF HOUR HAS COME UP TO ONE HALF MILE AND WINDS TO
THE WEST HAVE BACKED INTO THE SOUTHWEST AHEAD OF NRN PLAINS
SHORTWAVE AND FRONTAL SYSTEM. 12Z ILX SOUNDING AND NAM FORECAST
SOUNDINGS CONTINUE TO SHOW MOISTURE LIMITED TO BELOW 950 MB AND THAT
WILL CONTINUE THRU TNT. MIXING DOWN FROM ABOUT 925MB THIS AFTN
SHOULD GET US INTO THE UPPER 40S TO LOWER 50S...WHICH IS REFLECTED
IN THE CURRENT ZONE FCSTS. ONLY PROBLEM AREA WILL BE ACRS THE FAR
EAST...ESPECIALLY IF THE FOG IS SLOW TO BURN OFF EARLY THIS AFTN.
MAY HAVE TO ADJUST THE NUMBERS DOWN THERE IF WE SEE THOSE TRENDS
UNFOLD THE FIRST FEW HOURS OF THE AFTN. OTHER THAN SOME MINOR TWEEKS
TO HOURLY TEMPS AND WINDS...NO OTHER CHANGES MADE TO ZONES.
HYDRO ISSUES WITH WEEKEND SYSTEM WL BE ADDRESSED WITH AN UPDATED ESF
EARLY THIS AFTERNOON.
&&
.PREV DISCUSSION...
HEAVY RAIN FOR THE WEEKEND WITH STRONG SPRING-LIKE SYSTEM REMAINS
THE GREATEST FORECAST CONCERN WITH THIS PACKAGE.
SHORT TERM...WEDNESDAY THROUGH FRIDAY...
TODAY...DENSE FREEZING FOG ACROSS MOST OF THE CWA THIS MORNING IS
BRINGING WITH IT A NICE FROST DEPOSIT. YOU MAY SEE SOME NICE FROST
FORMATIONS ON YOUR CAR WINDSHIELDS THIS MORNING. MORNING COMMUTERS
NEED TO BE AWARE OF BLACK ICE THREAT ON ROADS AND SIDEWALKS... IN
ADDITION TO NEAR ZERO VISIBILITY AT TIMES. FOG WILL BE AT ITS MOST
DENSE IN OPEN RURAL AREAS WHERE MELTING SNOWPACK IS OTHERWISE
UNDISTURBED/UNPLOWED. WE EXPECT THE FOG TO BURN OFF BY MID-MORNING
AS RIDGE AXIS SHIFTS SOUTHEAST... ALLOWING SOUTHERLY FLOW TO MIX UP
THE BOUNDARY LAYER A BIT. SUNSHINE SHOULD ALSO HELP AS THERE IS
LITTLE IN THE WAY OF CLOUD COVER OVERHEAD. FOG IS ALSO RELATIVELY
SHALLOW... 88D RADOME LIGHT STILL SHARPLY VISIBLE OUTSIDE.
SHOULD CONTINUE TO SEE SNOWMELT THIS AFTERNOON... ADDING TO THE
BOUNDARY LAYER MOISTURE... BUT A CLIPPER SYSTEM MOVING ACROSS LAKE
SUPERIOR TONIGHT SHOULD KEEP GRADIENT TIGHT ENOUGH TO KEEP WINDS
AROUND 6-10 KTS OVERNIGHT... WHICH SHOULD MINIMIZE FOG POTENTIAL.
THURSDAY...NORTHWEST LOW LEVEL FLOW WILL CONTINUE... WHICH SHOULD
RESULT IN TEMPERATURES ABOUT 5 DEGREES LOWER THAN TODAY. STILL WE
WILL BE IN LOWER TO UPPER 40S NORTH TO SOUTH... AND CONTINUED
SNOWMELT IS EXPECTED. RIDGE AXIS MOVES OVER THE WESTERN HALF OF THE
CWA THURSDAY NIGHT... AND ANOTHER FOGGY NIGHT LOOKS LIKELY UNLESS WE
CAN GET SIGNIFICANT HIGH LEVEL CLOUD COVER TO MOVE IN.
FRIDAY/SATURDAY STORM SYSTEM...
POTENT STORM SYSTEM WILL BE TAKING SHAPE IN THE LEE OF THE ROCKIES
FRIDAY MORNING AS A POWER TROUGH MOVES INTO THE WESTERN U.S.
HAVE BEEN NOTICING A DIURNAL FLIP-FLOP BETWEEN THE 00Z AND 12Z RUNS
OF THE ECMWF AND GFS MODELS THE PAST FEW NIGHTS. 00Z GFS RUNS HAVE
BEEN BENEFITING FROM EXTRA AIRCRAFT/DROPSONDE DATA OVER THE
OTHERWISE DATA-SPARSE NORTH PACIFIC... COURTESY OF THE WINTER STORM
RECONNAISSANCE /WSR07/ PROJECT. IT IS UNKNOWN WHETHER OR NOT THESE
EXTRA DATA HAVE BEEN INGESTED INTO THE ECMWF OR GEM.
00Z RUNS OF THE ECMWF HAVE BEEN TENDING TO DEVELOP OUR LEE SIDE LOW
OVER NORTHEASTERN COLORADO... WHEREAS THE THE 12Z RUNS HAVE BEEN
DEVELOPING THE LOW IN SOUTHEAST CO...DITTO FOR ALL RUNS OF THE GFS
AND THE GEM. THE GEM AND ECMWF ARE PREFERRED HERE DUE TO THEIR
SUPERIOR RESOLUTION PER NCEP. ALSO UNLESS THINGS HAVE RECENTLY BEEN
TWEAKED... THE GFS MODEL ITSELF TENDS TO HAVE TROUBLE WITH LEE SIDE
LOW FORMATION JUST AS A FUNCTION OF MODEL PHYSICS/COORDINATE
SYSTEM.
00Z RUNS OF BOTH THE ECMWF AND GFS... AS WELL AS THE GEM... HAVE
BEEN ADVERTISING A SLIGHTLY FARTHER SOUTH SOLUTION TO THE SFC LOW
TRACK VERSUS THE 12Z GFS/ECMWF. WOULD NORMALLY PREFER THE FARTHER
NORTH SOLUTION AS RIDGING OUT AHEAD OF THIS SYSTEM SHOULD BE FAIRLY
STRONG GIVEN THE HIGHLY AMPLIFIED PATTERN AND BLOCKING LOW OVER THE
MARITIMES. NCEP SUGGESTING THE FARTHER SOUTH TRACK GIVEN THE EXTRA
DATA... BUT NEED TO BE CAUTIOUS HERE AS DROPSONDE DATA PROBABLY
WOULD NOT IMPACT FORECASTS DOWNSTREAM OF THE SYSTEM... AND POSITION
OF LONGWAVE TROUGH OVER THE MARITIMES MAY BE JUST AS IMPORTANT HERE.
OVERALL... THE DISAGREEMENTS IN TRACK MAKE LITTLE DIFFERENCE FOR OUR
FORECAST... BUT A FARTHER NORTH SOLUTION WOULD TEND TO FAVOR SVR WX
THREAT MORE ON SATURDAY... AND MAY ALSO MEAN QUICKER DRY SLOTTING
AND LESS WRAP AROUND PRECIP. SUCH DETAILS ARE NEVER SET IN STONE
THIS FAR OUT IN THE FORECAST.
FOR NOW... WILL TAKE THE PROVERBIAL BLEND OF THE AVAILABLE
GUIDANCE. NORMALLY WOULD PREFER ECMWF IN SUCH CASES... BUT IT HAS
BEEN A LITTLE UNSTABLE WITH THE FORWARD SPEED OF THIS SYSTEM... AND
THE MOST RECENT 00Z RUN IS ABOUT 12 HOURS FASTER THAN THE GFS...
WHICH AGAIN IS NOT FAVORED GIVEN THE BLOCKY PATTERN.
WITH THE SLOWER SOLUTION IN MIND... I AM STILL A LITTLE SHY ABOUT
INCREASING POPS WITH THE WARM ADVECTION ON FRIDAY... AND WILL
CONTINUE TO FOCUS POPS TOWARDS SATURDAY AND ESPECIALLY SATURDAY
NIGHT. SATURDAY NIGHT LOOKS LIKE THE BEST BET FOR HEAVIEST PRECIP
NO MATTER WHICH SOLUTION ONE GOES WITH NOW. THEREFORE... HAVE
DECIDED TO BOOST POPS INTO THE CATEGORICAL RANGE... WHICH IS A
LITTLE UNUSUAL FOR DAY 4.
LONG TERM...SUNDAY THROUGH TUESDAY...
WILL CONTINUE WITH CHANCE POPS SUNDAY WITH POSSIBLE WRAP AROUND
COMING IN BEHIND THE DRY SLOT. COULD EVEN BE IN THE FORM OF SNOW AS
COLD AIR WRAPS IN SUNDAY AFTERNOON ACROSS THE NORTH. FORECAST
BEYOND DAY 5 UNCHANGED WITH THIS PACKAGE.
.HYDROLOGY...
HYDRO DISCUSSION BELOW UNCHANGED FROM 3 PM TUE PACKAGE.
GROUND TEMPS ARE BELOW FREEZING WITH AN AMPLE SNOW COVER ACROSS MOST
OF CENTRAL AND EASTERN IL. OBSERVER REPORTS INDICATED AN AVERAGE OF
AN INCH OR MORE OF WATER CONTENT IN THE SNOW COVER. THIS SNOW IS
EXPECTED TO MELT THE NEXT SEVERAL DAYS...WITH MUCH OF THE WATER
RUNNING OFF INTO AREA WATERSHEDS. WHATEVER SNOW DOES NOT MELT BY
THIS WEEKEND WILL RAPIDLY DISSIPATE WITH MODERATE TO HEAVY RAINFALL
FORECAST FOR SATURDAY INTO EARLY SUNDAY. FORECAST RAINFALL AMOUNTS
OF 1.00 TO 1.50 INCHES...ALONG WITH THE MELTING SNOW COULD CAUSE
PROBLEMS FOR AREA RIVERS THIS WEEKEND INTO EARLY NEXT WEEK. SEE THE
HYDROLOGIC OUTLOOK /CHIESFILX/ ISSUED BY OUR OFFICE AT 1240 PM TODAY
FOR MORE DETAILS.
ANOTHER CONSIDERATION IS FOR URBAN FLOODING THIS WEEKEND. THE
RAINFALL MAY NOT BE ABLE TO REACH STORM SEWERS THAT ARE CLOGGED BY
UNMELTED SNOW OR OTHER DEBRIS. THUS...FLASH FLOODING COULD BE A
PROBLEM SATURDAY AFTERNOON THROUGH SATURDAY NIGHT.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SMITH/HARDIMAN
AREA FORECAST DISCUSSION
NWS LINCOLN IL
328 AM CST WED FEB 21 2007
.DISCUSSION...
HEAVY RAIN FOR THE WEEKEND WITH STRONG SPRING-LIKE SYSTEM REMAINS
THE GREATEST FORECAST CONCERN WITH THIS PACKAGE.
SHORT TERM...WEDNESDAY THROUGH FRIDAY...
TODAY...DENSE FREEZING FOG ACROSS MOST OF THE CWA THIS MORNING IS
BRINGING WITH IT A NICE FROST DEPOSIT. YOU MAY SEE SOME NICE FROST
FORMATIONS ON YOUR CAR WINDSHIELDS THIS MORNING. MORNING COMMUTERS
NEED TO BE AWARE OF BLACK ICE THREAT ON ROADS AND SIDEWALKS... IN
ADDITION TO NEAR ZERO VISIBILITY AT TIMES. FOG WILL BE AT ITS MOST
DENSE IN OPEN RURAL AREAS WHERE MELTING SNOWPACK IS OTHERWISE
UNDISTURBED/UNPLOWED. WE EXPECT THE FOG TO BURN OFF BY MID-MORNING
AS RIDGE AXIS SHIFTS SOUTHEAST... ALLOWING SOUTHERLY FLOW TO MIX UP
THE BOUNDARY LAYER A BIT. SUNSHINE SHOULD ALSO HELP AS THERE IS
LITTLE IN THE WAY OF CLOUD COVER OVERHEAD. FOG IS ALSO RELATIVELY
SHALLOW... 88D RADOME LIGHT STILL SHARPLY VISIBLE OUTSIDE.
SHOULD CONTINUE TO SEE SNOWMELT THIS AFTERNOON... ADDING TO THE
BOUNDARY LAYER MOISTURE... BUT A CLIPPER SYSTEM MOVING ACROSS LAKE
SUPERIOR TONIGHT SHOULD KEEP GRADIENT TIGHT ENOUGH TO KEEP WINDS
AROUND 6-10 KTS OVERNIGHT... WHICH SHOULD MINIMIZE FOG POTENTIAL.
THURSDAY...NORTHWEST LOW LEVEL FLOW WILL CONTINUE... WHICH SHOULD
RESULT IN TEMPERATURES ABOUT 5 DEGREES LOWER THAN TODAY. STILL WE
WILL BE IN LOWER TO UPPER 40S NORTH TO SOUTH... AND CONTINUED
SNOWMELT IS EXPECTED. RIDGE AXIS MOVES OVER THE WESTERN HALF OF THE
CWA THURSDAY NIGHT... AND ANOTHER FOGGY NIGHT LOOKS LIKELY UNLESS WE
CAN GET SIGNIFICANT HIGH LEVEL CLOUD COVER TO MOVE IN.
FRIDAY/SATURDAY STORM SYSTEM...
POTENT STORM SYSTEM WILL BE TAKING SHAPE IN THE LEE OF THE ROCKIES
FRIDAY MORNING AS A POWER TROUGH MOVES INTO THE WESTERN U.S.
HAVE BEEN NOTICING A DIURNAL FLIP-FLOP BETWEEN THE 00Z AND 12Z RUNS
OF THE ECMWF AND GFS MODELS THE PAST FEW NIGHTS. 00Z GFS RUNS HAVE
BEEN BENEFITING FROM EXTRA AIRCRAFT/DROPSONDE DATA OVER THE
OTHERWISE DATA-SPARSE NORTH PACIFIC... COURTESY OF THE WINTER STORM
RECONNAISSANCE /WSR07/ PROJECT. IT IS UNKNOWN WHETHER OR NOT THESE
EXTRA DATA HAVE BEEN INGESTED INTO THE ECMWF OR GEM.
00Z RUNS OF THE ECMWF HAVE BEEN TENDING TO DEVELOP OUR LEE SIDE LOW
OVER NORTHEASTERN COLORADO... WHEREAS THE THE 12Z RUNS HAVE BEEN
DEVELOPING THE LOW IN SOUTHEAST CO...DITTO FOR ALL RUNS OF THE GFS
AND THE GEM. THE GEM AND ECMWF ARE PREFERRED HERE DUE TO THEIR
SUPERIOR RESOLUTION PER NCEP. ALSO UNLESS THINGS HAVE RECENTLY BEEN
TWEAKED... THE GFS MODEL ITSELF TENDS TO HAVE TROUBLE WITH LEE SIDE
LOW FORMATION JUST AS A FUNCTION OF MODEL PHYSICS/COORDINATE
SYSTEM.
00Z RUNS OF BOTH THE ECMWF AND GFS... AS WELL AS THE GEM... HAVE
BEEN ADVERTISING A SLIGHTLY FARTHER SOUTH SOLUTION TO THE SFC LOW
TRACK VERSUS THE 12Z GFS/ECMWF. WOULD NORMALLY PREFER THE FARTHER
NORTH SOLUTION AS RIDGING OUT AHEAD OF THIS SYSTEM SHOULD BE FAIRLY
STRONG GIVEN THE HIGHLY AMPLIFIED PATTERN AND BLOCKING LOW OVER THE
MARITIMES. NCEP SUGGESTING THE FARTHER SOUTH TRACK GIVEN THE EXTRA
DATA... BUT NEED TO BE CAUTIOUS HERE AS DROPSONDE DATA PROBABLY
WOULD NOT IMPACT FORECASTS DOWNSTREAM OF THE SYSTEM... AND POSITION
OF LONGWAVE TROUGH OVER THE MARITIMES MAY BE JUST AS IMPORTANT HERE.
OVERALL... THE DISAGREEMENTS IN TRACK MAKE LITTLE DIFFERENCE FOR OUR
FORECAST... BUT A FARTHER NORTH SOLUTION WOULD TEND TO FAVOR SVR WX
THREAT MORE ON SATURDAY... AND MAY ALSO MEAN QUICKER DRY SLOTTING
AND LESS WRAP AROUND PRECIP. SUCH DETAILS ARE NEVER SET IN STONE
THIS FAR OUT IN THE FORECAST.
FOR NOW... WILL TAKE THE PROVERBIAL BLEND OF THE AVAILABLE
GUIDANCE. NORMALLY WOULD PREFER ECMWF IN SUCH CASES... BUT IT HAS
BEEN A LITTLE UNSTABLE WITH THE FORWARD SPEED OF THIS SYSTEM... AND
THE MOST RECENT 00Z RUN IS ABOUT 12 HOURS FASTER THAN THE GFS...
WHICH AGAIN IS NOT FAVORED GIVEN THE BLOCKY PATTERN.
WITH THE SLOWER SOLUTION IN MIND... I AM STILL A LITTLE SHY ABOUT
INCREASING POPS WITH THE WARM ADVECTION ON FRIDAY... AND WILL
CONTINUE TO FOCUS POPS TOWARDS SATURDAY AND ESPECIALLY SATURDAY
NIGHT. SATURDAY NIGHT LOOKS LIKE THE BEST BET FOR HEAVIEST PRECIP
NO MATTER WHICH SOLUTION ONE GOES WITH NOW. THEREFORE... HAVE
DECIDED TO BOOST POPS INTO THE CATEGORICAL RANGE... WHICH IS A
LITTLE UNUSUAL FOR DAY 4.
LONG TERM...SUNDAY THROUGH TUESDAY...
WILL CONTINUE WITH CHANCE POPS SUNDAY WITH POSSIBLE WRAP AROUND
COMING IN BEHIND THE DRY SLOT. COULD EVEN BE IN THE FORM OF SNOW AS
COLD AIR WRAPS IN SUNDAY AFTERNOON ACROSS THE NORTH. FORECAST
BEYOND DAY 5 UNCHANGED WITH THIS PACKAGE.
.HYDROLOGY...
HYDRO DISCUSSION BELOW UNCHANGED FROM 3 PM TUE PACKAGE.
GROUND TEMPS ARE BELOW FREEZING WITH AN AMPLE SNOW COVER ACROSS MOST
OF CENTRAL AND EASTERN IL. OBSERVER REPORTS INDICATED AN AVERAGE OF
AN INCH OR MORE OF WATER CONTENT IN THE SNOW COVER. THIS SNOW IS
EXPECTED TO MELT THE NEXT SEVERAL DAYS...WITH MUCH OF THE WATER
RUNNING OFF INTO AREA WATERSHEDS. WHATEVER SNOW DOES NOT MELT BY
THIS WEEKEND WILL RAPIDLY DISSIPATE WITH MODERATE TO HEAVY RAINFALL
FORECAST FOR SATURDAY INTO EARLY SUNDAY. FORECAST RAINFALL AMOUNTS
OF 1.00 TO 1.50 INCHES...ALONG WITH THE MELTING SNOW COULD CAUSE
PROBLEMS FOR AREA RIVERS THIS WEEKEND INTO EARLY NEXT WEEK. SEE THE
HYDROLOGIC OUTLOOK /CHIESFILX/ ISSUED BY OUR OFFICE AT 1240 PM TODAY
FOR MORE DETAILS.
ANOTHER CONSIDERATION IS FOR URBAN FLOODING THIS WEEKEND. THE
RAINFALL MAY NOT BE ABLE TO REACH STORM SEWERS THAT ARE CLOGGED BY
UNMELTED SNOW OR OTHER DEBRIS. THUS...FLASH FLOODING COULD BE A
PROBLEM SATURDAY AFTERNOON THROUGH SATURDAY NIGHT.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
FREEZING FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR
ILZ027>031-036>038-040>057-061>063-066>068.
&&
$$
SHORT/LONG TERM...HARDIMAN
HYDRO...MILLER
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
105 PM EST WED FEB 21 2007
.AVIATION...THE EDGE OF DENSE FOG WAS RETREATING NORTHEAST...SO HAVE
ADJUSTED CLEARING TIMES IN TAFS TO COINCIDE WITH EXPECTED TIME OF
CLEARING AT TERMINALS. CONCERN FOR FOG TO TRY TO REFORM THIS
EVENING...BUT LOW LEVEL WINDS PICKING UP FROM THE SW...CONDITIONS
SHOULD BECOME VFR OR CLOSE TO VFR LATE OVERNIGHT.
&&
.UPDATE...
THE FOG WAS STARTING TO MIX OUT SOUTH OF THE AREA PER LATEST
SATELLITE AND SURFACE REPORTS. HOWEVER...AN ACARS REPORT INDICATED
DEEP SATURATION OVER NORTHERN IL. HAVE EXTENDED THE DENSE FREEZING
FOG ADVISORY UNTIL 17Z. SNOW COVER BELOW A RELATIVELY DEEP RADIATION
INVERSION WILL CAUSE DENSE FOG TO PERSIST LONGER.
&&
.PREV DISCUSSION... /ISSUED 458 AM EST WED FEB 21 2007/ SHORT
TERM...
THE BIG STORY FOR THE TODAY AND TONIGHT TIME FRAME IS THE DENSE
FREEZING FOG THIS MORNING AND SUBSEQUENTLY WHAT THE FREEZING FOG
AND SNOW PACK WILL DO TO TODAYS HIGH TEMPERATURES. DENSE FREEZING
FOG HAS DEVELOPED ACROSS THE CWA REDUCING VISIBILITIES TO NEAR
ZERO IN MANY PLACES. THEREFORE WILL BE KEEPING THE DENSE FREEZING
FOG ADVISORY GOING TIL 15Z. THEN WITH SUCH A DENSE FOG...HOW
QUICKLY OR SLOWLY WILL IT DISSIPATE LATER THIS MORNING AFTER
SUNRISE. THE WIND IS EXPECTED TO BEGIN BLOWING AROUND MID MORNING
AND SOUNDINGS ALSO NEAR THE SURFACE ARE SHOWING THE FOG TO LIFT
AROUND THIS TIME. SO HAVE THE SKY COVERAGE DECREASING QUICKLY
AFTER MID MORNING WITH THE FOG DISSIPATING. THE FOG MAY LIFT AS
STRATUS LAYER FIRST BEFORE SKY ARE PARTLY CLOUDY THIS
AFTERNOON...BUT THIS WILL HAVE TO BE WATCHED. THE SNOW ON THE
GROUND IS EXPECTED TO KEEP TEMPERATURES LOWER THAN WHAT THEY WOULD
NORMALLY BE WITHOUT ANY SNOW ON THE GROUND...AND ALSO LOWER THAN
MOS GUIDANCE...BUT THE FOG WILL ALSO BE A FACTOR. 850MB
TEMPERATURES DO NOT REALLY CHANGE THAT MUCH FOR TODAY. FORECASTED
HIGH TEMPERATURES FOR TODAY WERE ALREADY BELOW MOS GUIDANCE AND
WITH THINKING THAT THE FREEZING FOG AND SNOW ON THE GROUND ARE
GOING TO BE PLAYERS FOR TODAY...JUST DROPPED TODAYS HIGHS BY ONE.
THIS COULD BE TOO HIGH BUT WILL LET LATER SHIFT MONITOR
TEMPERATURES TO SEE IF THEY REALLY ARE INCREASING OR ARE
STRUGGLING TO INCREASE. THIS AFTERNOON THEN IS EXPECTED TO BE
PARTLY CLOUDY. A SURFACE AND UPPER LEVEL TROUGH MOVE THROUGH THE
AREA TONIGHT. THE GFS IS SHOWING JUST A LITTLE BIT OF QPF WITH IT
AND THE NAM IS DRY WITH THE TROUGH. WILL STAY CONSISTENT WITH OUR
DRY FORECAST AND KEEP TONIGHT DRY. IF THE GFS IS CORRECT...ANY
PRECIP WILL STILL BE VERY LIGHT.
LONG TERM...
THURSDAY THROUGH TUESDAY.
..SIGNIFICANT RIVER FLOODING RISK FOR THIS WEEKEND INTO NEXT WEEK...
00Z NAM-WRF AND 00Z GFS ARE IN FAIRLY SIMILAR AGREEMENT SYNOPTIC
WISE IN THE IMMEDIATE LONG TERM PERIOD THROUGH FRIDAY NIGHT...SO
WILL USE A BLEND OF BOTH.
BIGGEST CONCERN ON THURSDAY WILL BE THE WIND. FAST MOVING S/WV AND
ASSOCIATED SFC LOW PRESSURE WILL MOVE FROM ERN MICHIGAN TO OFF THE
SRN NEW ENGLAND COAST BY THURSDAY EVENING. THE PRESSURE GRADIENT
BETWEEN THE SFC LOW AND HIGH PRESSURE BUILDING INTO THE NRN PLAINS
WILL BRING BREEZY TO WINDY CONDITIONS. WINDS ALOFT WILL BE QUITE
STRONG...AROUND 40 KNOTS AS SEEN AT 925 MB. WITH CAA AND DAY TIME
MIXING...SOME OF THESE WINDS WILL BE TRANSFERRED TO THE SFC. WILL
EMPLOY 35 TO 40 MPH GUSTS IN THE ZONES. THE NAM-WRF AND THE GFS
CONTINUE TO DIFFER ON THE AMOUNT OF LOW LVL MOISTURE THAT WILL BE
FOUND ACRS THE REGION ON THURSDAY. THE NAM-WRF IS FAIRLY DRY WHILE
THE GFS IS FAIRLY MOIST WITHIN THE 925 MB TO 850 MB LAYER. INSTEAD
OF PICKING ONE OVER THE OTHER...BELIEVE THAT A BLEND OF THE TWO IS
IN ORDER. SKIES MAY START OUT PARTLY CLOUDY TO PERHAPS MOSTLY
CLEAR. THEN...WITH DAY TIME HEATING...CUMULUS/STRATOCUMULUS CLOUDS
SHOULD FORM...BEING MOST NUMEROUS ACRS THE NE CWFA. WILL LAYER SKY
CONDITION FROM PARTLY CLOUDY SOUTHWEST TO MOSTLY CLOUDY NE. 850 MB
TEMPS FALL BETWEEN -4 C TO -9 C ACRS THE REGION. PREVIOUS FCST
HIGHS SEEM TOO WARM...AND HAVE THUS LOWERED THEM ACRS THE BOARD
INTO THE MID AND UPPER 30S.
FOR THURSDAY NIGHT INTO FRIDAY...HIGH PRESSURE WILL BUILD EASTWARD
ACRS THE WESTERN GREAT LAKES. SKIES WILL BECOME MOSTLY CLEAR
THURSDAY NIGHT...WITH MOSTLY SUNNY CONDITIONS EXPECTED THROUGH THE
MORNING HOURS ON FRIDAY. SOME WAA INDUCED MID AND HIGH LVL CLOUDS
WILL CREATE PARTLY CLOUDY CONDITIONS DURING FRIDAY AFTERNOON.
AGAIN...PREVIOUS FCST TEMPS APPEAR TO BE TOO WARM THURSDAY NIGHT AND
FRIDAY...SO HAVE ALSO LOWERED.
FOR THE PERIOD FRIDAY NIGHT THROUGH SUNDAY...LONG RANGE MODELS
CONTINUE TO ADVERTISE A SIGNIFICANT STORM SYSTEM WHICH WILL AFFECT
MUCH OF THE LOWER 48 UNITED STATES THIS WEEKEND. THE GFS HAS
OSCILLATED THE MOST ON THE FCST TRACK OF DEEPENING LOW PRESSURE ACRS
THE PLAINS INTO THE WRN GREAT LAKES SATURDAY NIGHT INTO SUNDAY
NIGHT. THE ECMWF AND CANADIAN HAVE BEEN MORE CONSISTENT. IN EITHER
CASE...DEEPENING SFC LOW PRESSURE IS FCST TO MOVE FROM ERN KANSAS
SATURDAY NIGHT TO A POSITION ACRS WRN WISCONSIN BY SUNDAY NIGHT.
WAA INDUCED PCPN WELL AHEAD OF THIS SYSTEM APPEARS THAT IT WILL BE
DELAYED UNTIL AT LEAST SATURDAY AFTN AND HAVE THUS REMOVED MORNING
PCPN FROM THE FCST. HAVE KEPT THE CHC OF RAIN ACRS THE REGION FOR
SATURDAY AFTN. DEPENDING ON HOW TEMPS WARM ON SATURDAY AND HOW FAST
WAA INDUCED PCPN REACHES THE REGION...THERE COULD STILL BE SOME PCPN
TYPE ISSUES ACRS OUR NRN TIER ZONES. HAVE OPTED TO NOT TRY AND PIN
DOWN THIS POTENTIAL PROBLEM ATTM...AND WILL ALLOW A FEW MORE FUTURE
MODEL RUNS TO COME IN BEFORE TAKING A DIFFERENT COURSE OF ACTION.
WHAT DOES SEEM DEFINITE AT THIS POINT IN TIME WILL BE THE POTENTIAL
FOR HEAVY RAIN SATURDAY NIGHT INTO THE FIRST PART OF SUNDAY.
SIGNIFICANT LOW LVL AND UPR LVL DYNAMICS WILL COMBINE WITH A DEEP
MOISTURE SURGE STRAIGHT OUT OF THE GULF OF MEXICO TO BRING SUCH A
THREAT. HAVE RAISED POPS TO THE LIKELY CATEGORY SATURDAY NIGHT
INTO SUNDAY. THE REGION CONTINUES TO HAVE A SNOW COVER WITH ABOUT
ONE TO TWO INCHES OF WATER EQUIVALENT. IN ADDITION...THE GROUND
WILL CONTINUE TO BE SEMI FROZEN THROUGH SATURDAY AS TEMPERATURES
FALL BELOW FREEZING AT NIGHT. FURTHERMORE...ICE CONTINUES ACRS
MANY RIVERS...CREEKS AND STREAMS ACRS THE REGION. ALL THE ABOVE
INGREDIENTS POINT TO A SIGNIFICANT FLOODING EVENT SOMETIME THIS
WEEKEND...CONTINUING INTO EARLY NEXT WEEK. THE SEVERITY OF
FLOODING WILL BE HIGHLY DEPENDENT ON HOW MUCH SNOW WATER
EQUIVALENT THE REGION CAN LOSE BETWEEN NOW AND WHEN IT RAINS AND
HOW MUCH ICE REMAINS ACRS AREA RIVERS AND TRIBUTARIES. WILL UPDATE
FLOOD POTENTIAL OUTLOOK THIS MORNING TO HIGHLIGHT AND EMPHASIZE
THE FLOOD THREAT.
FOR THE REMAINDER OF THE EXTENDED...SUNDAY NIGHT INTO
TUESDAY...COLDER AIR WILL FILTER BACK INTO THE REGION IN THE WAKE OF
A COLD FRONT SUNDAY AFTN/EVENING. WRAP AROUND MOISTURE AND EMBEDDED
UPR LVL DISTURBANCES WITHIN MAIN UPR LVL LOW WILL BRING A THREAT
OF RAIN/SNOW SUNDAY NIGHT...AND SNOW SHOWERS ON MONDAY. SOME OF
THE EXTENDED MODELS INDICATE THAT PERHAPS THE REGION WILL DRY OUT
BY TUESDAY. BEING THAT THIS IS DAY SEVEN IN THE EXTENDED...HAVE
OPTED TO LEAVE THIS PERIOD ALONE FOR NOW.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING FOG ADVISORY UNTIL 3 PM EST /1 PM CST/ FOR
INZ005>009-015>018-024-025.
MI...FREEZING FOG ADVISORY UNTIL 3PM FOR MIZ079>080.
OH...FREEZING FOG ADVISORY UNTIL 3 PM FOR
OHZ001-002-004-005-015-016-024-025.
LM...NONE.
&&
$$
UPDATE...SKIPPER
SHORT TERM...LOTHAMER
LONG TERM....HICKMAN
AVIATION...SKIPPER
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
933 AM EST WED FEB 21 2007
.UPDATE...
THE FOG WAS STARTING TO MIX OUT SOUTH OF THE AREA PER LATEST
SATELLITE AND SURFACE REPORTS. HOWEVER...AN ACARS REPORT INDICATED
DEEP SATURATION OVER NORTHERN IL. HAVE EXTENDED THE DENSE FREEZING
FOG ADVISORY UNTIL 17Z. SNOW COVER BELOW A RELATIVELY DEEP RADIATION
INVERSION WILL CAUSE DENSE FOG TO PERSIST LONGER.
&&
.AVIATION...
VERY DENSE FREEZING FOG HAS FORMED ACROSS THE AREA. IT WILL TAKE
A LITTLE BIT OF TIME FOR THE FOG TO DISSIPATE...AND IS NOT
EXPECTED TO DISSIPATE TIL MID TO LATE MORNING. DO NOT EXPECT VFR
CONDITIONS UNTIL THIS AFTERNOON. IT IS POSSIBLE FOR RUNWAYS TO BE
ICY THIS MORNING TIL TEMPERATURES WARM UP ABOVE THE FREEZING MARK.
TEMPERATURES ARE NOT EXPECTED TO REACH ABOVE FREEZING TIL NOON AND
AFTER. THE WIND SHOULD BEGIN TO BLOW AROUND MID MORNING...WHICH
SHOULD HELP TO DISSIPATE THIS FOG. BUT WITH SUCH A DENSE FOG...IT
WILL TAKE A BIT TO DISSIPATE. THEN TONIGHT THE WIND WILL TURN TO
THE SOUTHWEST TO WEST AND INCREASE IN SPEED. VISIBILITIES AND
CEILINGS ARE EXPECTED TO BE VFR TONIGHT.
&&
.PREV DISCUSSION... /ISSUED 458 AM EST WED FEB 21 2007/
SHORT TERM...
THE BIG STORY FOR THE TODAY AND TONIGHT TIME FRAME IS THE DENSE
FREEZING FOG THIS MORNING AND SUBSEQUENTLY WHAT THE FREEZING FOG
AND SNOW PACK WILL DO TO TODAYS HIGH TEMPERATURES. DENSE FREEZING
FOG HAS DEVELOPED ACROSS THE CWA REDUCING VISIBILITIES TO NEAR
ZERO IN MANY PLACES. THEREFORE WILL BE KEEPING THE DENSE FREEZING
FOG ADVISORY GOING TIL 15Z. THEN WITH SUCH A DENSE FOG...HOW
QUICKLY OR SLOWLY WILL IT DISSIPATE LATER THIS MORNING AFTER
SUNRISE. THE WIND IS EXPECTED TO BEGIN BLOWING AROUND MID MORNING
AND SOUNDINGS ALSO NEAR THE SURFACE ARE SHOWING THE FOG TO LIFT
AROUND THIS TIME. SO HAVE THE SKY COVERAGE DECREASING QUICKLY
AFTER MID MORNING WITH THE FOG DISSIPATING. THE FOG MAY LIFT AS
STRATUS LAYER FIRST BEFORE SKY ARE PARTLY CLOUDY THIS
AFTERNOON...BUT THIS WILL HAVE TO BE WATCHED. THE SNOW ON THE
GROUND IS EXPECTED TO KEEP TEMPERATURES LOWER THAN WHAT THEY WOULD
NORMALLY BE WITHOUT ANY SNOW ON THE GROUND...AND ALSO LOWER THAN
MOS GUIDANCE...BUT THE FOG WILL ALSO BE A FACTOR. 850MB
TEMPERATURES DO NOT REALLY CHANGE THAT MUCH FOR TODAY. FORECASTED
HIGH TEMPERATURES FOR TODAY WERE ALREADY BELOW MOS GUIDANCE AND
WITH THINKING THAT THE FREEZING FOG AND SNOW ON THE GROUND ARE
GOING TO BE PLAYERS FOR TODAY...JUST DROPPED TODAYS HIGHS BY ONE.
THIS COULD BE TOO HIGH BUT WILL LET LATER SHIFT MONITOR
TEMPERATURES TO SEE IF THEY REALLY ARE INCREASING OR ARE
STRUGGLING TO INCREASE. THIS AFTERNOON THEN IS EXPECTED TO BE
PARTLY CLOUDY. A SURFACE AND UPPER LEVEL TROUGH MOVE THROUGH THE
AREA TONIGHT. THE GFS IS SHOWING JUST A LITTLE BIT OF QPF WITH IT
AND THE NAM IS DRY WITH THE TROUGH. WILL STAY CONSISTENT WITH OUR
DRY FORECAST AND KEEP TONIGHT DRY. IF THE GFS IS CORRECT...ANY
PRECIP WILL STILL BE VERY LIGHT.
LONG TERM...
THURSDAY THROUGH TUESDAY.
..SIGNIFICANT RIVER FLOODING RISK FOR THIS WEEKEND INTO NEXT WEEK...
00Z NAM-WRF AND 00Z GFS ARE IN FAIRLY SIMILAR AGREEMENT SYNOPTIC
WISE IN THE IMMEDIATE LONG TERM PERIOD THROUGH FRIDAY NIGHT...SO
WILL USE A BLEND OF BOTH.
BIGGEST CONCERN ON THURSDAY WILL BE THE WIND. FAST MOVING S/WV AND
ASSOCIATED SFC LOW PRESSURE WILL MOVE FROM ERN MICHIGAN TO OFF THE
SRN NEW ENGLAND COAST BY THURSDAY EVENING. THE PRESSURE GRADIENT
BETWEEN THE SFC LOW AND HIGH PRESSURE BUILDING INTO THE NRN PLAINS
WILL BRING BREEZY TO WINDY CONDITIONS. WINDS ALOFT WILL BE QUITE
STRONG...AROUND 40 KNOTS AS SEEN AT 925 MB. WITH CAA AND DAY TIME
MIXING...SOME OF THESE WINDS WILL BE TRANSFERRED TO THE SFC. WILL
EMPLOY 35 TO 40 MPH GUSTS IN THE ZONES. THE NAM-WRF AND THE GFS
CONTINUE TO DIFFER ON THE AMOUNT OF LOW LVL MOISTURE THAT WILL BE
FOUND ACRS THE REGION ON THURSDAY. THE NAM-WRF IS FAIRLY DRY WHILE
THE GFS IS FAIRLY MOIST WITHIN THE 925 MB TO 850 MB LAYER. INSTEAD
OF PICKING ONE OVER THE OTHER...BELIEVE THAT A BLEND OF THE TWO IS
IN ORDER. SKIES MAY START OUT PARTLY CLOUDY TO PERHAPS MOSTLY
CLEAR. THEN...WITH DAY TIME HEATING...CUMULUS/STRATOCUMULUS CLOUDS
SHOULD FORM...BEING MOST NUMEROUS ACRS THE NE CWFA. WILL LAYER SKY
CONDITION FROM PARTLY CLOUDY SOUTHWEST TO MOSTLY CLOUDY NE. 850 MB
TEMPS FALL BETWEEN -4 C TO -9 C ACRS THE REGION. PREVIOUS FCST
HIGHS SEEM TOO WARM...AND HAVE THUS LOWERED THEM ACRS THE BOARD
INTO THE MID AND UPPER 30S.
FOR THURSDAY NIGHT INTO FRIDAY...HIGH PRESSURE WILL BUILD EASTWARD
ACRS THE WESTERN GREAT LAKES. SKIES WILL BECOME MOSTLY CLEAR
THURSDAY NIGHT...WITH MOSTLY SUNNY CONDITIONS EXPECTED THROUGH THE
MORNING HOURS ON FRIDAY. SOME WAA INDUCED MID AND HIGH LVL CLOUDS
WILL CREATE PARTLY CLOUDY CONDITIONS DURING FRIDAY AFTERNOON.
AGAIN...PREVIOUS FCST TEMPS APPEAR TO BE TOO WARM THURSDAY NIGHT AND
FRIDAY...SO HAVE ALSO LOWERED.
FOR THE PERIOD FRIDAY NIGHT THROUGH SUNDAY...LONG RANGE MODELS
CONTINUE TO ADVERTISE A SIGNIFICANT STORM SYSTEM WHICH WILL AFFECT
MUCH OF THE LOWER 48 UNITED STATES THIS WEEKEND. THE GFS HAS
OSCILLATED THE MOST ON THE FCST TRACK OF DEEPENING LOW PRESSURE ACRS
THE PLAINS INTO THE WRN GREAT LAKES SATURDAY NIGHT INTO SUNDAY
NIGHT. THE ECMWF AND CANADIAN HAVE BEEN MORE CONSISTENT. IN EITHER
CASE...DEEPENING SFC LOW PRESSURE IS FCST TO MOVE FROM ERN KANSAS
SATURDAY NIGHT TO A POSITION ACRS WRN WISCONSIN BY SUNDAY NIGHT.
WAA INDUCED PCPN WELL AHEAD OF THIS SYSTEM APPEARS THAT IT WILL BE
DELAYED UNTIL AT LEAST SATURDAY AFTN AND HAVE THUS REMOVED MORNING
PCPN FROM THE FCST. HAVE KEPT THE CHC OF RAIN ACRS THE REGION FOR
SATURDAY AFTN. DEPENDING ON HOW TEMPS WARM ON SATURDAY AND HOW FAST
WAA INDUCED PCPN REACHES THE REGION...THERE COULD STILL BE SOME PCPN
TYPE ISSUES ACRS OUR NRN TIER ZONES. HAVE OPTED TO NOT TRY AND PIN
DOWN THIS POTENTIAL PROBLEM ATTM...AND WILL ALLOW A FEW MORE FUTURE
MODEL RUNS TO COME IN BEFORE TAKING A DIFFERENT COURSE OF ACTION.
WHAT DOES SEEM DEFINITE AT THIS POINT IN TIME WILL BE THE POTENTIAL
FOR HEAVY RAIN SATURDAY NIGHT INTO THE FIRST PART OF SUNDAY.
SIGNIFICANT LOW LVL AND UPR LVL DYNAMICS WILL COMBINE WITH A DEEP
MOISTURE SURGE STRAIGHT OUT OF THE GULF OF MEXICO TO BRING SUCH A
THREAT. HAVE RAISED POPS TO THE LIKELY CATEGORY SATURDAY NIGHT
INTO SUNDAY. THE REGION CONTINUES TO HAVE A SNOW COVER WITH ABOUT
ONE TO TWO INCHES OF WATER EQUIVALENT. IN ADDITION...THE GROUND
WILL CONTINUE TO BE SEMI FROZEN THROUGH SATURDAY AS TEMPERATURES
FALL BELOW FREEZING AT NIGHT. FURTHERMORE...ICE CONTINUES ACRS
MANY RIVERS...CREEKS AND STREAMS ACRS THE REGION. ALL THE ABOVE
INGREDIENTS POINT TO A SIGNIFICANT FLOODING EVENT SOMETIME THIS
WEEKEND...CONTINUING INTO EARLY NEXT WEEK. THE SEVERITY OF
FLOODING WILL BE HIGHLY DEPENDENT ON HOW MUCH SNOW WATER
EQUIVALENT THE REGION CAN LOSE BETWEEN NOW AND WHEN IT RAINS AND
HOW MUCH ICE REMAINS ACRS AREA RIVERS AND TRIBUTARIES. WILL UPDATE
FLOOD POTENTIAL OUTLOOK THIS MORNING TO HIGHLIGHT AND EMPHASIZE
THE FLOOD THREAT.
FOR THE REMAINDER OF THE EXTENDED...SUNDAY NIGHT INTO
TUESDAY...COLDER AIR WILL FILTER BACK INTO THE REGION IN THE WAKE OF
A COLD FRONT SUNDAY AFTN/EVENING. WRAP AROUND MOISTURE AND EMBEDDED
UPR LVL DISTURBANCES WITHIN MAIN UPR LVL LOW WILL BRING A THREAT
OF RAIN/SNOW SUNDAY NIGHT...AND SNOW SHOWERS ON MONDAY. SOME OF
THE EXTENDED MODELS INDICATE THAT PERHAPS THE REGION WILL DRY OUT
BY TUESDAY. BEING THAT THIS IS DAY SEVEN IN THE EXTENDED...HAVE
OPTED TO LEAVE THIS PERIOD ALONE FOR NOW.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING FOG ADVISORY UNTIL NOON /11 AM CST/ THIS MORNING FOR
FOR INZ003>009-012>018-020-022>027-032>034.
MI...FREEZING FOG ADVISORY UNTIL NOON FOR MIZ077>081.
OH...FREEZING FOG ADVISORY UNTIL NOON FOR OHZ001-
002-004-005-015-016-024-025.
LM...NONE.
&&
$$
UPDATE...SKIPOPER
SHORT TERM...LOTHAMER
LONG TERM....HICKMAN
AVIATION...LOTHAMER
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
111 AM EST WED FEB 21 2007
.AVIATION...
DENSE FREEZING FOG HAS FORMED ACROSS THE AREA AND AT BOTH SBN AND
FWA. THIS FOG IS NOT EXPECTED TO BEGIN DISSIPATING UNTIL AFTER
SUNRISE. THE FOG COULD THEN LIFT INTO A LOW STRATUS LAYER BEFORE
SKIES BECOME PARTLY CLOUDY FOR THE REST OF THE TAF PERIOD. THE
WIND IS EXPECTED TO BEGIN AROUND MID MORNING WHICH SHOULD ALSO
HELP DISPEL THE FREEZING FOG. ONCE THE WIND DOES BEGIN...IT WILL
THEN BE BLOWING OUT OF THE SOUTHWEST.
&&
.UPDATE... /ISSUED 949 PM EST TUE FEB 20 2007/
EVE SOUNDINGS INDICATED A LITTLE MORE FAVORABLE LOW LEVEL
HYDROLAPSE FOR DENSE FOG DEVELOPMENT THAN SUGGESTED BY PRE-00Z
TAMDAR DATA. PATCHY DENSE FOG BEING REPORTED ALREADY THIS EVENING
BY AUTOMATED SURFACE OBS AND SPOTTERS. SOME CIRRUS MOVING INTO THE
AREA ATTM BUT SHOULD BE SHORT LIVED AND NOT EXPECTED TO BE
SUFFICIENT TO LIMIT FURTHER RADIATIONAL COOLING. THUS, EXPECT FOG
TO CONT TO LOWER VSBYS AND BECOME MORE WIDESPREAD OVERNIGHT AS SFC
HIGH MOVES ACROSS THE AREA. OTHER PROBLEM THIS EVENING IS WITH
BLACK ICE. MELTING SNOW WAS RAPIDLY REFREEZING THIS EVENING DUE TO
THE STRONG RADIATIONAL COOLING, ESPECIALLY ON BLACKTOP. THIS WILL
RESULT IN ICY SPOTS ON ROADS/SIDEWALKS OVERNIGHT AND WED MORNING.
DENSE FOG SHOULD ALSO RESULT IN SOME ADDITIONAL GLAZING WITH
GROUND SURFACES ALREADY VERY MOIST AND TEMPERATURES FALLING WELL
BLO FREEZING. THUS, ISSUED A FREEZING FOG ADVISORY OVERNIGHT
UNTIL 15Z WED. NO OTHER SGFNT CHANGES ATTM AS GOING LOWS IN THE
L-M20S LOOK REASONABLE.
&&
.UPDATE... /ISSUED 644 PM EST TUE FEB 20 2007/
UPDATED MAINLY TO FRESHEN WORDING IN ZONES AS SHOWERS HAVE MOVED
EAST OUT OF THE CWA EARLY THIS EVENING. REST OF THE NIGHT SHOULD
BE DRY WITH RADIATIONAL COOLING FOG/STRATUS DVLPG AS SFC HIGH
MOVES ACROSS THE AREA.
&&
.PREV DISCUSSION... /ISSUED 311 PM EST TUE FEB 20 2007/
SHORT TERM...
SEVERAL FORECAST CHALLENGES FOR THE SHORT TERM PACKAGE. SHORT WAVE
RACING OUT OF ILLINOIS WILL EXIT THE AREA EARLY THIS EVENING. VIS
IMAGES SHOWING CLEARING NEAR THE IN/IL STATE LINE. THIS CLEARING
SHOULD PROGRESS EAST ACROSS THE FORECAST AREA THIS EVENING. HIGH
PRESSURE WILL SETTLE ACROSS THE AREA LEADING TO LIGHT OR CALM
WINDS. THE COMBINATION OF THESE FACTORS WITH MELTING SNOWPACK AND
SOME LIGHT RAINFALL TODAY WILL SET THE STAGE FOR POSSIBLE FOG AND
STRATUS DEVELOPMENT TONIGHT. NAM AND GFS HAVE DIFFERENT IDEAS ON
WHAT WILL OCCUR...WITH THE NAM MORE PESSIMISTIC...SHOWING A STRONG
RADIATION INVERSION DEVELOPING AND STRATUS AND FOG FORMING UNDER
IT. GFS DOES NOT DEVELOP THIS. THE ONLY NEGATIVE FACTOR FOR FOG
AND STRATUS IS THE DRYING OCCURRING UPSTREAM THIS AFTERNOON WITH
SURFACE DEWPOINTS DROPPING INTO THE MID AND UPPER 20S.
HOWEVER...GIVEN ALL THE OTHER POSITIVE FACTORS AND STAYING WITH
PERSISTENCE AND CONTINUITY OF PRESENT FORECAST...WILL CONTINUE FOG
AND STRATUS FORMATION OVERNIGHT. HENCE SKIES BECOMING MOSTLY CLEAR
THIS EVENING...THEN MOSTLY CLOUDY AFTER MIDNIGHT WITH STRATUS AND
FOG DEVELOPMENT. SHOULD TAKE SOME TIME TO BURN OFF FOG AND STRATUS
WEDNESDAY. INCREASING FLOW IN THE AFTERNOON SHOULD HELP SCATTER
THINGS OUT.
WITH CLEAR SKIES THIS EVENING AND STILL RESIDUAL SNOWPACK...SHOULD
SEE TEMPS DROP QUICKLY THEN LEVEL OUT WHEN FOG FORMS. TEMPS TRICKY
ON WEDNESDAY DEPENDING ON HOW FAST FOG MIXES OUT. AGAIN STAYED WITH
PERSISTENCE FOR NOW WHICH FALLS NEAR THE LOW END OF MOS GUIDANCE.
LONG TERM....
WEDNESDAY THROUGH TUESDAY...
WEATHER PATTERN CONTINUES TO DEAMPLIFY ACROSS THE UNITED STATES. A
FAIRLY STRONG SHORT WAVE SYSTEM WILL PASS NORTH OF THE AREA
WEDNESDAY NIGHT WITH ANOTHER COLD FRONT EXPECTED TO PASS ACROSS THE
AREA. MOISTURE IS LIMITED BEING MOSTLY TRAPPED IN THE LOWEST 5KFT.
MODEL GUIDANCE PUSHES SOME LIFT ACROSS THE AREA AT THE SAME
TIME...BUT WITH LIMITED MOISTURE...ELECTED TO KEEP WEDNESDAY NIGHT
DRY. MINOR CHANGES WERE MADE TO THE LOW TEMPERATURE FORECAST.
ONCE THIS SYSTEM IS PAST...A STRONG MID LEVEL RIDGE OF HIGH PRESSURE
WILL PASS ACROSS THE AREA THURSDAY AND FRIDAY. COLD AIR WILL MOVE
ACROSS THE AREA...BUT ARCTIC AIR MASSES WILL REMAIN WELL NORTH OF
THE WESTERN LOWER GREAT LAKES REGION. MADE MINOR CHANGES TO
TEMPERATURES FORECASTS FOR THURSDAY AND FRIDAY. THIS RIDGE IS BEING
GENERATED BY A STRONG SHORT WAVE TROF DIGGING INTO THE WEST COAST
AREA. THESE TWO SYSTEMS WILL DEVELOP A MAJOR SURFACE LOW PRESSURE
SYSTEM OVER EASTERN COLORADO AND WESTERN KANSAS. BOTH THE ECMWF/GFS
PLACE THE SYSTEM THERE...WITH THE ECMWF MOVING THE LOW FASTER THAN
THE GFS. WITH TIMING UNCERTAINTY HAVE ELECTED TO KEEP THE CURRENT
FORECAST OF RAIN DURING THE DAY SATURDAY AND INTO SUNDAY.
HOWEVER...THERE CHANCES ARE INCREASING THAT THE PRECIPITATION MAY
HOLD OFF INTO SATURDAY AFTERNOON. MINOR CHANGES WERE MADE TO THE
HIGH TEMPERATURE FORECAST FOR SATURDAY...LOWERING THEM IN OUR NORTH.
THE POTENTIAL EXISTS FOR HEAVY RAIN BOTH SATURDAY AND SUNDAY ALONG
WITH AN INCREASED CHANCE OF FLOODING. WITH A MORE PROGRESSIVE ZONAL
FLOW EXPECTED TO CONTINUE ACROSS THE AREA ANOTHER...SHORT WAVE
SYSTEM WILL FOLLOW BRINGING A CHANCE OF SNOW ON MONDAY AND SNOW WITH
RAIN SOUTH ON TUESDAY.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING FOG ADVISORY UNTIL 10 AM EST /9 AM CST/ THIS MORNING
FOR INZ003>009-012>018-020-022>027-032>034.
MI...FREEZING FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR
MIZ077>081.
OH...FREEZING FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR OHZ001-
002-004-005-015-016-024-025.
LM...NONE.
&&
$$
SHORT TERM...LASHLEY
LONG TERM....LAMBERTY
AVIATION...LOTHAMER
UPDATE...TAYLOR
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
935 PM EST THU FEB 22 2007
.SHORT TERM...
WATER VAPOR LOOP SHOWS A VIGOROUS SHORT WAVE SLIDING SOUTHEAST FROM
THE EASTERN GREAT LAKES...AS RIDGING OCCURS ALONG THE ROCKIES. ACARS
400-250MB WIND OBSERVATIONS REVEAL A 120-165KT NORTHWESTERLY JET
FROM THE UPPER MIDWEST THROUGH THE MID ATLANTIC...WHILE A 110-130KT
SOUTHERLY STREAM JET EXTENDS FROM THE FOUR CORNERS REGION EAST INTO
THE GULF STATES. 20Z SURFACE ANALYSIS PLACED A 999MB OCCLUDED
CYCLONE NORTH OF LAKE ONTARIO. THE OCCLUDED/COLD FRONT HAS MOVED TO
THE EAST...AND EXTENDED SOUTHWEST THROUGH THE GULF STATES AND
PLAINS. THE NEXT COLD FRONT EXTENDED SOUTHWEST FROM THE CYCLONE
THROUGH THE MIDWEST WHERE IT WAS STALLING. A TROUGH WAS LOCATED IN
THE LEE OF THE APPALACHIANS.
PRESSURE GRADIENT BETWEEN A DEEPENING CYCLONE IN THE WESTERN
ATLANTIC OCEAN AND THE HIGH RIDGING SOUTH ACROSS THE CENTRAL CONUS
IS SUPPORTING GUSTY WINDS ACROSS THE REGION. COLD ADVECTION WILL
MAINTAIN DRY ADIABATIC LAPSE RATES WITHIN THE LOWER
ATMOSPHERE...ENCOURAGING MOMENTUM TO TRANSPORT TO THE SURFACE
OVERNIGHT. HAVE NOT SEEN ANY 50KT WIND GUSTS ACROSS THE FORECAST
AREA THUS FAR...EVEN KHSP (AN AWOS JUST SOUTHWEST OF THE FORECAST
AREA AT 3793 FT)...HAS ONLY GUSTED TO 48KTS. THIS GIVES CREDENCE TO
THE 18Z NAM/GFS WHICH FORECAST SOUNDINGS ON THE BUFKIT INTERFACE
INDICATE MOMENTUM TRANSFER IN THE 40-48KT RANGE THROUGH THE
REMAINDER OF THE EVENT. ACCELERATION CENTERED NEAR 850MB OVERHEAD
TONIGHT IS MOST LIKELY PARTIALLY ATTRIBUTED TO THE SUBSIDENCE
INVERSION LOWERING...WITH WINDS ACCELERATING ABOVE THE INVERSION DUE
TO THE LOSS OF FRICTION FORCES BELOW. MIXING DEPTH WILL BECOME
SHALLOWER OVERNIGHT AS THE SUBSIDENCE INVERSION LOWERS. THUS HAVE
DOWNGRADED THE HIGH WIND WARNING ALONG AND WEST OF THE BLUE RIDGE TO
A WIND ADVISORY.
SECONDARY COLD FRONT WILL BE APPROACHING FROM PENNSYLVANIA LATE
TONIGHT...WHICH SHOULD PROVIDE A FORCING MECHANISM TO SUPPORT CLOUDS
AND SNOW SHOWERS INTO THE BALTIMORE METRO AREA. GUSTY NORTHWEST
WINDS ARE ALSO SUPPORTING THE TRANSPORT OF UPSLOPE MOISTURE EASTWARD
INTO THE SHENANDOAH VALLEY (THE WINDS ARE STRONG ENOUGH WHERE THE
TRANSPORT CHARACTERISTICS OUTWEIGH THE DOWNSLOPE COMPONENT).
ALONG AND WEST OF THE ALLEGHENY FRONT...15Z SHORT RANGE ENSEMBLES
CLUSTER AT BOTH 0.15" AND 0.5" OF LIQUID EQUIVALENT PRECIPITATION
(AT KEKN)...SHUTTING OFF JUST BEFORE SUNRISE. HAVE SIDED WITH THE
LOWER CLUSTER...WITH LAKE ERIE BEING LARGELY FROZEN OVER. AS THE
SYNOPTIC SYSTEM CONTINUE TO DEEPEN TO THE EAST...THE LOW LEVEL
MOISTURE DEPTH WILL BECOME SHALLOWER EARLY FRIDAY MORNING.
&&
.AVIATION...
PRESSURE GRADIENT WILL SUPPORT WIND GUSTS TO 40KTS
OVERNIGHT...DECREASING TO ABOUT 30KT FRIDAY AFTERNOON AS THE
GRADIENT BEGINS TO RELAX. STRATO-CU AND SNOW SHOWERS WILL APPROACH
NORTHERN TERMINALS BEFORE DISSIPATING IN STRONG DOWNSLOPE FLOW.
UPSLOPE/LAKE ENHANCEMENT EVENT WILL BE ENDING MIDDAY FRIDAY AS
ANTICYCLONIC FLOW BUILDS IN TO THE APPALACHIANS.
&&
.MARINE...
12Z MET/MAV MOS AT THOMAS POINT INDICATE SUSTAINED WINDS NEAR 25KT
THROUGH FRIDAY. PROXIMITY 12Z GFS/18Z NAM BUFKIT FORECAST SOUNDINGS
INDICATE WIND GUSTS UP TO 45KT OVERNIGHT AND FRIDAY MORNING. ICE
COVERAGE HAS DECREASED DUE TO THE WARMER TEMPERATURES.
&&
.TIDES...
CURRENT TIDAL DEPARTURES ARE SLIGHTLY ABOVE ASTRONOMICAL
PREDICTIONS. THE LUNAR CYCLE IS WAXING TOWARD A QUARTER MOON (34
PERCENT FULL). THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND
NOAA EXTRATROPICAL STORM SURGE MODEL INDICATE -2FT TIDAL DEPARTURES
LATE TONIGHT AND FRIDAY RESULTING FROM BLOWOUT CONDITIONS. A MARINE
WEATHER STATEMENT (WBCMWSLWX) HAS BEEN ISSUED WITH FURTHER DETAILS.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WIND ADVISORY UNTIL 10 AM EST FRIDAY FOR DCZ001.
MD...WIND ADVISORY UNTIL 10 AM EST FRIDAY FOR
MDZ003>007-009>011-013-014-016>018-501-502.
SNOW ADVISORY UNTIL 4 AM EST FRIDAY FOR MDZ501.
VA...WIND ADVISORY UNTIL 10 AM EST FRIDAY FOR VAZ021-025>031-
036>042-050>057.
WV...WIND ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ050>055-501>504.
SNOW ADVISORY UNTIL 4 AM EST FRIDAY FOR WVZ501-503.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM FRIDAY TO 6 AM EST SATURDAY
FOR ANZ530>537.
GALE WARNING UNTIL 10 PM EST FRIDAY FOR ANZ530>537.
&&
SHORT TERM/AVIATION/MARINE/TIDES...ROGOWSKI
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1015 PM EST THU FEB 22 2007
.UPDATE...
MAIN FCST ISSUES OVERNIGHT ARE TEMPS AND LINGERING LIGHT LES.
AT THE SFC...HIGH PRES WAS BUILDING OVER NRN ONTARIO WITH A RIDGE
EXTENDING S ACROSS WRN LAKE SUPERIOR/ERN MN. WITH ARRIVAL OF RIDGE
AXIS AND STRENGTHENING LAND BREEZES/CONVERGENCE...LAKE EFFECT CLOUDS
AND PROBABLY SOME FLURRIES/-SHSN ARE REDEVELOPING OVER WRN LAKE
SUPERIOR. OVER ERN LAKE SUPERIOR...UNDER NRLY WINDS...LIGHT LES
CONTINUES FROM THE TIP OF THE KEWEENAW AROUND COPPER HARBOR S TO ERN
MARQUETTE/NRN DELTA/ALGER COUNTIES. ELSEWHERE...AWAY FROM LES...
SKIES ARE GENERALLY CLEAR AND TEMPS ARE FALLING FAIRLY QUICKLY. AS
OF 03Z...TEMPS OVER THE INTERIOR W ARE WELL DOWN INTO THE SINGLE
DIGITS IN THE TYPICAL COLD SPOTS.
WITH LAND BREEZES CONTINUING TO STRENGTHEN OVER WRN UPPER MI...DO
NOT EXPECT LAKE EFFECT CLOUDS/FLURRIES DEVELOPING OVER WRN LAKE
SUPERIOR TO SPREAD TO THE SHORE...ESPECIALLY SINCE SFC RIDGE AXIS
WILL CONTINUE DRIFTING E...RESULTING IN VEERING OF THE SYNOPTIC WIND
FIELD. HOWEVER...CLOUDS/LIGHT LES EXTENDING FROM COPPER HARBOR NWD
WILL LIKELY BRUSH THE SHORELINE OVER THE WRN KEWEENAW OVERNIGHT AS
WINDS VEER WITH SFC RIDGE DRIFTING E. OVER ERN LAKE SUPERIOR...
EXPECT LIGHT LES TO PERSIST THRU THE NIGHT. AS WINDS VEER MORE NERLY
DURING THE NIGHT...LES WILL TRY TO SPREAD W ACROSS THE NCNTRL FCST
AREA...BUT LAND BREEZES WILL WORK TO INHIBIT/SLOW THE WWD MOVEMENT.
SO...EXPECT FLURRIES/-SHSN TO PERSIST MAINLY OVER MARQUETTE COUNTY
INTO NRN DELTA/ALGER COUNTIES. WITH HIGH SNOW TO WATER RATIO OF THE
SNOW THAT IS FALLING...FLUFFY ACCUMULATIONS OF AROUND 1 INCH SEEM
LIKELY.
AS FOR TEMPS...WILL DROP MINS INTO THE SINGLE DIGITS BLO ZERO OVER
THE INTERIOR W HALF AS MOSTLY CLEAR SKIES THRU MUCH OF NIGHT AND
LIGHT/CALM WINDS WILL ALLOW TEMPS TO FALL STEADILY.
&&
.PREV DISCUSSION (ISSUED AT 410 PM EST)...
WV IMAGERY AND RUC ANALYSIS INDICATED A DEPARTING MID/UPPER LEVEL
LOW OVER GEORGIAN BAY. A BROAD RDG WAS LOCATED OVER THE WRN PLAINS
DOWNSTREAM FROM THE NEXT SIGNIFICANT TROF MOVING ONSHORE INTO THE
WRN CONUS. AT THE SFC...NNW FLOW PREVAILED ACRS THE CWA BTWN LOW
PRES OVER LAKE ONTARIO AND A RDG FROM NRN ONTARIO/MANITOBA INTO WRN
MN. AS THE 850-700 MOISTURE HAS THINNED OUT...PER KSAW TAMDAR
SNDGS...THE MULTIPLE WIND PARALLEL LES BANDS HAVE DIMINISHED DURING
THE AFTERNOON. THE HIGHEST REFLECTIVITIES REMAINED OVER ERN
MARQUETTE AND WRN ALGER COUNTIES. THE LES HAS ALSO DIMINISHED OR
ENDED OVER THE WEST AS THE VIS LOOP SHOWED THE BACK EDGE OF THE LAKE
CLOUDS HAD ALMOST MOVED ONSHORE. LES BANDS HAD ALSO THINNED OUT OR
DISSIPATED E OF MUNISING.
SHORT TERM (TONIGHT AND FRI)...
MAIN FCST CONCERNS ARE LES TRENDS.
SATELLITE AND RADAR TRENDS ALONG WITH THE 12Z/18Z NAM AND LCL
HIRESWRF-ARW SUGGEST THAT THE REMAINING LES BANDS WILL CONTINUE TO
WEAK AND GRADUALLY SHIFT SHIFT INTO N CNTRL UPR MI THIS EVENING AS
THE WINDS BACK NE. HOWEVER...WITH INVERSION HEIGHTS FALLING AOB 3K
FT AND CONTINUED 850-700 DRYING...LITTLE MORE THAN SCT LIGHT SNOW
SHOWERS OR FLURRIES ARE EXPECTED BY LATE THIS EVENING. ANY
ADDITIONAL ACCUMULATIONS SHOULD BE LESS THAN AN INCH. WITH ENOUGH
CLEARING INLAND ALONG WITH LIGHT WINDS...TEMPS SHOULD FALL CLOSE TO
0F. OTHERWISE...LAKE CLOUDS WILL KEEP MIN TEMPS FROM DROPPING OFF AS
MUCH N CNTRL.
EXPECT INCREASING MID/HIGH CLOUDS FROM SW TO NE WITH WAA PATTERN
AHEAD OF THE DEVELOPING WRN CONUS TROF. DIVERGENT ACYC NRLY FLOW
WITH INVERSION HEIGHT BLO 3K FT SHOULD MINIMIZE POTENTIAL FOR ANY
LINGERING LIGHT LES EVEN THOUGH SOME LAKE CLOUDS MAY LINGER OVER
N CNTRL UPR MI.
LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)...
TAKING A LOOK AT THE 500MB ANALYSIS OVER THIS PERIOD...WE WILL START
OUT WITH THE HIGH AMPLITUDE RIDGE SITUATED FROM NORTHCENTRAL
MANITOBA THROUGH KDLH...AND INTO WESTERN ILLINOIS. THIS RIDGE
SHOULD BE OVERHEAD...OVER THE UPPER PENINSULA 06Z SATURDAY THROUGH
06Z SUNDAY. DURING THIS SAME TIME WE WILL BE MONITORING THE
FORMATION OF THE CUT OFF LOW ACROSS THE DESERT SOUTHWEST. CONTINUE
TO SEE SOME MODEL CHANGES OVER THE PAST 24 HOURS...BUT MODEL TO
MODEL CONSISTENCY SEEMS TO REMAIN PRETTY GOOD. AS A
RESULT...CONTINUED TO SIDE CLOSE TO THE GFS AND ECMWF WHICH SEEMED
TO BE MORE IN LINE WITH EACH OTHER OVER THE PAST COUPLE OF RUNS THAN
24 HOURS AGO. SO...WITH FUTURE FORECAST ISSUANCES WE WILL LIKELY
NEED TO DECIDE ON WHERE TO ISSUE A WATCH...FOR SNOW.
JUST A FEW DAYS AGO WE WERE FIGURING THAT SOME MIXED PRECIPITATION
WOULD BE EXPECTED OVER THE UPPER PENINSULA THIS WEEKEND. NOW...WITH
THE LOW SHIFTED FURTHER AND FURTHER TO OUR SOUTH...ALL SNOW IS NOW
FORECAST...WITH THE HIGHEST AMOUNTS REMAINING ACROSS THE SOUTHERN
HALF OF THE CWA...THAT IS UNTIL THE COLD ENOUGH AIR WRAPS BACK INTO
THE AREA TO ALLOW FOR LAKE EFFECT OR LAKE ENHANCEMENT SUNDAY NIGHT
INTO MONDAY ALONG WITH MORE FAVORABLE WINDS.
AFTER OUR CLOUDY AND WET WEEKEND...WE ARE FIGURING MOST OF MONDAY
NIGHT THROUGH TUESDAY NIGHT TO BE DRY. YET ANOTHER SYSTEM WILL
SWEEP IN FROM THE SOUTHWEST FOR MID WEEK INTO THE END OF THE WORK
WEEK. TIMING ON THIS ONE WILL LIKELY CHANGE OVER THE NEXT COUPLE OF
DAYS...AND MAY BE SLOWER THAN WHAT WE CURRENTLY HAVE...GIVEN THE
LARGE RIDGE IN BETWEEN THE TWO STORM SYSTEMS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
ROLFSON (UPDATE)
JLB (SHORT TERM)
KF (LONG TERM)
AREA FORECAST DISCUSSION
NWS GAYLORD MI
957 PM EST THU FEB 22 2007
.UPDATE...SKIES HAVE CLEARED ACROSS MUCH OF NORTHERN MICHIGAN THIS
EVENING WITH THE EXCEPTION OF AREAS WEST OF US-131 WHERE LAKE
STREAMERS ORIGINATING OVER CENTRAL LAKE SUPERIOR MAKING THEIR WAY
DOWN ACROSS NORTHERN LAKE MICHIGAN. RADAR SHOWING SOME WEAK
RETURNS IN THESE BANDS INDICATING AT LEAST SOME FLURRIES. 00Z APX
SOUNDING SHOWS AN INVERSION AROUND 890MB...ALBEIT A BIT EAST OF
THE TRAJECTORIES OFF THE LAKE...BUT AN AIRCRAFT SOUNDING OUT OF
MQT AROUND 01Z PLACES INVERSION AROUND 870MB. LOW LEVEL WINDS
EXPECTED TO VEER MORE NORTHERLY OVERNIGHT...KAPX/KMQT VWP SUGGEST
THIS ALREADY STARTING TO OCCUR...WITH EVEN MORE OF A NORTHEAST
FLOW ACROSS EASTERN UPPER WHICH SHOULD CUT OFF THE LAKE SUPERIOR
EFFECTIVE FETCH. SO FLURRY ACTIVITY EXPECTED TO SHIFT WESTWARD
WITH TIME AND WANE AS THE NIGHT WEARS ON. OTHERWISE SKIES WILL
REMAIN MOSTLY CLEAR ELSEWHERE WITH WINDS CONTINUING TO DIMINISH AS
SURFACE RIDGE BUILDS INTO THE WESTERN LAKES.
JPB
&&
.PREV DISCUSSION... /ISSUED 350 PM EST THU FEB 22/
LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW POTENT SHORTWAVE
AND ASSOCIATED LOW PRESSURE MOVING EAST OF THE FORECAST AREA WITH
MOST OF THE SNOW SHOWERS ALSO MOVING EAST OVER LAKE HURON. JUST A
FEW SCATTERED FLURRIES STILL LINGERING OVER THE HIGHER ELEVATIONS
OF NORTHERN LOWER AND RIGHT ALONG THE LAKE HURON SHORELINE FROM
ALPENA TO OSCODA. WIDESPREAD STRATO CU DECK IS SLOWLY ERODING FROM
WEST TO EAST OVER THE PAST COUPLE HOURS OR SO. IN FACT...THE
MAJORITY OF EASTERN UPPER IS JUST ABOUT CLEAR WHILE PELLSTON HAS
JUST TURNED SCATTERED AS LOW LEVEL WINDS TURN TO THE NORTH AND
SUBSIDENCE BEHIND THE WAVE IS SCOURING OUT THE LOW LEVEL MOISTURE
FAIRLY WELL. SPEAKING OF THE WINDS...AFTER SEVERAL REPORTS OF
GUSTS TO 50 MPH EARLY TODAY...WINDS HAVE BEEN SLOWLY DIMINISHING
THIS AFTERNOON ACROSS THE CWA. IT IS STILL BREEZY NONETHELESS WITH
SUSTAINED NW WINDS BETWEEN 15 TO 20KTS AND GUSTS BETWEEN 25 AND
35KTS STILL WIDESPREAD. MAIN FORECAST CONCERNS FOR THE REST OF
TONIGHT ARE SNOW SHOWER CHANCES...WIND SPEEDS...AND MARINE
HEADLINES.
HEADLINES...SINCE ONLY LINGERING FLURRIES REMAIN...AND SUSTAINED
WINDS/GUSTS ARE WELL BELOW ADVISORY CRITERIA...AND CONDITIONS WILL
IMPROVE FROM HERE ON OUT...WILL LET SNOW AND BLOWING SNOW ADVISORY
AND WIND ADVISORY EXPIRE WITH THE 4 PM ISSUANCE. GALE WARNINGS WILL
CONTINUE FOR ALL NEARSHORE ZONES THROUGH MIDNIGHT SINCE WINDS IN THE
MIXED LAYER STILL HAVE THE POTENTIAL TO REACH GALE CRITERIA.
TONIGHT...STRONG SHORTWAVE AND ASSOCIATED LOW PRESSURE WILL MOVE
QUICKLY TO THE EASTERN GREAT LAKES THIS EVENING. NORTHERLY WINDS
WILL PERSIST BUT WILL GRADUALLY WIND DOWN AS THE PRESSURE GRADIENT
RELAXES AND CORE OF THE 6HR PRESSURE RISES MOVES EAST. 900-700MB RH
IN EXCESS OF 75 PCT WILL TRY TO HANG ON ACROSS THE FAR EASTERN
CWA...AND WITH DELTA T`S BETWEEN 13C AND 15C...A FEW FLURRIES ARE
STILL POSSIBLE RIGHT ALONG THE LAKE HURON SHORELINE FROM ROGERS CITY
TO OSCODA EARLY THIS EVENING. BUT INCREASING SUBSIDENCE (900-700MB
RH OF APPROX 50 PCT FALLING TO 20 PCT BY MIDNIGHT) AND LOW INVERSION
HEIGHTS OF 2.5KFT WILL OVERSPREAD THE REGION AND PREVENT PRECIP
POINTS WEST. THEREFORE...WE WILL SEE CLEARING FROM WEST TO EAST
OVERNIGHT WITH EXCEPTION OVER NNW TO N FLOW REGIMES WHERE SCATTERED
LAKE CLOUDS WILL TRY TO HOLD ON. HAVE LOWERED MIN TEMPS A COUPLE
DEGREES BUT NOT NEARLY AS MUCH AS MAV GUIDANCE SINCE BELIEVE WIND
SPEEDS WILL KEEP TEMPS A LITTLE HIGHER THAN WHAT GUIDANCE WANTS.
TOMORROW...RIDGING ALOFT AND AT THE SURFACE WILL CONTINUE TO WORK
ITS WAY ACROSS MICHIGAN. WITH 850-500RH BETWEEN 10 TO 25
PCT...NORTHERN MICHIGAN WILL ENJOY A SUNSHINE FILLED DAY. THE
EXCEPTION MAY BE AREAS ADJACENT TO LAKE MICHIGAN AND LAKE HURON
WHERE A NORTH WIND MAY BRING IN SCATTERED LAKE CLOUDS WITH DELTA T/S
BETWEEN 11C AND 13C...ESPECIALLY DURING THE MORNING. BUT WITH
INVERSION HEIGHTS AROUND 2.5KFT AND INCREASING SUBSIDENCE THROUGH
THE DAY...EXPECT THESE CLOUDS TO MIX OUT FAIRLY QUICKLY DURING THE
MORNING. SOME HIGH CLOUDS WILL APPROACH ACROSS THE SW CWA BY LATE
AFTERNOON...BUT A GENERALLY QUIET DAY. MIXING TO 925 MB REVEALS
HIGHS RANGING FROM THE UPPER TEENS ACROSS EASTERN UPPER...TO THE
MIDDLE 20S ACROSS NW AND CENTRAL LOWER.
MPC
LONG TERM...MODELS ARE IN PRETTY GOOD AGREEMENT TODAY WITH THE NAM
COMING INTO LINE MORE WITH THE GFS THAN IT WAS YESTERDAY. BOTH
HOWEVER ARE SLOWING THE TIMING OF THE PRECIPITATION OVERNIGHT ON
SATURDAY BY ABOUT ANOTHER 6 HOURS AND WOULDN`T BE SURPRISED IF THE
SNOW DIDN`T ARRIVE UNTIL SUNDAY MORNING AT THE RATE OF SLOWING.
FRIDAY NIGHT/SATURDAY...THE SFC HIGH MOVES INTO THE REGION AND
PROVIDES THE TYPICALLY DRY NORTH TO NORTHEAST FLOW. THIS KEEPS THE
SKY CLEAR THROUGH SATURDAY MORNING WITH ONLY HIGH CLOUDS JUST
CREEPING IN. THIS WILL ALLOW THE TEMPERATURES TO DROP INTO THE
SINGLE DIGITS OR EVEN BELOW ZERO NEAR PLN. THE 700-500 MB MOISTURE
INCREASES AND ALLOWS THE MID AND HIGH CLOUDS TO MOVE BACK INTO THE
REGION. THE SFC FLOW REMAINS EASTERLY, SO WOULD EXPECT THAT THE DRY
AIR WILL KEEP THE LOWER LEVEL MOISTURE OUT OF N LOWER AND E UPPER
THROUGH THE DAY.
SATURDAY NIGHT...THE LOWER LEVEL (850 MB AND LOWER) MOISTURE MOVES
INTO THE REGION. THE MODELS HAVE BEEN SLOWING THE TIMING OF THE SNOW
WITH THIS SYSTEM. WOULD NOT BE SURPRISED IF THE MODELS WILL BACK OFF
ANOTHER 6 HOURS AND PUT THE ONSET OF PRECIPITATION TO SUNDAY,
HOWEVER, HAVE CUT THE POPS BACK IN THE EVENING TO JUST NW LOWER FOR
THE MOST PART AND ALLOWING IT INTO E UPPER DURING THE OVERNIGHT AS
THE OCCLUDED FRONT MOVES INTO THE REGION.
SUNDAY...WILL GO LIKELY POPS, SINCE THE MODELS HAVE BEEN ARE COMING
INTO AGREEMENT ON THE TIMING AND TYPE OF PRECIPITATION. YESTERDAY
THERE WAS A CONCERN FOR THE THE MID LEVEL MOISTURE STRIPPING OFF AS
A DRY SLOT IN THE 700-500 MB LAYER MOVED OVER THE REGION, AND
PRESENTED A POSSIBILITY OF FREEZING DRIZZLE. TODAY, HOWEVER, THE GFS
IS SATURATED AND THE NAM IS PRETTY CLOSE TO SATURATION. SO WILL
LEAVE THE SNOW IN AS THE PRECIPITATION TYPE. SUNDAY NIGHT, THE SNOW
WILL CONTINUE AS THE SFC AND 500 MB LOW MOVE SOUTH OF US-10 KEEPING
US SATURATED AND COLD ENOUGH FOR SNOW ALL NIGHT LONG. THIS IS
BEGINNING TO LOOK MORE LIKE A BIGGER DEAL THAN WE WERE LOOKING AT
YESTERDAY WITH UP TO 6 INCHES POSSIBLE IN THE N LOWER SPECIFICALLY
HERE AT THE OFFICE IF THE GFS IS RIGHT.
EXTENDED (MONDAY THROUGH THURSDAY)...MONDAY, THE SFC LOW GOES
OVERHEAD AS THE SYSTEM STACKS UP. THIS IS LEADING US TO BELIEVE A
WEAKENING STORM WITH LITTLE IN THE WAY OF PRECIPITATION. THE 850
TEMPERATURES AND THE SOUNDINGS SUGGEST SNOW, SO WILL CONTINUE WITH
THE CHANCE OF SNOW. TUESDAY, THE COLD FRONT MOVES THROUGH THE REGION
AND A BRIEF PERIOD OF SNOW SHOWERS MOVES THROUGH WITH IT. THERE
COULD BE SOME WEAK LAKE ENHANCEMENT, BUT WITH THE 850 TEMPERATURES
AROUND -10 TO -12C ON BOTH THE GFS AND ECMWF, WILL KEEP THE LOW
CHANCE POPS. WEDNESDAY, THE RIDGE AXIS MOVE THROUGH THE REGION. SO
WILL GO WITH A DRYING FORECAST. THURSDAY, WILL HAVE A CHANCE FOR
SNOW NOW, BUT COULD SEE IT EITHER WAY AS THE SFC LOW MOVES UP OUT OF
THE PLAINS AND INTO THE GREAT LAKES.
LUTZ
&&
.APX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
415 PM EST WED FEB 21 2007
.SYNOPSIS...
WV IMAGERY AND RUC ANALYSIS INDICATED A ZONAL PATTERN ACRS THE
CONUS WITH A POTENT SHRTWV AND TIGHT CIRCULATION OVER NW MN. AT THE
SFC(20Z)...A 998 MB LOW WAS LOCATED NEAR KINL WITH A FRONT DRAPED TO
THE SOUTH THROUGH ERN MN. A 6 MB/3 HR PRES RISE MAX OVER NRN ND
TRAILED A SECONDARY COLD FRONT FROM NW MN INTO S CNTRL ND. RADARS
INDICATED THE INITIAL PCPN BAND...SUPPORTED BY STRONG 700-500
QVECTOR CONV AND 295K ISENTROPIC LIFT...WAS MOVING INTO W UPR MI. SO
FAR...ONLY SCT PCPN LIGHT PCPN WAS NOTED OVER THE NRN MN. CANADIAN
RADARS SHOWED THE MAIN SNOW BAND FROM NEAR CYQT TO THE WNW. WITH SFC
TEMPS INTO THE UPPER 40S OVER NW WI INTO W UPR MI AND WARM PROFILE
INDICATED ON AREA TAMDAR SNDGS...RAIN WAS NOTED OVER MOST OF THE
AREA WITH SNOW FROM NE MN...KCKC TO CYQT.
.SHORT TERM(TONIGHT AND THU)
EXPECT THE INITIAL BAND OF PCPN TO SWING QUICKLY ACRS THE AREA WITH
MAINLY RAIN BECOMING MIXED WITH OR CHANGING TO SNOW THIS EVENING AS
THE PCPN MOVES INTO THE COLDER AIR TO THE NORTHEAST. SOME
EVAPORATIVE COOLING INTO THE 950-700 DRY LAYER ALONG WITH DYNAMICS
LIFT AS THE AREA OF STRONG QVECTOR CONV AND HEIGHT FALLS MOVE IN
SHOULD ALSO AID IN TRANSITION TO SNOW. UPSTREAM TRENDS AND
NAM/GFS/LAPSWRF-ARW SUGGEST QPF TO AROUND 0.10 INCH WOULD BE
POSSIBLE FROM LATE AFTERNOON THROUGH EARLY EVENING. HOWEVER...WITH
WARM TEMPS ANY SNOWFALL THIS EVENING SHOULD REMAIN LESS THAN
INCH...EXCEPT OVER THE NRN KEWEENAW WHERE A QUICK INCH OR TWO MAY BE
POSSIBLE.
AS THE LOW MOVES THROUGH ERN LK SUPERIOR AROUND 06Z AND TO NEAR THE
NORTH END OF LK HURON BY 12Z STRONG WINDS AND WRAP-ROUND MOISTURE
WILL MOVE INTO NORTH AND EAST UPPER MI. THE 12Z/18Z NAM IN GENERALLY
AGREEMENT WITH THE GFS/CANADIAN GEM SHOWED A REASONABLE DEPICTION OF
THE EXPECTED LOW TRACK AND WAS USED FOR THE DETAILS. THE STRONGEST
ISALLOBARIC PUSH AHEAD OF A 7 MB/3 HR PRES RISE MAX LINED UP BEST
WITH THE PREVAILING NW OR NNW WINDS NEAR 12Z FROM MARQUETTE
EASTWARD. THE KEWEENAW IS ALSO CLOSE ENOUGH TO THIS FEATURE TO SEE
STRONG WINDS AFTER MIDNIGHT. SO...EXPECT WINDS INTO THE 20-30 MPH
RANGE WITH SOME GUSTS TO 40-50 MPH FOR SEVERAL HOURS...ESPECIALLY
THE LAKE SHORE AND OVER EXPPOSED HIGHER TERRAIN. ALTHOUGH THE 850 MB
TEMPS TO AROUND -10C WILL ONLY PROVIDE MARGINAL INSTABILITY...THE
CONVERGENT CYCLONIC FLOW AND DEEP MOISTURE SHOULD BE ENOUGH TO
PRODUCE LAKE ENHANCED SNOW WITH AMOUNTS IN THE 1-3 INCH RANGE.
SO...SN/BLSN ADVY WAS ISSUED TO COVER THE COMBINATION OF HAZARDS
EXPECTED LATE TONIGHT INTO THU MORNING.
AS THE DEEPER MOISTURE DEPARTS BY MIDDAY AND THE SFC RDG BUILDS
TOWARD THE AREA ANY LES SHOULD TAPER OFF QUICKLY WITH ONLY MINIMAL
ADDITIONAL ACCUMULATIONS.
&&
.LONG TERM (THURSDAY NIGHT THROUGH WEDNESDAY)...
MAIN FORECAST DILEMMA THIS PERIOD WILL BE OUR WEEKEND STORM
SYSTEM...WINDS ACROSS THE LAKES AND SNOW. NO LARGE SCALE CHANGES
WERE MADE WITH THIS FORECAST PACKAGE...AND SINCE THIS STORM IS STILL
SEVERAL DAYS AWAY...WILL NOT DO MUCH MORE THAN REFRESH THE WORDING
IN THE HWO TO HIGHLIGHT THE SCALE OF THE SYSTEM.
WILL BEGIN THE PERIOD THURSDAY NIGHT WITH THE SURFACE LOW AND
INVERTED TROUGH CONTINUING TO SLOWLY EXIT THE AREA...AS HIGH
PRESSURE SLIDES IN FROM NORTHWESTERN ONTARIO. EVEN WITH THE RIDGE
OVERHEAD...A FEW LAKE EFFECT FLURRIES ALONG THE AREA MAY STILL BE
POSSIBLE...GIVEN NE WINDS DEVELOPING AS COOL 850MB TEMPS SLIDE IN.
850MB TEMPS WILL BE THE COOLEST...AT LEAST COMPARED TO THE PAST
SEVERAL DAYS...WITH LAKESHORE READINGS AROUND -15C THURSDAY EVENING.
AFTERWARD...WITH THE LARGE RIDGE TAKING HOLD...YET ANOTHER WARMING
TREND IS FIGURED...WITH 850MB TEMPERATURE READINGS BECOMING TOO WARM
TO PRODUCE LAKE EFFECT PRECIPITATION. HIGH CLOUDS ARE FIGURED TO
ENCROACH ON THE REGION FRIDAY AFTERNOON...WITH A SLOW THICKENING AND
LOWERING THROUGH SATURDAY AFTERNOON.
HIGH PRESSURE WILL THEN GENERALLY BE IN CONTROL OF THE REGION
THROUGH THE END OF THE WORK WEEK...BEFORE BEING SQUEEZED OUT OF THE
PICTURE AHEAD OF OUR NEXT STORM SYSTEM. DID MAKE MINOR CHANGES TO
OVERNIGHT LOW TEMPERATURES FRIDAY NIGHT INTO SATURDAY
MORNING...COOLER EAST AND WARMER WEST UNDER MORE ABUNDANT CLOUDS.
THE 500MB RIDGE WILL BE DIRECTLY OVERHEAD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. WE WILL CONTINUE TO MONITOR THE DEVELOPMENT OF THE
SYSTEM ACROSS THE FOUR CORNERS REGION FRIDAY NIGHT INTO SATURDAY.
ONCE AGAIN AT 500MB...THE NAM IS THE FIST OF THE OUTLIERS TO BE
NOTED...DEVELOPING THE CUT OFF LOW MUCH FURTHER SOUTH AND EASTWARD
BY 06Z SATURDAY. AT THIS POINT...12Z SATURDAY...THE CANADIAN AND
ECMWF...SLOWER AND SLIGHTLY MORE NORTHWEST WITH THIS FEATURE SEEM TO
BE ON THE MARK. THE GFS IS BEING SINGLED OUT WITH POSSIBLE FEEDBACK
ISSUES OVER THE SOUTHERN PLAINS STATES TO START OUT THE WEEKEND.
THIS MAY BE RESULTING IN A SOLUTION THAT IS CLOSER TO THE NAM. IT
TOO HAS BEEN DISCREDITED FOR OUR WEEKEND STORM SYSTEM. AS A
RESULT...HAVE UTILIZED HPC GRIDS...WHICH IS A COMBINATION OF THE
SLOWER AND MORE NORTHWESTWARD ECMWF AND TO A LESSER EXTEND THE
CANADIAN MODEL. THE 12Z GFS SEEMED TO HAVE AN EVEN BETTER GRASP ON
THE SITUATION...BEING CONSISTENT WITH ITS 06Z RUN...AND NOT TOO FAR
FROM THE PREVIOUSLY FAVORED ECMWF SOLUTION.
TAKING A BETTER LOOK AT THE SURFACE PATTERN...THE LOW DEVELOPING OFF
THE ROCKIES FRIDAY NIGHT INTO SATURDAY MORNING WILL PROGRESS OUR
WAY. IT IS ANTICIPATED TO BE OVER SOUTHERN WISCONSIN BY 00Z
MONDAY...BEFORE SLIDING ACROSS CENTRAL LAKE MICHIGAN OVERNIGHT AND
OVER THE NORTHCENTRAL MICHIGAN BY 12Z MONDAY. WITH THE LOW TRACKING
THAT FAR TO THE SOUTH OF THE UPPER PENINSULA...IT WILL BE DIFFICULT
TO WRAP ENOUGH WARM AIR AROUND...TO PRODUCED ANY MIXED
PRECIPITATION. THE WARMEST 850MB TEMPS OVER THIS TIME PERIOD ARE -3
TO -4C 00-12Z SUNDAY ACROSS LUCE...EASTERN ALGER AND DELTA
COUNTIES. SO...HAVE KEPT SNOW ONLY.
AFTER THIS SYSTEM KICKS OUT OF THE FORECAST AREA MONDAY NIGHT INTO
TUESDAY...A ZONAL TO MORE RIDGE TYPE PATTERN WILL SET UP ACROSS THE
NATION...AND IN PARTICULAR THE UPPER PENINSULA.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
SNOW AND BLOWING SNOW ADVISORY FROM 5 AM TO 1 PM EST THURSDAY FOR
MIZ006-007-014-085.
SNOW AND BLOWING SNOW ADVISORY FROM 3 AM TO 11 AM EST THURSDAY
FOR MIZ005.
SNOW AND BLOWING SNOW ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM
EST THURSDAY FOR MIZ001-003.
GALE WARNING LAKE SUPERIOR AND LAKE MICHIGAN.
&&
$$
.SHORT TERM...JLB
.LONG TERM...KF
AREA FORECAST DISCUSSION
NWS RALEIGH NC
955 PM EST THU FEB 22 2007
.SHORT TERM /REST OF TONIGHT/...
EVEN THOUGH THE 00Z GSO SOUNDING SHOWS A NICE DRY ADIABATIC LAYER
THROUGH 750 MB AND 35KT WINDS ONLY 2 KFT ABOVE THE
GROUND...SUSTAINED WINDS AND WIND GUSTS ACROSS CENTRAL NC HAVE
DROPPED OFF SIGNIFICANTLY SINCE JUST PRIOR TO SUNSET. EVEN
AIRCRAFT SOUNDINGS TAKEN NEAR 00Z AT RDU AND 01Z AT GSO STILL SHOW
DRY ADIABATIC LAPSE RATES UP TO 750-800 MB WITH 35KT WINDS AT 2
KFT AND 45KT WINDS AT 3.5 KFT...YET FEW OBS ACROSS THE AREA ARE
STILL GUSTING TO EVEN 25 KTS. JUST GLANCING AT THE SOUNDINGS ONE
WOULD THINK WINDS SHOULD BE GUSTING HIGHER...HOWEVER...TEMPS HAVE
FALLEN INTO THE LOW/MID 50S BEHIND THE DRY COLD FRONT AND SOME
DEGREE OF LOW-LEVEL STABILIZATION MUST BE HINDERING MIXING ENOUGH
TO PREVENT HIGHER MOMENTUM AIR ALOFT FROM REACHING THE SURFACE.
WILL UPDATE THE FORECAST THIS EVENING TO LOWER WINDS ACROSS THE
AREA TONIGHT PER OBSERVATION TRENDS THE PAST SEVERAL HOURS. HAVE
ALREADY CANCELLED WIND ADVISORY FOR THE NW PIEDMONT...WITH
SUSTAINED WINDS OF ONLY 15-20 MPH AND GUSTS NO HIGHER THAN 30-35
MPH EXPECTED BEFORE WINDS FURTHER DECREASE OVERNIGHT. -VINCENT
&&
.PREV DISCUSSION...
/ISSUED 255 PM EST THU FEB 22 2007/
SHORT TERM /TONIGHT THROUGH SUNDAY/...
..WIND ADVISORY IN EFFECT FOR THE NORTHWEST PIEDMONT THROUGH
MIDNIGHT TONIGHT FRIDAY AND RED FLAG WARNING ALL ZONES THROUGH
MIDNIGHT TONIGHT...
STRONG WINDS THE CONCERN AS STRONG SUBSIDENCE DRYING BEHIND THE
DEPARTING H5 SHORT WAVE AND SURFACE DRY FRONTAL PASSAGE. WINDS WILL
BE SUSTAINED AT 20-30 MPH WITH GUSTS TO NEAR 50 IN THE NW... AND
15-25 WITH GUSTS TO 40-45 MPH ELSEWHERE. WINDS WILL DIMINISH LATE AS
THE PRESSURE GRADIENT RELAXES AND WITH NOCTURNAL COOLING AND
STABILIZATION. STRONG CAA TONIGHT WILL BE OFFSET BY THE VERY WARM
BOUNDARY LAYER THIS EVENING. LOWS ABOVE MOS A GOOD BET... RANGING
FROM 34 NORTHWEST TO 42 SE. -PWB
FRIDAY: IN THE WAKE OF THE DEPARTING FRONT... QUIET BUT BREEZY
CONDITIONS ARE EXPECTED.. WITH THE ONLY CLOUDS BEING SCATTERED
CIRRUS SPREADING IN FROM THE NW. OUR LOCAL HIGH TEMPERATURE SCHEME
WITH A DRY ADIABATIC LOW LEVEL PROFILE SUPPORTS HIGHS FROM 52 NE TO
61 SW... CLOSE TO GFS MOS GUIDANCE VALUES. SEE BELOW FOR FIRE
WEATHER CONCERNS.
FRIDAY NIGHT THROUGH SUNDAY: COOL HIGH PRESSURE NOSES IN FROM THE
NORTH-NORTHWEST THROUGH SATURDAY... ALTHOUGH FORECAST THICKNESSES
ARE CLOSE TO NORMAL AND EXPECT HIGHS OF 54-61 NE-SW SATURDAY AFTER
MORNING LOWS OF 25-32. HIGH CLOUDS SHOULD BE ON THE INCREASE OVER NC
SATURDAY AS THE STRONG STORM SYSTEM OVER THE NATION`S MIDSECTION
WINDS UP... BUT THESE CLOUDS SHOULD REMAIN THIN AS MID LEVEL RIDGING
HOLDS OVER THE EAST COAST. THE BOUNDARY LAYER AS WELL AS THE ENTIRE
COLUMN SATURATES QUICKLY SATURDAY NIGHT AS THE FRONT APPROACHES FROM
THE WEST. HAVE KEPT CHANCE POPS AFTER MIDNIGHT IN THE FAR WESTERN
CWA... BUT DROPPED POPS ELSEWHERE UNTIL AFTER 12Z SUNDAY WITH MODEL
SOLUTIONS CONVERGING ON PLACING THE BULK OF THE LIFT CLOSER TO THE
CORE OF THE LOW LEVEL JET AS IT TRAVERSES CENTRAL NC. HAVE GONE WITH
HIGH LIKELY POPS THROUGH SUNDAY... ALTHOUGH IF THIS CURRENT TIMING
HOLDS IN LATER FORECASTS... RAIN CHANCES COULD BE RAISED. THE MODELS
HAVE BEEN CONSISTENT IN OCCLUDING THIS SYSTEM WITH A TRIPLE POINT
LOW DEVELOPING NEAR THE CENTRAL NC/VA BORDER... AND THIS WILL HAVE
RAMIFICATIONS ON SUNDAY`S HIGH TEMPERATURE. THE GFS HAS TRENDED MUCH
COOLER ACROSS OUR NORTHERN TIER... KEEPING IT MOSTLY NORTH OF THE
WARM FRONT... AND THE LATEST NAM HAS FOLLOWED SUIT. HAVE GONE WITH
HIGHS SUNDAY OF 50 NW TO 65 SE. WHILE OUR SHEAR VALUES GO THROUGH
THE ROOF WITH A FORECAST SRH OVER 800 M2/S2 AT GSO... THE BEST
INSTABILITY (EVEN ELEVATED) IS EXPECTED TO BE SUPPRESSED TO OUR
SOUTH. HAVE KEPT A MENTION OF ISOLATED THUNDER ACROSS THE SOUTHERN
HALF OF THE CWA... BUT WE`LL KEEP AN EYE ON THIS FOR LATER
FORECASTS. -GIH
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT ON A SWIFT EASTWARD EXIT
OF THE PRECIP PRIOR TO SUNDAY EVENING AS THE TRIPLE POINT LOW SHIFTS
OFF THE VA COAST... SO MIDNIGHT SHIFT ADJUSTMENTS OF A QUICKER END
AND LOWER EVENING POPS LOOK GOOD. THE MID LEVEL REFLECTION OF THE
WEEKEND STORM SYSTEM PUSHES THROUGH THE EASTERN GREAT LAKES INTO THE
NORTHEAST AND EASTERN CANADA AND SLOWS AS IT APPROACHES THE SOUTH
END OF THE VORTEX SOUTH OF GREENLAND. THE BLOCKING PATTERN OVER
CANADA RESULTS IN A FAST AND BROADLY CYCLONIC MID LEVEL FLOW ACROSS
THE CENTRAL AND SOUTHERN UNITED STATES MONDAY/TUESDAY. THE GFS AND
ECMWF DROP A WEAK TROUGH SLOWLY SOUTHEAST THROUGH NC MONDAY... AND
WHILE IT WILL BE ACCOMPANIED BY A 110+ KT UPPER JETLET... WESTERLY
FLOW JUST ABOVE THE BOUNDARY LAYER SHOULD ALLOW IT TO HAVE MINIMAL
IMPACT IN CENTRAL NC. OTHERWISE... A WEAK HIGH PRESSURE RIDGE WILL
BUILD INTO NC FROM THE NORTHWEST INTO TUESDAY. ON WEDNESDAY/THURSDAY
THE WEST COAST LONGWAVE TROUGH SHIFTS EASTWARD INTO THE ROCKIES WITH
BUILDING RIDGING DOWNSTREAM AS THIS SYSTEM AMPLIFIES OVER THE WESTERN
PLAINS... A SOLUTION AGREED UPON BY THE MAJORITY OF GFS ENSEMBLE
MEMBERS. AS THE SURFACE PRESSURE RIDGE AXIS PUSHES TO OUR
NORTHEAST... RETURN FLOW SHOULD PRODUCE INCREASING WARM ADVECTION
CLOUDINESS WEDNESDAY NIGHT INTO THURSDAY. PATCHY SHOWERS ARE
POSSIBLE BY THURSDAY... BUT THE WIDESPREAD HEAVIER SHOWERS SHOULD BE
CONFINED CLOSER TO THE SURFACE FRONT WHICH HOLDS WELL TO OUR WEST
THROUGH THURSDAY. WILL KEEP POPS AT JUST A SLIGHT CHANCE. REGARDING
TEMPERATURES... EXPECT NEAR TO SLIGHTLY ABOVE NORMAL VALUES
MONDAY/TUESDAY WITH LOW LEVEL THICKNESSES FORECAST TO BE CLOSE TO
CLIMATOLOGY. THE MID LEVEL RIDGING AND LOW LEVEL WARM AIR ADVECTION
SHOULD YIELD A RETURN TO MILDER TEMPERATURES FOR WEDNESDAY AND
ESPECIALLY THURSDAY. -GIH
AVIATION /18Z-18Z/...
STRONG GUSTY WNW WINDS JUST BEHIND THE COLD FRONT WILL CONTINUE
THROUGH THE EVENING. THE HIGHER GUSTS OF 45 KTS WILL OCCUR AT
KINT/KGSO... WITH GUSTS TO 40 KTS POSSIBLE ELSEWHERE. WINDS DIMINISH
TO LIGHT TOWARD DAYBREAK AS PRESSURE GRADIENT IS EXPECTED TO RELAX
LATE.-PWB
FIRE WEATHER...
A STRONG DRY FRONT WILL PRESS OFFSHORE LATE THIS AFTERNOON. VERY
STRONG SUBSIDENCE DRYING AND WARMING BEHIND THE FRONT WILL AID IN
EXTREME FIRE WEATHER CONDITIONS.
ALL METEOROLOGICAL PARAMETERS WILL BE MET FOR A RED FLAG WARNING
THIS AFTERNOON AND EVENING. STRONG WINDS (20-30 MPH WITH GUSTS TO
40+ MPH)... VERY LOW RHS (10-19 PERCENT)... AND WARM TEMPS (LOWER TO
MID 70S) WILL COMBINE TO DRY OUT THE 1 AND 10 HOUR FINE FUEL
MOISTURE LEVELS. AFTER COORDINATION WITH THE NORTH CAROLINA FOREST
SERVICE... WILL HAVE A RED FLAG WARNING IN EFFECT THROUGH MIDNIGHT
TONIGHT. RH RECOVERY WILL BE LITTLE THROUGH 1200 AM. SOME RECOVERY
TO AROUND 60-70 PERCENT WITH LIGHT WINDS TOWARD DAYBREAK.-PWB
RED FLAG CONDITIONS LOOK MARGINAL FOR FRIDAY. RELATIVE HUMIDITIES
WILL BE CRITICAL... IN THE 18-23% RANGE... BUT GUSTS MAY NOT REACH
THE 30 MPH CRITERION. WILL ADD A SPECIAL STATEMENT MENTIONING FRIDAY
CONDITIONS IN THE FIRE WEATHER FORECAST PRODUCT... AND WE WILL
RE-EVALUATE THE POTENTIAL FOR ANOTHER RFW TOMORROW. -GIH
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
&&
$$
SHORT TERM...VINCENT
|