AREA FORECAST DISCUSSION...UPDATED
NWS MOUNT HOLLY NJ
AFDPHI 1000 AM EST TUE JAN 9 2007
.UPDATE #2...
HAVE ISSUED AN UPDATE TO THE PUBLIC AND MARINE FCSTS AND ALL
ASSOCIATED GRIDDED PRODUCTS THIS MORNING FOR SEVERAL REASONS.
FIRST, HAVE REMOVED TEMPORAL REFERENCES TO MORNING. SECOND, HAVE
MADE SOME ADJUSTMENTS TO CLOUD COVER BASED ON CURRENT AND EXPECTED
SATELLITE TRENDS. MOST OF THE REGION ALREADY HAS A BKN MID-LEVEL
DECK, SO WILL JUST GO WITH MOSTLY CLOUDY IN THESE AREAS AND
INCREASING CLOUDINESS ELSEWHERE FOR BREVITY. THIRD, ADJUSTED SOME
WINDS, MAINLY ON THE MARINE.
MOST IMPORTANTLY, BASED ON SOME CURRENT ACARS SOUNDINGS THAT HAVE
THE FREEZING LEVEL AOA 2000 FEET AND HIGH TEMPERATURES CURRENTLY
FCST TO BE IN THE 40S IN MOST LOCATIONS, HAVE OPTED TO REMOVE ALL
REFERENCES TO SNOW SHOWERS OR FLURRIES FOR ALL BUT THE NWRN ZONES,
WHERE TEMPS WILL BE COOLER AND ELEVATION ALSO COMES INTO PLAY.
&&
.UPDATE #1...
/ISSUED 625 AM TUE JAN 9 2007/
UPDATED THE CWF TO DROP THE ONGOING SCA FLAG FOR THE WATERS.
SEAS AT 44009 HAVE DECREASED TO 4 FT AND THERE ARE ONLY A FEW G25
OVER THE WATERS ATTM. THE WINDS WILL SUBSIDE FURTHER THIS MORNING AS
THEY VEER AROUND TO SW. I HAVE PLACED A NEW HAZARD GRID FOR THE
NEXT EXPECTED SCA FLAG FOR TONIGHT. I HAVE STARTED IT AT 10 PM.
&&
.PREV DISCUSSION...
/ISSUED 355 AM EST TUE JAN 9 2007/
SYNOPSIS...
AFTER YESTERDAY`S COLD FRONTAL PASSAGE, A RETURN TO COLDER WEATHER
HAS ARRIVED. HOWEVER, A BIT OF WARMING WILL TAKE PLACE TODAY AS A
CLIPPER SYSTEM DIVES TO OUR SOUTH THIS AFTERNOON AND EVENING. BEHIND
THIS FEATURE, A SHOT OF COLD AIR WILL INTRUDE THE REGION, HOWEVER
THIS WILL BE TRANSIENT AS A MILDER TREND WILL GET UNDERWAY YET AGAIN
FOR THE END OF THE WEEK AND WEEKEND. A RATHER ACTIVE FRONTAL SYSTEM
WILL TAKE SHAPE FROM THE GREAT LAKES ALL THE WAY TO THE CENTRAL GULF
COAST STATES. THIS ENTIRE FRONTAL FEATURE WILL SERVE AS A CONDUIT
FOR SOME WAVES OF LOW PRESSURE AS COLDER AND COLDER AIR GETS PULLED
SOUTHWARD INTO THE PLAINS. GRADUALLY IT APPEARS A TURN TO COLDER
WEATHER IS IN OUR FUTURE BEYOND THIS UPCOMING WEEKEND, BUT AT THIS
POINT IN TIME THE UNCERTAINTY OF THE COLD BECOMING LOCKED IN IS LOW.
SHORT TERM /TODAY THROUGH WEDNESDAY/...
ALL IS RELATIVELY QUIET TO START THINGS OFF EARLY THIS MORNING,
ALTHOUGH THE WINDS HAVE HELD UP IN MOST SPOTS SO FAR. TODAY WILL
FEATURE THE ARRIVAL OF ANOTHER UPPER-LEVEL TROUGH WHICH WILL DRIVE A
CLIPPER SYSTEM TO OUR SOUTH. WAA OCCURRING AHEAD OF THIS FEATURE IS
EVIDENT BY THE BACKING FLOW ACROSS THE OHIO VALLEY ALONG WITH AN
INCREASE IN CLOUDS. CLOUDS WILL BE ON THE INCREASE TODAY ACROSS THE
CWA, MAINLY IN THE MID TO HIGH LEVEL KIND, ALTHOUGH MANY AREAS
SHOULD BE ABLE TO SNEAK IN A GOOD DEAL OF SUNSHINE FIRST THING THIS
MORNING. THE MAIN QUESTION TODAY REVOLVES AROUND PRECIPITATION
CHANCES. WITH THE CLIPPER AND ASSOCIATED DYNAMICS TAKING A TRACK
FURTHER TO OUR SOUTH, THIS IS NOT ALL THAT FAVOR FOR MOST OF OUR
REGION. ALSO, THE 00Z RAOBS DEPICTED A RATHER DRY AIRMASS IN PLACE
WHICH IS ALSO EVIDENT BY THE LOW DEWPOINTS WHICH ADVECTED IN LATE
YESTERDAY.
FORECAST SOUNDINGS FROM AROUND THE REGION THROUGH TODAY SHOW
INCREASING INSTABILITY ALOFT, SEEN BY THE TOTAL TOTALS RISING INTO
THE 50S THIS AFTERNOON /AROUND 60 ACROSS THE DELMARVA/. NO QUESTION
THERE IS DECENT AMOUNT COLD AIR ALOFT AIDING IN THE INSTABILITY,
HOWEVER THE BULK OF THE LIFT WITH THE CLIPPER CRUISES TO OUR SOUTH
WHICH LEAVES NOT MUCH FOR MOST OF OUR CWA. THE BEST CHC IS TARGETED
ACROSS OUR DELMARVA ZONES /SUPPORT FROM BOTH THE GFS AND NAM/ AS
THEY WILL BE CLOSER TO THE STRONG DYNAMICS /UPPER TROUGH TAKING
ON SOMEWHAT OF A NEGATIVE TILT/, AND PERHAPS OUR WESTERN ZONES AS
ANY ACTIVITY THAT TRIES TO FORM TO OUR WEST REACHES THERE BEFORE
FALLING APART. EVEN THE HIGHER RESOLUTION NAM IS NOT ALL THAT
EXCITED ABOUT PRECIPITATION CHCS/COVERAGE TODAY EXCEPT ACROSS THE
DELMARVA, HOWEVER AM A LITTLE WEARY GIVEN SOME INSTABILITY ALOFT.
IT SHOULD BE NOTED THAT THE STRONG DYNAMICS AND INSTABILITY WILL BE
BATTLING A RATHER DRY SUB CLOUD LAYER. BUFKIT SOUNDINGS ACROSS THE
DELMARVA INDICATE GOOD OMEGA NEAR THE DENDRITIC ZONE LATER THIS
AFTERNOON AND EARLY THIS EVENING. THE BOUNDARY LAYER COULD BE A
LITTLE TO WARM TO JUSTIFY SNOW, HOWEVER BASED ON THE COLDER
TEMPERATURES ALOFT AND THAT THE 0C ISOTHERM IS FORECAST NEAR 2,000
FEET, WE WILL GO WITH CHC POPS /40-ISH/ ACROSS THE DELMARVA AND
INDICATE RAIN AND SNOW SHOWERS. THE WESTERN ZONES WE WILL CARRY A
30-ISH POP FOR SNOW SHOWERS PERHAPS SOME RAINDROPS MIXED IN.
ELSEWHERE, WE WILL CARRY THE POTENTIAL FOR SOME FLURRIES OR
SPRINKLES BASED ON THE INSTABILITY ALOFT.
FOLLOWING THE PASSAGE OF THE CLIPPER SYSTEM AND UPPER-LEVEL TROUGH,
A SURFACE LOW WILL DEVELOP OFF THE COAST TONIGHT. THE MODEL GUIDANCE
SHOWS PRECIPITATION NOT TO FAR OFFSHORE, AND THIS SYSTEM SHOULD TAKE
OFF GIVEN THE INCREASED BAROCLINICITY THAT WILL BE DEVELOPING AS
EVEN COLDER AIR ALOFT MOVES OVER THE WARMER WATERS. WE WILL HOLD
ONTO A 40-ISH POP ACROSS THE DELMARVA REGION FOR A FEW HOURS THIS
EVENING AS THE CLIPPER SYSTEM MOVES THROUGH AND A SURFACE LOW
ORGANIZES OFF THE COAST. A SHOT OF COLDER AIR WILL THEN SETTLE IN
FOR TONIGHT AND WEDNESDAY. CLOUDS MAY TEND TO LINGER FOR AWHILE
TONIGHT ALONG THE COAST /SURFACE LOW DEVELOPMENT/ AND ALSO THE
NORTHWEST ZONES /LAKE INDUCED/. THE HIGHER RESOLUTION MODELS ARE NOT
TO EXCITED ABOUT BRINGING LAKE EFFECT FLURRIES OR SNOW SHOWERS INTO
THE POCONOS, HOWEVER WITH THE WEST TO NORTHWEST FLOW AND DEEPENING
COLD AIR, WE WILL KEEP FLURRIES MENTIONED.
IT WILL BE TURNING RATHER BRISK TONIGHT AND ESPECIALLY WEDNESDAY
WITH CAA, A TIGHTENING PRESSURE GRADIENT, AND FORECAST SOUNDINGS
SHOW GOOD MIXING. AS A RESULT, WE HAVE BUMPED UP THE SUSTAINED
WINDS AND GUSTS A LITTLE MORE ESPECIALLY ON WEDNESDAY.
USED THE MAV SURFACE DEWPOINTS FOR TODAY AS THE MET VALUES WERE
ALREADY A LITTLE TO HIGH EARLY THIS MORNING. AS FOR TEMPERATURES,
USED A BLEND OF THE MODEL GUIDANCE, WHICH DID NOT MAKE SIGNIFICANT
CHANGES TO CONTINUITY.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
NO MAJOR CHANGES WERE MADE TO THIS TIME FRAME. AFTER OUR QUICK SHOT
OF COLD AIR TONIGHT THROUGH WEDNESDAY NIGHT, LOOKING TO THE WEST
SHOWS MUCH COLDER AIR PLUNGING INTO MONTANA AND THE DAKOTAS STARTING
AROUND THURSDAY. THIS ARCTIC AIR SHOULD SLOWLY DRIFT SOUTHEASTWARD
WITH TIME, STRENGTHENING A BAROCLINIC ZONE IN THE CENTRAL PART OF
THE NATION. MOISTURE MOVING NORTHWARD WILL CAUSE SOME ISSUES FOR THE
FOLKS IN THE PLAINS AND PARTS OF THE GREAT LAKES, HOWEVER WE WILL
REMAIN ON THE WARM SIDE.
HIGH PRESSURE BUILDING IN WEDNESDAY NIGHT WILL ALLOW THE PRESSURE
GRADIENT TO RELAX, SETTING UP A DECENT RADIATIONAL COOLING NIGHT. A
POTENTIAL FLY IN THE OINTMENT REGARDING IDEAL RADIATIONAL COOLING
CONDITIONS WILL BE THE WAA THAT IS FORECAST TO BE GETTING UNDERWAY
WEDNESDAY NIGHT AT 850 MB. THIS MAY GENERATE SOME HIGH LEVEL
CLOUDINESS FOR AT LEAST PARTS OF OUR CWA. BELOW IS THE DISCUSSION
FROM YESTERDAY`S DAY SHIFT WITH SOME ADDITIONS HERE AND THERE.
FOR THURSDAY, WE KEPT MAXIMUM TEMPERATURES ABOVE GUIDANCE AS PER
PLUS 0C 850 MB TEMPERATURES FORECAST FOR THE END OF THE DAY. THERE
ARE MODEL DIFFERENCES WITH RESPECT TO THE PRECIPITATION CHCS TOWARD
AND DURING THE WEEKEND. A COLD FRONT IS FORECAST TO APPROACH OUR
CWA ON FRIDAY BUT NOT COME CLOSE ENOUGH TO INCLUDE CHCS FOR NOW
FRIDAY DAY. THIS IS A COMPROMISE BETWEEN THE MORE AND LESS
AGGRESSIVE MODEL SOLUTIONS. WE DID MAINTAIN SOME LOW CHCS MAINLY THE
NORTHERN HALF OF OUR CWA FOR FRIDAY NIGHT. THE FRONT IS THEN
FORECAST TO STALL NORTH OR NEAR OUR CWA ON SATURDAY AND WE WILL KEEP
LOW CHC POPS IN THE SAME AREAS. BEST CHCS FOR PRECIPITATION WILL
COME SUNDAY INTO MONDAY AS WAVY COLD FRONT MOVES ACROSS OUR CWA.
WILL HAVE TO WATCH SURFACE LOW DEVELOPMENT ALONG THIS FRONT AS THAT
WILL SLOW THE EASTWARD PROGRESSION, POTENTIALLY DELAYING THE MAIN
PRECIPITATION SHIELD. ANY CHC FOR SNOW ATTM WILL DEPEND UPON HOW
MANY MORE FUTURE WAVES THERE WILL BE ON THE SLOW MOVING FRONT BEYOND
NEXT MONDAY. THIS IS THE PATTERN CHANGE COLD FRONTAL PASSAGE AND THE
MODELS HAVE DIFFERED WITH RESPECT TO HOW QUICKLY THIS FRONT MOVES
INTO AND CLEARS OUR CWA. THEREFORE CONFIDENCE ABOUT THE TIMING IS
SLIGHTLY LOWER THAN NORMAL. WE DID LIKE HPC/S THOUGHTS OF GOING
HIGHER THAN GUIDANCE ON THE WEEKEND FOR CONSISTENCY SAKE IF WE TRULY
DO GET AND REMAIN IN THE WARM SECTOR.
LONG RANGE MODELS ARE TAKING THE ENTIRE BAROCLINIC ZONE AND SLIDING
IT EASTWARD MARKING A CHANGE TO COLDER WEATHER IN THE EAST AFTER
ABOUT JANUARY 16TH. THE PACIFIC EXPRESS TRAIN IS FORECAST TO BE
DERAILED WITH STRONG RIDGING EXPECTED BY ALL THE MEDIUM RANGE MODELS
IN THE EASTERN PACIFIC. THUS THE EPO TELECONNECTION INDEX IS FORECAST
TO GO NEGATIVE, A FEATURE WE HAVE NOT SEEN WE BELIEVE SINCE LATE
OCTOBER/EARLY NOVEMBER. THIS IS USUALLY A COLD INDICATOR FOR THE
EAST. BUT IN OUR POND THE NAO IS FORECAST TO REMAIN POSITIVE, WHICH
NORMALLY MEANS A MILDER REGIME. IT LOOKS AS THOUGH THE UNSEASONABLY
WARM PATTERN WILL END FOR AWHILE AFTER THIS UPCOMING WEEKEND. HOW
COLD IT GETS WILL DEPEND UPON HOW MUCH RIDGING EXTENDS INTO ALASKA
AND WESTERN CANADA /OR FURTHER NORTH/ VERSUS REMAINING IN THE
EASTERN PACIFIC. ONE QUESTION IS REGARDING THE EXTENT OF THE
SOUTHEASTWARD INTRUSION OF THE COLDER AIR MAKING IT EAST OF THE
APPALACHIANS. THE MORE RIDGING THAT GETS INTO THE WESTERN U.S. AND
WESTERN CANADA, THE HIGHER THE AMPLITUDE TOWARD THE POLE, THUS THE
COLDER THE SHOTS WILL BE HERE. IN ADDITION, THE STRENGTH OF THE
SOUTHEASTERN RIDGE MAY BE THE KEY PLAYER ON WHERE THE TRUE
BAROCLINIC ZONE BECOMES SITUATED DURING THE MIDDLE TO LATE PORTION
OF THIS MONTH AS MOISTURE LOOKS TO LURK CLOSE BY. STAY TUNED.
AVIATION /09Z-06Z/...
CLEAR SKIES AND GENTLE WEST WINDS OVER THE TAF SITES EARLY THIS
MORNING. MID LEVEL CLOUDINESS IS INDICATED ON SATELLITE OVER THE
OHIO VALLEY AND IT IS EXPECTED TO CONTINUE EASTWARD OVER OUR AREA
THIS MORNING AND INTO THE AFTERNOON. I HAVE SPED UP THE TIMING OF
THE ARRIVAL AND AMOUNT OF CLOUDS WHEN COMPARED TO THE PREVIOUS TAFS.
WRF MODEL SHOWING SOME MINOR PRECIP SOUTH OF THE TAF SITES TODAY AND
THE GFS ALSO PRODUCING SOME MINOR PRECIP MAINLY SOUTH THIS EVENING.
I HAVE LEFT PRECIP OUT OF MY TAFS, SINCE THE AIRMASS IS VERY DRY AND
THE MOS PROBS ARE LOW. SFC WINDS WILL BACK AROUND TO SW THIS MORNING
AND REMAIN THERE MUCH OF THE DAY. SPEEDS WILL INCREASE TO AROUND 10
TO 15 KT. TONIGHT THE WINDS WILL VEER TO NW AND REMAIN MODERATE.
CLOUDS ARE EXPECTED TO BREAK UP TONIGHT AS HIGH PRESSURE STARTS TO
BUILD IN.
MARINE...
LOOKS LIKE WE WILL BE ABLE TO TAKE THE SCA FLAG DOWN AT 12Z THIS
MORNING. THE FLAG WON`T HAVE TO BE STOWED TOO FAR AWAY THOUGH AS IT
WILL BE FLYING AGAIN TONIGHT. PROGRESSIVE SFC RIDGE OVER THE WATERS
THIS MORNING WILL MOVE OFFSHORE TODAY AS A TROUGH APPROACHES FROM
THE WEST. LOOKS LIKE SUB-SCA THIS AFTERNOON WITH THE STRENGTHENING
SW FLOW BUT WATER/AIR TEMP DIFFERENCES SMALL. LOW PRESSURE SHOWN BY
BOTH WRF AND GFS DEVELOPING WELL OFF THE VA/NC SHORE AND DEEPENING
WHILE IT MOVES OFF TO THE NE. GOOD GRADIENT OVER THE WATERS SHOULD
PROVIDE GOOD 25KT WINDS WITH NEAR GALE GUSTS. IF I TAKE DOWN THE SCA
AT 12Z WITH AN UPDATE...I WILL PLACE THE NEW SCA FLAG FOR TONIGHT IN
THE HAZARDS GRIDS. START TIME AROUND 03Z LOOKS GOOD FOR NOW. ONCE
THE GRADIENT SLACKENS ON WED...WE WILL PROBABLY GO UNTIL LATER FRI
WITHOUT ANY FLAGS.
HYDROLOGY...
ANY PRECIPITATION THIS AFTERNOON INTO TONIGHT SHOULD BE ON THE LIGHT
SIDE. THE NEXT POTENTIALLY SIGNIFICANT QPF EVENT LOOKS LIKE LATER
THIS WEEKEND AND EARLY NEXT WEEK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 AM EST
THURSDAY FOR ANZ430-431-450>455.
&&
$$
UPDATE #1...OHARA
UPDATE #2...NIERENBERG
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 531 AM CST TUE JAN 9 2007
.DISCUSSION FOR MORNING GRIDS/ZONES...
330 AM CST
UPPER LEVEL SPEED MAX/SHEARED OUT VORTICITY MAX FROM THE NORTHERN
PLAINS INTO THE MID MISSISSIPPI RIVER VALLEY WILL CONTINUE TO SHIFT
INTO THE SOUTHERN GREAT LAKES REGION TODAY. SATELLITE IMAGERY THIS
MORNING INDICATING EXPANSIVE AREA OF LOW/MID CLOUD DECK ON THE
CYCLONIC SHEAR SIDE OF THIS JET STREAK. SHORT TERM MODEL PROGS DO
INDICATE WEAK 700-600 HPA LAYER Q-VEC CONVG WORKING ACROSS MAINLY
SOUTHERN PORTIONS OF THE FORECAST AREA THROUGH MIDDAY. EXPECTING
NORTHERN HALF OF CWA TO REMAIN PARTLY CLOUDY THIS MORNING...BUT MAY
SEE MORE EXTENSIVE CLOUDINESS ACROSS SOUTHERN HALF OF THE FORECAST
AREA THIS MORNING...BUT THEN PARTLY SUNNY CONDITIONS ARE EXPECTED
ACROSS THE ENTIRE CWA BY EARLY THIS AFTERNOON. SECONDARY TROUGH AXIS
CURRENTLY EXTENDS FROM SOUTHERN WISCONSIN INTO CENTRAL IOWA WITH
3-HOURLY SFC PRESSURE RISES OF 5 MB ACROSS SERN SD/SWRN MN. RATHER
DEEP MIXED LAYER TO DEVELOP TODAY AS THIS REINFORCING CAA WORKS INTO
THE AREA...AND MIXING DOWN OF 900 HPA MODEL THERMAL PROGS GENERALLY
RESULT IN MAX TEMPS THIS AFTERNOON FAIRLY CLOSE TO INHERITED
FORECAST OF LOW 30S NORTH TO MID 30S SOUTH. QUITE BREEZY TODAY ALSO
WITH GUSTS UP TO 25 TO 30 MPH DEVELOPING LATE THIS MORNING AND
ESPECIALLY THIS AFTERNOON.
LARGE SCALE SUBSIDENCE TO INCREASE THIS EVENING AS TAIL OF SHEARED
OUT UPPER LEVEL VORT MAX CONTINUES TO SLIDE EAST OF THE AREA...AND
AS BROAD UPPER LEVEL RIDGE ACROSS THE WESTERN CONUS MOVES INTO THE
NORTHERN PLAINS. SKIES SHOULD CLEAR THIS EVENING...WITH POSSIBLY
SOME INCREASE IN MID/HIGH LEVEL CLOUDS TOWARD WED MORNING WITH MORE
PRONOUNCED MID LEVEL WAA TRACKING INTO THE AREA IN ASSOCIATION WITH
THE MID LEVEL RIDGE. TEMP FORECAST FOR WEDNESDAY SHAPING UP RATHER
TRICKY RIGHT NOW GIVEN SURFACE RIDGE AXIS DEPARTING AND STRONGEST
LOW LEVEL SOUTHERLIES NOT WORKING INTO NORTHERN ILLINOIS UNTIL LATE
AFTERNOON. MIXING SHOULD BE RATHER POOR ON WEDNESDAY SO DID NUDGE
TEMPS DOWN A FEW DEGREES WITH HIGHS GENERALLY FROM MID 30S NORTH TO
AROUND 40 FAR SOUTH.
MODELS BEGIN TO DIVERGE BIT IN THE WEDNESDAY NIGHT THROUGH FRIDAY IN
DEALING WITH EVOLUTION OF A NORTHERN STREAM TROUGH WORKING ACROSS
SOUTHERN CANADA AND ASSOCIATED COLD FRONTAL PASSAGE TIMING. NAM/WRF
IS QUITE A BIT SLOWER WITH THE PROGRESSION OF THIS FEATURE THAN THE
GFS WHICH SEEMS TO HAVE SUPPORT FROM A MAJORITY OF THE OTHER MODELS
AND HPC PREFERENCE. MAIN IMPACT OF THIS DIFFERENCE ON THIS FORECAST
IS ON COLD FRONTAL TIMING THURSDAY NIGHT INTO FRIDAY...BUT BY THIS
TIME WRF/GFS ACTUALLY BEGIN TO A CONVERGE WITH THIS TIMING AS
FRONTAL PROGRESSION SLOWS WITH MAIN NORTHERN STREAM WAVE MOVING
ACROSS EASTERN CANADA. THURSDAY SHOULD BE WINDY IN ADVANCE OF THIS
FRONT WITH A TIGHT LOW LEVEL HEIGHT GRADIENT...AND THIS LOOKS TO BE
THE WARMEST DAY OF THE FORECAST WITH TEMPS GENERALLY IN THE MID TO
UPPER 40S. IT STILL APPEARS SFC FRONT SHOULD STALL OUT FRIDAY NIGHT
JUST SOUTH OF THE FORECAST AREA WITH SOUTHERN STREAM UPPER TROUGH
THEN BECOMING THE MAIN FEATURE OF INTEREST. MAINTAINED PROLONGED
PERIOD OF HIGH CHANCE POPS FROM THUR-SUN OF RA/SN WITH A SERIES OF
SHORT WAVES INTERACTING WITH THIS BAROCLINIC ZONE. THERMAL PROFILES
DO SUGGEST PERIODIC POTENTIAL OF SLEET/FRZ RAIN THROUGH THIS PERIOD
BEGINNING MAINLY BY FRIDAY NIGHT...BUT STILL VERY DIFFICULT TO GET
TOO DETAILED IN THIS REGARD YET.
MARSILI
&&
.AVIATION...
531 AM CST
S/WV DIGGING THROUGH SRN IL EARLY THIS MRNG...ASSOCIATED WITH STRONG
JET STRK...125 KTS AT 500 HPA PER PROFILERS OVR MO. SHEARED VORT
CHANNEL XTNDS NORTHWEST ACROSS IA BEHIND THIS SYSTEM...AND WRF/GFS
BRING THIS SHEARED VORT TAIL ACROSS FCST AREA THRU MRNG HOURS TODAY.
FCST SNDGS AND TSECTS INDICATE MAIN MOISTURE ABOVE 700 HPA...AND
935Z ACARS SOUNDING FROM KRFD WITH DEWPOINT TRACE DISPLAYS THIS
WELL. THEREFORE...AM EXPECTING VFR CONDITIONS TO PREVAIL ACROSS
TERMINAL SITES WITH CLOUDS GENERALLY AT OR ABOVE 12 KFT. SNDGS DO
INDICATE PERIOD OF VFR STRATOCU POSSIBLE THIS AFTN AS LLVL CAA
REALLY KICKS IN...THOUGH LCLS AROUND 4 KFT. ONCE MID LEVEL TROF AXIS
PASSES THIS AFTN...DEEP SUBSIDENCE AND DRY LLVLS ERODE STRATOCU
DECK...THUS XPCT JUST SOME THIN CI ALONG ANTICYCLONIC SIDE OF UPPER
JET OVRNGT.
MAIN FCST FOCUS REALLY THEN IS WINDS. RELATIVELY TIGHT SFC PRESSURE
GRADIENT ACROSS WRN LAKES/MS VLY...WITH 5 MB/3 HR PRES RISE MAXIMA
ACROSS SRN MN/NRN IA AT 11Z INDICATIVE OF SECONDARY SFC TROF. NW
WINDS 310-320 DEG ALREADY GUSTING INTO MID/UPR 20 KT RANGE IN
ISALLOBARIC GRADIENT AREA OVER NERN IA...AND ALTHOUGH THIS XPCTD TO
WEAKEN A BIT NEXT SVRL HOURS NAM BUFFER SNDGS INDICATE POTENTIAL FOR
MID 20 KT GUSTS ACROSS NRN IL TODAY AS WELL. GRADIENT SLOWLY RELAXES
THIS EVENING ALLOWING GUSTS TO FADE...WITH SFC RIDGE AXIS APPRCHG
TOWARD 12Z END OF TAF PERIOD ON WED MORNING.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...SMALL CRAFT ADV IN EFFECT WINTHROP HARBOR TO GARY THROUGH
TONIGHT.
SMALL CRAFT ADV IN EFFECT GARY TO MICHIGAN CITY THROUGH
WEDNESDAY MORNING.
GALE WARNING NORTH THIRD THIS MORNING.
&&
$$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 1128 AM EST TUE JAN 9 2007
.SHORT TERM...
HV TWEAKED THE ONSET OF THE CLDS IN THE ERN PART OF THE CWA BACK A
FEW HRS..ALTHO THEY ARE STILL ON THE WAY. WORDING FOR DC/BALT IS
"CHC OF RA/SN LATE" NO ACCUM IS ANTICIPATED...ALTHO FLAKES DURG
EVE DRIVE COULD ALWAYS BE PROBLEMATIC.
LOOKED AT DOLLY SODS WX CAM...SNSH OCCURRING...BUT LGT. XPCTG THESE
TO INCRS DURG AFTN AFTR CD FROPA. SNOW ADVSRY RMNS IN EFFECT.
WOODY!
&&
.PREV DISCUSSION...
/ISSUED 410 AM EST TUE JAN 9 2006/
SHORT TERM (TONIGHT THROUGH TUESDAY)...
WATER VAPOR LOOP SHOWS A LONG WAVE TROUGH ACROSS THE NORTH CENTRAL
CONUS...WITH EMBEDDED WAVES MOVING EAST ACROSS THE TENNESSEE VALLEY
AND SOUTHEAST ACROSS THE MIDWEST. ACARS 400-250MB WIND OBSERVATIONS
REVEAL 140-180KT WINDS ROUND THE AFOREMENTIONED TROUGH.
A CLEAR START TO THE DAY WILL QUICKLY DETERIORATE WITH THE APPROACH
OF A STRONG SHORTWAVE. THE VERTICAL MOTION COUPLET OF THE WAVE
ACROSS SOUTHERN ILLINOIS HAS BEEN INCREASINGLY MORE IMPRESSIVE
THROUGH THE NIGHT ON WATER VAPOR IMAGERY. GFS/NAM IN AGREEMENT THAT
THIS WAVE FEEDING INTO THE LONGWAVE TROUGH WILL ALLOW THE TROUGH TO
BECOME NEGATIVE TILTED BEGINNING LATE TODAY...CAUSING SIGNIFICANT
CYCLOGENESIS OFFSHORE TONIGHT. DEEP LAYER LAPSE RATES BETWEEN 1000MB
AND 500MB ARE FORECAST TO BE STEEP...NEAR 7.5C/KM. GIVEN THE
SYNOPTIC SITUATION...AM CONCERNED THAT VERTICAL MOTION CAUSED BY THE
SHORT WAVE LATE THIS AFTERNOON MAY BE ENOUGH TO ALLOW A 1-2 HOUR
SNOW SHOWER BURST.
0C HEIGHT IS JUST OFF THE SURFACE AT 2KFT. DRY AIRMASS (PRECIPITABLE
WATER VALUE OF 0.19 AT 00Z KIAD RAOB) WILL ALLOW EVAPORATIONAL
COOLING. DYNAMICAL COOLING MAY BE A SIGNIFICANT FACTOR WITH
IMPRESSIVE VERTICAL MOTION SHOWN BY THE NAM DURING THE LATE
AFTERNOON. THIS VERTICAL MOTION IS WITHIN THE DENDRITIC SNOW GROWTH
RANGE...WHICH WOULD FAVOR LARGE DENDRITE FORMATION WITHIN THE CLOUD
LAYER (WITH A SHORT TRIP WITHIN THE WARM SUB-CLOUD LAYER TO THE
GROUND). THERE IS ALSO INDICATION OF FRONTOGENESIS IN THE 700-850MB
LAYER AS THE SYSTEM BEGINS TO DEEPEN...WHICH WOULD SUPPORT
PRECIPITATION DEVELOPMENT EAST OF THE MOUNTAINS.
THERE IS LESS UNCERTAINTY ALONG THE WESTERN SLOPES OF THE MOUNTAINS
WHERE TEMPERATURES ARE ALREADY SUPPORTIVE OF SNOW...AND IN FACT SNOW
HAS ALREADY BEEN REPORTED AT KEKN AS OF 09Z. BEHIND THE WARM
ADVECTION AND LEADING EDGE OF THE COLD ADVECTION
PRECIPITATION...UPSLOPE SNOW WILL PERSIST THROUGH THE NIGHT...AS THE
SKY EAST OF THE MOUNTAINS BECOMES MOSTLY CLEAR TO PARTLY CLOUDY.
HAVE ISSUED A SNOW ADVISORY WITH 03Z SHORT RANGE ENSEMBLES AT KEKN
INDICATING A MEAN OF 0.37" OF SNOW LIQUID EQUIVALENT THROUGH 12Z
EARLY WEDNESDAY MORNING...AND A MAX OF 0.85". CURRENT SNOW FORECAST
IN THE MOUNTAINS IS 1-3" TODAY AND 1-2" TONIGHT. WIND GUSTS OF 35
MPH ACROSS THE REGION TONIGHT WILL ALLOW WIND CHILLS TO NEAR ZERO
ACROSS THE HIGHER TERRAIN LATE TONIGHT.
AVIATION...
STRONG WAVE WILL ALLOW UPPER TROUGH TO GO NEGATIVE TILT BEGINNING
LATE THIS AFTERNOON. MID LEVEL CLOUDS WILL MOVE IN DURING THE
MORNING. THERE COULD BE A BRIEF SHOT OF IFR CLOUDS/VISIBILITIES WITH
RAIN/SNOW SHOWERS ASSOCIATED WITH THE LEADING EDGE OF THE COLD
ADVECTION. NORTHWEST DOWNSLOPE FLOW WILL DEVELOP BY EVENING AND
ALLOW MUCH OF THE CLOUDS TO DISSIPATE.
MARINE...
00Z GFS/ETA MOS AT THOMAS POINT BOTH SUGGEST SUSTAINED WINDS WILL BE
IN THE 10-15KT RANGE TODAY...AND 15-20KT RANGE TONIGHT. 00Z NAM
PROXIMITY LAND BUFKIT FORECAST SOUNDINGS SUGGEST ADDITIONAL WIND
GUST MOMENTUM OF 20 KNOTS BETWEEN 14-20Z...WHILE THE 00Z GFS
INDICATES GUSTS BETWEEN 18-22 KNOTS. BOTH THE 00Z NAM AND GFS
INDICATE 30KT WIND GUSTS THIS EVENING AND TONIGHT BEHIND THE COLD
FRONT. SINCE THE LULL IS ONLY SEVERAL HOURS...WILL HAVE ONE SMALL
CRAFT ADVISORY BEGINNING AT 14Z TODAY.
IN NW FLOW STRONG SCA WINDS ARE LIKELY TO CONTINUE ON WED. HAVE
EXTENDED THE PREVIOUSLY ISSUED SCA INTO WEDNESDAY. WINDS WILL
QUICKLY DIMINISH WED EVNG AS HIGH MOVES INTO THE MID ATLC.
LONG TERM...WEDNESDAY THROUGH MONDAY...
UPSLOPE SNOW SHWRS SHOULD COME TO AN END BY MIDDAY WED AS UPPER
TROUGH SWINGS TO THE E AND TRAJECTORIES BECOME LESS FAVORABLE OFF
THE GRT LKS. HWVR COLDEST TEMPS ALOFT PERSIST THROUGH THE DAY WED.
WILL INDICATE A STRONG TOPOGRAPHICAL EFFECT ON WED WITH TEMPS IN THE
HIGHER TERRAIN ONLY IN THE LOWER TO MID 20S. WED NGT THE FLOW REGIME
BEGINS TO BACK TO SW...THOUGH THE WARMING TREND WILL BE VERY SLOW
THROUGH THE END OF THE WEEK. SFC HIGH MOVES OFFSHORE BY FRIDAY AND
WARMER TEMPS SURGE N AS A RESULT. MAX TEMPS FRI-SUN WILL WARM WELL
INTO THE 50S TO AROUND 60 IN THE SE CWFA (DURING THE COLDEST TIME
OF THE YR...THESE TEMPS WILL BE NEARLY 20 DEG ABOVE NORMAL).
WED NGT THROUGH FRI WILL REMAIN A DRY FCST WITH HIGH PRES SLOWLY
MOVING OFF THE CST.
WARM SECTOR FOR MUCH OF THE WKEND. HAVE BACKED POPS DOWN JUST A HAIR
SAT-SUN WITH THE BEST CHCS RELEGATED TO W OF THE BL RIDGE. ATTM IT
REALLY DOESN`T LOOK LIKE MUCH PRECIP SHOULD REACH THE I-95 CORRIDOR
TIL SUN NGT WITH THE APPROACH OF A STRONG COLD FRONT. EXCELLENT
RIBBON OF LIFT IN CONJ WITH THE FRONT LATE SUN NGT AND MON...WILL
INDICATE 40 POPS DURING THIS GENERAL TIMEFRAME. WILL HOLD ON TO THE
COOLER TEMPS BEHIND THE FRONT MON AND ESP ON TUE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...SNOW ADVISORY UNTIL 4 AM EST WEDNESDAY FOR MDZ501.
VA...SNOW ADVISORY UNTIL 4 AM EST WEDNESDAY FOR VAZ021.
WV...SNOW ADVISORY UNTIL 4 AM EST WEDNESDAY FOR WVZ054-501-503.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST WEDNESDAY FOR ANZ530>537.
&&
$$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 410 AM EST TUE JAN 9 2006
.SHORT TERM (TONIGHT THROUGH TUESDAY)...
WATER VAPOR LOOP SHOWS A LONG WAVE TROUGH ACROSS THE NORTH CENTRAL
CONUS...WITH EMBEDDED WAVES MOVING EAST ACROSS THE TENNESSEE VALLEY
AND SOUTHEAST ACROSS THE MIDWEST. ACARS 400-250MB WIND OBSERVATIONS
REVEAL 140-180KT WINDS ROUND THE AFOREMENTIONED TROUGH. 04Z SURFACE
ANALYSIS PLACED A TROUGH IN THE LEE OF THE APPALACHIANS. A COLD
FRONT WAS CROSSING CHICAGO AND SAINT LOUIS...WITH A SECOND TRAILING
COLD FRONT SINKING SOUTH THROUGH THE UPPER MIDWEST.
A CLEAR START TO THE DAY WILL QUICKLY DETERIORATE WITH THE APPROACH
OF A STRONG SHORTWAVE. THE VERTICAL MOTION COUPLET OF THE WAVE
ACROSS SOUTHERN ILLINOIS HAS BEEN INCREASINGLY MORE IMPRESSIVE
THROUGH THE NIGHT ON WATER VAPOR IMAGERY. GFS/NAM IN AGREEMENT THAT
THIS WAVE FEEDING INTO THE LONGWAVE TROUGH WILL ALLOW THE TROUGH TO
BECOME NEGATIVE TILTED BEGINNING LATE TODAY...CAUSING SIGNIFICANT
CYCLOGENESIS OFFSHORE TONIGHT. DEEP LAYER LAPSE RATES BETWEEN 1000MB
AND 500MB ARE FORECAST TO BE STEEP...NEAR 7.5C/KM. GIVEN THE
SYNOPTIC SITUATION...AM CONCERNED THAT VERTICAL MOTION CAUSED BY THE
SHORT WAVE LATE THIS AFTERNOON MAY BE ENOUGH TO ALLOW A 1-2 HOUR
SNOW SHOWER BURST. WITH TEMPERATURES REACHING INTO THE MID 40S...NO
ACCUMULATION IS EXPECTED EAST OF THE MOUNTAINS...HOWEVER THERE MAY
BE A SOCIETAL IMPACT WITH THE FIRST POSSIBILITY OF FLAKES ACROSS THE
GREATER WASHINGTON METRO AREA (CLOSE TO EVENING RUSH HOUR).
OF COURSE THERE WILL BE A CHALLENGE TO SEE SNOW FLAKES THIS
AFTERNOON AFTER HIGHS IN THE MID 40S (A BIT COOLER THAN MOS GIVEN
RAPID INCREASE IN CLOUDS EXPECTED THIS MORNING). 0C HEIGHT IS JUST
OFF THE SURFACE AT 2KFT. DRY AIRMASS (PRECIPITABLE WATER VALUE OF
0.19 AT 00Z KIAD RAOB) WILL ALLOW EVAPOARATIONAL COOLING. DYNAMICAL
COOLING MAY BE A SIGNIFICANT FACTOR WITH IMPRESSIVE VERTICAL MOTION
SHOWN BY THE NAM DURING THE LATE AFTERNOON. THIS VERTICAL MOTION IS
WITHIN THE DENDRITIC SNOW GROWTH RANGE...WHICH WOULD FAVOR LARGE
DENDRITE FORMATION WITHIN THE CLOUD LAYER (WITH A SHORT TRIP WITHIN
THE WARM SUB-CLOUD LAYER TO THE GROUND). THERE IS ALSO INDICATION OF
FRONTOGENESIS IN THE 700-850MB LAYER AS THE SYSTEM BEGINS TO
DEEPEN...WHICH WOULD SUPPORT PRECIPITATION DEVELOPMENT EAST OF THE
MOUNTAINS.
THERE IS LESS UNCERTAINTY ALONG THE WESTERN SLOPES OF THE MOUNTAINS
WHERE TEMPERATURES ARE ALREADY SUPPORTIVE OF SNOW...AND IN FACT SNOW
HAS ALREADY BEEN REPORTED AT KEKN AS OF 09Z. BEHIND THE WARM
ADVECTION AND LEADING EDGE OF THE COLD ADVECTION
PRECIPITATION...UPSLOPE SNOW WILL PERSIST THROUGH THE NIGHT...AS THE
SKY EAST OF THE MOUNTAINS BECOMES MOSTLY CLEAR TO PARTLY CLOUDY.
HAVE ISSUED A SNOW ADVISORY WITH 03Z SHORT RANGE ENSEMBLES AT KEKN
INDICATING A MEAN OF 0.37" OF SNOW LIQUID EQUIVALENT THROUGH 12Z
EARLY WEDNESDAY MORNING...AND A MAX OF 0.85". CURRENT SNOW FORECAST
IN THE MOUNTAINS IS 1-3" TODAY AND 1-2" TONIGHT. WIND GUSTS OF 35
MPH ACROSS THE REGION TONIGHT WILL ALLOW WIND CHILLS TO NEAR ZERO
ACROSS THE HIGHER TERRAIN LATE TONIGHT.
&&
.AVIATION...
STRONG WAVE WILL ALLOW UPPER TROUGH TO GO NEGATIVE TILT BEGINNING
LATE THIS AFTERNOON. MID LEVEL CLOUDS WILL MOVE IN DURING THE
MORNING. THERE COULD BE A BRIEF SHOT OF IFR CLOUDS/VISIBILITIES WITH
RAIN/SNOW SHOWERS ASSOCIATED WITH THE LEADING EDGE OF THE COLD
ADVECTION. NORTHWEST DOWNSLOPE FLOW WILL DEVELOP BY EVENING AND
ALLOW MUCH OF THE CLOUDS TO DISSIPATE.
&&
.MARINE...
00Z GFS/ETA MOS AT THOMAS POINT BOTH SUGGEST SUSTAINED WINDS WILL BE
IN THE 10-15KT RANGE TODAY...AND 15-20KT RANGE TONIGHT. 00Z NAM
PROXIMITY LAND BUFKIT FORECAST SOUNDINGS SUGGEST ADDITIONAL WIND
GUST MOMENTUM OF 20 KNOTS BETWEEN 14-20Z...WHILE THE 00Z GFS
INDICATES GUSTS BETWEEN 18-22 KNOTS. BOTH THE 00Z NAM AND GFS
INDICATE 30KT WIND GUSTS THIS EVENING AND TONIGHT BEHIND THE COLD
FRONT. SINCE THE LULL IS ONLY SEVERAL HOURS...WILL HAVE ONE SMALL
CRAFT ADVISORY BEGINNING AT 14Z TODAY.
IN NW FLOW STRONG SCA WINDS ARE LIKELY TO CONTINUE ON WED. HAVE
EXTENDED THE PREVIOUSLY ISSUED SCA INTO WEDNESDAY. WINDS WILL
QUICKLY DIMINISH WED EVNG AS HIGH MOVES INTO THE MID ATLC.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY A QUARTER FOOT BELOW ASTRONOMIC
PREDICTIONS. THE LUNAR CYCLE IS WANING FROM A FULL MOON (71% FULL).
BLOWOUT CONDITIONS WERE EXPERIENCED YESTERDAY BEHIND THE COLD FRONT.
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM FORECASTS WATER
LEVELS TO RECOVER TO PREDICTED LEVELS AGAIN TODAY...WHILE THE NOAA
EXTRATROPICAL STORM SURGE MODEL IS CURRENTLY OVER-FORECASTING WATER
LEVELS.
&&
.LONG TERM...WEDNESDAY THROUGH MONDAY...
UPSLOPE SNOW SHWRS SHOULD COME TO AN END BY MIDDAY WED AS UPPER
TROUGH SWINGS TO THE E AND TRAJECTORIES BECOME LESS FAVORABLE OFF
THE GRT LKS. HWVR COLDEST TEMPS ALOFT PERSIST THROUGH THE DAY WED.
WILL INDICATE A STRONG TOPOGRAPHICAL EFFECT ON WED WITH TEMPS IN THE
HIGHER TERRAIN ONLY IN THE LOWER TO MID 20S. WED NGT THE FLOW REGIME
BEGINS TO BACK TO SW...THOUGH THE WARMING TREND WILL BE VERY SLOW
THROUGH THE END OF THE WEEK. SFC HIGH MOVES OFFSHORE BY FRIDAY AND
WARMER TEMPS SURGE N AS A RESULT. MAX TEMPS FRI-SUN WILL WARM WELL
INTO THE 50S TO AROUND 60 IN THE SE CWFA (DURING THE COLDEST TIME
OF THE YR...THESE TEMPS WILL BE NEARLY 20 DEG ABOVE NORMAL).
WED NGT THROUGH FRI WILL REMAIN A DRY FCST WITH HIGH PRES SLOWLY
MOVING OFF THE CST.
WARM SECTOR FOR MUCH OF THE WKEND. HAVE BACKED POPS DOWN JUST A HAIR
SAT-SUN WITH THE BEST CHCS RELEGATED TO W OF THE BL RIDGE. ATTM IT
REALLY DOESN`T LOOK LIKE MUCH PRECIP SHOULD REACH THE I-95 CORRIDOR
TIL SUN NGT WITH THE APPROACH OF A STRONG COLD FRONT. EXCELLENT
RIBBON OF LIFT IN CONJ WITH THE FRONT LATE SUN NGT AND MON...WILL
INDICATE 40 POPS DURING THIS GENERAL TIMEFRAME. WILL HOLD ON TO THE
COOLER TEMPS BEHIND THE FRONT MON AND ESP ON TUE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...SNOW ADVISORY FROM 10 AM THIS MORNING TO 4 AM EST WEDNESDAY
FOR MDZ501.
VA...SNOW ADVISORY FROM 10 AM THIS MORNING TO 4 AM EST WEDNESDAY
FOR VAZ021.
WV...SNOW ADVISORY FROM 10 AM THIS MORNING TO 4 AM EST WEDNESDAY
FOR WVZ054-501-503.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EST
WEDNESDAY FOR ANZ530>537.
&&
$$
SHORT TERM/HYDROLOGY/AVIATION/TIDES...ROGOWSKI
LONG TERM...BROTHERTON
MARINE...ROGOWSKI/BROTHERTON
AREA FORECAST DISCUSSION...CORRECTED
NWS GAYLORD MI
AFDAPX 938 PM EST WED JAN 10 2007
...CORRECTED WATCH/WARNING/ADVISORY STATEMENT BELOW...
.UPDATE...SFC/RUC/SATELLITE/RADAR AND UPPER ANALYSIS SHOWING
ELEVATED WARM FRONTAL ZONE DRAPED ACROSS NRN MICHIGAN WITH NICE
H7-H5 FGEN AND ASSOCIATED MID LEVEL MOISTURE BAND FROM FAR NRN LAKE
MICHIGAN TO FAR NE LOWER MICHIGAN. ECHOES SEEN ON RADAR ARE NOT
HITTING THE SFC...AND ARE PURE VIRGA AT THIS POINT. THERE IS SOME
MINOR LAKE EFFECT FLURRIES THAT HAVE BEEN PESTERING THE MANISTIQUE
AREA THROUGH THE COURSE OF THE NIGHT...WHERE H8 TEMPS HAVE LINGERED
AROUND THE -8C RANGE...BARELY COLD ENOUGH FOR DEEP ENOUGH OVER LAKE
INSTABILITY...AND JUST ENOUGH FETCH TO RESULT IN FLURRIES. AIR IS
WARMING ACROSS THIS ENTIRE AREA THROUGH THE NIGHT...AND LAKE EFFECT
WILL COME TO AN END. LOW CLOUDS IN THIS AREA WILL FOLLOW...ENDING
LATE TONIGHT.
AS THE NIGHT WEARS ON...ELEVATED WARM FRONTAL/MOISTURE/FGEN BAND
WILL LIFT INTO EASTERN UPPER MICHIGAN AND DEPART ALL BUT NRN
CHIPPEWA COUNTY BY DAYBREAK. THIS AREA OF CONCERN WILL THEN LIFT OUT
OF ALL OF EASTERN UPPER BY 15Z TOMORROW. BOTH GFS/NAM SHOWING
STRONGER H8 WINDS/WAA DEVELOPING TONIGHT AND INTO EARLY TOMORROW
MORNING...ALONG WITH EASTWARD ADVANCEMENT OF WEAKISH SHORTWAVE
ENERGY AHEAD OF SFC LOW PRESSURE...WHICH WILL RIDE ACROSS EASTERN
LAKE SUPERIOR TOMORROW AFTERNOON. THIS IS GOING TO RESULT IN A FEW
CONCERNS...
THE FGEN WILL STRENGTHEN OVERNIGHT RESULTING IN BETTER CHANCES FOR
THE MOISTURE CHANNEL TO SQUEEZE OUT SOME LIGHT SNOW ACROSS MAINLY
EASTERN UPPER/CHIPPEWA COUNTY...AND THROUGH MIDNIGHT FOR CHEBOYGAN
AND PELLSTON AREAS AS WINDS HAVE BACKED INTO A E/ENE DIRECTION OFF
LAKE HURON (POSSIBLE LAKE HELP). TOTAL OVERNIGHT SNOWFALL WILL BE
MINIMAL AT BEST...BUT AN INCH IS NOT OUT OF THE QUESTION FOR EASTERN
CHIP AND MACKINAC COUNTIES WITH A LITTLE EARLY HELP FROM LAKE HURON.
ALSO...AS LOW LEVEL WINDS RAMP UP WITH H8 SPEEDS REACHING
50KTS...GALES BECOME A CONCERN...EVEN UNDER THE INCREASINGLY STABLE
BOUNDARY LAYER. CURRENT WARNINGS IN EFFECT FOR THE NEARSHORE WATERS
ALONG LAKE MICHIGAN LOOK REASONABLE ATTM WITH THE HELP OF COASTAL
CONVERGENCE...BUT WITH WIND SPEEDS THIS STRONG...AND HIGH RESOLUTION
NAM12 SUGGESTING A SHALLOW MIXED LAYER TAPPING INTO 35-40 KNOTS OVER
THE MAJORITY OF THE NEARSHORE WATERS...WILL GO AHEAD AND EXPAND
GALES TO ALL BUT THE STRAITS TO PRESQUE ISLE...WHERE THE SE-SW WINDS
WILL RESULT IN MINIMAL OVER WATER TRAJECTORY. SURELY WOULD EXPECT TO
SEE SPEEDS JUST OFF THE SFC...SUCH AS THE MACKINAC BRIDGE...AND IN
THE HIGHER TERRAIN OF INTERIOR NRN LOWER MICHIGAN PICK UP INTO THE
20-30KT RANGE AT TIMES OVERNIGHT WITH HIGHER GUSTS AT THE BRIDGE.
WILL INCLUDE STRONGER WINDS IN THE FORECAST FOR THESE AREAS. THIS
WARMING AND STRONG WINDS WILL ALSO ALLOW FOR TEMPERATURES TO
INCREASE THROUGH THE NIGHT...REACHING THE MIDDLE 20S TO LOWER 30S BY
DAYBREAK.
AVIATION...LOW LEVEL WIND SHEAR WILL ONLY RAMP UP FURTHER TONIGHT.
APX VAD WINDS ONLY SHOWING 15-20KTS RIGHT NOW AT 2KFT...BUT 25-30KTS
AT 2KFT ARE ALREADY SWEEPING INTO THE GTV BAY REGION. CURRENT TAFS
ALREADY HAVE THIS SCENARIO LAID OUT...AND FORESEE NO CHANGES HERE AT
THE 06Z ISSUANCES. MVFR CEILINGS TO REMAIN UP IN EASTERN UPPER WITH
SOUTHERLY FLOW OFF FAR NRN LAKES MICHIGAN AND HURON...BUT LOW LEVEL
MOISTURE CHANNEL IS EXPECTED TO DEVELOP AS EARLY AS LATE TONIGHT AND
INTO THE TVC/PLN AIRPORTS. THIS IS PORTRAYED IN THE CURRENT TAFS AS
WELL..AND FORESEE NO CHANGES TO THIS ATTM. SMD
&&
.PREV DISCUSSION ISSUED AT 416 PM EST WED JAN 10 2007
DISCUSSION....EARLY THIS AFTERNOON...LATEST SURFACE/RUC ANALYSIS AND
VIS/IR/WV/RADAR IMAGERY SHOW HIGH PRESSURE OVER THE SOUTHERN PLAINS
WHOSE SURFACE RIDGE AXIS BISECTS LOWER MICHIGAN. LOW LEVEL WINDS
STARTING TO REFLECT THE AXIS PASSAGE WITH LIGHT LAKE EFFECT SNOW
SHOWERS OVER NW LOWER AND TIP OF THE MITT DIMINISHING AS THE
DISORGANIZED BANDS ARE TRYING TO ORIENT THEMSELVES IN THE SW-NE
DIRECTION. THESE BANDS ARE ALSO FIGHTING PLENTY OF DRY AIR AS ACARS
SOUNDINGS FROM PLN AND TVC SHOW INVERSION HEIGHTS CONTINUING TO FALL
TO AROUND 860MB. AWAY FROM THE LES BANDS...SKIES HAVE TURNED PARTLY
TO MOSTLY SUNNY. MEANWHILE UPSTREAM...STRONG SHORTWAVE NOW OVER
ALBERTA AND ASSOCIATED LOW PRESSURE IS TRUCKING EAST ALONG THE
CANADIAN BORDER...HELPING TO TIGHTEN THE PRESSURE GRADIENT OVER THE
PLAINS. WARM AIR ADVECTION CLOUDS RIDING OVER THE 850MB WARM FRONT
LOCATED OVER THE UPPER MISSISSIPPI RIVER VALLEY ARE STARTING TO
CROSS LAKE MICHIGAN...AND WILL EVENTUALLY MAKE IT ACROSS THE CWA
LATE THIS AFTERNOON/EVENING. THE INTERACTION OF THIS WARM FRONT AS
IT MOVES NORTHEAST TONIGHT...AND WEAKENING LES WILL BE THE MAIN
FORECAST CONCERN TONIGHT.
TONIGHT...UPSTREAM SHORTWAVE WILL MAKE IT TO MANITOBA (ASSOCIATED
SURFACE LOW PRESSURE TO WESTERN ONTARIO) BY 12Z THURSDAY MORNING.
THIS WAVE WILL HELP INCREASE THE SOUTHERLY FLOW AHEAD OF IT AND PUSH
A 850MB WARM FRONT TO THE NORTHEAST TO NORTHERN LOWER BY 12Z. AS IT
DOES SO...850MB TEMPERATURES MODERATE ALOT FROM MINUS 6-9C AT 00Z
OVER NORTHERN LAKE MICHIGAN TO 0 TO MINUS 3 BY 12Z. A SURGE OF
MOISTURE WILL ACCOMPANY THIS WAA...WHICH REDUCES CONDENSATION
PRESSURE DEFICITS ON THE 285K AND 290K ISENTROPIC SURFACES TO LESS
THAN 10MB BY APPROXIMATELY 03Z. NAM/GFS SOUNDINGS DIFFER
OVERNIGHT...WITH THE NAM NOT NEARLY AS MOIST BELOW 800MB AS THE
GFS. WITH ONSHORE FLOW OVER EASTERN UPPER FROM LAKE MICHIGAN WHILE
DELTA T/S REMAINING ABOVE 8C DURING THE EVENING...LIKE THE MORE
MOIST SCENARIO DEPICTED BY THE GFS...AND WILL KEEP CHANCE POPS
ACROSS EASTERN UPPER AFTER 03Z. LOWER LEVELS LOOK TO DRY OVER
NORTHERN LOWER FOR PRECIP AT THIS TIME. TEMPERATURES WILL BOTTOM
OUT DURING THE EVENING TONIGHT BUT THEN SLOWLY RISE OVERNIGHT WITH
THE INCOMING WARM AIR.
MARINE...TIGHTENING PRESSURE GRADIENT COMBINED WITH OVER-LAKE
INSTABILITY AND COASTAL CONVERGENCE WILL CREATE WIND SPEEDS AT 925MB
TO 40-50KTS TONIGHT AND GALE FORCE WIND GUSTS ALONG THE LAKE
MICHIGAN SHORELINE FROM MANISTEE TO THE STRAITS. ELSEWHERE...MIXING
TO 925MB REVEALS WIND GUSTS COULD POTENTIALLY REACH BETWEEN 30-35
KNOTS...OR JUST BELOW GALE FORCE...SO WILL INTRODUCE SMALL CRAFTS
EVERYWHERE ELSE.
MPC
FOR THE REMAINDER OF THE WEEK...COLD AIR CONTINUES TO MODERATE AND
RAPIDLY MOVE EAST OF THE REGION EARLY ON WHILE LOW AMPLITUDE MID
LEVEL RIDGING DEVELOPS OVER THE EASTERN STATES...BUT NEXT CORE OF
COLD AIR DESCENDS INTO THE NRN ROCKIES. ONE PIECE OF ENERGY (NOW
NEAR LAKE WINNIPEG) FORECAST TO MOVE ACROSS SOUTHERN CANADA WITH AN
ASSOCIATED LOW PRESSURE SYSTEM AND COLD FRONT SLOWING MOVING THROUGH
AND IMPACTING THE REGION THURSDAY THROUGH FRIDAY. MAIN FORECAST
ISSUES FOR THE NEAR TERM REVOLVE AROUND PRECIP CHANCES AND TYPE AS
THIS SYSTEM PASSES THROUGH.
THURSDAY...AS MENTIONED ABOVE...NRN STREAM SHORTWAVE AND ASSOCIATED
SFC LOW FORECAST TO SLOWLY MOVE INTO ONTARIO DURING THE DAY...WITH A
WARM FRONT LIFTING THROUGH THE REGION OVERNIGHT/EARLY THURSDAY AND
TRAILING COLD FRONT APPROACHING THE REGION BY LATE AFTERNOON. DECENT
SHOT OF WARM ADVECTION MAY BE ENOUGH TO PRODUCE BAND OF LIGHT
SNOWFALL ACROSS EASTERN UPPER MICHIGAN THURSDAY MORNING AND WILL
KEEP A CHANCE GOING IN THE FORECAST FOR THAT AREA...ALTHOUGH LOWER
LAYERS ARE A BIT ON THE DRY SIDE. BUT WITHOUT ANY HELP FROM THE
LAKES (TEMPS TOO WARM) ANY ACCUMULATIONS SHOULD BE ON THE LIGHT
SIDE. THURSDAY AFTERNOON...NORTHERN MICHIGAN WELL INTO THE WARM
SECTOR WITH STRONG SW WINDS CONTINUING AND AFTERNOON TEMPS WARMING
BACK INTO THE 30S TO AROUND 40 (WOULD BE EVEN WARMER WERE IT NOT FOR
THE SNOW COVER). MEANWHILE...BOTH NAM AND PARTICULARLY THE GFS
DEPICT SUBSTANTIAL MOISTENING IN THE SUB 800 MB LAYER DURING THE
AFTERNOON (WARMER THAN -6C) AHEAD OF THE APPROACHING FRONT...WHILE
MOISTURE ALOFT STRIPS OUT. NOT MUCH OUT THERE UPSTREAM TODAY IN
TERMS OF LOW CLOUDS TO HANG YOUR HAT ON...BUT CAN SEE THIS TAKING
SHAPE AS WARMER/MOIST AIR SURGES NORTH ACROSS THE SNOW COVER IN
NORTHERN MICHIGAN. REMOVED MENTION OF ANY RAIN/SNOW FROM THE
FORECAST FOR THE AFTERNOON...BUT MAY BE ENOUGH MOISTURE THERE TO GET
SOME DRIZZLE GOING ESPECIALLY ACROSS THE HIGHER TERRAIN AREAS.
THURSDAY NIGHT THROUGH FRIDAY...COLD FRONT SLOWLY PRESSES EAST/SE
THROUGH THE AREA THURSDAY NIGHT INTO EARLY FRIDAY AND SETTLE TO OUR
SOUTH. ALTHOUGH STILL QUITE A BIT OF UNCERTAINLY REGARDING POPS
DURING THIS TIMEFRAME...PERHAPS ENOUGH FORCING/MOISTURE ALONG THE
FRONT TO SQUEEZE OUT MEASURABLE PRECIP BOTH THURSDAY NIGHT INTO
FRIDAY...WITH PRIMARILY SNOW OVER THE NRN TWO-THIRDS OF THE CWA AND
RAIN/SNOW OVER THE SOUTH. ALSO...AS COLDER AIR SLOWLY FILTERS INTO
THE REGION...SHOULD START TO GET THE LAKES MORE INVOLVED BY FRIDAY.
BUT OVERALL ACCUMULATIONS LOOKING TO BE ON THE MINOR SIDE AT THIS
POINT.
SATURDAY THRU WEDNESDAY...FRONT CONTINUES TO SAG SOUTH OF THE REGION
BY EARLY SATURDAY WITH COLDER AIR ONCE AGAIN SETTLING INTO THE STATE
FOR THE WEEKEND. SPLIT FLOW REGIME EMERGES ACROSS THE LOWER 48
STATES BY THE END OF THE WEEK AND HEADING INTO THE WEEKEND...WITH A
CLOSED MID LEVEL LOW SLOWLY DROPPING SOUTHWARD ALONG THE WEST COAST
INTO THE 4 CORNERS REGION AND LOW AMPLITUDE RIDGING OVER THE EASTERN
HALF OF THE CONUS. LATEST MEDIUM RANGE GUIDANCE SUGGESTS BROAD NRN
STREAM HIGH PRESSURE WILL SETTLE ACROSS THE NRN PLAINS AND WESTERN
GREAT LAKES SATURDAY INTO EARLY SUNDAY WITH TEMPS RUNNING NEAR
NORMAL. STILL COLD ENOUGH HOWEVER FOR SOME LIGHT LAKE SNOW SHOWERS
DURING THIS TIME ALTHOUGH PROBLEMATIC THIS FAR OUT TO PINPOINT THE
EXACT FLOW REGIME AND LOCATIONS WITH THE BEST CHANCES FOR SNOW. BY
LATE IN THE WEEKEND AND EARLY NEXT WEEK...SRN STREAM CUTOFF SYSTEM
LOOKING TO LIFT THROUGH THE OHIO VALLEY AND INTO NEW ENGLAND. SYSTEM
COULD PRODUCE A DECENT AMOUNT OF SNOW (SYSTEM AND LAKE ENHANCED)
ACROSS LOWER MICHIGAN IF CURRENT SCENARIO PANS OUT. THEN AGAIN...
MEDIUM RANGE SOLUTIONS HAVE SHOWN A GOOD AMOUNT OF UNCERTAINTY WITH
REGARD TO LOCATION OF THE STORM TRACK AND TIMING/LOCATION OF
DEEPENING WAVES RIDING ALONG THE BAROCLINIC ZONE UP THROUGH THE
REGION. BEHIND THIS SYSTEM AS IT STANDS RIGHT NOW...SOME OF THE
COLDEST AIR OF THE YEAR GETS PULLED INTO NRN MICHIGAN FOR TUESDAY
AND WEDNESDAY...WHILE STRONG HIGH PRESSURE BUILDS INTO THE PLAINS
AND WESTERN GREAT LAKES. HOWEVER...WITH THE COLD AIR IN PLACE WILL
HAVE CONTINUING CHANCES FOR SNOW SHOWERS.
ADAM
&&
.APX...WATCHES/WARNINGS/ADVISORIES...
GALE WARNING...TONIGHT THROUGH THURSDAY....
LMZ323-341-342-344-345-LSZ321-LHZ346-348-349.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 405 PM EST TUE JAN 9 2007
.SYNOPSIS...
20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED TROUGHING
DIGGING DOWN THE WEST COAST OF BRITISH COLUMBIA INTO THE PACIFIC
NW...RIDGING OVER SOUTHERN ALBERTA AND SASKATCHEWAN AND A LARGE
TROUGH COVERING THE GREAT LAKES. WITHIN THIS LARGE TROUGH...A 510
DAM UPPER LOW WAS LOCATED HALF WAY BETWEEN LAKE SUPERIOR AND JAMES
BAY. 850MB TEMPS ARE FAIRLY COLD UNDER AND IMMEDIATELY WEST OF THE
UPPER LOW...AS NOTED BY THE -27C TEMP AT PICKLE LAKE ONTARIO (CWPL)
AT 12Z. EVEN AWAY FROM THE UPPER LOW...INL AND MOOSONEE ONTARIO
REPORTED AROUND -18C AT 12Z. WITH 45 KT NW 850MB WINDS AT BOTH INL
AND CWPL...THESE COLD READINGS CONTINUE TO FLOW INTO THE CWA...
RESULTING IN PLENTY OF LAKE EFFECT SNOW SHOWERS. HOWEVER...THESE
SNOW SHOWERS HAVE OVERALL BEEN WEAK DUE TO A COMBINATION OF FACTORS.
FIRST IS DRY AIR ADVECTION...NOTED BY BELOW ZERO F DEWPOINTS ON THE
NORTH SIDE OF LAKE SUPERIOR. SECOND...INVERSION HEIGHTS AT MOST ARE
AROUND 7000 FT BASED ON THE 12Z TAMDAR SOUNDING FROM SAWYER.
THIRD...THE FLOW IS MAINLY UNIDIRECTIONAL...CAUSING MULTI-PARALLEL
BANDS WHICH NORMALLY DO NOT PRODUCE MUCH SNOWFALL...ESPECIALLY BY
THEMSELVES. ALTHOUGH THE SNOW MAY NOT BE THAT STRONG...THE WINDS
HAVE BEEN. MUCH OF THE 850MB WIND OBSERVED ON THE SOUNDINGS UPSTREAM
IS BEING MIXED DOWN TO THE LAKE SUPERIOR SURFACE DUE TO THE COLD
ADVECTION...AND GALE FORCE WINDS OR WIND GUSTS HAVE BEEN REPORTED AT
MANY SITES OVER THE EASTERN 2/3 OF LAKE SUPERIOR TODAY. AWAY FROM
THE LAKE EFFECT SNOW IN THE SOUTH CENTRAL U.P....SKIES HAVE BEEN
MAINLY PARTLY CLOUDY...THANKS TO THE DRY AIR ADVECTION. AS FAR AS
THE SURFACE PRESSURE PATTERN GOES...A 1028MB HIGH PRESSURE RIDGE WAS
CENTERED OVER WESTERN MINNESOTA WHILE 980S MB LOW PRESSURE WAS OVER
NE QUEBEC.
&&
.SHORT TERM (TONIGHT AND WED)...
UPPER TROUGH OVER THE GREAT LAKES WILL CONTINUE TO MOVE TO THE EAST
OVER THE NEXT 24 HOURS DUE TO THE RIDGE OVER MONTANA BEING PUSHED
EASTWARD BY THE BRITISH COLUMBIA TROUGH. BY 00Z THU...THE RIDGE
AXIS IS PROGGED TO BE LOCATED OVER THE CWA...ALLOWING WARMER
TEMPERATURES ALOFT TO MOVE INTO THE AREA. UNTIL THEN...HOWEVER...
850MB TEMPS ARE EXPECTED TO REMAIN ON THE COLD SIDE WITH READINGS
AROUND -20C THIS EVENING ONLY WARMING TO -13 TO -17C BY 12Z WED.
SINCE LAKE SURFACE TEMPERATURES ARE AROUND 4C...LAKE EFFECT SNOW
SHOWERS WILL CONTINUE. ONE DIFFERENCE TONIGHT FROM TODAY...
THOUGH...WILL BE THE WIND DIRECTION BACKING AS THE SURFACE RIDGE
OVER WESTERN MINNESOTA MOVES TO WESTERN UPPER MICHIGAN BY 12Z. THIS
BACKING...COMBINED WITH PERSISTENT DRY AIR ADVECTION SHOULD KEEP
AMOUNTS DOWN IN THE WESTERN U.P.. WITH THE BETTER FETCH LENGTH ON
EASTERN LAKE SUPERIOR...ALLOWING FOR A LITTLE MOISTENING...HAVE KEPT
2 TO 4 INCH AMOUNTS GOING TONIGHT IN THE UPSLOPE AREAS OF THE
EASTERN U.P.. AS THE SURFACE RIDGE CONTINUES MOVING ACROSS ON WED
DUE TO THE UPPER RIDGE BEING PUSHED EASTWARD...THE LAKE EFFECT SNOW
IS EXPECTED TO END FOR THE NORTHERN U.P.. HOWEVER...THE SOUTHERLY
WIND DEVELOPING ON THE BACK SIDE OF THE HIGH IS EXPECTED TO RESULT
IN DECENT DEEP ISENTROPIC LIFTING ACROSS THE CWA...AS SHOWN BY THE
NAM AND GFS. ALTHOUGH SOME DRY AIR EXISTS IN THE 750-900MB LAYER...
THE VERTICAL MOTION DUE TO THE WARM ADVECTION MAY BE ENOUGH TO
PRODUCE SOME LIGHT SNOW...ESPECIALLY OVER THE NW PORTION OF THE CWA
IN THE AFTERNOON WHERE BETTER MOISTURE IS PRESENT. THEREFORE HAVE
RAISED POPS. ALSO HAVE HIGHER POPS IN SOUTHERN SCHOOLCRAFT COUNTY
WHERE SOUTHERLY WINDS AND COOL TEMPS AT 850MB (RISING TO -7C BY 00Z
THU OVER NORTHERN LAKE MICHIGAN) MAY BRING LAKE EFFECT SNOW THERE.
BLUSTERY CONDITIONS OBSERVED TODAY WILL BEGIN TO DECREASE TONIGHT...
AND ESPECIALLY BY WED MORNING AS THE RIDGE MOVES IN. THE DECREASE...
ALONG WITH SOME CLEARING IN THE SOUTHWESTERN U.P. MAY ALLOW TEMPS
TO FALL TO NEAR ZERO TONIGHT...ESPECIALLY GIVEN THE DRY ATMOSPHERE.
AS THE RIDGE CROSSES THE CWA ON WED...SOUTHERLY WINDS PICKING BACK
UP WILL HELP TO WARM THE TEMPERATURES...BOTH ALOFT AND AT THE
SURFACE...ESPECIALLY IN DOWNSLOPE AREAS. HOWEVER...THE WIND WILL
MAKE IT FEEL COOLER SINCE READINGS ARE ONLY EXPECTED IN THE 20S TO
AT MOST 30F PER MET/MAV GUIDANCE.
.LONG TERM (WED NIGHT THROUGH TUE)...
WED NIGHT/THU...SHORTWAVE WILL TRACK FROM SRN SASKATCHEWAN/MANITOBA
WED EVENING TO ONTARIO THU AFTN WITH ASSOCIATED SFC LOW PASSING JUST
N OF LAKE SUPERIOR. STRONG ISENTROPIC ASCENT WILL BE THE RULE WED
NIGHT...BUT WITH FOCUS OF STRONGEST ASCENT/DEEP LAYER MOISTENING
GENERALLY ACROSS N HALF OF LAKE SUPERIOR INTO ONTARIO.
CANADIAN/GFS/UKMET RUNS HAVE BEEN VERY CONSISTENT ON THIS. MIXING
RATIOS OF 2-3G/KG ON 290K SFC (ROUGHLY 700-750MB) SUPPORT GENERAL
3-5 INCH SNOW ACCUMULATIONS IN AXIS OF BEST LIFT/MOISTENING WHICH
WILL BE JUST N OF HERE...BUT SRN FRINGE OF SNOW SHOULD IMPACT NRN
AND ERN UPPER MI. HAVE PAINTED 1 TO MAYBE 2 INCH ACCUMULATIONS ON
THE KEWEENAW. SIMILAR AMOUNTS ARE POSSIBLE OVER THE E WHERE THERE
MIGHT ALSO BE A BRIEF WINDOW FOR LAKE ENHANCEMENT IN SSW FLOW OFF
LAKE MICHIGAN. TEMPS WED NIGHT WILL LIKELY REMAIN STEADY OR SLOWLY
RISE FROM EARLY EVENING READINGS DUE TO BLUSTERY S WINDS/WAA AND
CLOUD COVER. 850MB WINDS OF 50 KTS AND 8MB/6HR PRES FALL MAX PASSING
JUST N OF LAKE SUPERIOR WILL WORK TO KEEP SFC WINDS GUSTY. SHOULD
ESPECIALLY BE GUSTY OVER THE ERN FCST AREA WHICH IS FAVORED IN S
WIND SITUATIONS (LOCATIONS SUCH AS KISQ/KERY/GRAND MARAIS AND
MARQUETTE).
PERSISTENT...BUT WEAKER ISENTROPIC ASCENT WILL CONTINUE THU SO ANY
LINGERING -SN SHOULD DIMINISH OR EVEN END. SHORTWAVE/SFC LOW ARE
WEAKER THAN PREVIOUS MODEL RUNS...SO COLDER AIR WILL BE SLOWER TO
SLIP BACK INTO THE AREA. IN FACT...IT MAY NOT BE UNTIL LATE THU
NIGHT THAT AIRMASS BECOMES COLD ENOUGH TO GET LES GOING AGAIN OFF
LAKE SUPERIOR.
THU NIGHT/FRI...COMBINATION OF RIGHT ENTRANCE OF JET STREAK RUNNING
FROM JUST N OF LAKE SUPERIOR TO QUEBEC AND A WEAK SHORTWAVE LIFTING
INTO THE GREAT LAKES SHOULD RESULT IN SOME LIGHT SNOW SPREADING N OF
THE COLD FRONT THAT WILL PASS THRU UPPER MI THU AFTN/EVENING. HAVE
INCLUDED MID RANGE CHC POPS LATE THU NIGHT/FRI MORNING OVER THE SE
FCST AREA. MEANWHILE...LES SHOULD PICK UP A BIT OFF LAKE SUPERIOR
FRI AS LAKE-850MB DELTA-T INCREASES TO 13-18C WITH DECENT MOISTURE
PROFILE FOR A TIME.
SAT THRU TUE...WILL BE A COLD PERIOD THAT COULD POTENTIALLY TURN
QUITE COLD. OTHER THAN THE COLD...MAIN FCST CHALLENGE IS THE
POSSIBILITY OF A WIDESPREAD SYNOPTIC SNOW OVER THE FCST AREA DURING
THE WEEKEND. 00Z/12Z RUNS IN GENERAL HAVE TRENDED TOWARD A BETTER
POTENTIAL FOR SNOW COMPARED TO YESTERDAY AS THERE ARE A FEW MODEL
RUNS INDICATING A SIGNIFICANT SNOW EVENT NOW. ON SAT...ATTENTION
WILL BE ON ENERGY OVER THE SW CONUS. AS SYSTEM LIFTS NE...ONE
COMPLICATION IS THE DEGREE OF INTERACTION WITH SHORTWAVE ENERGY
DROPPING S THRU CNTRL CANADA. 00Z UKMET HAS A LITTLE MORE
INTERACTION THAN THE OTHER MODELS AND ACTUALLY BRINGS A STRONG
NEGATIVE TILT SHORTWAVE INTO THE UPPER LAKES SUN WITH ASSOCIATED
984MB SFC LOW INTO NCNTRL WI BY 00Z MON. WOULD END UP BEING A MIXED
PCPN EVENT FOR A GOOD PART OF FCST AREA WITH HVY SNOW OVER THE FAR
W. GULF MOISTURE INFLOW WOULD BE EXCELLENT TO PROVIDE HVY PCPN. THIS
IS A HUGE CHANGE FROM PREVIOUS UKMET RUNS WHICH EITHER HELD ENERGY
BACK OVER THE SW OR BROUGHT A WEAK WAVE INTO THE OHIO VALLEY. 12Z
UKMET TRENDED WEAKER...BUT STILL HAS A DECENT SFC LOW TRACKING THRU
NRN LWR MI WHICH WOULD PROVIDE WIDESPREAD SIGNIFICANT SNOW TO FCST
AREA SUN. ECMWF HAS TRENDED STRONGER WITH SHORTWAVE AND FARTHER N
WITH SFC LOW (SRN PLAINS TO NW IL ACROSS NRN LWR MI)...BUT IT
MAINTAINS THE OVERALL POSITIVE TILT TROF ORIENTATION THAT HAS BEEN
THE CONSENSUS SOLUTION IN RECENT DAYS. STILL...00Z RUN OFFERS A
QUICK HITTING MDT/HVY SNOW EVENT FOR FCST AREA SAT NIGHT/SUN...
ESPECIALLY NW 2/3RDS. 12Z ECMWF IS NEARLY IDENTICAL TO 00Z. 00Z/06Z
GFS SOLUTIONS ARE SIMILAR TO THE BULK OF ITS RUNS THE LAST FEW
DAYS...WHICH IS TO BRING SFC LOW THRU SE LWR MI. THIS WOULD BRING
NRN EDGE OF SYNOPTIC SNOW INTO FCST AREA WITH LAKE ENHANCEMENT UNDER
N OR NE WINDS. GFS ENSEMBLES SHOW ONE MEMBER WITH SFC LOW TRACKING
INTO ERN UPPER MI...BUT REMAINDER OF MEMBERS ARE CLUSTRED CLOSE TO
00Z/06Z OPERATIONAL GFS TRACK WITH ONLY TIMING ISSUES. 12Z GFS HAS
SHIFTED LOW TRACK S A BIT. 00Z CANADIAN WAS MOST SUPPRESSED WITH SFC
LOW TRACK...BUT 12Z RUN NOW BRINGS A 995MB SFC LOW INTO SRN LWR MI
MON. OVERALL...MODEL RUNS SINCE 12Z/8JAN SUGGEST A BETTER POTENTIAL
OF GETTING SYNOPTIC SNOW INTO UPPER MI...SO WILL INCLUDE CHC POPS
ALL AREAS LATE SAT NIGHT/SUN. SYSTEM WILL OBVIOUSLY BE SOMETHING TO
WATCH OVER THE COMING DAYS AS THERE IS POTENTIAL FOR A SIGNIFICANT
SNOW. WILL MAKE A MENTION OF THIS POSSIBILITY IN HAZARDOUS WEATHER
OUTLOOK. IN THE WAKE OF THE SYSTEM...COLDER AIR WILL DUMP INTO THE
UPPER LAKES. 00Z GFS BROUGHT BACK THE IDEA OF 850MB TEMPS HEADING
TOWARD -30C LATE MON...BUT THAT IS STILL AN OUTLIER SOLUTION. WILL
MORE LIKELY SEE 850MB TEMPS OF -20 TO -25C...SO BLO NORMAL TEMPS
SHOULD BE THE RULE EARLY NEXT WEEK. OF COURSE...LES WILL CONTINUE
NEAR LAKE SUPERIOR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW AND BLSN ADVY UNTIL 4 AM WED MIZ006-007-085.
GALE WARNING LAKE SUPERIOR AND LSZ245>248.
&&
$$
AJ (SHORT TERM)
ROLFSON (LONG TERM)
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1138 AM EST TUE JAN 9 2007
.SYNOPSIS...
16Z WATER VAPOR LOOP AND 12Z RAOBS SHOWED UPPER TROUGHING COVERING
ALL OF THE GREAT LAKES WHILE RIDGING EXTENDING FROM THE NORTHERN
ROCKIES INTO ALBERTA AND SASKATCHEWAN. WITHIN THIS TROUGH...A 510
DAM UPPER LOW CAN BE SEEN MOVING ACROSS NORTHEAST ONTARIO. 850MB
TEMPS ARE FAIRLY COLD UNDER AND IMMEDIATELY WEST OF THE UPPER
LOW...AS NOTED BY THE -27C TEMP AT PICKLE LAKE ONTARIO (CWPL). EVEN
AWAY FROM THE UPPER LOW...INL AND MOOSONEE ONTARIO REPORTED AROUND
-18C. WITH 45 KT NW 850MB WINDS AT BOTH INL AND CWPL...THESE COLD
READINGS CONTINUE TO FLOW INTO THE CWA...RESULTING IN PLENTY OF LAKE
EFFECT SNOW SHOWERS. HOWEVER...THESE SNOW SHOWERS HAVE OVERALL BEEN
WEAK DUE TO A COMBINATION OF FACTORS. FIRST IS DRY AIR ADVECTION...
NOTED BY BELOW ZERO F DEWPOINTS ON THE NORTH SIDE OF LAKE SUPERIOR.
SECOND...INVERSION HEIGHTS AT MOST ARE AROUND 7000 FT BASED ON THE
12Z TAMDAR SOUNDING FROM SAWYER. THIRD...THE FLOW IS MAINLY
UNIDIRECTIONAL...CAUSING MULTI-PARALLEL BANDS WHICH NORMALLY DO NOT
PRODUCE MUCH SNOWFALL...ESPECIALLY BY THEMSELVES. ALTHOUGH THE SNOW
MAY NOT BE THAT STRONG...THE WINDS HAVE BEEN. MUCH OF THE WIND SPEED
OBSERVED ON THE SOUNDINGS UPSTREAM IS BEING MIXED DOWN TO THE LAKE
SUPERIOR SURFACE DUE TO THE COLD ADVECTION...AND GALE FORCE WINDS OR
WIND GUSTS HAVE BEEN REPORTED AT MANY SITES OVER THE EASTERN 2/3 OF
THE LAKE. AWAY FROM THE LAKE EFFECT SNOW IN THE SOUTH CENTRAL
U.P....SKIES HAVE BEEN MAINLY PARTLY CLOUDY...THANKS TO THE DRY AIR
ADVECTION. AS FAR AS THE SURFACE PRESSURE PATTERN GOES...A 1028MB
HIGH PRESSURE RIDGE WAS CENTERED OVER THE PLAINS WHILE 980S MB LOW
PRESSURE WAS OVER NE QUEBEC.
&&
.UPDATE...
THE UPPER RIDGE OVER THE NORTHERN ROCKIES WILL BE PUSHED EASTWARD TO
THE PLAINS BY THIS EVENING BY A TROUGH DIGGING DOWN THE WEST COAST
OF BRITISH COLUMBIA. THIS RIDGE IS PROGGED TO PUSH THE UPPER TROUGH
OVER THE GREAT LAKES...AND THE UPPER LOW OVER NE ONTARIO...EASTWARD.
THEREFORE UPPER MICHIGAN WILL NOT SEE THE COLD 850MB TEMPS OBSERVED
AT PICKLE LAKE...BUT READINGS AROUND -20C ARE EXPECTED OVER LAKE
SUPERIOR BY 22Z. THEREFORE MULTI-PARALLEL BAND LAKE EFFECT SNOW
SHOWERS WILL PERSIST. INVERSION HEIGHTS SHOULD RISE AS THE COLD AIR
ADVECTS IN...WHICH MAY CAUSE THE LAKE EFFECT TO INTENSIFY.
HOWEVER...SINCE THE COLD AIR IS ALSO BRINGING IN DRIER DEWPOINTS...
THE EFFECT OF THE INVERSION HEIGHT INCREASE MAY BE NEGATED. IN
ADDITION...WITH COLDER AND DRIER AIR MOVING IN OVER THE RELATIVELY
WARM WATER...CLOUD BASES MAY RISE ABOVE THE SNOW GROWTH LAYER...OR
THE SNOW GROWTH LAYER WILL BECOME VERY SMALL. ANOTHER PROBLEM THAT
HAS BEEN OCCURRING FOR SNOWFALL AMOUNTS THIS MORNING IS THE STRONG
WINDS WHICH ARE BOTH BREAKING PART THE SNOWFLAKES AND NOT ALLOWING
SNOW TO STAY IN ONE SPOT AND ACCUMULATE. FOR NOW HAVE DECIDED TO
CONTINUE THE GOING FORECAST...WITH AMOUNTS NEAR THE MINIMUM FOR
ADVISORY CRITERIA IN THE EASTERN U.P.. LESSER AMOUNTS ARE FORECAST
IN THE WESTERN U.P. DUE TO THE SHORTER FETCH FOR NW WINDS ACROSS
WESTERN LAKE SUPERIOR.
SINCE THE PRESSURE GRADIENT IS EXPECTED TO REMAIN TIGHT THROUGH THIS
AFTERNOON AND COLD AIR ADVECTION IS OCCURRING...WINDS SHOULD REMAIN
BLUSTERY OR EVEN INTENSIFY A BIT. BASED ON OBSERVATIONS FROM GRANITE
ISLAND AND GRAND MARAIS...HAVE EXPANDED THE GALE WARNING TO INCLUDE
A FEW MORE LAKE SUPERIOR NEARSHORE ZONES AND ALSO CHANGE OUR LAKE
EFFECT SNOW ADVISORY TO A LAKE EFFECT SNOW AND BLOWING SNOW
ADVISORY.
AS FAR AS TEMPERATURES GO...NOT MUCH RISE IS EXPECTED GIVEN THE COLD
AIR ADVECTION. THEREFORE HAVE LOWERED HIGHS A FEW DEGREES FROM THE
PREVIOUS FORECAST.
ZFP...WSW AND GRID UPDATES ALREADY OUT.
&&
.PREV DISCUSSION...
THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE SNOWFALL
POTENTIAL FOR TODAY AND TONIGHT.
WATER VAPOR IMAGERY AND RUC DEPICT A LONGWAVE TROUGH OVER EASTERN
CANADA AND A BROAD RIDGE OVER THE NORTHERN ROCKIES. WEAK SHORTWAVE
SLIDING DOWN THE LEE OF THE ROCKIES RIDGE IS OVER SOUTHERN U.P. A
DEEPER SHORTWAVE IS OVER THE EASTERN DAKOTAS STRETCHING INTO
MISSOURI. THIS IS FOLLOWED BY ANOTHER SHORTWAVE OVER SOUTHERN
SASKATCHEWAN. SURFACE ANALYSIS DEPICTS A RIDGE OVER WESTERN DAKOTAS
RUNNING NORTH THROUGH SASKATCHEWAN AND A DEEP LOW OVER EASTERN
QUEBEC. A SURFACE LOW IS MOVING ASHORE OVER SOUTHERN BRITISH
COLUMBIA...WITH A WARM FRONT STRETCHING SOUTH FROM IT THROUGH
CENTRAL MONTANA. STRONG WINDS AND LIGHT SNOW IS ACCOMPANYING THE
SHORTWAVE OVER THE DAKOTAS OTHERWISE LITTLE PRECIPITATION IS
OCCURRING. 850MB TEMPERATURE ANALYSIS SHOW A POCKET OF COLD AIR OVER
WESTERN ONTARIO...WHERE THE TEMPERATURES DROP TO -24C. THIS IS
PRODUCING A DELTA-T OVER NORTHERN LAKE SUPERIOR OF AROUND 21C.
SOUNDINGS CONTINUE TO SHOW DRY BELOW 900MB. THE LOWEST INVERSION IS
AROUND 3K FEET WHICH APPEARS TO BE HAMPERING LES SNOW GROWTH.
A WEAK MID LEVEL LOW ROTATING THROUGH THE BASE OF THE LONGWAVE
TROUGH WILL MOVE FROM NORTHEAST MANITOBA THROUGH NORTHERN ONTARIO
INTO SOUTHERN JAMES BAY TODAY. A WEAK SHORTWAVE ROTATING AROUND THE
JAMES BAY LOW WILL SWEEP THROUGH EASTERN LAKE SUPERIOR INTO EASTERN
U.P...WHILE THE DAKOTA SHORTWAVE SLIDES INTO EXTREME WESTERN LAKE
SUPERIOR AND EASTERN WISCONSIN. THE SURFACE RIDGE WILL SLIDE INTO
MINNESOTA AND WESTERN ONTARIO. A SURFACE LOW WILL BE OVER SOUTHERN
BRITISH COLUMBIA MOVING INTO WESTERN ALBERTA. THE COLD POOL OF
AIR WILL SLIP INTO EAST CENTRAL ONTARIO AND SPILL OVER INTO EASTERN
LAKE SUPERIOR CAUSING A LAKE-850MB DELTA-T OF 24C. THE INVERSION
WILL LIFT TODAY REACHING 5K FEET OVER WESTERN LAKE SUPERIOR AND TO
AROUND 7K FEET OVER EAST. SOUNDING FORECAST DEPICTS A SATURATED
LAYER BETWEEN 900MB AND 850MB OVER MOST OF THE FORECAST AREA.
CONDITIONS ARE EXPECTED TO BE A LITTLE DRIER BELOW 900MB. SURFACE
TEMPERATURES REMAIN IN THE SINGLE DIGITS OVER WESTERN ONTARIO...AND
-4C TO -9C OVER NORTHERN MANITOBA. TRAJECTORY PROGS INDICATE THAT
THE ONTARIO AIR MASS WILL SLIDE OVER THE FORECAST AREA. THUS...THE
INSTABILITY WILL LIKELY PRODUCE SNOW AND SNOW SHOWERS...HOWEVER...
THE AMOUNT OF SNOWFALL SHOULD BE FAIRLY LIMITED. SURFACE WINDS WILL
REMAIN STRONG (25 TO 35 KTS) OVER LAKE SUPERIOR. THIS WILL ALSO
SHORTEN THE EFFECTIVE FETCH ACROSS THE LAKE. THUS EXPECT SNOWFALL
AMOUNTS TO BE ON THE ORDER TO 2 TO 4 INCHES ACROSS THE KEWEENAW
PENINSULA AND OVER THE SNOW PRONE AREAS OF EASTERN U.P.
MODELS CONTINUE TO BE IN VERY GOOD AGREEMENT. THE ONTARIO SHORTWAVE
WILL SWING INTO SOUTHWEST QUEBEC DRAWING THE WEAK SHORTWAVE QUICKLY
ACROSS THE FORECAST AREA TONIGHT. Q-VECTORS SUGGEST MOSTLY
DIVERGENCE ACROSS THE AREA BY LATE TONIGHT. THE MID LEVEL RIDGE WILL
SHIFT INTO MANITOBA. THE SOUNDING FORECAST SHOW THE INVERSION WILL
LOWER OVERNIGHT TO 2.5K FEET OVER THE WEST TO 4.5K FEET OVER THE
EAST. WHERE LES SHOULD CONTINUE. MEANWHILE...THE SURFACE RIDGE WILL
MOVE OVER THE FORECAST AREA WEAKENING THE GRADIENT WINDS. THUS THE
WINDS SHOULD DIE DOWN INCREASING THE FETCH LENGTH OVER THE EASTERN
PART OF THE LAKE. THIS SEEMS TO FAVOR A BETTER POTENTIAL SNOWFALL
OVER THE EASTERN COUNTIES.
THE MID LEVEL RIDGE WILL SLIDE OVER THE UPPER GREAT LAKES WHILE A
MID LEVEL LOW MOVES INTO SOUTHWEST MANITOBA ON WEDNESDAY. THE
SURFACE LOW WILL ALSO MOVE INTO SOUTHWEST MANITOBA DRAGGING A COLD
FRONT INTO THE DAKOTAS. THE SURFACE RIDGE WOULD DEVELOP OVER EASTERN
U.S. SLOWING THE PROGRESSION OF THE MANITOBA LOW AND MAY EVEN DIVERT
IT A LITTLE NORTHEAST. 850MB THERMAL TROUGH WILL BEGIN TO MOVE EAST.
THE DELTA-T`S WILL LOWER TO AROUND 15C AS WARM AIR ADVECTS IN FROM
THE SOUTHWEST IN THE FLOW AROUND THE LOW OVER MANITOBA. 290K
ISENTROPIC ANALYSIS SUGGEST FAIRLY SIGNIFICANT LOW LEVEL ASCENT
ACROSS THE FORECAST AREA AHEAD OF THE NEXT SYSTEM. DEEP MOISTURE IS
DEPICTED TO PASS OVER NORTHERN ONTARIO. THE AVAILABLE MOISTURE...
ISENTROPIC ASCENT AND LOW LEVEL ADIABATIC LIFT ASSOCIATED WITH THE
COOL 850MB TEMPERATURES APPEARS TO GIVE A CHANCE OF DEVELOPING SOME
SNOW ACROSS THE AREA. THE LACK OF INSTABILITY IN THE MID LEVELS...
AND THE SHORT TIME PERIOD OF DEEP MOISTURE SWEEPING THROUGH THE AREA
WILL SET THE PACE FOR THE AMOUNT OF LAKE EFFECT SNOWS.
THE MID LEVEL SHORTWAVE OVER WISCONSIN WILL RACE ACROSS THE FORECAST
AREA WEDNESDAY NIGHT. THE SURFACE LOW WILL SPEED INTO THE CWQT AREA
DRAGGING A COLD FRONT INTO WESTERN U.P. MODELS SUPPORT HAVE
SIGNIFICANT AMOUNT OF LOW LEVEL MOISTURE OVER THE FORECAST AREA.
ISENTROPIC ASCENT AHEAD OF THE FRONTAL BOUNDARY WILL ADD THE LIFT TO
DEVELOP SNOWS ACROSS THE AREA.
THE SHORTWAVE WILL SAIL ACROSS CENTRAL ONTARIO...AND REMAIN NORTH OF
THE FORECAST AREA ON THURSDAY. A COLD FRONT WILL SWEEP THROUGH THE
FORECAST AREA. DELTA-T`S OVER LAKE SUPERIOR WILL BE AROUND 16C. COLD
AIR WILL BE ADVECTING INTO THE AREA WITH AN 850MB THERMAL TROUGH OF
AROUND -22C MOVING INTO MANITOBA AND NORTH DAKOTA. LAKE EFFECT SNOW
STILL SHOULD HANG IN THERE. DRY AIR MOVING INTO THE AREA WILL BE THE
LIMITING FACTOR AGAIN. THERE WILL BE ONLY A NARROW LAYER OF MOISTURE
BETWEEN 850MB AND 900MB. ANY SNOW FALL SHOULD BE LIGHT.
A WEAK SHORTWAVE WILL SWEEP INTO THE SOUTHERN PART OF THE FORECAST
AREA ON THURSDAY NIGHT...OTHERWISE...THE SHORTWAVES WILL STAY IN THE
FLOW OVER CENTRAL ONTARIO. THE COLD FRONT WILL EXIT THE EASTERN U.P.
ALLOWING COLD AIR TO ADVECT INTO THE REGION. A POOL OF COLD AIR WILL
SETTLE OVER SOUTHERN MANITOBA AND WESTERN ONTARIO. A DELTA-T OF 22C
WILL OCCUR OVER ALONG THE NORTHWEST SHORE OF LAKE SUPERIOR. A
LARGE DOME OF HIGH PRESSURE WILL EXPAND OVER THE NORTHERN PLAINS AND
SOUTH CENTRAL CANADA. THE ANTI-CYCLONIC FLOW WILL PRODUCE A NORTH
WIND ACROSS THE AREA. THIS WILL PRODUCE SOME LAKE EFFECT SNOW
SHOWERS ACROSS THE NORTHERN U.P. THE DRY AIR BEHIND THE FRONT WILL
LIMIT THE AMOUNT OF SNOWFALL.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW AND BLOWING SNOW ADVISORY UNTIL 4 AM WED
MIZ006-007-085.
GALE WARNING LAKE SUPERIOR AND LSZ245>248.
&&
$$
AJ (UPDATE)
DLG (PREV DISCUSSION)
AREA FORECAST DISCUSSION...UPDATED
NWS BUFFALO NY
AFDBUF 920 PM EST WED JAN 10 2007
.UPDATE...
TIME TO CHANGE GEARS ACROSS THE FORECAST AREA AS MESOSCALE LAKE
EFFECT IS IN THE PROCESS OF GIVING WAY TO SYNOPTIC SCALE WARM AIR
ADVECTION. FIRST...LETS ADDRESS THE DYING LAKE EFFECT ACTIVITY.
THE FLURRIES AND VERY LIGHT SNOW SHOWERS HAVE BASICALLY ENDED
ACROSS THE WESTERN COUNTIES. WHILE THE 00Z KBUF SOUNDING INDICATED
H85 TEMPS OF -14C OVER LAKE ERIE...A 01Z AIRCRAFT SOUNDING AT KCLE
DEPICTED AN H85 TEMP OF ONLY -8C. THIS VERIFIES WHAT THE GUIDANCE
HAS BEEN ADVERTISING...STRONG WARM AIR ADVECTION. THE CAP OVER LK
ERIE WAS ARND 5K FT BUT WILL DROP TO ABOUT 2.5K FT BY DAYBREAK.
OFF LK ONTARIO...H8 TEMPS OF -14 TO -15C (AS PER ROC AND SYR
AIRCRAFT SOUNDINGS) AT 00Z WILL BE SLOWER TO GIVE WAY TO THE WARM
AIR ADVECTION. THE CAP ON THE EAST END OF THE LAKE IS UP AROUND 7K
FT...SO THIS HAS ALLOWED FOR NUMEROUS LAKE SNOW SHOWERS TO PERSIST
FROM WAYNE COUNTY TO SOUTHERN SECTIONS OF OSWEGO COUNTY. THE
LIKELY POPS FOR THIS AREA WILL DROP OFF TO CHC THEN EVENTUALLY TO
SLGT CHC POPS BY DAYBREAK.
THE WARM ADVECTION CAN BE SEEN ON THE IR LOOP AS WELL. PLENTY OF
MID LEVEL MOISTURE (ALTO-CU) IS SHOWN OVER LOWER MICHIGAN AS OF
02Z AND THIS CLOUD COVER WILL GRADUALLY SPREAD ACROSS OUR FORECAST
AREA DURING THE WEE HOURS OF THE MORNING. THE 00Z KBUF SOUNDING
ALSO SHOWED IMPRESSIVE WARM AIR ADVECTION UNDERWAY ABOVE 800MB.
CONTINUITY GENERALLY LOOKS GOOD...BUT WILL TWEAK THE TIMING AND
POPS THROUGH 15Z FOR COUNTIES SOUTHEAST OF LK ONTARIO TO BETTER
DEFINE THE ENDING OF THE LAKE EFFECT -SHSN.
RSH
&&
.PREV DISCUSSION...
/ISSUED 627 PM EST WED JAN 10 2007/
UPDATE...
HAVE UPDATED GRIDS...ZONES AND ALPHA NUMERICS TO REFLECT GREATER
AREAL COVERAGE SOUTHEAST OF LAKE ONTARIO. POPS RAISED TO LIKELY
FOR OSWEGO COUNTY. REMAINDER OF CONTINUITY LEFT INTACT FOR NOW.
RSH
PREV DISCUSSION...
/ISSUED 416 PM EST WED JAN 10 2007/
SHORT TERM /TODAY THROUGH SATURDAY/...
LINGERING LK ACTIVITY EAST OF LAKE ERIE SHLD END BY THIS EVENING
WITH LAKE EFFECT LINGERING SE OF LAKE ONTARIO THROUGH MUCH OF THE
NIGHT BUT IN A WEAKENED STATE SO WILL DROP ALL WARNINGS AND
ADVISORIES. INVERSION CRASHES OFF LAKE ERIE AND DROPS TOWARD
MORNING SE OF LAKE ONTARIO AS RIDGE BUILDS INTO THE AREA.
STRONG WAA ON BACK SIDE OF DEPARTING RIDGE THURSDAY WILL HELP
WARM TEMPERATURES ABOVE NORMAL. SOME MID TO UPPER CLOUDS
ASSOCIATED WITH THE WAA WILL MOVE NE THURSDAY MORNING WITH SKIES
BECOMING PTLY TO MOSTLY SUNNY. TEMPS RISE TO WELL ABV NORMAL LVLS
AGAIN THUSDAY...INTO THE 40S MANY AREAS.
THURSDAY NIGHT, MOISTURE INCREASES LATE AHEAD OF COLD FRNT OVER THE
CENTRAL LKS. MOST AREAS SHLD SEE RAIN SHOWERS BUT MIXED PRECIP
POSSIBLE NORTH COUNTRY AND INTERIOR OF SOUTHERN TIER.
FRIDAY, A SW FLOW OF MILD, MOIST AIR WILL BE OVER THE REGION AHEAD
OF COLD FRONT OVER THE CENTRAL LAKES. WILL GO WITH CHANCE OF SHOWERS
FRIDAY WITH A MIX POSSIBLE OVER THE HIGHER TERRAIN OF THE NORTH
COUNTRY. WILL INCREASE POPS TO LKLY BY AFTERNOON WEST OF THE GENSEEE
VALLEY AS MOISTURE AND LIFT INCREASES OVER THE AREA SPREADING NE
FROM THE OHIO VALLEY. FRIDAY NIGHT A WAVE OF LOW PRESSURE MOVING NE
ALNG THE COLD FRONT WILL CONTUE TO SPREWADE MOISTURE OVER THE AREA.
WILL GO WITH LKLY POPS FOR SHOWERS WITH A MIX POSSIBLE LATE LK
ONTARIO NORTHWARD. ON SATURDAY THE FRONT DROPS SOUTH OF THE AREA
WITH HIGH PRESSURE OVER QUEBEC SPREADING DRIER AIR SOUTHWARD DURING
THE AFTERNOON. WILL GO CHANCE SHWR IN THE MRNG GENERALLY SOUTH OF
LAKE ONTARIO WITH THE CHANCE POPS LINGERING INTO THE AFTERNOON ALONG
THE STATE LINE.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
BY SATURDAY NIGHT AN UPPER LEVEL TROUGH WILL BE IN THE WEST...POISED
TO KICK EASTWARD AND BRING MORE ACTIVE WEATHER TO NEW YORK FOR EARLY
NEXT WEEK. MORE ON THAT IN A BIT...
CLOSER TO THE SURFACE...THE COLD FRONT THAT WILL HAVE MOVED THROUGH
ON SATURDAY WILL STALL TO OUR SOUTH OVER OR JUST SOUTH OF PA BY
SUNDAY MORNING. THIS BAROCLINIC BOUNDARY WILL BE THE SOURCE OF A
LOW CONFIDENCE FORECAST FROM SATURDAY NIGHT THROUGH MONDAY IN TERMS
OF PRECIPITATION...PRECIPITATION TYPE...AND TEMPERATURES.
WITH THAT UNCERTAINTY IN MIND...EXPECT SEVERAL SURFACE LOWS TO
DEVELOP ALONG THIS BOUNDARY...WHICH SHOULD INITIALLY EXTEND FROM PA
SOUTHEASTWARD TO TX. THE FIRST SHOULD SPREAD PRECIPITATION
NORTHWARD ON SUNDAY...AFFECTING A GOOD PORTION OF PA AND PROBABLY
INTO NY AS WELL. WILL LEAN TOWARD A WETTER SCENARIO AND BRING A MIX
OF PRECIPITATION INTO THE AREA. SOUNDINGS SHOW A WARM LAYER
EXTENDING FROM 800MB TO THE SURFACE ALONG THE PA BORDER...WARM
ENOUGH FOR ALL RAIN...AND A TEMPERATURE PROFILE BELOW FREEZING
THROUGHOUT THE COLUMN UP NORTH TOWARD WATERTOWN. SO IN
BETWEEN...FROM NORTH OF THE SOUTHERN TIER INTO LAKE ONTARIO...A WEAK
WARM LAYER ALOFT OR POSSIBLY ISOTHERMAL LAYER NEAR 0C INDICATES THE
POSSIBILITY OF A MIX OF PRECIPITATION FOR SUNDAY. FOR A MAJOR ICE
EVENT...WE WOULD NEED A LARGE HIGH BUILDING NEAR MONTREAL TO FEED
COLD AIR INTO WESTERN NY...AND WE DO NOT GET THAT UNTIL SUNDAY
NIGHT. THE 5C LAKE ONTARIO WATERS WITH A NORTHEAST FLOW MAY ALSO
MINIMIZE THE THREAT FOR FREEZING PRECIPITATION...AT LEAST FOR THE
LOWER ELEVATION AREAS ALONG LAKE ONTARIO FROM ABOUT I-90 NORTH. SO
AT LEAST FOR SUNDAY...THE POTENTIAL MIX OF PRECIPITATION SHOULD NOT
AMOUNT TO MUCH IN TERMS OF HAZARDOUS WEATHER.
A BIGGER CONCERN COMES SUNDAY NIGHT WHEN A RIDGE DOES BUILD TOWARD
MONTREAL AND A SECOND SURFACE WAVE RIDES UP THE BAROCLINIC BOUNDARY
INTO THE OHIO VALLEY. WITH THIS FEATURE...WE GET A SURGE OF WARM
AIR ALOFT WHILE THE LOWEST LAYERS OF THE ATMOSPHERE REMAIN AT OR
BELOW FREEZING...INCREASING THE CHANCES OF A FREEZING RAIN EVENT.
ON MONDAY...THE WARM AIR WORKS ITS WAY TO THE SURFACE FOR MOST OF
WESTERN NY...AND THE THREAT OF FREEZING RAIN QUICKLY BECOMES LIMITED
TO THE NORTH COUNTRY. THE OHIO VALLEY SURFACE LOW BECOMES THE
DOMINANT FEATURE AND DEEPENS AS IT HEADS ACROSS WESTERN NY DURING
THE AFTERNOON WHILE THE UPPER LEVEL LOW THAT WAS OVER THE
INTERMOUNTAIN WEST OVER THE WEEKEND STRENGTHENS AND HEADS
NORTHEAST.
THIS SETS UP A SHORT-LIVED STRONG WIND SCENARIO WITH A VERY STRONG
COLD FRONT CROSSING THE AREA DURING THE AFTERNOON. TEMPS COOL
DRAMATICALLY AT 850MB...FROM +5C AT 18Z MONDAY TO A CHILLY -19C BY
06Z TUESDAY. WINDS ALOFT NEAR 50KTS WOULD MIX DOWN TO THE SURFACE
WITH THE PASSAGE OF THE COLD FRONT...AT LEAST FOR A FEW HOURS.
MONDAY NIGHT...DESPITE THE 25C DIFFERENCE BETWEEN THE LAKE
TEMPERATURE AND 850MB...THIS PATTERN DOES NOT LOOK CONDUCIVE TO LAKE
EFFECT...AT LEAST INITIALLY...AS THE MOISTURE IS SCOURED AWAY
QUICKLY BEHIND THE DEPARTING LOW. INSTABILITY AND MORE MOISTURE MAY
BECOME AVAILABLE LATER TUESDAY AND/OR WEDNESDAY WHEN A SHORTWAVE
DROPS DOWN ACROSS THE NORTHERN GREAT LAKES REGION AND CROSSES
WESTERN NY BY WEDNESDAY MORNING. SO LAKE EFFECT WILL LIKELY
RETURN...BUT LIKE OUR DEC 1 WIND EVENT AND SUBSEQUENT LAKE
EFFECT...WE MAY HAVE TO WAIT 24-36 HOURS AFTER THE STRONG COLD FRONT
TO GET SIGNIFICANT SNOW.
AVIATION /21Z-18Z/...
LAKE EFFECT SHOWERS ARE DIMINISHING RAPIDLY AS A SURFACE RIDGE
BUILDS INTO THE REGION. THROUGH 00Z THERE IS THE POSSIBILITY OF
SOME LOCATIONS SOUTHEAST OF THE LAKES DROPPING BRIEFLY TO IFR...BUT
THE VAST MAJORITY OF WESTERN NEW YORK WILL QUICKLY IMPROVE AS THE
EVENING PROGRESSES. THE RIDGE AXIS WILL MOVE ACROSS WESTERN NY BY
THURSDAY MORNING. THE NEXT CONCERN WILL BE STRONG WINDS ALOFT THAT
WILL DEVELOP NEAR OR AFTER 18Z...WITH POSSIBLE WIND SHEAR AS A
SOUTHWESTERLY 45KT LOW LEVEL JET MOVES ACROSS THE STATE THURSDAY
AFTERNOON AND EVENING.
MARINE...
NORTHWEST WINDS WILL WEAKEN OVERNIGHT AS A RIDGE BEGINS TO BUILD
INTO THE EASTERN GREAT LAKES. THE RIDGING WILL BRING WINDS BACK TO
SOUTHWEST TO SOUTH ON THURSDAY AND FRIDAY.
SMALL CRAFT ADVISORIES WILL REMAIN IN EFFECT THROUGH THIS EVENING OR
OVERNIGHT TO ACCOUNT FOR WAVE HEIGHTS.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LEZ040-
041.
SMALL CRAFT ADVISORY UNTIL 1 AM EST THURSDAY FOR
LOZ042>045.
&&
$$
UPDATE...RSH
SHORT TERM...JJP
LONG TERM...ZAFF
AVIATION...ZAFF
MARINE...ZAFF
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
AFDGRB 445 AM CST TUE JAN 9 2007
.SHORT TERM...TODAY THROUGH WEDNESDAY...FORECAST CONCERNS THIS PERIOD
WINDS AND LAKE EFFECT OVER FAR NORTH CENTRAL.
UPPER FEATURES OF INTEREST THIS PERIOD...CLIPPER SYSTEM MOVING SOUTHEAST
THROUGH THE LAKES TODAY AND UPPER RIDGE SHIFTING EAST INTO THE PLAINS.
NORTHWEST FLOW WILL GIVE WAY TO MORE OF A ZONAL PATTERN ON WED. BRIEF
COOL DOWN TODAY...WITH TEMPERATURES RETURNING TO WELL ABOVE NORMAL ON
WED.
TODAYS FORECAST MORE INLINE WITH CURRENT SATELLITE TRENDS WITH LESS
CLOUDINESS EXPECTED. AREA OF LOW CLOUDS AND FLURRIES MOVING THROUGH
NORTHERN MN ATTM AHEAD OF SHORT WAVE MOVING SOUTHEAST OUT OF THE
DAKOTAS. GIVEN DRY TAMDAR SOUNDINGS FROM LAST EVENING...EXPECT TO SEE A
CONTINUED DIMINISHING TREND AS IT MOVES INTO WI...THOUGH MAY ALLOW FOR
SOME MOISTENING TO ENHANCE LAKE SHOWER ACTIVITY OVER LAKE SUPERIOR...
WHICH AT THIS TIME HAS NOT AMOUNTED TO MUCH. LAKE INDUCED TROUGH OVER
LAKE KEEPING WINDS TOO WESTERLY...WITH SAXON HARBOR OFFSHORE AT THIS
TIME. OVERALL...HAVE BACKED DOWN FROM PREVIOUS FORECAST WITH WINDS
NEVER BECOMING VERY FAVORABLE FOR SHOWERS TO REACH INTO VILAS COUNTY.
LOOK FOR A RATHER COLD AND BLUSTERY DAY TODAY UNDER CAA REGIME. STRONG
NW GRADIENT EXPECTED THIS MORNING AS SURFACE HIGH SHIFTS EAST. PROFILERS
SUPPORT GFS WINDS WITH 925MB WINDS AROUND 30 KTS THIS MORNING. HAVE
STAYED AT SCA LEVELS FOR LAKE FORECASTS.
REGARDING TEMPERATURES...HAVE STAYED CLOSED TO GFS.
.LONG TERM...WED NGT THRU NXT MON. MAIN FCST CHALLENGE CONTS TO BE SNOW
TRENDS THU NGT/FRI AND AGAIN SUNDAY NGT/MON BEFORE A RETURN TO TRUE
WINTER TEMPS ARRIVE EARLY NXT WEEK.
THE PRES GRAD TO REMAIN TIGHT OVR THE GREAT LKS WED NGT BETWEEN THE HI
PRES LOCATED OVR THE MID-ATLANTIC STATES AND LOW PRES OVR THE UPR
MIDWEST. THE GFS APRS TOO FAST BRINGING THE CDFNT INTO WI CONSIDERING
THE STIFF SW WNDS ALOFT AHD OF IT. PCPN CHCS APR TO REMAIN TO OUR NORTH
WHERE BETTER FORCING AND LIFT TO RESIDE...WHILE DRY MID LVL ATM REMAINS
OVR NE WI. DO NOT EXPECT TEMPS TO FALL VERY MUCH WED NGT DUE TO THE
STRENGTH OF THE WNDS AND WAA THRU THE NGT. A SFC LOW MOVG ACROSS ONTARIO
WL DRAG THE CDFNT ACROSS MOST OF WI ON THU. PBLM REMAINS DEPTH OF MSTR
INVOLVED AS BETTER GULF MSTR TO ONLY BE REACHING THE MIDWEST WHILE
BETTER FORCING CONTS TO PASS BY TO OUR NORTH. NOT OVERLY IMPRESSED WITH
THIS WHOLE SYSTEM AND PREFER TO LWR POPS TO ONLY SLGT CATEGORY WITH MOST
OF NE WI LUCKY TO SEE MORE THAN A TRACE OF PCPN. TEMPS SEEM TO WARM UP
ENUF OVR E-CNTRL WI TO HAVE ANY PCPN FALL AS A RAIN/SNOW MIX AND THIS
ALREADY COVERED BY PREV FCST.
AS AN UPR TROF CONTS TO DIG ACROSS THE WRN U.S. THU NGT...THE MEAN FLOW
EAST OF THE CONTINENTAL DIVIDE WL BECOME MORE SW. AS THE CDFNT TRIES TO
PUSH EWD...IT WL BECOME PARALLEL WITH THIS MEAN FLOW AND SLOW DOWN. THE
COLDER AIR OVERSPREADING WI THU NGT IS EXPECTED TO TIGHTEN THE
BAROCLINIC ZN OVR THE RGN AND WITH THE POTENTIAL OF A SFC WAVE TO MOV NE
ALONG THE CDFNT...A CHC OF LGT SNOW IS PSBL ESP OVR E-CNTRL WI. NEED TO
ALSO WATCH NRN WI FOR POTENTIAL LK EFFECT SNOW SHWRS AS 8H TEMPS DROP TO
AROUND -15C OVR WRN LK SUPERIOR. IF TRAJS BECOME FAVORABLE...THERE WOULD
BE SOME ACCUMULATING SNOW IN THE FAVORED SNOWBELT RGNS OF NRN WI.
SYNOPTIC SITN OF TIGHT BAROCLINIC ZN/SFC WAVE MOVG UP THE CDFNT CARRIES
OVR INTO FRI MORNING...THUS CHC POPS NEED GENERALLY ACROSS THE SE HALF
OF THE FCST AREA. ACCUMULATIONS APR TO BE MINOR AT THIS POINT AS TSTMS
OVR THE OHIO RIVER VALLEY INTERCEPT GULF MSTR RETURN. NORTHERLY WNDS AND
COLD 8H TEMPS WOULD KEEP A CONTINUED THREAT OF LK EFFECT SNOW SHWRS FOR
NRN WI THRU FRI. AS CANADIAN HI PRES PUSHES INTO THE NRN PLAINS FRI
AFTERNOON...OLD CDFNT SHOULD MOV FAR ENUF EAST SUCH THAT SNOW OVR E-
CNTRL WI WL BE DIMINISHING.
THE HI PRES BUILDS TOWARD THE WRN GREAT LKS FRI NGT SENDING DRIER AIR
INTO WI. TRAJS WOULD TURN NE WHICH IS NOT A GOOD DIR FOR LK EFFECT OVR
NRN WI...THUS CANNOT SEE MORE THAN FLURRIES FOR VILAS CNTY. AS FOR THE
REST OF NE WI...NOT CONVINCED ABT SNOW CHCS DESPITE A SOMEWHAT TIGHT
BAROCLINIC ZN OVR WI. WHILE SOME FLURRIES ARE PSBL...PREFER TO TRY AND
FIND A DRY PERIOD DURING THIS ACTIVE PERIOD. ENUF DRY AIR ON EASTERLY
WNDS SHOULD PRECLUDE ANY PCPN GOING INTO SAT EVEN THO CLDS TO BE ON THE
INCREASE AS THE UPR TROF MAKES AN EWD MOV INTO THE CNTRL U.S.
STILL APRS THAT THIS UPR TROF WL MAKE A MOV TOWARD THE WRN GREAT LKS BY
SUNDAY AS A 130+ KT UPR JET ROUNDS THE BASE OF THE TROF. ANTICIPATE A
SFC LOW TO DVLP OVR THE SRN PLAINS SAT NGT AND RACE NE INTO THE ERN
GREAT LKS ON SUNDAY. THIS TRACK WOULD GENERALLY KEEP HEAVIER PCPN TO OUR
SOUTH AND EAST...BUT ACCUMULATING SNOW ON THE ORDER OF 2 TO 4 INCHES ARE
PSBL BY 00Z MON ESP OVR E-CNTRL WI. PCPN TO DIMINISH SUNDAY NGT AS THE
SFC LOW HEADS TOWARD THE CANADIAN MARITIMES AND INITIAL UPR TROF ROTATES
EWD. MAIN STORY BY EARLY NXT WEEK TO BE THE INFLUX OF MUCH COLDER AIR
INTO THE RGN. WL HAVE TO WATCH FOR ANOTHER ROUND OF LK EFFECT SNOWS FOR
NRN WI AS 8H TEMPS PLUNGE TO AT LEAST -20C.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
TE/KALLAS
WEATHER.GOV/GREENBAY