AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 230 PM PST SUN FEB 4 2007
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT AND WEAK OFFSHORE FLOW WILL
CONTINUE MOSTLY CLEAR SKIES THROUGH MONDAY WITH NEAR RECORD HIGH
TEMPERATURES. LOCAL GUSTY WINDS THROUGH AND BELOW MOUNTAIN CANYONS
AND PASSES AT TIMES THROUGH MONDAY. HIGH PRESSURE WILL WEAKEN WITH
COOLER WEATHER AND INCREASING CLOUDS WEDNESDAY THROUGH FRIDAY. UPPER
LEVEL LOW PRESSURE WILL BRING A CHANCE OF SHOWERS NEXT WEEKEND.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY-WED)...CLEAR TODAY EXCEPT FOR A FEW CI. ACARS
SOUNDINGS HAD WEAK E-NE WINDS IN THE LOW LEVELS AND MODERATELY
STRONG NW WINDS ALOFT. OFFSHORE GRADIENTS WITH ABOUT -8 MB SAN-TPH.
A HIGH AMPLITUDE RIDGE OF HIGH PRESSURE ALOFT WILL SLOWLY SHIFT E
AND WEAK OFFSHORE FLOW WILL CONTINUE THROUGH MON. THIS WILL BRING
MOSTLY CLEAR SKIES WITH JUST A FEW HIGH CLOUDS AT TIMES AND ANOTHER
WARM DAY MON. THERE COULD BE SOME NEAR RECORD MAX TEMPS MON WITH
SOME WARMER INLAND VALLEY LOCATIONS GETTING CLOSE TO 90 DEGREES. THE
OFFSHORE GRADIENTS WILL CAUSE LOCAL GUSTY WINDS THROUGH AND BELOW
MOUNTAIN CANYONS AND PASSES AT TIMES THROUGH MON...BUT MOST WINDS
WILL REMAIN BELOW ADVISORY STRENGTH. THE WARM DRY OFFSHORE FLOW WILL
INCREASE THE FIRE WEATHER HAZARD. THE HIGH ALOFT WILL WEAKEN AND
SHIFT FARTHER E TUE AND WEAK ONSHORE FLOW WILL RETURN FOR A LITTLE
COOLING. A WEAK UPPER TROUGH WILL APPROACH FROM THE W WED WHICH WILL
FURTHER DECREASE LOCAL HEIGHTS AND INCREASE THE ONSHORE GRADIENTS.
THIS WILL BRING MORE COOLING WED WITH INCREASING HIGH CLOUDINESS IN
SW WINDS ALOFT. PATCHY MARINE LAYER CLOUDS AND FOG COULD RETURN TUE
NIGHT AND WED MORNING.
&&
.LONG TERM (THU-SUN)...STRONG LOWER LATITUDE FLOW WILL PREVAIL
ACROSS THE PAC AND THIS WILL MAKE THE TIMING OF SHORT WAVES
DIFFICULT. IT CURRENTLY LOOKS LIKE THE TROUGH MOVING THROUGH THU AND
FRI WILL BE TOO WEAK TO BRING ANY PRECIP TO OUR AREA.
HOWEVER...THERE WILL BE MORE CLOUDS AND COOLING. PREVIOUS MODEL RUNS
HAD A STRONGER TROUGH OF LOW PRESSURE COULD BRING PRECIP NEXT
WEEKEND BUT THE LATEST GFS RUN SHOW WEAK RIDING. WILL KEEP SLIGHT
CHANCES OF PRECIP IN THE FORECAST FOR NOW.
&&
.AVIATION...
OFFSHORE FLOW WILL CONTINUE THROUGH MONDAY BRINGING VFR CONDITIONS
WITH A MOSTLY CLEAR SKY AND UNRESTRICTED VISIBILITIES.
LOCAL GUSTY NORTHEAST WINDS THROUGH AND BELOW MOUNTAIN PASSES AND
CANYONS WITH ASSOCIATED UP AND DOWN DRAFTS AND LOW LEVEL WIND SHEAR
THROUGH MONDAY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...DVA
AVIATION...HORTON
AREA FORECAST DISCUSSION...UPDATED
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 939 AM EST SUN FEB 4 2007
.SHORT TERM /REST OF TODAY/...
S/WV EVIDENT IN OBS/STLT ENTERING SRN WVA. PCPN /SNW/ AHD OF IT
APPCHG SRWN ZNS. DOUBT MUCH OF THE PCPN WL SURVIVE CROSSING THE
APPLCHNS...BUT THE MID/UPR MSTR /AKA CLDS/ WL. CUD SEE UP TO AN
INCH IN FAR WRN HIGHLAND/PNDLTN CNTYS TDA. LTL/NONE ELSW. SHARP
DEMARKATION ON VSBL SATPIX WL CROSS CWFA...SO SRN CNTYS SHUD BE
MOCLDY WHILE NRN CNTYS MOSUN. WL ATTEMPT TO CREATE GRIDS/ZONES TO
ADEQUATELY REFLECT THAT THINKING.
WNDS RATHER BENIGN ATTM. GUSTS SHUD RTN ON BACK SIDE OF VORT.
HWVR...TEMPS WL BE WARM ENUF BY THEN SO CRIT WONT BE MET ANYWHERE
TIL TNGT. WSW FOR CHILLS NEEDS TO BE REISSUED THIS MRNG ANYWAY. IT
WIBIS W/ A SUSPENSION OF THE WND CHILL ADVSRY DURING THE MIDDAY
AND AFTN HRS.
LAMP GDNC AND RAOB FULL SUN TEMPS IN LINE W/ GOING MAXT FCST.
GRANTED...SRN CNTYS WONT BE RECEIVING FULL SUN...BUT THERE WL BE
A PINCH OF WAA INSTEAD. WL LEAVE TEMP FCST AS IS.
&&
.AVIATION /15Z-12Z/...
VFR CONDS THRU PD. GUSTY WNW WNDS RTN FOR THE AFTN/EVE BHD S/WV.
MRB TAF NIL FOR CONTD FAA COMMS PRBLMS. LIKELY WL ISSUE TAF NIL
AMD AT 18Z SINCE WX SITUATION BENIGN...AND SUSPEND IF LWR FLGT
CATEGORIES THREATEN.
&&
.MARINE...
WNDS BLO SCA CRIT ATTM...BUT SHUD RTN TAFTN ONCE S/WV CROSSES
WATERS. WL CARRY HEADLINE ALONG.
&&
.PREV DISCUSSION...
/ISSUED 300 AM EST SUN FEB 4 2007/
SHORT TERM (TODAY AND TONIGHT)...
WATER VAPOR LOOP SHOWS UPPER LEVEL MOISTURE STREAMING FROM TEXAS
NORTHEAST OFF THE NEW ENGLAND COAST. A WAVE HAS PASSED EAST INTO NEW
ENGLAND...AS THE NEXT SHORT WAVE ENTERS THE TENNESSEE VALLEY. ACARS
400-250MB WIND OBSERVATIONS REVEAL A 175-220KT SOUTHWESTERLY JET
EXTENDS FROM THE PLAINS THROUGH THE MID ATLANTIC AND ALONG THE NEW
ENGLAND COAST. 04Z SURFACE ANALYSIS PLACED A COLD FRONT FROM NEW
YORK STATE SOUTHWEST ALONG THE APPALACHIANS INTO THE PLAINS. A
TROUGH WAS NOTED IN THE LEE OF THE APPALACHIANS. A 1029MB
ANTICYCLONE DOMINATED THE GULF COAST STATES...WITH A 1028MB
ANTICYCLONE ACROSS THE MIDWEST.
HIGH CLOUDINESS ASSOCIATED WITH THE UPPER LEVEL JET WILL BE PUSHING
SOUTHEAST EARLY THIS MORNING WITH THE JET AXIS. MEANWHILE...UPSLOPE
MOISTURE REMAINS ACROSS THE MOUNTAINS WITH CLEAR SKIES IN BETWEEN.
CLOUDS ASSOCIATED WITH THE NEXT SHORT WAVE WILL OVERSPREAD PRIMARILY
THE SOUTHERN FORECAST AREA TODAY FROM THE TENNESSEE VALLEY. WENT
WITH LOWER NGM MOS GUIDANCE FOR HIGHS TODAY...A FEW DEGREES COOLER
THAN YESTERDAY WITH RENEWED COLD ADVECTION. WINDS WILL BEGIN TO GUST
FROM THE WEST WITH MIXING LATE THIS MORNING AND AFTERNOON. WIND
CHILLS ACROSS MUCH OF THE INITIAL ADVISORY AREA WILL BE NEAR
CRITERIA DURING MUCH OF THE AFTERNOON...SO DECIDED TO KEEP THE
ADVISORY GOING THROUGH THE DAY.
THE PASSAGE OF THE SHORT WAVE SHOULD REINVIGORATE THE UPSLOPE SNOW
SHOWERS TONIGHT...AND BRING A PERIOD OF MOSTLY CLOUDY SKIES ACROSS
THE WESTERN AND NORTHERN FORECAST AREA WITH COLD ADVECTION
STRATO-CU. LOW LEVEL LAPSE RATES APPEAR FAVORABLE TO ALLOW MIXING
WIND GUSTS OF 30 MPH TO THE SURFACE AT TIMES TONIGHT. WENT ON THE
HIGHER SIDE OF MOS FOR LOW TEMPERATURES DUE TO THE MIXED BOUNDARY
LATER. THIS STILL PLACED MOST OF THE FORECAST AREA WEST OF THE BLUE
RIDGE AND ALONG THE PENNSYLVANIA BORDER INTO WIND CHILL ADVISORY
RANGE LATE TONIGHT AND MONDAY MORNING.
AVIATION...
COLD FRONT PRESSING THROUGH THE EASTERN FORECAST AREA CONTINUES TO
SUPPORT A WIND SHIFT AND SOME COLD ADVECTION STRATO-CU...WHILE UPPER
LEVEL MOISTURE RESIDES ALONG THE UPPER LEVEL JET AXIS. EXPECT CLOUDS
ASSOCIATED WITH THE NEXT SHORT WAVE FROM THE TENNESSEE VALLEY TO
STREAM INTO THE AREA DURING THE DAY AS THE UPPER LEVEL JET AXIS
SHIFTS TO THE SOUTHEAST. COLD ADVECTION TONIGHT WILL VEER WINDS AND
PROVIDE GUSTS...WITH ANOTHER OPPORTUNITY FOR STRATO-CU.
MARINE...
SMALL CRAFT ADVISORY IS IN EFFECT.
00Z ETA/GFS MOS AT THOMAS POINT INDICATES SUSTAINED WINDS WILL
INCREASE TO 20KT BEGINNING THIS AFTERNOON. 00Z PROXIMITY NAM/GFS
BUFKIT FORECAST SOUNDINGS INDICATE WIND GUST POTENTIAL OF 25KT TO
30KT TONIGHT.
STILL A RATHER STRONG GRAD FORCE MON EVNG SO HAVE EXTENDED THE SCA
WINDS TIL ABOUT 10 PM. NOT A LOT OF CONFIDENCE IN SCA WINDS
CONTINUING BEYOND THAT TIMEFRAME SO HAVE DROPPED WINDS BACK BELOW 20
KTS MON NGT AND LATER PERIODS.
TIDES...
WATER LEVELS ARE CURRENTLY UP TO A HALF FOOT ABOVE ASTRONOMICAL
PREDICTIONS. THE LUNAR CYCLE IS AT FULL MOON (96% FULL).
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL SURGE MODEL BOTH SUGGEST WATER LEVELS FALL UP TO A
FOOT BELOW ASTRONOMIC PREDICTIONS THIS AFTERNOON.
LONG TERM...MONDAY THROUGH SATURDAY...
COLDEST AIRMASS OVERHEAD MONDAY AND EARLY TUESDAY ACROSS OUR AREA.
WE WILL CONTINUE TO UNDERCUT MOS TEMPS SEVERAL DEGREES THROUGH
TUESDAY ALTHOUGH LATEST MOS PREDICTIONS NOW REFLECT THE COLD AIRMASS
MUCH BETTER THAN PREVIOUS RUNS. WIND CHILL HEADLINES WILL LIKELY BE
NEEDED INTO TUESDAY MORNING...MAINLY FOR THE PREDICTED MIN TEMPS AS
THE WINDS WILL NOT BE ALL THAT STRONG AT THAT POINT.
UPSLOPE SNOW SHOWERS WILL BE WAINING BY MONDAY EVENING...ONLY TO BE
RE-INVIGORATED AROUND TUESDAY EVENING ON THE CUSP OF ANOTHER CLIPPER
AND WEAK LOW PRES WAVE. THIS SYSTEM SEEMS TO DROP FROM EASTERN KY
INTO SOUTHERN VA AND ANY PRECIP SHOULD BE SHUNTED TO THE SOUTH OF
OUR AREA...SAVE THE WESTERN HIGHLANDS.
SLIGHT MODERATING TEMPS THU AND FRI AND THEN ANOTHER CLIPPER IS
EXPECTED TO PASS THROUGH SOMETIME AROUND FRI OR SAT...BRINGING
COLDER TEMPS BACK TO THE REGION.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR MDZ003>007-501-502.
VA...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR VAZ021-025>031.
WV...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR WVZ050>055-501>504.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST MONDAY FOR ANZ530>537.
&&
$$
UPDATED SHORT TERM/AVIATION/MARINE...HTS
PREVIOUS DISCUSSION...ROGOWSKI/JB
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 300 AM EST SUN FEB 4 2007
.SHORT TERM (TODAY AND TONIGHT)...
WATER VAPOR LOOP SHOWS UPPER LEVEL MOISTURE STREAMING FROM TEXAS
NORTHEAST OFF THE NEW ENGLAND COAST. A WAVE HAS PASSED EAST INTO NEW
ENGLAND...AS THE NEXT SHORT WAVE ENTERS THE TENNESSEE VALLEY. ACARS
400-250MB WIND OBSERVATIONS REVEAL A 175-220KT SOUTHWESTERLY JET
EXTENDS FROM THE PLAINS THROUGH THE MID ATLANTIC AND ALONG THE NEW
ENGLAND COAST. 04Z SURFACE ANALYSIS PLACED A COLD FRONT FROM NEW
YORK STATE SOUTHWEST ALONG THE APPALACHIANS INTO THE PLAINS. A
TROUGH WAS NOTED IN THE LEE OF THE APPALACHIANS. A 1029MB
ANTICYCLONE DOMINATED THE GULF COAST STATES...WITH A 1028MB
ANTICYCLONE ACROSS THE MIDWEST.
HIGH CLOUDINESS ASSOCIATED WITH THE UPPER LEVEL JET WILL BE PUSHING
SOUTHEAST EARLY THIS MORNING WITH THE JET AXIS. MEANWHILE...UPSLOPE
MOISTURE REMAINS ACROSS THE MOUNTAINS WITH CLEAR SKIES IN BETWEEN.
CLOUDS ASSOCIATED WITH THE NEXT SHORT WAVE WILL OVERSPREAD PRIMARILY
THE SOUTHERN FORECAST AREA TODAY FROM THE TENNESSEE VALLEY. WENT
WITH LOWER NGM MOS GUIDANCE FOR HIGHS TODAY...A FEW DEGREES COOLER
THAN YESTERDAY WITH RENEWED COLD ADVECTION. WINDS WILL BEGIN TO GUST
FROM THE WEST WITH MIXING LATE THIS MORNING AND AFTERNOON. WIND
CHILLS ACROSS MUCH OF THE INITIAL ADVISORY AREA WILL BE NEAR
CRITERIA DURING MUCH OF THE AFTERNOON...SO DECIDED TO KEEP THE
ADVISORY GOING THROUGH THE DAY.
THE PASSAGE OF THE SHORT WAVE SHOULD REINVIGORATE THE UPSLOPE SNOW
SHOWERS TONIGHT...AND BRING A PERIOD OF MOSTLY CLOUDY SKIES ACROSS
THE WESTERN AND NORTHERN FORECAST AREA WITH COLD ADVECTION
STRATO-CU. LOW LEVEL LAPSE RATES APPEAR FAVORABLE TO ALLOW MIXING
WIND GUSTS OF 30 MPH TO THE SURFACE AT TIMES TONIGHT. WENT ON THE
HIGHER SIDE OF MOS FOR LOW TEMPERATURES DUE TO THE MIXED BOUNDARY
LATER. THIS STILL PLACED MOST OF THE FORECAST AREA WEST OF THE BLUE
RIDGE AND ALONG THE PENNSYLVANIA BORDER INTO WIND CHILL ADVISORY
RANGE LATE TONIGHT AND MONDAY MORNING.
&&
.AVIATION...
COLD FRONT PRESSING THROUGH THE EASTERN FORECAST AREA CONTINUES TO
SUPPORT A WIND SHIFT AND SOME COLD ADVECTION STRATO-CU...WHILE UPPER
LEVEL MOISTURE RESIDES ALONG THE UPPER LEVEL JET AXIS. EXPECT CLOUDS
ASSOCIATED WITH THE NEXT SHORT WAVE FROM THE TENNESSEE VALLEY TO
STREAM INTO THE AREA DURING THE DAY AS THE UPPER LEVEL JET AXIS
SHIFTS TO THE SOUTHEAST. COLD ADVECTION TONIGHT WILL VEER WINDS AND
PROVIDE GUSTS...WITH ANOTHER OPPORTUNITY FOR STRATO-CU.
&&
.MARINE...
SMALL CRAFT ADVISORY IS IN EFFECT.
00Z ETA/GFS MOS AT THOMAS POINT INDICATES SUSTAINED WINDS WILL
INCREASE TO 20KT BEGINNING THIS AFTERNOON. 00Z PROXIMITY NAM/GFS
BUFKIT FORECAST SOUNDINGS INDICATE WIND GUST POTENTIAL OF 25KT TO
30KT TONIGHT.
STILL A RATHER STRONG GRAD FORCE MON EVNG SO HAVE EXTENDED THE SCA
WINDS TIL ABOUT 10 PM. NOT A LOT OF CONFIDENCE IN SCA WINDS
CONTINUING BEYOND THAT TIMEFRAME SO HAVE DROPPED WINDS BACK BELOW 20
KTS MON NGT AND LATER PERIODS.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY UP TO A HALF FOOT ABOVE ASTRONOMICAL
PREDICTIONS. THE LUNAR CYCLE IS AT FULL MOON (96% FULL).
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL SURGE MODEL BOTH SUGGEST WATER LEVELS FALL UP TO A
FOOT BELOW ASTRONOMIC PREDICTIONS THIS AFTERNOON.
&&
.LONG TERM...MONDAY THROUGH SATURDAY...
COLDEST AIRMASS OVERHEAD MONDAY AND EARLY TUESDAY ACROSS OUR AREA.
WE WILL CONTINUE TO UNDERCUT MOS TEMPS SEVERAL DEGREES THROUGH
TUESDAY ALTHOUGH LATEST MOS PREDICTIONS NOW REFLECT THE COLD AIRMASS
MUCH BETTER THAN PREVIOUS RUNS. WIND CHILL HEADLINES WILL LIKELY BE
NEEDED INTO TUESDAY MORNING...MAINLY FOR THE PREDICTED MIN TEMPS AS
THE WINDS WILL NOT BE ALL THAT STRONG AT THAT POINT.
UPSLOPE SNOW SHOWERS WILL BE WAINING BY MONDAY EVENING...ONLY TO BE
RE-INVIGORATED AROUND TUESDAY EVENING ON THE CUSP OF ANOTHER CLIPPER
AND WEAK LOW PRES WAVE. THIS SYSTEM SEEMS TO DROP FROM EASTERN KY
INTO SOUTHERN VA AND ANY PRECIP SHOULD BE SHUNTED TO THE SOUTH OF
OUR AREA...SAVE THE WESTERN HIGHLANDS.
SLIGHT MODERATING TEMPS THU AND FRI AND THEN ANOTHER CLIPPER IS
EXPECTED TO PASS THROUGH SOMETIME AROUND FRI OR SAT...BRINGING
COLDER TEMPS BACK TO THE REGION.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WIND CHILL ADVISORY UNTIL 12 PM EST MONDAY FOR MDZ003-501-502.
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR MDZ004>007.
VA...WIND CHILL ADVISORY UNTIL 12 PM EST MONDAY FOR VAZ021.
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR VAZ025>031.
WV...WIND CHILL ADVISORY UNTIL 12 PM EST MONDAY FOR WVZ050-051-054-
055-501>504.
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM EST MONDAY
FOR WVZ052-053.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST MONDAY FOR ANZ530>537.
&&
$$
SHORT TERM/AVIATION/MARINE/TIDES...ROGOWSKI
LONG TERM...BROTHERTON
MARINE...ROGOWSKI/BROTHERTON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1050 PM EST MON FEB 5 2007
...LOW WIND CHILLS TO CONTINUE INTO TUE MORNING...
.UPDATE...RECEIVED A SPOTTER REPORT FM MOHAWK INDICATING LES WAS
ACCUMULATING AT THE RATE OF AN INCH/HR FM MOHAWK-DELAWARE IN
KEWEENAW COUNTY. THIS OBSERVATION FITS IN NICELY WITH OBSVD
CONFLUENT WIND FIELDS WITH 340 DIRECTION AT P59-UPPER ENTRANCE OF
THE PORTAGE CANAL AND 260 FLOW REPORTED AT CMX/210 AT ONTONAGON.
HOWEVER...AS SHRTWV NOW DROPPING SE FM ONTARIO INTO THE UPR
LKS...EXPECT LLVL WINDS TO SHIFT MORE NW OVER THE KEWEENAW PENINSULA
AS SHOWN ON LATEST NAM AND PUSH THESE HEAVER BANDS INTO AREAS S OF
CALUMET WHERE MODEL SHOWS SHARPER CNVGC SETTING UP AFT 06Z. BUMPED
UP SN FCST FOR THESE AREAS TO AS MUCH AS 5 INCHES ADDITIONAL AFT 03Z
BASED ON SPOTTER OBSVD SN RATE AND ELEVATED INVRN TO NR H8 WITH
APRCH OF SHRTWV AS SHOWN ON 00Z TAMDAR SDNG FM CMX. VERY DRY AIR
UPSTREAM PER SFC DWPTS WELL BLO -20F/OBSVD 00Z INL RAOB AND LOWER
INVRN ARND H9 DEPICTED ON INL RAOB/TAMDAR SDNG FM CYQT AS WELL AS
SHIFTING WINDS THRU 06Z/DNVA AND SINKING INVRN BASE IN WAKE OF
SHRTWV LATER SUG WRNG AMTS ARE NOT LIKELY.
IN GENERAL...WINDS OVER LAND ARE LESS THAN 10 MPH/WIND CHILL
HEADLINE CRITERIA. EVEN SO...THE WIND CHILL VALUE AT A NUMBER OF
PLACES HAS REACHED OR IS CLOSE TO ADVY CRITERIA. SINCE CANCELING THE
ADVY BECAUSE WINDS IN GENERAL ARE TOO LGT MIGHT CONVEY TO THE PUBLIC
THE THREAT OF DANGEROUS COLD IS NOT THERE...WL LET THE ADVY RIDE.
KC
.PREVIOUS DISCUSSION (ISSUED AT 400 PM)...
.SHORT TERM (TONIGHT AND TUE)...
UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE ACROSS THE ROCKIES AND
WEST COAST...AND A DEEP BROAD 500 MB TROUGH ACROSS THE ERN HALF OF
THE U.S. AND THE CIRCUMPOLAR VORTEX WELL TO THE NORTHEAST THIS
MORNING. PATTERN DOES NOT CHANGE MUCH WITH UPPER LEVEL FLOW FROM THE
NNW FOR A WHILE.
NAM SHOWING A SHORTWAVE WITH A 500 MB LOW HEADING SE THIS EVENING
AND WILL AFFECT THE AREA TONIGHT WITH ANOTHER SHORTWAVE TO AFFECT
THE AREA FOR TUE AFTERNOON. NAM SHOWING 850-500 MB Q-VECTOR
CONVERGENCE WITH THIS FIRST SHORTWAVE PASSING ACROSS THE AREA THIS
AFTERNOON AND EVENING WITH MORE Q-VECTOR CONVERGENCE ACROSS THE ERN
HALF OF THE CWA TUE AFTERNOON. WITH WEST TO NORTHWEST WINDS
CONTINUING...LAKE EFFECT SNOW WILL CONTINUE TO BE A PROBLEM THROUGH
TUE. ONLY PROBLEM IS...AIRMASS IS VERY DRY IN THE LOW LEVELS AND
THIS HAS EATEN INTO THE SNOW ACCUMULATIONS WHICH HAVE NOT BEEN ALL
THAT IMPRESSIVE IN THE WEST OR REALLY THE EAST FOR THAT MATTER.
SPOTTER REPORTS EARLIER TODAY FROM THE KEWEENAW...HOUGHTON AND
ONTONAGON COUNTIES HAD SNOWFALL OF 2-3 INCHES IN THE 24 HOURS. OVER
THE EAST...VAN MEER OVER TOWARDS MUNISING HAD 9.7 INCHES IN 24
HOURS. WILL CONTINUE THE WINTER STORM WARNING FOR TONIGHT FOR THE
SNOW AND ALSO WIND CHILL VALUES DO GET DOWN CLOSE TO ADVISORY
LEVELS...SO WILL KEEP THE WARNING UP AND NOT EXTEND IT. THINKING IS
THAT THE ERN LAKE EFFECT SNOW BELTS WILL SEE 1-4 INCHES OF SNOW
TONIGHT AND 1-3 INCHES OF SNOW FOR TUE AS FETCH IS LONGEST THERE AND
DRY AIR WILL NOT AFFECT THAT AREA AS MUCH AS FURTHER WEST. WARNING
IS JUSTIFIED FOR THE SNOW AND FOR THE LOW VISIBILITIES. AS FOR
FURTHER WEST...THE DRY AIR IS AFFECTING THE SNOW AND WILL GO 1-3
INCHES TONIGHT AND AGAIN FOR TUE. THERE COULD BE A DOMINANT BAND
ACROSS THE WEST WITH THE NAM SHOWING STRONG 950 MB CONVERGENCE
ACROSS ONTONAGON AND HOUGHTON COUNTIES THROUGH THE NIGHT WITH WEST
WINDS AT KIWD AND NW AT KCMX...SO THERE COULD BE SOME DECENT SNOW
AMOUNTS THERE. DRY AIR WILL COME INTO PLAY THOUGH AND WILL CONTINUE
THE LAKE EFFECT SNOW AND BLOWING SNOW ADVISORY FOR HOUGHTON...
KEWEENAW AND ONTONAGON COUNTIES THROUGH TUE FOR THE COMBO OF SNOW
AND LOW VISIBILITIES.
WIND CHILL VALUES WILL FALL TO -25F TO -34F TONIGHT THROUGH TUE
MORNING AND WENT ADVISORY FOR EVERYWHERE ELSE. THERE COULD BE A FEW
PLACES THAT COULD SEE WIND CHILLS TO -40F...BUT THEY SHOULD BE FEW
AND FAR BETWEEN AS WIND SPEEDS WILL BE BORDERLINE TONIGHT FOR
ADVISORY LEVELS AND IF WINDS STAY UP...TEMPERATURES WILL NOT FALL AS
LOW AS PREDICTED. WENT CLOSE TO MAV GUIDANCE FOR LOWS AND HIGHS
TONIGHT THROUGH TUE BUT MADE SOME ADJUSTMENTS DOWNWARD FOR
TEMPERATURES TONIGHT SINCE COLD AIR HAS BEEN STUBBORN TO MODIFY.
WILL HAVE LIGHT WINDS AND CLEAR SKIES FOR THE MOST PART EXCEPT IN
THE LES SNOW BELTS...SO NOT INCONCEIVABLE TO GO BELOW GUIDANCE FOR
TONIGHT.
.LONG TERM (TUE NIGHT THROUGH NEXT MON)...
TUE NIGHT AND WED...UPPER LEVEL PATTERN REMAINS BASICALLY THE SAME
THROUGH THE PERIOD WITH AN UPPER LOW REMAINING SITUATED OVER NW
ONTARIO AND SHRTWVS RIDING DOWN THE WEST SIDE OF IT. THERE REMAINS
SOME UNCERTAINTY REGARDING TIMING OF THESE SHRTWVS...AS NOTED BY THE
NAM AND UKMET SHOWING ONE MOVING ACROSS LAKE SUPERIOR WED MORNING
WHEREAS THE GFS...ECMWF AND REGIONAL CANADIAN SHOW NO SIGNAL OF THIS
SHRTWV. HOWEVER...IT APPEARS THAT WHETHER THESE SHRTWVS ARE THERE OR
NOT IS FAIRLY INSIGNIFICANT SINCE THEY ALL LACK MOISTURE. THEREFORE
LITTLE ACTIVITY IS ANTICIPATED AWAY FROM LAKE EFFECT. PROBABLY THE
MAIN INFLUENCE FROM THE SHRTWVS WILL BE TO BRING IN SLIGHTLY COLDER
AIR AND LIFT INVERSIONS UP...WHICH WITH DIURNAL COOLING MAY HELP
ENHANCE LAND BREEZE/LAKE INDUCED TROUGHING CONVERGENCE ZONES. BOTH
THE GFS AND NAM GENERALLY MAINTAIN AN 850MB TEMP AROUND -20C...WHICH
WILL ALLOW FOR AT LEAST A 50MB DENDRITIC SNOW GROWTH LAYER.
THEREFORE HAVE INCREASED SNOW TO WATER RATIOS TO 25 TO 1 FROM THE 15
TO 20 TO 1 THAT HAVE BEEN OBSERVED RECENTLY. IN ADDITION...KEPT THE
GREATEST ACCUMULATIONS AT NIGHT DUE TO THE LARGER LAND/WATER
TEMPERATURE GRADIENT WHICH ENHANCES LOW LEVEL CONVERGENCE. RIGHT NOW
THE GREATEST ACCUMULATIONS LOOK TO BE IN THE SAME AREA THEY HAVE
BEEN FOR ABOUT THE PAST WEEK...OVER ONTONAGON COUNTY INTO TWIN LAKES
AND BETWEEN THE PICTURED ROCKS NATIONAL LAKESHORE AND WHITEFISH
POINT. IF ONE OF THESE SHRTWVS CAN CONTAIN BETTER MOISTURE...
WARNINGS MAY NEED TO BE CONSIDERED...BUT AS OF RIGHT NOW...
ADVISORIES LOOK TO SUFFICE. AS FAR AS TEMPERATURES GO...TUESDAY
NIGHT LOOKS LIKE ANOTHER COOL NIGHT IN THE INTERIOR WITH WINDS
DROPPING DOWN TO 5 MPH AND PARTLY CLOUDY SKIES. HOWEVER...WITH A
WARMER TUE...HAVE NOT WENT AS COLD AS TONIGHT...BUT STILL HAVE LOWS
10 TO 15 BELOW. GIVEN THE LOW 850MB TEMPS... MAINTAINED A COOL WED
AND STAYED TOWARD THE LOWER END OF GUIDANCE...WHICH HAS BEEN
VERIFYING WELL AS OF LATE.
WED NIGHT AND THU...MORE DISAGREEMENTS START SHOW UP WITH THE WAY
FEATURES EVOLVE DURING THIS TIME PERIOD OVER SE CANADA...WHICH HAVE
SOME IMPACTS TO THE CWA. THERE DOES APPEAR FROM ALL MODELS THAT A
STRONGER AND DEEPER WEST TO EAST UPPER LEVEL TROUGH WILL BE CROSSING
THE CWA...THE QUESTION IS WHEN. THE NAM IS THE FASTEST BY FAR...
BRINGING THE TROUGH ACROSS WED NIGHT. IN ITS SCENARIO...A FAIRLY
STRONG BAND OF SNOW IS SHOWN TO DROP SOUTH ACROSS LAKE SUPERIOR. THE
UKMET IS THE SLOWEST...STILL SHOWING THE TROUGH UP IN HUDSON BAY AT
12Z THU. THE GFS AND ECMWF ARE A COMPROMISE...HAVING IT CROSS LAKE
SUPERIOR DURING THE DAY THU. DECIDED TO FOLLOW THIS COMPROMISE
IDEA...WHICH RESULTS IN KEEPING SOME LAND BREEZE/LAKE INDUCED TROUGH
FROM ONTONAGON EASTWARD TO WHITEFISH POINT...WITH THE GREATEST
ACCUMULATIONS ALONG THIS BAND. THEN ON THU...EXPANDED THE CHANCE
POPS TO INCLUDE MORE OF UPPER MICHIGAN AS LOW LEVEL FLOW BECOMES
MORE UNIFORM NORTHWESTERLY BEHIND THE SHRTWV TROUGH. HOWEVER...HAVE
STILL KEPT THE FAR SOUTH CENTRAL DRY AS THIS AREA SINCE UNCERTAINTY
EXISTS ON HOW MUCH MOISTURE THE SHRTWV TROUGH WILL HAVE.
TEMPERATURES DURING THIS PERIOD LOOK TO STAY FAIRLY SIMILAR TO THOSE
FROM TUE NIGHT AND WED AS 850MB TEMPS ARE PROGGED TO BE SIMILAR.
THU NIGHT THROUGH MON...OPERATIONAL MODELS ARE STILL IN FAIRLY GOOD
AGREEMENT THROUGH THIS PERIOD...THOUGH THERE ARE SOME DIFFERENCES
REGARDING HOW QUICK THE COLD AIR EXITS THE AREA (WHICH WAS NOTED IN
YESTERDAYS 12Z CYCLE). FROM THU NIGHT THROUGH SUN...THE UPPER FLOW
IS PROGGED TO REMAIN NORTHWESTERLY...WHICH HELPS BRING IN THE NEXT
COLD SHOT OF AIR THAT PREVIOUS GFS AND ECMWF RUNS HAVE SHOWN THE
PAST FEW DAYS. THE 06Z GFS CONTINUES TO STAY ON THE TRACK OF
BRINGING AN UPPER LOW SOUTHEASTWARD THROUGH ONTARIO FROM FRI INTO
SAT...ALLOWING 850MB TEMPS OF -24C TO CROSS LAKE SUPERIOR.
HOWEVER...THE 00Z ECMWF KEEPS THIS UPPER LOW FARTHER NORTH...
CROSSING NORTHERN ONTARIO AND QUEBEC. THEREFORE THE BULK OF THE
COLDER AIR...WITH 850MB TEMPS OF -28C OR LOWER...STAYS TO THE NORTH
OF HERE. NONETHELESS...THE ECMWF STILL BRINGS -20 TO -24C AIR ACROSS
LAKE SUPERIOR SAT INTO SUN. THEREFORE...THE IDEA OF MAINTAINING LES
POPS IN WNW LOW LEVEL FLOW PER SEA LEVEL PRESSURE PROGS...LOOKS FINE
THROUGH AT LEAST SUNDAY...WITH TEMPERATURES REMAINING BELOW NORMAL.
ON MONDAY...THE MODELS DIFFER WITH HOW FAST CONDITIONS WILL WARM
UP...WITH THE 06Z GFS QUITE A BIT FASTER THAN THE 00Z ECMWF
SUGGESTING RETURN FLOW SET UP BY 12Z MON. AS WAS THE CASE
YESTERDAY...PREFER TO FOLLOW THE SLOWER ECMWF...WHICH HAS A SURFACE
RIDGE AXIS MOVING OVER THE AREA AROUND 00Z TUE. THEREFORE WILL KEEP
LES CHANCES GOING INTO AT LEAST MON MORNING. THIS MATCHES UP WELL
TOO WITH HPC PROGS.
MICHELS (SHORT TERM)
AJ (LONG TERM)
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 8 AM EST TUE MIZ006-007-085.
LAKE EFFECT SNOW AND BLOWING SNOW ADVISORY UNTIL 7 PM EST TUE
MIZ001>003.
WIND CHILL ADVISORY TO 12 PM EST TUE MIZ004-005-009>014-084
HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR.
&&
$$
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 924 PM EST MON FEB 5 2007
.UPDATE...
LOW LEVEL CONVERGENCE CONTINUES TO FOCUS SOME LAKE STRATO CU AND
FLURRIES ALONG THE I-94 AND M 59 CORRIDORS. THE LATEST NAM12
SUGGESTS THIS WILL CONTINUE THROUGH MUCH OF THE NIGHT. THE REST OF
THE FORECAST AREA IS GENERALLY CLEAR. WOULD EXPECT THESE
CONDITIONS TO PERSIST THROUGH THE NIGHT BASED ON LATEST NAM. WILL
THUS UPDATE THE WEATHER GRIDS TO REFLECT THIS.
THE COMBINATION OF MIN TEMPS TONIGHT AND WINDS ARE STILL EXPECTED
TO KEEP WIND CHILL READINGS IN THE -10 TO -15C RANGE...BELOW
ADVISORY CRITERIA. THE ONLY MAJOR UPDATE TO THE TEMPERATURES WAS
TO LOWER MIN TEMPS ACROSS LENAWEE AND MONROE COUNTIES DUE TO THE
SOUTHWEST SURFACE FLOW INHIBITING AIRMASS MODIFICATION FROM LAKE
MICHIGAN. TEMPS IN NORTHERN INDIANA ARE ALREADY SUB ZERO.
&&
.PREV DISCUSSION...ISSUED 611 PM EST MON FEB 5 2007
AVIATION...
ARCTIC HIGH PRESSURE OVER THE MISSISSIPPI VALLEY WILL BUILD INTO
THE UPPER OHIO VALLEY TONIGHT. THIS WILL MAINTAIN WESTERLY FLOW
OVER LAKE MICHIGAN AND SOUTHWESTERLY FLOW OVER FAR SOUTHERN LOWER
MI...CAUSING THE AREA OF CONVERGENCE ALONG THE I-94 CORRIDOR TO
PERSIST THROUGH THE NIGHT. INVERSION HEIGHTS ARE FORECAST TO
REMAIN AROUND 4K FEET INTO TUES MORNING. HOWEVER...EXPECT LOSS OF
DIURNAL COMPONENT WILL CAUSE SOME OF THE STRATO CU TO SCATTER OUT
DURING THE EVENING. SO EXPECT VFR CONDITIONS INTO TUES MORNING. A
WEAKENING PRESSURE GRADIENT SHOULD ALSO ALLOW WINDS TO SUBSIDE TO
LESS THAN 12 KNOTS BY 02Z.
PREV DISCUSSION...ISSUED 313 PM EST MON FEB 5 2007
SHORT TERM...
ANOTHER COLD NIGHT IN STORE...AS CLOUDS FROM LAKE MICHIGAN HAVE
STRUGGLED TO ADVANCE EASTWARD...EVEN WITH THE DIURNAL ENHANCEMENT
HELPING TO RAISE INVERSION HEIGHTS UP TOWARD 4000 FEET PER DTW
TAMDAR DATA. THE GOOD NEWS IS THE SUNSHINE HAS HELPED BOOST MAX
TEMPS TO AROUND 10 DEGREES THIS AFTERNOON...A GOOD 3-5 DEGREES
WARMER COMPARED TO YESTERDAY.
PRESSURE GRADIENT OVER SOUTHERN LOWER MICHIGAN TONIGHT LOOKS TO BE
ABOUT 2 MB LESS WHEN COMPARED TO THIS MORNING. THIS SHOULD TRANSLATE
TO LOWS AT OR BELOW ZERO EVERYWHERE...AND HAVE UNDERCUT GFS MOS
GUIDANCE BY A GOOD 5 DEGREES IN MOST SPOTS. A FAR AS WIND CHILLS
GO...WITH THE WEAKER GRADIENT...WINDS LOOK TO BE BORDERLINE...AROUND
10 MPH...WITH WIND CHILLS HOVERING RIGHT AROUND -20 F (ADVISORY
CRITERIA). WILL HOLD OFF ON THE ADVISORY...AS WIND CHILLS OF -20 F
OR COLDER ARE NOT EXPECTED TO BE WIDESPREAD...NOR ARE THEY EXPECTED
FOR AN EXTENDED PERIOD OF TIME.
DRY AIRMASS CONTINUES TO LIMIT LAKE EFFECT ACTIVITY...AND SEE NO
SIGNIFICANT CHANGES INTO TONIGHT. THE WESTERN CLOUD
EDGE/CONDENSATION OVER LAKE MICHIGAN HAS ACTUALLY BEEN PULLING EAST
THIS AFTERNOON.
TOMORROW LOOKS TO BE A DIFFERENT STORY...AS UPPER WAVE CURRENTLY
OVER NORTHERN ALBERTA QUICKLY DIVES SOUTHEAST...TRACKING ALONG THE
SOUTHERN MICHIGAN BORDER...PER NAM/GFS TROPOPAUSE PRESSURE FIELDS.
THIS SHOULD AT LEAST ALLOW FOR AN ENHANCEMENT TO THE I-94/M-59
CONVERGENT BAND. HOWEVER...MODELS IMPLYING MOST/ALL OF THE SYNOPTIC
SNOW WILL STAY SOUTH OF THE BORDER AS MAIN 850-700 MB THETA
GRADIENT REMAINS CONFINED TO THE SOUTHERN OHIO VALLEY...WITH LITTLE
IN THE WAY OF MOISTURE TRANSPORT INTO SOUTHERN LOWER MICHIGAN. STILL
A LITTLE LEARY THE UPPER WAVE MAY BE DRAWN A LITTLE FARTHER NORTH
THAN INDICATED...AND WILL CARRY A 50 POP FOR M-59 AND POINTS SOUTH.
NO CHANGES TO MAXES TOMORROW...LOWER TEENS EXPECTED.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY
VERY LITTLE CHANGE IN THE ONGOING PATTERN THROUGH THE WEEKEND AS
SEVERAL STRONG SHORTWAVES DIG INTO THE EASTERN NORTH AMERICAN UPPER
TROUGH AND KEEP THE EASTERN CANADIAN POLAR VORTEX WELL-ESTABLISHED.
THIS WILL MAINTAIN A COLD AIRMASS ACROSS THE REGION WITH HIGHS ONLY
IN THE TEENS/LOWER 20S AND LOWS IN THE SINGLE DIGITS TO OCCASIONALLY
BELOW ZERO.
THE FIRST OF THESE SHORTWAVES WILL BE PASSING SOUTH OF THE REGION
TUESDAY EVENING. THERE MAY BE SOME LEFTOVER LIGHT SNOW OVER THE FAR
SOUTHERN CWA FROM THIS SYSTEM (OR AT LEAST AN ENHANCEMENT TO LAKE
EFFECT SNOW SHOWERS FROM THE MOISTURE IT WILL BRING)...BUT OVERALL
IT WILL JUST ENSURE THAT THE STATUS QUO HOLDS...AND WE REMAIN IN THE
SAME TEMPERATURE REGIME. THE NEXT SHORTWAVE WILL DROP DOWN FROM THE
ARCTIC CIRCLE AND SPIN AROUND THE POLAR VORTEX. SO...EXPECT THIS
FEATURE TO BRING A RESURGENCE OF COLDER AIR BY LATE FRIDAY INTO
SATURDAY. ATTM...IT APPEARS THIS AIRMASS IS SOME 5-7 DEGREES C
MILDER THAN THE ARCTIC AIRMASS OF THIS PAST WEEKEND...SO DO NOT
EXPECT TEMPERATURES TO STRUGGLE QUITE AS MUCH.
THE FORECAST FOR SNOW SHOWERS REMAINS TRICKY...AT LEAST IN TRYING TO
PICK OUT THE DAY(S) THAT HAVE THE BEST CHANCE OF LIGHT ACCUMULATION.
NO LARGE STORM SYSTEMS ARE ON THE WAY...AND ANY ACCUMULATING SNOWS
WILL MAINLY BE LAKE EFFECT/ENHANCED SNOW SHOWERS. AFTER A PERIOD OF
ENHANCED SNOW SHOWER ACTIVITY TO START THE LONG TERM FORECAST...THE
GENERAL FORECAST WILL BE FOR PERIODIC FLURRIES IN THE WEDNESDAY AND
THURSDAY TIMEFRAME...WITH MORE WIDESPREAD SNOW SHOWERS BY FRIDAY AND
SATURDAY AS THE AFOREMENTIONED ARCTIC SHORTWAVE DIVES THROUGH THE
GREAT LAKES.
AT THE VERY END OF THE FORECAST...THE AMPLIFIED PATTERN CONTINUES TO
SHOW SOME SIGNS OF RELAXING...WHICH WOULD ALLOW MORE INTRUSION OF
PACIFIC AIR INTO THE REGION...AND LESS INTRUSION OF THE COLDEST AIR
FROM THE ARCTIC. WILL MAINTAIN THE SLIGHT MODERATION IN THE SUNDAY
TO MONDAY TIMEFRAME GIVEN SOME CONSISTENCY IN GFS RUNS DURING THE
PAST FEW DAYS FOR THIS BASIC SCENARIO. STILL...TEMPERATURES SHOULD
REMAIN LARGELY BELOW NORMAL.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING...SOUTH HALF UNTIL 7 AM TUESDAY.
SMALL CRAFT ADVISORY...LHZ441-LHZ442 UNTIL 7 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LHZ421 UNTIL 7 AM TUESDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FOR WINDS...UNTIL 7 AM TUESDAY.
&&
$$
AVIATION/UPDATE...CONSIDINE
SHORT TERM...SF
LONG TERM....DG
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 611 PM EST MON FEB 5 2007
.AVIATION...
ARCTIC HIGH PRESSURE OVER THE MISSISSIPPI VALLEY WILL BUILD INTO
THE UPPER OHIO VALLEY TONIGHT. THIS WILL MAINTAIN WESTERLY FLOW
OVER LAKE MICHIGAN AND SOUTHWESTERLY FLOW OVER FAR SOUTHERN LOWER
MI...CAUSING THE AREA OF CONVERGENCE ALONG THE I-94 CORRIDOR TO
PERSIST THROUGH THE NIGHT. INVERSION HEIGHTS ARE FORECAST TO
REMAIN AROUND 4K FEET INTO TUES MORNING. HOWEVER...EXPECT LOSS OF
DIURNAL COMPONENT WILL CAUSE SOME OF THE STRATO CU TO SCATTER OUT
DURING THE EVENING. SO EXPECT VFR CONDITIONS INTO TUES MORNING. A
WEAKENING PRESSURE GRADIENT SHOULD ALSO ALLOW WINDS TO SUBSIDE TO
LESS THAN 12 KNOTS BY 02Z.
.PREV DISCUSSION...ISSUED 313 PM EST MON FEB 5 2007
SHORT TERM...
ANOTHER COLD NIGHT IN STORE...AS CLOUDS FROM LAKE MICHIGAN HAVE
STRUGGLED TO ADVANCE EASTWARD...EVEN WITH THE DIURNAL ENHANCEMENT
HELPING TO RAISE INVERSION HEIGHTS UP TOWARD 4000 FEET PER DTW
TAMDAR DATA. THE GOOD NEWS IS THE SUNSHINE HAS HELPED BOOST MAX
TEMPS TO AROUND 10 DEGREES THIS AFTERNOON...A GOOD 3-5 DEGREES
WARMER COMPARED TO YESTERDAY.
PRESSURE GRADIENT OVER SOUTHERN LOWER MICHIGAN TONIGHT LOOKS TO BE
ABOUT 2 MB LESS WHEN COMPARED TO THIS MORNING. THIS SHOULD TRANSLATE
TO LOWS AT OR BELOW ZERO EVERYWHERE...AND HAVE UNDERCUT GFS MOS
GUIDANCE BY A GOOD 5 DEGREES IN MOST SPOTS. A FAR AS WIND CHILLS
GO...WITH THE WEAKER GRADIENT...WINDS LOOK TO BE BORDERLINE...AROUND
10 MPH...WITH WIND CHILLS HOVERING RIGHT AROUND -20 F (ADVISORY
CRITERIA). WILL HOLD OFF ON THE ADVISORY...AS WIND CHILLS OF -20 F
OR COLDER ARE NOT EXPECTED TO BE WIDESPREAD...NOR ARE THEY EXPECTED
FOR AN EXTENDED PERIOD OF TIME.
DRY AIRMASS CONTINUES TO LIMIT LAKE EFFECT ACTIVITY...AND SEE NO
SIGNIFICANT CHANGES INTO TONIGHT. THE WESTERN CLOUD
EDGE/CONDENSATION OVER LAKE MICHIGAN HAS ACTUALLY BEEN PULLING EAST
THIS AFTERNOON.
TOMORROW LOOKS TO BE A DIFFERENT STORY...AS UPPER WAVE CURRENTLY
OVER NORTHERN ALBERTA QUICKLY DIVES SOUTHEAST...TRACKING ALONG THE
SOUTHERN MICHIGAN BORDER...PER NAM/GFS TROPOPAUSE PRESSURE FIELDS.
THIS SHOULD AT LEAST ALLOW FOR AN ENHANCEMENT TO THE I-94/M-59
CONVERGENT BAND. HOWEVER...MODELS IMPLYING MOST/ALL OF THE SYNOPTIC
SNOW WILL STAY SOUTH OF THE BORDER AS MAIN 850-700 MB THETA
GRADIENT REMAINS CONFINED TO THE SOUTHERN OHIO VALLEY...WITH LITTLE
IN THE WAY OF MOISTURE TRANSPORT INTO SOUTHERN LOWER MICHIGAN. STILL
A LITTLE LEARY THE UPPER WAVE MAY BE DRAWN A LITTLE FARTHER NORTH
THAN INDICATED...AND WILL CARRY A 50 POP FOR M-59 AND POINTS SOUTH.
NO CHANGES TO MAXES TOMORROW...LOWER TEENS EXPECTED.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY
VERY LITTLE CHANGE IN THE ONGOING PATTERN THROUGH THE WEEKEND AS
SEVERAL STRONG SHORTWAVES DIG INTO THE EASTERN NORTH AMERICAN UPPER
TROUGH AND KEEP THE EASTERN CANADIAN POLAR VORTEX WELL-ESTABLISHED.
THIS WILL MAINTAIN A COLD AIRMASS ACROSS THE REGION WITH HIGHS ONLY
IN THE TEENS/LOWER 20S AND LOWS IN THE SINGLE DIGITS TO OCCASIONALLY
BELOW ZERO.
THE FIRST OF THESE SHORTWAVES WILL BE PASSING SOUTH OF THE REGION
TUESDAY EVENING. THERE MAY BE SOME LEFTOVER LIGHT SNOW OVER THE FAR
SOUTHERN CWA FROM THIS SYSTEM (OR AT LEAST AN ENHANCEMENT TO LAKE
EFFECT SNOW SHOWERS FROM THE MOISTURE IT WILL BRING)...BUT OVERALL
IT WILL JUST ENSURE THAT THE STATUS QUO HOLDS...AND WE REMAIN IN THE
SAME TEMPERATURE REGIME. THE NEXT SHORTWAVE WILL DROP DOWN FROM THE
ARCTIC CIRCLE AND SPIN AROUND THE POLAR VORTEX. SO...EXPECT THIS
FEATURE TO BRING A RESURGENCE OF COLDER AIR BY LATE FRIDAY INTO
SATURDAY. ATTM...IT APPEARS THIS AIRMASS IS SOME 5-7 DEGREES C
MILDER THAN THE ARCTIC AIRMASS OF THIS PAST WEEKEND...SO DO NOT
EXPECT TEMPERATURES TO STRUGGLE QUITE AS MUCH.
THE FORECAST FOR SNOW SHOWERS REMAINS TRICKY...AT LEAST IN TRYING TO
PICK OUT THE DAY(S) THAT HAVE THE BEST CHANCE OF LIGHT ACCUMULATION.
NO LARGE STORM SYSTEMS ARE ON THE WAY...AND ANY ACCUMULATING SNOWS
WILL MAINLY BE LAKE EFFECT/ENHANCED SNOW SHOWERS. AFTER A PERIOD OF
ENHANCED SNOW SHOWER ACTIVITY TO START THE LONG TERM FORECAST...THE
GENERAL FORECAST WILL BE FOR PERIODIC FLURRIES IN THE WEDNESDAY AND
THURSDAY TIMEFRAME...WITH MORE WIDESPREAD SNOW SHOWERS BY FRIDAY AND
SATURDAY AS THE AFOREMENTIONED ARCTIC SHORTWAVE DIVES THROUGH THE
GREAT LAKES.
AT THE VERY END OF THE FORECAST...THE AMPLIFIED PATTERN CONTINUES TO
SHOW SOME SIGNS OF RELAXING...WHICH WOULD ALLOW MORE INTRUSION OF
PACIFIC AIR INTO THE REGION...AND LESS INTRUSION OF THE COLDEST AIR
FROM THE ARCTIC. WILL MAINTAIN THE SLIGHT MODERATION IN THE SUNDAY
TO MONDAY TIMEFRAME GIVEN SOME CONSISTENCY IN GFS RUNS DURING THE
PAST FEW DAYS FOR THIS BASIC SCENARIO. STILL...TEMPERATURES SHOULD
REMAIN LARGELY BELOW NORMAL.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING...SOUTH HALF UNTIL 7 AM TUESDAY.
SMALL CRAFT ADVISORY...LHZ441-LHZ442 UNTIL 7 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LHZ421-LHZ443 UNTIL 7 AM TUESDAY.
SMALL CRAFT ADVISORY FOR WINDS...LHZ422 UNTIL 7 AM TUESDAY.
LAKE ST CLAIR...SMALL CRAFT ADVISORY FOR WINDS...LCZ460 UNTIL 7 AM TUESDAY.
MI WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FOR WINDS...UNTIL 7 AM TUESDAY.
&&
$$
AVIATION...CONSIDINE
SHORT TERM...SF
LONG TERM....DG
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
AFDFSD 1057 AM CST SUN FEB 4 2007
.DISCUSSION...
THE BIG CHILL AGAIN THE FOCUS OF SHORT TERM. PER 1616Z TAMDAR RAOB
FOR KSUX AND 12Z KABR RAOB...FAIRLY ISOTHERMAL THRU LOWEST 300 HPA.
PROFILERS AT NLG AND WDL...ESPECIALLY THE LATTER...SUGGEST FAIRLY
STRONG WNDS AGAIN SITTING JUST OFF THE SFC...WITH LOW LVL RIDGE AXIS
PROTECTING AREAS FROM THE JAMES VALLEY AND W. FOR THIS REASON...
DROPPED A BIT EARLY THE WRN WIND CHILL ADVY. IF NLG PROFILER
CORRECT...WL LKLY CONTINUE TO EXPERIENCE ISSUES WITH WINDS DROPPING
OFF MUCH ALG THE I29 CORRIDOR...AND 30KTS IN LOWER GATE OF WDL
ALONG WITH CONTINUED LOW LVL CAA PRETTY MUCH KEEP ERN AREAS WELL
UNDER DANGEROUS WIND CHILL THREAT PER FCST...UNTIL BETTER WIND
DECOUPLING THIS EVENING. WL LKLY BE ABLE TO WHITTLE A BIT MORE OF
WIND CHILL ADVY AWAY THAN JUST THE REMAINING EXPIRING SEGMENT THRU
LOWER JAMES VALLEY AT NOON.
ONE ISSUE FOR TDA IS MID AND HIGH CLOUDS STREAMING IN FROM THE NW.
THICKEST CLDS LKLY TO REMAIN ACRS THE FAR WRN CWA THIS AFTN...BUT
TIME SECTIONS SUGGEST THAT WL NOT DISSIPATE HEADING SE...SO UPPED
SKY GRIDS CONSIDERABLY TODAY AND TONIGHT. THIS INTRODUCES A BIT OF
CONCERN THAT LOWS WL NOT REACH NEARLY AS COLD TNGT AS FCST IN AREAS
W OF A LINE FROM KHON TO KSUX WHERE CLOUDS LKLY TO BE A MORE SIG
ISSUE. HOWEVER...VERY LIGHT WINDS WL MAKE ANY CLEARING PERIOD
SUSCEPTABLE TO DRASTIC TEMP DROPS...SO WL ONLY PUSH LOWS UP A HALF
TO FULL CATEGORY FOR THE MOMENT.
&&
.PREV DISCUSSION...
ANOTHER FRIGID DAY ON TAP OVER THE REGION AS COLD SURFACE HIGH
CURRENTLY CENTERED ALONG THE U.S. AND CANADIAN BORDER CONTINUES TO
SLIDE SOUTHWARD. WILL REMAIN BREEZY ENOUGH THROUGH THE DAY TO KEEP
THE WIND CHILL ADVISORY GOING OVER MOST OF THE AREA THROUGH EARLY
TONIGHT...THOUGH THE ADVISORY WILL DROP OFF OVER OUR SOUTHWESTERN
ZONES BY AFTERNOON AS TEMPERATURES WARM AND WINDS LEVEL OFF AS HIGH
PRESSURE AXIS DROPS INTO THE AREA. STILL APPEARS THAT THE COLDEST
NIGHT IN THIS ARCTIC EPISODE WILL BE TONIGHT...WITH HIGH PRESSURE
PARKED OVERHEAD AND RESULTANT VERY LIGHT WINDS OVER THE FA. COLDEST
READINGS WILL BE THROUGH THE NORTHEASTERN HALF OF THE CWA CLOSEST TO
THE HIGH PRESSURE CENTER. THE SOUTHWESTERN PORTIONS OF THE CWA WILL
BE A CONSIDERABLE AMOUNT WARMER...BEING FURTHER ON THE BACKSIDE OF
THE HIGH...AS WELL AS FEELING THE EFFECT OF INCREASING CLOUDS WITH
WAA IN THE MID LEVELS.
WARMED TEMPERATURES SOME ON MONDAY WITH RESPECT TO PREVIOUS FORECAST
WITH MODELS COMING IN SEVERAL DEGREES WARMER THAN BEFORE. AS HAS
BEEN ADVERTISED THE PAST COUPLE OF DAYS...STRONG BAROCLINIC BAND
WILL SET UP OVER THE WESTERN PORTIONS OF THE CWA BY MONDAY
AFTERNOON...WITH STRONG MID LEVEL WAA...AND DECENT LOWER LEVEL
FRONTOGENESIS...WHICH WILL PUSH EASTWARD OVER THE CWA ON MONDAY NIGHT
AND TUESDAY. UPPED THE POPS SLIGHTLY FROM THE PREVIOUS FORECAST
WITH THESE DYNAMICS AS THEY CROSS OUR FA. STILL LOOKS LIKE
TEMPERATURES WILL RISE OVER THE AREA DURING THE OVERNIGHT HOURS OF
MONDAY INTO TUESDAY WITH THE WAA IN PROGRESS. LIGHT PRECIPITATION
SHOULD END FROM WEST TO EAST BY TUESDAY AFTERNOON AS BEST DYNAMICS
PUSH EASTWARD.
WEAK SHORTWAVE DROPS SOUTHWARD THROUGH OUR AREA ON WEDNESDAY...AND
KEPT BROADBRUSHED SMALL CHANCE POPS OVER THE CWA FOR WEDNESDAY INTO
EARLY WEDNESDAY NIGHT WITH THE SYSTEM. DID JUST NOTE THAT THE LATEST
GFS RUN KEPT THE BEST ENERGY WITH THIS FEATURE TO OUR SOUTHWEST...SO
WE WILL HAVE TO SEE HOW IT PANS OUT. AS FOR TEMPERATURES THROUGH
THE END OF THE WEEK...WHILE WE WILL SEE SOME MODERATION...ESPECIALLY
IN COMPARISON WITH THE CURRENT BOUT OF BITTER COLD...IT STILL WILL
REMAIN MUCH BELOW NORMAL WITH SMALL SHOTS OF REINFORCING COLD AIR
EVERY COUPLE DAYS OR SO.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WIND CHILL ADVY UNTIL 9 PM IAZ001>003-012>014-020>022-031-
032.
MN...WIND CHILL ADVY UNTIL 9 PM MNZ071-072-080-081-089-090-097-
098.
NE...WIND CHILL ADVY UNTIL 9 PM FOR NEZ014.
WIND CHILL ADVY UNTIL NOON FOR NEZ013.
SD...WIND CHILL ADVY UNTIL 9 PM FOR SDZ038>040-053>056-060>062-
066-067-071.
WIND CHILL ADVY UNTIL NOON FOR SDZ059-065-069-070.
&&
$$
CHAPMAN/JM
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 915 AM PST SUN FEB 4 2007
.SYNOPSIS...HIGH PRESSURE ALOFT WILL REBUILD OVER THE AREA THROUGH
TONIGHT...SLOWLY DRYING OUT THE REGION. DRY WEATHER WILL PREVAIL ON
MONDAY UNDER HIGH PRESSURE ALOFT...ALTHOUGH THE DAY WILL START OFF
FOGGY. A LOW PRESSURE SYSTEM IS EXPECTED TO APPROACH ON
TUESDAY...RESULTING IN A CHANCE OF RAIN OVER SOUTHWEST WASHINGTON IN
THE AFTERNOON. LOOK FOR UNSETTLED WEATHER THE REST OF THIS WEEK.
&&
.SHORT TERM...GOOEY DAY TODAY. UPPER RIDGE BUILDING STEADILY OVER
THE REGION AND THE IMMEDIATE RESULT IS THE RAIN LIFTING NORTH OF THE
REGION. CURRENTLY MAIN AREAS OF PRECIP ARE STREAMING BY NORTH OF
WASHINGTON...WHILE JUST CLIPPING THE NORTHERN OLYMPIC PENINSULA AND
NORTHWEST INTERIOR. WITH MOIST AIR MASS IN PLACE OVER THE AREA
STILL GETTING A SPIT OR SPATTER HERE AND THERE OVER THE REST OF THE
AREA. AS THE RIDGE BUILDS...MID AND UPPER LEVELS WILL CONTINUE TO
DRY UP BRINGING AN END TO THE PRECIP.
MAIN PROBLEM IS ALL THE LOW LEVEL MOISTURE THAT IS BEING LEFT
BEHIND. ACARS SOUNDINGS SHOW AN INVERSION ABOUT 800-1000 FEET OFF
THE GROUND WITH LIGHT OFFSHORE FLOW BELOW THE INVERSION...AND DECENT
SW FLOW ABOVE IT. UNTIL WE GET RID OF THE HIGHER CLOUDS AND OR
INCREASE THE OFFSHORE FLOW SIGNIFICANTLY...DON`T THINK WE WILL BE
ERODING THAT INVERSION ALL THAT QUICKLY. AT THIS POINT THINK WE
WILL ONLY SEE LIMITED IMPROVEMENT TODAY AND THEN MAINLY SOUTHERN
AREAS. ONCE THE SUN GOES DOWN TONIGHT...THE GOO WILL LIKELY LOCK IN
AS THE OFFSHORE GRADIENTS ARE NOT ALL THAT STRONG AND RADIATIONAL
COOLING SHOULD STRENGTHEN THE INVERSION. WILL HAVE TO WAIT UNTIL
MONDAY BEFORE WE BREAK OUT AND SEE THE SUN ON A LARGER SCALE.
WITH THE BULK OF THE RAIN PRETTY MUCH OVER FOR A LARGE PART OF THE
AREA WILL UPDATE THE FORECAST TO LOWER THREAT OF STEADIER RAIN...AND
REPLACE IT WITH LOCAL DRIZZLE...SPOTTY LIGHT RAIN WORDING...ALONG
WITH HITTING THE FOG A BIT MORE. CERNIGLIA
.LONG TERM...FROM PREVIOUS DISCUSSION...THIS PERIOD WILL BE
DOMINATED BY AN UNSETTLED WEATHER REGIME AS A SERIES OF PAC STORMS
IN THE NRN BRANCH MOVE ACROSS THE REGION. SUSPECT THAT THE POPS MAY
STILL BE TOO LOW...ESPECIALLY FOR THE LATTER PART OF THE WEEK.
&&
.AVIATION...SLOPPY MORNING AVIATION WISE IN PROGRESS. MULTIPLE CLOUD
DECKS IN THE LOWER LAYERS WITH THE MAIN SC DECK AROUND 2000 FEET.
AREAS OF VISIBILITIES 1-3SM IN FOG AND CEILINGS 500 TO 1000 FEET
WITH PLENTY OF LOW LEVEL MOISTURE. SLOW IMPROVEMENT FROM THE SOUTH
TODAY WITH CEILINGS EXPECTED TO BE IN THE 2000 TO 3000 FOOT RANGE BY
MID TO LATE AFTERNOON WITH JUST ISOLATED REDUCED VISIBILITIES IN
FOG. NOT MUCH WIND IN THE LOWER LEVELS AS WELL SO EXPECT CONDITIONS
TO DETERIORATE TONIGHT BACK DOWN TO CEILINGS BELOW 1000 FEET WITH
AREAS OF VISIBILITIES 1-3SM IN FOG.
FOR KSEA...CEILINGS 2000 TO 3000 FEET THROUGH THE AFTERNOON HOURS
LOWERING BACK DOWN BELOW 1000 FEET 03-06Z. VISIBILITIES AS LOW AS 2
MILES UNTIL 21Z VISIBILITIES ALSO LOWER AGAIN AFTER 03Z TO 1-3SM IN
FOG. LIGHT WIND THROUGH THIS EVENING. FELTON
&&
.SEW WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY WEST
ENTRANCE TO THE STRAIT THIS MORNING.
$$
WEATHER.GOV/SEATTLE