AREA FORECAST DISCUSSION
NWS UPTON NY
126 PM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE BUILDING IN FROM THE MIDWEST THIS MORNING WILL MOVE
ACROSS THE REGION TODAY AND OFF THE NORTHEAST COAST TONIGHT.
ANOTHER LOW MOVES THROUGH THE GREAT LAKES AND SOUTHEASTERN CANADA
TONIGHT AND THURSDAY...BRINGING ANOTHER COLD FRONT THROUGH
THURSDAY AFTERNOON. HIGH PRESSURE BUILDS SOUTH OF THE AREA
FRIDAY...FOLLOWED BY AN ARCTIC COLD FRONT FRIDAY NIGHT. HIGH
PRESSURE BUILDS IN FROM CANADA SATURDAY. A COMPLEX STORM SYSTEM
APPROACHES FROM THE WEST SUNDAY...THEN MOVES THROUGH THE REGION
MONDAY AND MONDAY NIGHT. ANOTHER CANADIAN HIGH BUILDS TOWARD THE
REGION TUESDAY AS THE STORM REMAINS OVER THE CANADIAN MARITIMES.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
FORECAST APPEARS TO BE ON TRACK...SO NO CHANGES WILL BE MADE TO
THE ZONES OR GRIDS. AFTER A CHECK OF THE OKX 28/12Z SOUNDING AND
LOCAL ACARS SOUNDINGS...LOOKS LIKE WE`LL MIX UP TO AROUND 2500-3000
FT WHERE THE TEMPERATURE IS AROUND -4C. WITH DOWNSLOPE INFLUENCE
WEAKENING AS THE PRESSURE GRADIENT LOOSENS THIS AFTERNOON...AGREE
WITH CURRENT FORECAST FOR HIGHS GENERALLY IN THE LOW TO MID 40S.
PLENTY OF SUN WITH CIRRUS BECOMING MORE NOTICEABLE LATER THIS
AFTERNOON. THE PREVIOUS DISCUSSION FOLLOWS...
SURFACE TROUGH MOVING THROUGH THE REGION EARLY THIS
MORNING...BRINGING A REINFORCING SHOT OF COLD AIR. HAVE LEANED
TOWARD THE COLDER FWC NUMBERS...BUT THESE MAY BE TOO HIGH WITH
INITIAL COLD AIR USUALLY NOT HANDLED WELL IN THE SHORT TERM. WILL
SEE GUSTY WEST TO NORTHWEST WINDS QUICKLY DIMINISH EARLY THIS
MORNING AS THE GRADIENT QUICKLY WEAKENS BEHIND THE TROUGH. UPPER
FLOW MORE ZONAL WITH QUICK PROGRESSIVE FLOW.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
ZONAL UPPER FLOW WILL KEEP SYSTEMS PROGRESSIVE FOR TONIGHT AS
SURFACE HIGH BUILDS OFF THE NORTHEAST COAST AND NEXT SHORT WAVE
APPROACHES LATE TONIGHT. SYSTEM IS RATHER DRY AND HAVE REMOVED
PRECIPITATION FROM THE TONIGHT PERIOD. SOUTHERLY WARM ADVECTION
FLOW IS EXPECTED TO WARM THE BOUNDARY LAYER ENOUGH BEFORE THE
ONSET OF PRECIPITATION THURSDAY MORNING AND HAVE GONE WITH AN ALL
LIQUID EVENT. THERE COULD BE A FEW AREAS WHERE THE START OF THE
PRECIPITATION COULD BE MIXED. THIS SYSTEM MOVES THROUGH QUICKLY
TOO AND END CHANCES THURSDAY AFTERNOON.
COLD ADVECTION FOR THURSDAY NIGHT. AGAIN LEANED TOWARD THE COLDER
TEMPERATURES THURSDAY NIGHT. ZONAL FLOW CONTINUES THURSDAY NIGHT
INTO FRIDAY NIGHT WITH ANOTHER SHORT WAVE MOVING INTO THE AREA
FRIDAY NIGHT. BEST LIFT IS NORTH OF THE AREA FRIDAY NIGHT SO
REMOVED POPS FOR THIS PERIOD...WITH SURFACE COLD FRONT COMING
THROUGH DRY...WILL JUST SEE AN INCREASE IN CLOUDS.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
LONG TERM BASED ON A BLEND OF 12Z GEFS MEAN AND 12Z ECMWF. 12Z
GFS APPEARS TO BE AN OUTLIER...EVEN AMONGST ITS ENSEMBLE MEMBERS
(ONLY SUPPORTED BY 2 OF 12 ENSEMBLE MEMBERS)...IN BEING THE
STRONGEST/MOST PROGRESSIVE/FURTHEST SE WITH 500 MB LOW FOR THE
SYSTEM FOR EARLY NEXT WEEK. THAT BEING SAID...THERE IS A LARGE
DEGREE OF UNCERTAINTY IN LONG TERM ESPECIALLY FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT WITH QUITE A DEGREE OF SPREAD NOTED AMONG THE
ENSEMBLE MEMBERS OF BOTH THE GEFS AND CMC GLOBAL WITH THE STORM
SYSTEM PROGGED FOR EARLY NEXT WEEK.
APPEARS RATHER CHILLY AIRMASS FOR THIS TIME OF YEAR MOVES IN ON
SATURDAY WITH TEMPERATURES STRUGGLING TO HIT THE MID 30S INLAND
AND REACH 40 NYC METRO AND LONG ISLAND (UNDER CUT GUIDANCE BY 3-5
DEGREES)...BLEND OF MEX/MEX ENSEMBLE MEAN REASONABLE FOR THE COLD
ON SATURDAY NIGHT AND SUNDAY).
SUPPORTING CANADIAN HIGH IS FORECAST TO MOVE QUICKLY OFF TO THE
NORTHEAST BY SUNDAY NIGHT...SO THERE IS SOME QUESTION OF HOW MUCH
COLD AIR WILL BE IN PLACE AS PRECIPITATION SPREADS INTO THE REGION
SUNDAY NIGHT (GEFS ARGUES FOR MORE COLD AIR AND ECMWF ARGUES FOR
LESS). FOR NOW PLAID EITHER AS SNOW/RAIN AND SNOW/OR RAIN TO KEEP
THINGS SIMPLE...THOUGH WITH GENERAL CONSENSUS OF MAIN LOW PASSING
TO THE NORTH/WEST WITH COASTAL LOW DEVELOPING TO THE SOUTH...COULD
END UP WITH ISSUES WITH FREEZING PRECIP SUNDAY NIGHT INTO MONDAY
MORNING AS THINGS STAND...ESPECIALLY ACROSS INTERIOR PORTIONS OF
THE LOWER HUDSON VALLEY. LOW TRACK AND ECMWF AND GEFS 850 TEMPS
SUPPORT WARMER HIGHS THAN GUIDANCE ON MONDAY...(SHOULD SEE ABOVE
ZERO 850 TEMPS EVERY WHERE BY AROUND MIDDAY) SO WENT ABOVE WARMEST
GUIDANCE BY 3-5 DEGREES AND WENT WITH ALL RAIN IN THE AFTERNOON.
COLD AIR RETURNS MONDAY NIGHT AS THE SYSTEM DEPARTS...SO PRECIP
CHANGES BACK TO SNOW ACROSS NORTHEAST AREAS. SOME INDICATIONS LOW
COULD STALL OUT (12Z ECMWF DEVELOPS A CUT OFF LATER THAN GFS) SO
LINGERED SLIGHT CHANCE POPS INTO TUE OVER EASTERN AREAS.
BOTTOM LINE...IS THAT EXTENDED PERIOD SHOULD HAVE PREDOMINATELY
BELOW NORMAL TEMPERATURES (MAINLY WELL BELOW NORMAL) WITH AN
UNSETTLED WEATHER EARLY NEXT WEEK...THAT COULD POSE SOME PRECIP-
TYPE ISSUES...ESPECIALLY ACROSS AREAS NW OF METRO NYC.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
SURFACE HIGH BUILDS ACROSS THE TERMINALS THIS AFTERNOON WITH WINDS
BECOMING LIGHT AND VARIABLE BETWEEN 20Z AND 22Z. THERE WILL BE A
FEW CU AND SCT-BKN CIRRUS.
WINDS VEER AROUND TO THE SE AT LESS THAN 10 KT THIS EVENING AS THE
SURFACE HIGH MOVES OFFSHORE...GOING AROUND TO THE S AROUND 06Z.
CIRRUS CANOPY THICKENS AND LOWERS OVERNIGHT TO BETWEEN 15 AND 20
KFT. MODEL TIME HEIGHT CROSS SECTIONS SHOW A PRONOUNCED INCREASE
IN LOW-LEVEL MOISTURE...AROUND 950 MB...BENEATH THE BASE OF A
STRENGTHENING LOW-LEVEL INVERSION. AT THIS TIME...WILL GO WITH SCT
CLOUDS AROUND 3 KFT...BUT TURBULENT MIXING AT THE TOP OF THE
INVERSION MAY ALLOW TOO MUCH DRY AIR ENTRAINMENT FOR AN MVFR
CEILING.
AFTER 12Z THU...COLD FRONT APPROACHES IN THE MORNING WITH A
STRENGTHENING SLY FLOW AT 10 TO 15 KT WITH GUSTS UP TO 20 KT. VFR
CEILINGS WITH SCT CU BETWEEN 2 AND 3 KFT. FRONTAL PASSAGE WILL BE
JUST AFTER 18Z WITH MINIMAL CHANCES OF PCPN.
OUTLOOK FROM 18Z THURSDAY THROUGH MONDAY...
VFR THROUGH SAT. A LARGE-SCALE OVERRUNNING EVENT THEN DEVELOPS
SUN WITH SUB-VFR CONDITIONS SUN INTO MON.
&&
.MARINE...
GUSTS ACROSS THE WATERS HAVE NOW DIPPED BELOW 25 KT WITH PRESSURE
GRADIENT WEAKENING OVER THE AREA. WITH AN OFFSHORE FLOW...EXPECTING
THAT SEAS ON THE OCEAN WILL SUBSIDE BELOW 5 FT BY THIS
AFTERNOON...SO CURRENT FORECAST APPEARS TO BE ON TRACK. NO UPDATE
THEREFORE NECESSARY. THE PREVIOUS DISCUSSION FOLLOWS...
WINDS GUSTY ON BACK SIDE OF TROUGH...AND THESE WINDS SHOULD
DIMINISH RAPIDLY THIS MORNING WITH THE APPROACH OF HIGH PRESSURE.
GUSTY NW WINDS WILL TURN N...AND LIGHTEN TO UNDER 10 KTS BEFORE
BECOMING SOUTH LATE TODAY AND TONIGHT.
THESE SOUTHERLY WINDS ARE EXPECTED TO INCREASE TONIGHT AHEAD OF AN
APPROACHING COLD FRONT. SCA WINDS QUITE POSSIBLE THURSDAY AHEAD OF
AND BEHIND FRONT. GRADIENT REMAINS TIGHT THROUGH FRI WITH NEAR SCA
WINDS EXPECTED AS HIGH PRESSURE MOVES WELL TO THE SOUTH. GUSTY WINDS
PERSIST INTO SAT IN STRONG CAA IN WAKE OF POLAR FRONT.
LATE SATURDAY THROUGH SUNDAY...WINDS AND THUS SEAS MAY IMPROVE AS A
RIDGE OF HIGH PRESSURE BRIEFLY BUILDS ACROSS AREA WATERS...THEN MOVES
EAST. NEXT STORM SYSTEM WILL BRING WINDS RIGHT BACK UP FOR SUNDAY.
LOOKING AHEAD TO NEXT WEEK...COULD BE QUITE WINDY BEHIND THIS
STORM...WITH GALES POSSIBLE.
WAVE WATCH III FORECAST INITIALLY LOW AS WESTERLY WINDS HAVE KICKED
UP SEAS QUITE A BIT ACROSS EASTERN WATERS. OTHERWISE...WILL FOLLOW
CLOSELY FROM LATE TODAY ONWARD.
&&
.HYDROLOGY...
DRY WEATHER TODAY AND TONIGHT. THERE IS A CHANCE OF A MINOR
RAIN EVENT THURSDAY. A MORE SIGNIFICANT PRECIPITATION EVENT IS
EXPECTED SUNDAY INTO MONDAY WITH ONE HALF TO ONE INCH OF LIQUID
PRECIPITATION POSSIBLE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...NONE.
&&
$$
AVIATION...DW
AREA FORECAST DISCUSSION
NWS UPTON NY
947 AM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE BUILDING IN FROM THE MIDWEST THIS MORNING WILL MOVE
ACROSS THE REGION TODAY AND OFF THE NORTHEAST COAST TONIGHT.
ANOTHER LOW MOVES THROUGH THE GREAT LAKES AND SOUTHEASTERN CANADA
TONIGHT AND THURSDAY...BRINGING ANOTHER COLD FRONT THROUGH
THURSDAY AFTERNOON. HIGH PRESSURE BUILDS SOUTH OF THE AREA
FRIDAY...FOLLOWED BY AN ARCTIC COLD FRONT FRIDAY NIGHT. HIGH
PRESSURE BUILDS IN FROM CANADA SATURDAY. A COMPLEX STORM SYSTEM
APPROACHES FROM THE WEST SUNDAY...THEN MOVES THROUGH THE REGION
MONDAY AND MONDAY NIGHT. ANOTHER CANADIAN HIGH BUILDS TOWARD THE
REGION TUESDAY AS THE STORM REMAINS OVER THE CANADIAN MARITIMES.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
FORECAST APPEARS TO BE ON TRACK...SO NO CHANGES WILL BE MADE TO
THE ZONES OR GRIDS. AFTER A CHECK OF THE OKX 28/12Z SOUNDING AND
LOCAL ACARS SOUNDINGS...LOOKS LIKE WE`LL MIX UP TO AROUND 2500-3000
FT WHERE THE TEMPERATURE IS AROUND -4C. WITH DOWNSLOPE INFLUENCE
WEAKENING AS THE PRESSURE GRADIENT LOOSENS THIS AFTERNOON...AGREE
WITH CURRENT FORECAST FOR HIGHS GENERALLY IN THE LOW TO MID 40S.
PLENTY OF SUN WITH CIRRUS BECOMING MORE NOTICEABLE LATER THIS
AFTERNOON. THE PREVIOUS DISCUSSION FOLLOWS...
SURFACE TROUGH MOVING THROUGH THE REGION EARLY THIS
MORNING...BRINGING A REINFORCING SHOT OF COLD AIR. HAVE LEANED
TOWARD THE COLDER FWC NUMBERS...BUT THESE MAY BE TOO HIGH WITH
INITIAL COLD AIR USUALLY NOT HANDLED WELL IN THE SHORT TERM. WILL
SEE GUSTY WEST TO NORTHWEST WINDS QUICKLY DIMINISH EARLY THIS
MORNING AS THE GRADIENT QUICKLY WEAKENS BEHIND THE TROUGH. UPPER
FLOW MORE ZONAL WITH QUICK PROGRESSIVE FLOW.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
ZONAL UPPER FLOW WILL KEEP SYSTEMS PROGRESSIVE FOR TONIGHT AS
SURFACE HIGH BUILDS OFF THE NORTHEAST COAST AND NEXT SHORT WAVE
APPROACHES LATE TONIGHT. SYSTEM IS RATHER DRY AND HAVE REMOVED
PRECIPITATION FROM THE TONIGHT PERIOD. SOUTHERLY WARM ADVECTION
FLOW IS EXPECTED TO WARM THE BOUNDARY LAYER ENOUGH BEFORE THE
ONSET OF PRECIPITATION THURSDAY MORNING AND HAVE GONE WITH AN ALL
LIQUID EVENT. THERE COULD BE A FEW AREAS WHERE THE START OF THE
PRECIPITATION COULD BE MIXED. THIS SYSTEM MOVES THROUGH QUICKLY
TOO AND END CHANCES THURSDAY AFTERNOON.
COLD ADVECTION FOR THURSDAY NIGHT. AGAIN LEANED TOWARD THE COLDER
TEMPERATURES THURSDAY NIGHT. ZONAL FLOW CONTINUES THURSDAY NIGHT
INTO FRIDAY NIGHT WITH ANOTHER SHORT WAVE MOVING INTO THE AREA
FRIDAY NIGHT. BEST LIFT IS NORTH OF THE AREA FRIDAY NIGHT SO
REMOVED POPS FOR THIS PERIOD...WITH SURFACE COLD FRONT COMING
THROUGH DRY...WILL JUST SEE AN INCREASE IN CLOUDS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
LONG TERM BASED ON A BLEND OF 12Z GEFS MEAN AND 12Z ECMWF. 12Z
GFS APPEARS TO BE AN OUTLIER...EVEN AMONGST ITS ENSEMBLE MEMBERS
(ONLY SUPPORTED BY 2 OF 12 ENSEMBLE MEMBERS)...IN BEING THE
STRONGEST/MOST PROGRESSIVE/FURTHEST SE WITH 500 MB LOW FOR THE
SYSTEM FOR EARLY NEXT WEEK. THAT BEING SAID...THERE IS A LARGE
DEGREE OF UNCERTAINTY IN LONG TERM ESPECIALLY FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT WITH QUITE A DEGREE OF SPREAD NOTED AMONG THE
ENSEMBLE MEMBERS OF BOTH THE GEFS AND CMC GLOBAL WITH THE STORM
SYSTEM PROGGED FOR EARLY NEXT WEEK.
APPEARS RATHER CHILLY AIRMASS FOR THIS TIME OF YEAR MOVES IN ON
SATURDAY WITH TEMPERATURES STRUGGLING TO HIT THE MID 30S INLAND
AND REACH 40 NYC METRO AND LONG ISLAND (UNDER CUT GUIDANCE BY 3-5
DEGREES)...BLEND OF MEX/MEX ENSEMBLE MEAN REASONABLE FOR THE COLD
ON SATURDAY NIGHT AND SUNDAY).
SUPPORTING CANADIAN HIGH IS FORECAST TO MOVE QUICKLY OFF TO THE
NORTHEAST BY SUNDAY NIGHT...SO THERE IS SOME QUESTION OF HOW MUCH
COLD AIR WILL BE IN PLACE AS PRECIPITATION SPREADS INTO THE REGION
SUNDAY NIGHT (GEFS ARGUES FOR MORE COLD AIR AND ECMWF ARGUES FOR
LESS). FOR NOW PLAID EITHER AS SNOW/RAIN AND SNOW/OR RAIN TO KEEP
THINGS SIMPLE...THOUGH WITH GENERAL CONSENSUS OF MAIN LOW PASSING
TO THE NORTH/WEST WITH COASTAL LOW DEVELOPING TO THE SOUTH...COULD
END UP WITH ISSUES WITH FREEZING PRECIP SUNDAY NIGHT INTO MONDAY
MORNING AS THINGS STAND...ESPECIALLY ACROSS INTERIOR PORTIONS OF
THE LOWER HUDSON VALLEY. LOW TRACK AND ECMWF AND GEFS 850 TEMPS
SUPPORT WARMER HIGHS THAN GUIDANCE ON MONDAY...(SHOULD SEE ABOVE
ZERO 850 TEMPS EVERY WHERE BY AROUND MIDDAY) SO WENT ABOVE WARMEST
GUIDANCE BY 3-5 DEGREES AND WENT WITH ALL RAIN IN THE AFTERNOON.
COLD AIR RETURNS MONDAY NIGHT AS THE SYSTEM DEPARTS...SO PRECIP
CHANGES BACK TO SNOW ACROSS NORTHEAST AREAS. SOME INDICATIONS LOW
COULD STALL OUT (12Z ECMWF DEVELOPS A CUT OFF LATER THAN GFS) SO
LINGERED SLIGHT CHANCE POPS INTO TUE OVER EASTERN AREAS.
BOTTOM LINE...IS THAT EXTENDED PERIOD SHOULD HAVE PREDOMINATELY
BELOW NORMAL TEMPERATURES (MAINLY WELL BELOW NORMAL) WITH AN
UNSETTLED WEATHER EARLY NEXT WEEK...THAT COULD POSE SOME PRECIP-
TYPE ISSUES...ESPECIALLY ACROSS AREAS NW OF METRO NYC.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
FEW CU TODAY AS RIDGE BUILDS IN. NW WINDS AROUND 10 TO 12 KT THIS
MORNING WILL TURN TO THE NORTH AND LIGHTEN FURTHER AS THE HIGH
APPROACHES. COULD SEE AN OCCASIONAL GUST TO 15 TO 18 KTS THROUGH
MID MORNING.
LIGHT WINDS LATE THIS AFTERNOON AND EVENING WITH INCREASING
CIRRUS. EXPECT LIGHT SOUTH WINDS 5 TO 10 KTS LATER TONIGHT AS THE
HIGH PASSES WELL TO THE EAST AND RETURN FLOW SETS UP. COULD SEE
SCT 3 TO 4 KFT CLOUDS AS LOW LEVELS MOISTEN SOMEWHAT IN THIS
RETURN FLOW.
OUTLOOK FROM 12Z THURSDAY THROUGH SUNDAY...
MVFR CONDITIONS POSSIBLE THU MORNING AS A WARM FRONT
APPROACHES. COULD SEE BRIEF MVFR AGAIN THU AFTERNOON WITH THE
PASSAGE OF A COLD FRONT. THEREAFTER...VFR ANTICIPATED WITH HIGH
PRESSURE IN CONTROL. A LARGE-SCALE OVERRUNNING EVENT THEN
DEVELOPS SUN WITH SUB-VFR CONDITIONS LATE SUN.
&&
.MARINE...
GUSTS ACROSS THE WATERS HAVE NOW DIPPED BELOW 25 KT WITH PRESSURE
GRADIENT WEAKENING OVER THE AREA. WITH AN OFFSHORE FLOW...EXPECTING
THAT SEAS ON THE OCEAN WILL SUBSIDE BELOW 5 FT BY THIS
AFTERNOON...SO CURRENT FORECAST APPEARS TO BE ON TRACK. NO UPDATE
THEREFORE NECESSARY. THE PREVIOUS DISCUSSION FOLLOWS...
WINDS GUSTY ON BACK SIDE OF TROUGH...AND THESE WINDS SHOULD
DIMINISH RAPIDLY THIS MORNING WITH THE APPROACH OF HIGH PRESSURE.
GUSTY NW WINDS WILL TURN N...AND LIGHTEN TO UNDER 10 KTS BEFORE
BECOMING SOUTH LATE TODAY AND TONIGHT.
THESE SOUTHERLY WINDS ARE EXPECTED TO INCREASE TONIGHT AHEAD OF AN
APPROACHING COLD FRONT. SCA WINDS QUITE POSSIBLE THURSDAY AHEAD OF
AND BEHIND FRONT. GRADIENT REMAINS TIGHT THROUGH FRI WITH NEAR SCA
WINDS EXPECTED AS HIGH PRESSURE MOVES WELL TO THE SOUTH. GUSTY WINDS
PERSIST INTO SAT IN STRONG CAA IN WAKE OF POLAR FRONT.
LATE SATURDAY THROUGH SUNDAY...WINDS AND THUS SEAS MAY IMPROVE AS A
RIDGE OF HIGH PRESSURE BRIEFLY BUILDS ACROSS AREA WATERS...THEN MOVES
EAST. NEXT STORM SYSTEM WILL BRING WINDS RIGHT BACK UP FOR SUNDAY.
LOOKING AHEAD TO NEXT WEEK...COULD BE QUITE WINDY BEHIND THIS
STORM...WITH GALES POSSIBLE.
WAVE WATCH III FORECAST INITIALLY LOW AS WESTERLY WINDS HAVE KICKED
UP SEAS QUITE A BIT ACROSS EASTERN WATERS. OTHERWISE...WILL FOLLOW
CLOSELY FROM LATE TODAY ONWARD.
&&
.HYDROLOGY...
DRY WEATHER TODAY AND TONIGHT. THERE IS A CHANCE OF A MINOR
RAIN EVENT THURSDAY. A MORE SIGNIFICANT PRECIPITATION EVENT IS
EXPECTED SUNDAY INTO MONDAY WITH ONE HALF TO ONE INCH OF LIQUID
PRECIPITATION POSSIBLE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR ANZ350-
353-355.
&&
$$
SYNOPSIS...MET
NEAR TERM...JC/MET
SHORT TERM...MET
LONG TERM...MET
AVIATION...PW
MARINE...JC/PW
HYDROLOGY...MET
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
1039 AM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE WILL COVER THE AREA TODAY. A WEAK DRY COLD FRONT
WILL APPROACH TONIGHT AND MOVE THROUGH THURSDAY. HIGH PRESSURE
WILL BUILD OVER THE AREA FRIDAY AND SATURDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE CENTERED OVER THE MID-ATLANTIC STATES WILL MOVE EAST
TODAY. SKIES WILL BE CLEAR THIS AFTERNOON BUT MAY SEE SOME
STRATOCUMULUS APPROACH FROM THE SOUTH BY LATE AFTERNOON. LATEST
VISIBLE SATELLITE LOOP SHOWING AREA OF LOW CLOUDS SURGING
NORTHWARD FROM NE FL ALONG THE GA COAST. AFTERNOON FORECAST TEMPS
LOOK GOOD.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
HIGH PRESSURE WILL CONTROL THE WEATHER TODAY. AGREE WITH MODELS
BRINGING A WEAK DRY COLD FRONT TO THE AREA LATE TONIGHT AND
THURSDAY MORNING. NAM SHOWS SOME LOW LEVEL MOISTURE ADVECTED IN
FROM THE SOUTH AHEAD OF THE COLD FRONT LATE TONIGHT AND THURSDAY
MORNING AS WELL BUT NAM TIME SECTION SHOWS JUST SHALLOW MOISTURE
FROM 2-7 KFT. WILL GO PARTLY CLOUDY TONIGHT AND THURSDAY MORNING.
THURSDAY AFTERNOON IS CLEAR AGAIN AS FRONT IS GONE BY THAT TIME.
LOW TEMPERATURES FOR TONIGHT A BIT HIGHER AT UPPER 30S NORTH TO
MID 40S SOUTH. HIGH PRESSURE BUILDS IN BEHIND THE FRONT THURSDAY
NIGHT AND FRIDAY. COLDER THURSDAY NIGHT WITH LOWS IN THE 30S.
HIGHS FOR FRIDAY UPPER 50S TO LOWER 60S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MODELS SHOW NEARLY ZONAL FLOW FRIDAY NIGHT THROUGH SATURDAY NIGHT
AS SURFACE HIGH MOVES TO THE EAST AND NORTH OF THE AREA. A SHORT
WAVE ARRIVES SUNDAY AND DRAGS A COLD FRONT THROUGH THE AREA LATE
SUNDAY NIGHT AND MONDAY MORNING. WILL KEEP A 20-30 PERCENT CHANCE
FOR SHOWERS THIS PERIOD. HIGH TEMPERATURES GENERALLY IN THE 60S
FOR THE EXTENDED PERIOD. LOWS IN THE 30S FRIDAY NIGHT INCREASE TO
THE 40S SUNDAY NIGHT AND BACK INTO THE 30S MONDAY NIGHT BEHIND THE
COLD FRONT.
&&
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
WILL CONTINUE MENTION OF LLWS EARLY THIS MORNING...CONFIRMED BY
RECENT ACARS SOUNDINGS AT CAE. VFR CONDITIONS EXPECTED THROUGHOUT
MUCH OF THE TAF PERIOD. MODELS ARE INDICATING SOME ISENTROPIC LIFT
DEVELOPING TONIGHT...WITH POTENTIAL FOR SOME CLOUDINESS TO DEVELOP
OR MOVE NORTHWARD INTO THE REGION. WILL BRING IN SOME CLOUDS AFTER
06Z...BUT WILL KEEP VFR CIGS AT THIS TIME...IN LINE WITH LATEST
GFS LAMP GUIDANCE.
OTHERWISE...NO SIGNIFICANT AVIATION CONCERNS THROUGH SUNDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
620 AM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE WILL COVER THE AREA TODAY. A WEAK DRY COLD FRONT
WILL APPROACH TONIGHT AND MOVE THROUGH THURSDAY. HIGH PRESSURE
WILL BUILD OVER THE AREA FRIDAY AND SATURDAY.
&&
.NEAR TERM /UNTIL NOON TODAY/...
HIGH PRESSURE WILL COVER THE AREA THIS MORNING. SKIES WILL BE
CLEAR AND WINDS WILL BE LIGHT. TEMPERATURES IN THE UPPER 30S TO
LOWER 40S AT SUNRISE WILL INCREASE TO THE 50S BY NOON.
&&
.SHORT TERM /NOON TODAY THROUGH FRIDAY/...
HIGH PRESSURE WILL CONTROL THE WEATHER TODAY. AGREE WITH MODELS
BRINGING A WEAK DRY COLD FRONT TO THE AREA LATE TONIGHT AND
THURSDAY MORNING. NAM SHOWS SOME LOW LEVEL MOISTURE ADVECTED IN
FROM THE SOUTH AHEAD OF THE COLD FRONT LATE TONIGHT AND THURSDAY
MORNING AS WELL BUT NAM TIME SECTION SHOWS JUST SHALLOW MOISTURE
FROM 2-7 KFT. WILL GO PARTLY CLOUDY TONIGHT AND THURSDAY MORNING.
THURSDAY AFTERNOON IS CLEAR AGAIN AS FRONT IS GONE BY THAT TIME.
LOW TEMPERATURES FOR TONIGHT A BIT HIGHER AT UPPER 30S NORTH TO
MID 40S SOUTH. HIGH PRESSURE BUILDS IN BEHIND THE FRONT THURSDAY
NIGHT AND FRIDAY. COLDER THURSDAY NIGHT WITH LOWS IN THE 30S.
HIGHS FOR FRIDAY UPPER 50S TO LOWER 60S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MODELS SHOW NEARLY ZONAL FLOW FRIDAY NIGHT THROUGH SATURDAY NIGHT
AS SURFACE HIGH MOVES TO THE EAST AND NORTH OF THE AREA. A SHORT
WAVE ARRIVES SUNDAY AND DRAGS A COLD FRONT THROUGH THE AREA LATE
SUNDAY NIGHT AND MONDAY MORNING. WILL KEEP A 20-30 PERCENT CHANCE
FOR SHOWERS THIS PERIOD. HIGH TEMPERATURES GENERALLY IN THE 60S
FOR THE EXTENDED PERIOD. LOWS IN THE 30S FRIDAY NIGHT INCREASE TO
THE 40S SUNDAY NIGHT AND BACK INTO THE 30S MONDAY NIGHT BEHIND THE
COLD FRONT.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
WILL CONTINUE MENTION OF LLWS EARLY THIS MORNING...CONFIRMED BY
RECENT ACARS SOUNDINGS AT CAE. VFR CONDITIONS EXPECTED THROUGHOUT
MUCH OF THE TAF PERIOD. MODELS ARE INDICATING SOME ISENTROPIC LIFT
DEVELOPING TONIGHT...WITH POTENTIAL FOR SOME CLOUDINESS TO DEVELOP
OR MOVE NORTHWARD INTO THE REGION. WILL BRING IN SOME CLOUDS AFTER
06Z...BUT WILL KEEP VFR CIGS AT THIS TIME...IN LINE WITH LATEST
GFS LAMP GUIDANCE.
OTHERWISE...NO SIGNIFICANT AVIATION CONCERNS THROUGH SUNDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
342 AM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE WILL COVER THE AREA TODAY. A WEAK DRY COLD FRONT
WILL APPROACH TONIGHT AND MOVE THROUGH THURSDAY. HIGH PRESSURE
WILL BUILD OVER THE AREA FRIDAY AND SATURDAY.
&&
.NEAR TERM /UNTIL NOON TODAY/...
HIGH PRESSURE WILL COVER THE AREA THIS MORNING. SKIES WILL BE
CLEAR AND WINDS WILL BE LIGHT. TEMPERATURES IN THE UPPER 30S TO
LOWER 40S AT SUNRISE WILL INCREASE TO THE 50S BY NOON.
&&
.SHORT TERM /NOON TODAY THROUGH FRIDAY/...
HIGH PRESSURE WILL CONTROL THE WEATHER TODAY. AGREE WITH MODELS
BRINGING A WEAK DRY COLD FRONT TO THE AREA LATE TONIGHT AND
THURSDAY MORNING. NAM SHOWS SOME LOW LEVEL MOISTURE ADVECTED IN
FROM THE SOUTH AHEAD OF THE COLD FRONT LATE TONIGHT AND THURSDAY
MORNING AS WELL BUT NAM TIME SECTION SHOWS JUST SHALLOW MOISTURE
FROM 2-7 KFT. WILL GO PARTLY CLOUDY TONIGHT AND THURSDAY MORNING.
THURSDAY AFTERNOON IS CLEAR AGAIN AS FRONT IS GONE BY THAT TIME.
LOW TEMPERATURES FOR TONIGHT A BIT HIGHER AT UPPER 30S NORTH TO
MID 40S SOUTH. HIGH PRESSURE BUILDS IN BEHIND THE FRONT THURSDAY
NIGHT AND FRIDAY. COLDER THURSDAY NIGHT WITH LOWS IN THE 30S.
HIGHS FOR FRIDAY UPPER 50S TO LOWER 60S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MODELS SHOW NEARLY ZONAL FLOW FRIDAY NIGHT THROUGH SATURDAY NIGHT
AS SURFACE HIGH MOVES TO THE EAST AND NORTH OF THE AREA. A SHORT
WAVE ARRIVES SUNDAY AND DRAGS A COLD FRONT THROUGH THE AREA LATE
SUNDAY NIGHT AND MONDAY MORNING. WILL KEEP A 20-30 PERCENT CHANCE
FOR SHOWERS THIS PERIOD. HIGH TEMPERATURES GENERALLY IN THE 60S
FOR THE EXTENDED PERIOD. LOWS IN THE 30S FRIDAY NIGHT INCREASE TO
THE 40S SUNDAY NIGHT AND BACK INTO THE 30S MONDAY NIGHT BEHIND THE
COLD FRONT.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD. SOME TEMPORARY LIGHT
MVFR FOG IS POSSIBLE AT OGB THROUGH SUNRISE BUT IT IS NOT EXPECTED
TO BE SIGNIFICANT. WINDS ARE QUITE STRONG JUST OFF THE SURFACE WITH
VAD WIND PROFILES SHOWING NEARLY 40 KNOTS AT 1000 FT WITH SUPPORT
FROM A 0350Z ACARS SOUNDING. WILL INCLUDE LLWS FOR SEVERAL HOURS
THROUGH SUNRISE UNTIL SURFACE WINDS INCREASE OUT OF THE NORTHEAST
WEDNESDAY MORNING.
CLEAR SKIES ARE EXPECTED TODAY WITH COOL HIGH PRESSURE DOMINATING.
MODEL SOUNDINGS INDICATE AN INCREASE IN MOISTURE IN THE 700MB TO
900MB LAYER LATE TONIGHT WITH SOME WEAK ISENTROPIC LIFT IN THIS
LAYER. FOR NOW HAVE LEFT OUT OF THE TAF.
THERE IS SOME POTENTIAL FOR MVFR CEILINGS LATE TONIGHT INTO EARLY
THURSDAY...BUT CONFIDENCE IS NOT VERY HIGH AT THIS TIME.
OTHERWISE...NO SIGNIFICANT AVIATION CONCERNS THROUGH SUNDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
SYNOPSIS...07
NEAR TERM...07
SHORT TERM...07
LONG TERM...07
AVIATION...31
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
1219 AM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH WEDNESDAY. A WEAK DRY
COLD FRONT WILL MOVE THROUGH THURSDAY. HIGH PRESSURE WILL COVER
THE AREA FRIDAY AND SATURDAY.
&&
.NEAR TERM /THROUGH TODAY/...
MID LEVEL SHORT WAVE MOVING OVER THE AREA THIS AFTERNOON WITH
EXTENSIVE MID TO HIGH LEVEL CLOUDS. THESE CLOUDS SHOULD START
THINNING OUT EARLY THIS EVENING AS SHORT WAVE MOVES EAST OF THE
AREA. WILL GO MAINLY CLEAR AFTER 00Z. LOW LEVEL COLD ADVECTION
OVERNIGHT...SURFACE WINDS DECOUPLE TOWARD DAYBREAK EXPECT
TEMPERATURES NEAR MAV MOS GUIDANCE...MID 30S TO LOW 40S.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
HIGH PRESSURE OVER THE AREA WEDNESDAY AND AIRMASS DRY...AFTERNOON
MAXIMUM TEMPERATURES SHOULD BE A LITTLE HIGHER THAN TODAY. MODELS
SUGGEST COASTAL TROUGH DEVELOPMENT LATER IN THE DAY WITH SOME WEAK
ISENTROPIC LIFT MAINLY WEDNESDAY NIGHT THROUGH EARLY THURSDAY.
ENSEMBLE 850MB DEW POINT CHART SUGGEST BEST LOW LEVEL MOISTURE
WILL REMAIN ALONG THE COAST. MAV MOS GUIDANCE DOES SUGGEST SOME
CLOUDINESS OVERNIGHT WILL INCREASE SKY COVER GRIDS DURING THE
OVERNIGHT PERIOD. DECREASING CLOUDS THURSDAY MORNING WITH
CONTINUED MODERATION OF TEMPERATURES. APPEARS A DRY COLD FRONT
WILL PUSH THROUGH THE AREA LATE IN THE DAY.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
MODELS IN GOOD AGREEMENT THROUGH SATURDAY THEN SIGNIFICANT
DIFFERENCES NOTED. ZONAL FLOW THROUGH SATURDAY THEN MEAN UPPER
TROUGH IN THE NORTHERN PLAINS EAST TO THE GREAT LAKES REGION BY
TUESDAY. SURFACE LOW DEVELOPMENT IN THE PLAINS MOVING NORTHEAST
TOWARD GREAT LAKES MONDAY. INCREASING UNCERTAINTY IN THE SUNDAY THROUGH
MONDAY TIME FRAME. GFS MUCH MORE PROGRESSIVE PATTERN THAN ECMWF
AND ENSEMBLE MEAN. WILL FORECAST CHANCE RAIN SUNDAY THROUGH MONDAY
THEN COLD FRONT PASSAGE MONDAY NIGHT SHOULD RESULT IN DRY
CONDITIONS AND COOLER BY TUESDAY.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD. SOME TEMPORARY LIGHT
MVFR FOG IS POSSIBLE AT OGB THROUGH SUNRISE BUT IT IS NOT EXPECTED
TO BE SIGNIFICANT. WINDS ARE QUITE STRONG JUST OFF THE SURFACE WITH
VAD WIND PROFILES SHOWING NEARLY 40 KNOTS AT 1000 FT WITH SUPPORT
FROM A 0350Z ACARS SOUNDING. WILL INCLUDE LLWS FOR SEVERAL HOURS
THROUGH SUNRISE UNTIL SURFACE WINDS INCREASE OUT OF THE NORTHEAST
WEDNESDAY MORNING.
CLEAR SKIES ARE EXPECTED TODAY WITH COOL HIGH PRESSURE DOMINATING.
MODEL SOUNDINGS INDICATE AN INCREASE IN MOISTURE IN THE 700MB TO
900MB LAYER LATE TONIGHT WITH SOME WEAK ISENTROPIC LIFT IN THIS
LAYER. FOR NOW HAVE LEFT OUT OF THE TAF.
THERE IS SOME POTENTIAL FOR MVFR CEILINGS LATE TONIGHT INTO EARLY
THURSDAY...BUT CONFIDENCE IS NOT VERY HIGH AT THIS TIME.
OTHERWISE...NO SIGNIFICANT AVIATION CONCERNS THROUGH SUNDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO IL
310 PM CST WED NOV 28 2007
.DISCUSSION...
310 PM CST
MAIN FORECAST CONCERN IS ON STORM SYSTEM TO AFFECT THE AREA THIS
WEEKEND...WITH A POTENTIAL OF MIXED PRECIPITATION EVENTUALLY
BECOMING RAIN SATURDAY NIGHT.
IN THE SHORT TERM...20Z SURFACE OBS/MSAS ANALYSIS INDICATING COLD
FRONTAL BOUNDARY APPROACHING THE MISSISSIPPI RIVER AT THIS TIME. NO
PRECIP IS CURRENTLY ASSOCIATED WITH THIS FRONT...HOWEVER...SOME WEAK
RETURNS ARE NOTED BACK ACROSS SOUTHWEST IOWA MORE LIKELY IN
ASSOCIATION WITH SHEARED VORT MAX MOVING INTO THIS AREA FROM THE
CENTRAL PLAINS. FRONT TRACKS EAST THROUGH NORTHERN ILLINOIS AND
NORTHWEST INDIANA THIS EVENING. WINDS HAVE SLACKENED OFF LATE THIS
AFTERNOON IN A WEAKENING LOW LEVEL HEIGHT GRADIENT JUST AHEAD OF THE
SURFACE FRONT. AS WINDS SHIFT TO THE WEST NORTHWEST BEHIND THE
FRONT...EXPECTED RENEWED WIND GUSTS WITH THE COLD ADVECTION PERHAPS
TO AROUND 30 MPH THROUGH MUCH OF THE EVENING. ALTHOUGH PRECIP HAS
BEEN RATHER LIMITED TO THIS POINT...CANNOT DISCOUNT POSSIBILITY OF
SOME WIDELY SCATTERED LIGHT RAIN SHOWERS DEVELOPING THROUGH EARLY
THIS EVENING AS AFOREMENTIONED VORT MAX MOVES INTO NORTHERN
ILLINOIS. OTHERWISE...SKIES SHOULD CLEAR OVERNIGHT AS SYNOPTIC SCALE
SUBSIDENCE INCREASES IN THE WAKE OF THIS SHORT WAVE. DID NOT MAKE
ANY SIGNIFICANT CHANGES TO THE GOING MIN TEMP FORECAST
TONIGHT...GENERALLY IN THE LOW TO MID 20S.
THURSDAY SHOULD BE A PLEASANT DAY AS SURFACE RIDGE AXIS MOVES INTO
THE MID MS RIVER VALLEY WITH MOSTLY SUNNY SKIES AND WEAKER WINDS.
LOW LEVEL THERMAL TROUGH WILL DIG INTO THE WESTERN GREAT LAKES
TOMORROW WHICH SHOULD SET UP NORTH SOUTH GRADIENT TO MAX TEMPS
TOMORROW RANGING FROM LOW 30S NORTH TO AROUND 40 FAR SOUTH.
ACTIVE SHORT WAVE PATTERN WILL CONTINUE THURSDAY NIGHT INTO EARLY
FRIDAY AS WATER VAPOR IMAGERY ALREADY INDICATING NEXT SHORT WAVE TO
IMPACT THE AREA ENTERING THE PACIFIC NORTHWEST COAST. THIS SHORT
WAVE WILL ENTER A RATHER PRONOUNCED MID/UPPER LEVEL CONFLUENCE ZONE
ACROSS THE CENTRAL CONUS WHICH WILL SHEAR THIS UPPER LEVEL SHORT
WAVE AS IT APPROACHES THE REGION. WRF/GFS HAVE BEEN SOMEWHAT
CONSISTENT IN DEVELOPING MODEST LOW LEVEL FRONTOGENESIS AND A
STRENGTHENING UPPER JET STREAK ACROSS THE UPPER MIDWEST THURSDAY
NIGHT. GIVEN EXPECTED TRACK OF THIS WAVE AND TIGHTER LOW LEVEL
BAROCLINIC ZONE EXPECTED TO STRETCH FROM WESTERN IOWA INTO SOUTHERN
WISCONSIN THURSDAY NIGHT...CHANCE POPS FOR SNOW SHOWERS STILL SEEMS
REASONABLE. ONLY CHANGE MADE WAS TO SLIGHTLY MOVE UP TIMING ON THESE
CHANCE POPS FROM 06Z FRIDAY TO 18Z FRIDAY. A STRONGER HIGH WILL
BUILD INTO THE REGION FRIDAY AFTERNOON/EVENING.
FOCUS THEN SHIFTS TO LARGER SCALE UPPER TROUGH TO IMPACT THE AREA
THIS WEEKEND. LATEST MODEL RUNS INDICATING RATHER STRONG AGREEMENT
BETWEEN OPERATIONAL GFS/ECMWF...WITH NCEP ENSEMBLE MEANS ALSO
GENERALLY SUPPORTING THE OPERATIONAL GFS/ECMWF. CYCLOGENESIS IS
EXPECTED ACROSS THE SOUTHERN PLAINS/CENTRAL PLAINS SATURDAY NIGHT IN
RESPONSE TO DIGGING PACIFIC UPPER TROUGH. STRONG ISENTROPIC UPGLIDE
IN THE LOW/MID LEVELS IS EXPECTED TO OVERSPREAD NORTHERN ILLINOIS
SATURDAY MORNING. MAIN QUESTION FOR SATURDAY IS PRECIPITATION TYPE.
THE STRONG HIGH WILL LEAVE A COLD DRY AIR MASS IN PLACE EARLY
SATURDAY MORNING WHICH SHOULD LEAD TO SNOW INITIALLY. ON SATURDAY
AFTERNOON...EXPECTING ENOUGH LOW LEVEL WARM AIR TO ALLOW FOR MIXED
PRECIPITATION. LATEST GUIDANCE SUGGESTING WARM LAYER WOULD BE STRONG
ENOUGH FOR FREEZING RAIN MAINLY SOUTH OF INTERSTATE 80 WITH A SNOW
SLEET MIX ACROSS FAR NORTHERN ILLINOIS SATURDAY AFTERNOON. A BIT
EARLY TO SPEAK IN TERMS OF SNOWFALL AMOUNTS GIVEN MIXED NATURE OF
PRECIP WHICH MAY LIMIT ACCUMS...ALTHOUGH IT DOES APPEAR THERE WILL
BE A PERIOD OF ACCUMULATING SNOW POSSIBLE SATURDAY MORNING THROUGH
AT LEAST MID AFTERNOON. ON SATURDAY EVENING...PRECIP WILL GRADUALLY
CHANGE OVER TO RAIN AS LOW LEVEL WARM/MOIST ADVECTION INCREASES IN
ADVANCE OF SURFACE LOW EXPECTED TO TRACK ACROSS EASTERN IOWA. MAIN
UPPER TROUGH AXIS WILL SWING OUT OF THE SOUTHERN ROCKIES
SUNDAY...ALLOWING FOR CONTINUED RAIN INTO SUNDAY
AFTERNOON...POSSIBLY MIXING WITH OR CHANGING OVER TO SNOW BEFORE
ENDING LATE SUNDAY.
NOT MANY CHANGES MADE TO EXTENDED FORECAST. LATEST MEDIUM RANGE
MODELS INDICATING BROAD WESTERN CONUS UPPER RIDGE DEAMPLIFYING AS IT
BUILDS EASTWARD INTO THE PLAINS. CHILLY TEMPS FROM THE MID 20S TO
LOWER 30S SHOULD MODERATE BY WEDNESDAY TO HIGHS FROM THE LOWER 30S
TO UPPER 30S AS THIS RIDGE BUILDS EASTWARD.
MARSILI
&&
.AVIATION...
1151 AM CST
FOR THE 18Z TAFS...MAIN FOCUS ON GUSTY WINDS AND TIMING OF COLD
FRONTAL PASSAGE THIS EVENING.
LATEST SURFACE ANALYSIS DEPICTS TROUGH/COLD FRONT FROM NORTHWEST
WISCONSIN SOUTH ACROSS EASTERN IOWA. RELATIVELY TIGHT SURFACE
PRESSURE GRADIENT AHEAD OF THIS TROUGH...WITH 5+ MB/3HR PRESSURE
FALLS ACROSS THE WESTERN LAKES. THIS HAS RESULTED IN STRONG WIND
FIELD THIS MORNING...ESPECIALLY ABOVE THE SURFACE WHERE MORNING
ACARS SOUNDINGS HAVE BEEN INDICATING DEEP LAYER OF 50+ KNOT SOUTH
FLOW ABOVE ABOUT 2000 FEET AGL. RATHER DEEP LOW LEVEL INVERSION
HAS KEPT THINGS UNDER CONTROL AT GROUND LEVEL...WITH GUSTS
OCCASIONALLY INTO THE 20-25 KNOT RANGE. WEAK WARM FRONT TO LIFT
ACROSS TERMINAL SITES NEXT FEW HOURS SHOULD HELP INCREASE MIXING
AND PRODUCE MORE FREQUENT GUSTS...THOUGH GRADIENT ALSO WEAKENING
ESPECIALLY LATER THIS AFTERNOON AS BEST PRESSURE FALLS NOW
PROPAGATING OFF TO THE NORTHEAST AND SURFACE TROUGH APPROACHING.
THUS MAY EVEN LOSE GUSTS FOR A TIME THIS EVENING IN WEAKEST
GRADIENT JUST AHEAD OF THE FRONT ITSELF. SHORT RANGE MODEL
GUIDANCE IN PRETTY GOOD AGREEMENT WITH FROPA AROUND 01Z AT KRFD
AND 03-04Z ACROSS CHICAGO TERMINALS. WINDS GRADUALLY VEERING FROM
ABOUT 190 TO 240 DEG AHEAD OF FRONT...THEN SHIFTING 280-290 DEG
WEST NORTHWEST WITH FROPA. WINDY CONDITIONS RETURN THEN WITH LOW
LEVEL COLD ADVECTION...INCREASING GRADIENT AS TROUGH AXIS MOVES
THROUGH...AND DEEPENING OF LOW ACROSS LAKE SUPERIOR THIS EVENING
EXPECTED TO INCREASE WINDS AND DEPTH OF MIXED LAYER POST FRONTALLY
WITH GUSTS RISING BACK INTO THE 25-30 KNOT RANGE OVERNIGHT.
AS FOR CIGS/VIS...ISENTROPIC UPGLIDE PRODUCING GRADUALLY LOWERING
VFR CIGS THIS AFTERNOON AS DRY LOW LEVEL AIR MOISTENS FROM ABOVE.
WRF 290 KELVIN ISENTROPIC SURFACE DEPICTS THIS WELL WITH
CONDENSATION PRESSURE DEFICITS RAPIDLY DECREASING 21-00Z PERIOD. WRF
OMEGA/DIV-Q FIELDS INDICATE MOST FOCUSED LIFT OCCURS BY EARLY
EVENING WITH APPROACH OF MID LEVEL TROUGH AXIS...WITH POTENTIAL
FOR SPRINKLES LATE AFTERNOON/EARLY EVENING HOURS. HAVE MAINTAINED
VCSH FROM PREVIOUS TAFS...AND WHILE OVERALL EXPECT PREVAILING VFR
CONDITIONS HAVE INDICATED SCATTERED LAYER OF 2000-2500 FOOT BASES
DURING PERIOD OF POTENTIAL PRECIP. FORECAST SOUNDINGS/TIME
SECTIONS INDICATE RAPID DRYING OF LOW LEVELS LATE EVENING AS
COLD/DRY LOW LEVEL ADVECTION STRENGTHENS BEHIND FRONT...SUGGESTS
ANY MVFR POTENTIAL TO BE SHORT LIVED.
RATZER
&&
.MARINE...
202 PM CST
AN ACTIVE WEATHER PERIOD WILL CONTINUE ACROSS THE WESTERN LAKES
THROUGH THE WEEKEND.
LOW PRESSURE WILL CONTINUE TO DEEPEN AS IT MOVES FROM LAKE
SUPERIOR ACROSS EASTERN ONTARIO AND INTO SOUTHERN QUEBEC THROUGH
EARLY FRIDAY MORNING...WHILE A TRAILING COLD FRONT PUSHES ACROSS
LAKE MICHIGAN THIS EVENING. SOUTH GALE FORCE WINDS WILL
TEMPORARILY EASE AS THE GRADIENT WEAKENS IN THE VICINITY OF THE
SURFACE FRONT THIS EVENING...BEFORE WINDS SHIFT WEST AND RETURN TO
GALE FORCE OVERNIGHT. THE GRADIENT WILL THEN SLOWLY WEAKEN
THURSDAY AS THE LOW CONTINUES TO PULL AWAY OVER EASTERN
CANADA...AND HIGH PRESSURE BUILDS ACROSS THE OHIO VALLEY. ANOTHER
COLD FRONT WILL PUSH ACROSS THE WESTERN LAKES EARLY
FRIDAY...BEFORE HIGH PRESSURE BUILDS ACROSS THE WESTERN LAKES
FRIDAY NIGHT. THIS HIGH WILL DRIFT EAST ON SATURDAY...AS STRONG
LOW PRESSURE DEVELOPS ACROSS THE PLAINS. THIS LOW IS FORECAST TO
MOVE TO LAKE MICHIGAN BY SUNDAY...THEN DEEPEN SIGNIFICANTLY AS IT
CONTINUES ACROSS LAKE HURON AND SOUTHERN ONTARIO LATE SUNDAY AND
SUNDAY NIGHT. THIS WILL RESULT IN WINDS INCREASING TO NEAR GALE
FORCE OVER THE WEEKEND...ALONG WITH THE POTENTIAL FOR A MIX OF
SNOW...SLEET...FREEZING RAIN AND RAIN ACROSS THE REGION WITH THIS
STORM.
FOR THE ILLINOIS AND INDIANA NEARSHORE ZONES...GALE WARNING WILL
LIKELY BE ABLE TO BE DROPPED A FEW HOURS EARLY AND REPLACED BY A
SMALL CRAFT ADVISORY LATER THIS AFTERNOON...AS GRADIENT DECREASES
WITH APPROACH OF COLD FRONT.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 6 PM CST THIS AFTERNOON FOR LMZ740>745.
GALE WARNING UNTIL 12 PM CST THURSDAY FOR LMZ777-779.
&&
$$
WFO LOT
AREA FORECAST DISCUSSION
NWS CHICAGO IL
202 PM CST WED NOV 28 2007
.DISCUSSION...
336 AM CST
AFTER A BRIEF LULL IN THE ACTIVITY WITH A COOL...CRISP AFTERNOON
YESTERDAY...WEAK WARM ADVECTION HAS BEGUN IN ADVANCE OF THE
DEVELOPING SYSTEMS OVER THE PLAINS. ALL IS GOING ACCORDING TO
PLAN...BASED ON PREVIOUS THINKING...WITH A NRN STREAM SHORT WAVE
AND ASSOCIATED SFC LOW DEEPENING OVER THE DAKOTAS WHILE THE MIDDLE
STREAM SYSTEM DROPS OUT OF COLORADO AND DEEPENS OVER THE WESTERN
PLAINS. TEMPERATURES HAVE RECOVERED SOMEWHAT OVERNIGHT THOUGH THE
LOCAL AREA REMAINS NORTH OF A WARM FRONT EXTENDING FROM NWRN IOWA
TO THE LOWER OHIO VALLEY. HOWEVER...THIS LULL IN THE ACTIVE
WEATHER WILL QUICKLY COME TO AN END TODAY AS THE WARM FRONT LIFTS
TO THE NORTH...ALLOWING TEMPERATURES TO REBOUND INTO MIDDLE 40S TO
THE NORTH AND NEAR 50 FOR THE SRN LOCATIONS OF THE CWA. BUT WITH
THE INCREASED WARM ADVECTION WILL ALSO COME INCREASED MOISTURE AS
IS EVIDENT IN THE LATEST WATER VAPOR SATELLITE IMAGERY. HAVE MADE
SOME SLIGHT ADJUSTMENT TO THE NEAR TERM FORECAST BY INTRODUCING
PCPN INTO THE NWRN PORTIONS OF THE CWA BY EARLY AFTERNOON AND THEN
QUICKLY SPREADING EWD THROUGH THE EVENING AND OVERNIGHT TONIGHT.
PCPN TYPE WILL BE A BIT TRICKY AS THERE WILL BE A RACE BETWEEN
COLD ADVECTION ALOFT AND THE LOW LEVEL WARM ADVECTION IN ADVANCE
OF THE DEVELOPING SYSTEM TO THE EAST. SO HAVE GONE WITH A MIX OF
RA/SN INITIALLY FOR THE NWRN PORTIONS OF THE CWA WITH ALL RAIN FOR
THE REMAINDER. FOR THE REMAINDER OF THE SHORT TERM...THE NAM AND
GFS ARE IN QUITE GOOD AGREEMENT ON HANDLING THE TIMING AND
INTENSITY OF THE DEVELOPING NRN AND MIDDLE STREAM SYSTEMS AND THE
SUBSEQUENT PHASING OF THE 2 STREAMS TONIGHT. THE LATEST NAM AND
GFS RUNS ARE IN GOOD ENOUGH AGREEMENT BOTH FOR THE CURRENT RUN AND
WITH LAST NIGHT/S SOLUTIONS THAT FORECAST CONFIDENCE IS RELATIVELY
HIGH IN NOT DEVIATING TO FAR FROM THE NAM12 TRENDS AGAIN TONIGHT.
SO WILL EXPECT TO SEE A PERIOD OF RAIN AND MIXED RA/SN MOVE
THROUGH THE CWA THIS AFTERNOON AND EARLY EVENING BEFORE TAPERING
OFF TO LIGHT SNOW AND FLURRIES DURG THE LATE EVENING HOURS.
LOOKING AT ANOTHER BRIEF BREAK IN THE ACTION THURSDAY AS HIGH
PRESSURE RIDGING MOVES ACROSS THE MISSISSIPPI VALLEY...AND THROUGH
THE MIDWEST. A WEAK CLIPPER TRACKING THROUGH THE UPPER MIDWEST
COULD BRING A DUSTING OF LIGHT SNOW TO THE NRN TIER COUNTIES...BUT
EXPECT THAT ANY MORE SUBSTANTIAL SNOW WILL LIKELY BE CONFINED TO
SRN WI...WHERE THE BETTER MID LEVEL FORCING WILL BE.
UNFORTUNATELY...NAM/GFS MODEL SOLUTIONS BEGIN TO DIVERGE BY AROUND
72HRS...WITH THE NAM TRENDING TOWARD A FLATTER...MORE PROGRESSING
PATTERN AND THE GFS TRENDING TOWARD A MORE AMPLIFIED...SLOWER
PATTERN. THE 00Z GFS RUN IS QUITE SIMILAR TO THE 00Z ECMWF...SO
HAVE FOLLOWED THE GFS/ECMWF SOLUTION FOR FRIDAY EVENING THROUGH
SUNDAY. BASED ON THE LATEST GFS/ECMWF...HAVE MADE SOME ADJUSTMENT
TO THE PCPN FIELDS FOR THE WEEKEND. GENERALLY...THE IDEA HAS BEEN
TO BRING PCPN INTO THE CWA FOR THE WEEKEND...BUT...AS USUAL FOR
LATE FALL...PCPN TYPE HAS BEEN THE BIG QUESTION. SO WHILE THE
TEMPTATION IS THERE TO INCREASE POPS TO LIKELY OR EVEN
CATEGORICAL...WILL NOT GET TOO BOLD YET AND MAINTAIN HIGHER END
CHANCE. THE MAIN THING HOLDING BACK FROM INCREASING POPS TOO MUCH
IS THAT THERE ARE DIFFERENCES IN THE LATEST RUNS ON THE TRACK OF
THE MAIN WEATHER MAKER. MODEL CONSISTENCY IN THE DAYS 3-5 PERIOD
IS ENCOURAGING...BUT SINCE THERE ARE STILL SIGNIFICANT RUN TO RUN
DIFFERENCES IN THE GFS...WILL NOT GET TOO BOLD. THE MAIN
DIFFERENCE INTRODUCED TONIGHT IS THAT THE TRACK OF THE MAIN
SURFACE LOW IS MUCH FURTHER NORTH TONIGHT THAN WAS SEEN LAST
NIGHT. THE LATEST TRACK...THROUGH KANSAS...NRN MISSOURI...NRN
ILLINOIS AND THROUGH LOWER MICHIGAN...WOULD INDICATE LESS
POTENTIAL FOR SNOW AND MORE POTENTIAL FOR FREEZING RAIN...SLEET
AND A SLOPPY WINTRY MIX. HAVE TRIED TO CONVEY THIS IDEA IN THE
LATEST WEATHER GRIDS FOR THE PERIOD FROM SATURDAY MORNING THROUGH
SUNDAY NIGHT. THIS PERIOD WILL NEED TO BE CLOSELY MONITORED OVER
THE NEXT FEW DAYS...FOR POTENTIAL HEADLINES FOR THE UPCOMING
WEEKEND. BEYOND SUNDAY NIGHT...HAVE NOT MADE ANY SIGNIFICANT
ADJUSTMENT TO THE GOING FORECAST.
KREIN
&&
.AVIATION...
1151 AM CST
FOR THE 18Z TAFS...MAIN FOCUS ON GUSTY WINDS AND TIMING OF COLD
FRONTAL PASSAGE THIS EVENING.
LATEST SURFACE ANALYSIS DEPICTS TROUGH/COLD FRONT FROM NORTHWEST
WISCONSIN SOUTH ACROSS EASTERN IOWA. RELATIVELY TIGHT SURFACE
PRESSURE GRADIENT AHEAD OF THIS TROUGH...WITH 5+ MB/3HR PRESSURE
FALLS ACROSS THE WESTERN LAKES. THIS HAS RESULTED IN STRONG WIND
FIELD THIS MORNING...ESPECIALLY ABOVE THE SURFACE WHERE MORNING
ACARS SOUNDINGS HAVE BEEN INDICATING DEEP LAYER OF 50+ KNOT SOUTH
FLOW ABOVE ABOUT 2000 FEET AGL. RATHER DEEP LOW LEVEL INVERSION
HAS KEPT THINGS UNDER CONTROL AT GROUND LEVEL...WITH GUSTS
OCCASIONALLY INTO THE 20-25 KNOT RANGE. WEAK WARM FRONT TO LIFT
ACROSS TERMINAL SITES NEXT FEW HOURS SHOULD HELP INCREASE MIXING
AND PRODUCE MORE FREQUENT GUSTS...THOUGH GRADIENT ALSO WEAKENING
ESPECIALLY LATER THIS AFTERNOON AS BEST PRESSURE FALLS NOW
PROPAGATING OFF TO THE NORTHEAST AND SURFACE TROUGH APPROACHING.
THUS MAY EVEN LOSE GUSTS FOR A TIME THIS EVENING IN WEAKEST
GRADIENT JUST AHEAD OF THE FRONT ITSELF. SHORT RANGE MODEL
GUIDANCE IN PRETTY GOOD AGREEMENT WITH FROPA AROUND 01Z AT KRFD
AND 03-04Z ACROSS CHICAGO TERMINALS. WINDS GRADUALLY VEERING FROM
ABOUT 190 TO 240 DEG AHEAD OF FRONT...THEN SHIFTING 280-290 DEG
WEST NORTHWEST WITH FROPA. WINDY CONDITIONS RETURN THEN WITH LOW
LEVEL COLD ADVECTION...INCREASING GRADIENT AS TROUGH AXIS MOVES
THROUGH...AND DEEPENING OF LOW ACROSS LAKE SUPERIOR THIS EVENING
EXPECTED TO INCREASE WINDS AND DEPTH OF MIXED LAYER POST FRONTALLY
WITH GUSTS RISING BACK INTO THE 25-30 KNOT RANGE OVERNIGHT.
AS FOR CIGS/VIS...ISENTROPIC UPGLIDE PRODUCING GRADUALLY LOWERING
VFR CIGS THIS AFTERNOON AS DRY LOW LEVEL AIR MOISTENS FROM ABOVE.
WRF 290 KELVIN ISENTROPIC SURFACE DEPICTS THIS WELL WITH
CONDENSATION PRESSURE DEFICITS RAPIDLY DECREASING 21-00Z PERIOD. WRF
OMEGA/DIV-Q FIELDS INDICATE MOST FOCUSED LIFT OCCURS BY EARLY
EVENING WITH APPROACH OF MID LEVEL TROUGH AXIS...WITH POTENTIAL
FOR SPRINKLES LATE AFTERNOON/EARLY EVENING HOURS. HAVE MAINTAINED
VCSH FROM PREVIOUS TAFS...AND WHILE OVERALL EXPECT PREVAILING VFR
CONDITIONS HAVE INDICATED SCATTERED LAYER OF 2000-2500 FOOT BASES
DURING PERIOD OF POTENTIAL PRECIP. FORECAST SOUNDINGS/TIME
SECTIONS INDICATE RAPID DRYING OF LOW LEVELS LATE EVENING AS
COLD/DRY LOW LEVEL ADVECTION STRENGTHENS BEHIND FRONT...SUGGESTS
ANY MVFR POTENTIAL TO BE SHORT LIVED.
RATZER
&&
.MARINE...
202 PM CST
AN ACTIVE WEATHER PERIOD WILL CONTINUE ACROSS THE WESTERN LAKES
THROUGH THE WEEKEND.
LOW PRESSURE WILL CONTINUE TO DEEPEN AS IT MOVES FROM LAKE
SUPERIOR ACROSS EASTERN ONTARIO AND INTO SOUTHERN QUEBEC THROUGH
EARLY FRIDAY MORNING...WHILE A TRAILING COLD FRONT PUSHES ACROSS
LAKE MICHIGAN THIS EVENING. SOUTH GALE FORCE WINDS WILL
TEMPORARILY EASE AS THE GRADIENT WEAKENS IN THE VICINITY OF THE
SURFACE FRONT THIS EVENING...BEFORE WINDS SHIFT WEST AND RETURN TO
GALE FORCE OVERNIGHT. THE GRADIENT WILL THEN SLOWLY WEAKEN
THURSDAY AS THE LOW CONTINUES TO PULL AWAY OVER EASTERN
CANADA...AND HIGH PRESSURE BUILDS ACROSS THE OHIO VALLEY. ANOTHER
COLD FRONT WILL PUSH ACROSS THE WESTERN LAKES EARLY
FRIDAY...BEFORE HIGH PRESSURE BUILDS ACROSS THE WESTERN LAKES
FRIDAY NIGHT. THIS HIGH WILL DRIFT EAST ON SATURDAY...AS STRONG
LOW PRESSURE DEVELOPS ACROSS THE PLAINS. THIS LOW IS FORECAST TO
MOVE TO LAKE MICHIGAN BY SUNDAY...THEN DEEPEN SIGNIFICANTLY AS IT
CONTINUES ACROSS LAKE HURON AND SOUTHERN ONTARIO LATE SUNDAY AND
SUNDAY NIGHT. THIS WILL RESULT IN WINDS INCREASING TO NEAR GALE
FORCE OVER THE WEEKEND...ALONG WITH THE POTENTIAL FOR A MIX OF
SNOW...SLEET...FREEZING RAIN AND RAIN ACROSS THE REGION WITH THIS
STORM.
FOR THE ILLINOIS AND INDIANA NEARSHORE ZONES...GALE WARNING WILL
LIKELY BE ABLE TO BE DROPPED A FEW HOURS EARLY AND REPLACED BY A
SMALL CRAFT ADVISORY LATER THIS AFTERNOON...AS GRADIENT DECREASES
WITH APPROACH OF COLD FRONT.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 6 PM CST THIS AFTERNOON FOR LMZ740>745.
GALE WARNING UNTIL 12 PM CST THURSDAY FOR LMZ777-779.
&&
$$
WFO LOT
AREA FORECAST DISCUSSION
NWS CHICAGO IL
1151 AM CST WED NOV 28 2007
.DISCUSSION...
336 AM CST
AFTER A BRIEF LULL IN THE ACTIVITY WITH A COOL...CRISP AFTERNOON
YESTERDAY...WEAK WARM ADVECTION HAS BEGUN IN ADVANCE OF THE
DEVELOPING SYSTEMS OVER THE PLAINS. ALL IS GOING ACCORDING TO
PLAN...BASED ON PREVIOUS THINKING...WITH A NRN STREAM SHORT WAVE
AND ASSOCIATED SFC LOW DEEPENING OVER THE DAKOTAS WHILE THE MIDDLE
STREAM SYSTEM DROPS OUT OF COLORADO AND DEEPENS OVER THE WESTERN
PLAINS. TEMPERATURES HAVE RECOVERED SOMEWHAT OVERNIGHT THOUGH THE
LOCAL AREA REMAINS NORTH OF A WARM FRONT EXTENDING FROM NWRN IOWA
TO THE LOWER OHIO VALLEY. HOWEVER...THIS LULL IN THE ACTIVE
WEATHER WILL QUICKLY COME TO AN END TODAY AS THE WARM FRONT LIFTS
TO THE NORTH...ALLOWING TEMPERATURES TO REBOUND INTO MIDDLE 40S TO
THE NORTH AND NEAR 50 FOR THE SRN LOCATIONS OF THE CWA. BUT WITH
THE INCREASED WARM ADVECTION WILL ALSO COME INCREASED MOISTURE AS
IS EVIDENT IN THE LATEST WATER VAPOR SATELLITE IMAGERY. HAVE MADE
SOME SLIGHT ADJUSTMENT TO THE NEAR TERM FORECAST BY INTRODUCING
PCPN INTO THE NWRN PORTIONS OF THE CWA BY EARLY AFTERNOON AND THEN
QUICKLY SPREADING EWD THROUGH THE EVENING AND OVERNIGHT TONIGHT.
PCPN TYPE WILL BE A BIT TRICKY AS THERE WILL BE A RACE BETWEEN
COLD ADVECTION ALOFT AND THE LOW LEVEL WARM ADVECTION IN ADVANCE
OF THE DEVELOPING SYSTEM TO THE EAST. SO HAVE GONE WITH A MIX OF
RA/SN INITIALLY FOR THE NWRN PORTIONS OF THE CWA WITH ALL RAIN FOR
THE REMAINDER. FOR THE REMAINDER OF THE SHORT TERM...THE NAM AND
GFS ARE IN QUITE GOOD AGREEMENT ON HANDLING THE TIMING AND
INTENSITY OF THE DEVELOPING NRN AND MIDDLE STREAM SYSTEMS AND THE
SUBSEQUENT PHASING OF THE 2 STREAMS TONIGHT. THE LATEST NAM AND
GFS RUNS ARE IN GOOD ENOUGH AGREEMENT BOTH FOR THE CURRENT RUN AND
WITH LAST NIGHT/S SOLUTIONS THAT FORECAST CONFIDENCE IS RELATIVELY
HIGH IN NOT DEVIATING TO FAR FROM THE NAM12 TRENDS AGAIN TONIGHT.
SO WILL EXPECT TO SEE A PERIOD OF RAIN AND MIXED RA/SN MOVE
THROUGH THE CWA THIS AFTERNOON AND EARLY EVENING BEFORE TAPERING
OFF TO LIGHT SNOW AND FLURRIES DURG THE LATE EVENING HOURS.
LOOKING AT ANOTHER BRIEF BREAK IN THE ACTION THURSDAY AS HIGH
PRESSURE RIDGING MOVES ACROSS THE MISSISSIPPI VALLEY...AND THROUGH
THE MIDWEST. A WEAK CLIPPER TRACKING THROUGH THE UPPER MIDWEST
COULD BRING A DUSTING OF LIGHT SNOW TO THE NRN TIER COUNTIES...BUT
EXPECT THAT ANY MORE SUBSTANTIAL SNOW WILL LIKELY BE CONFINED TO
SRN WI...WHERE THE BETTER MID LEVEL FORCING WILL BE.
UNFORTUNATELY...NAM/GFS MODEL SOLUTIONS BEGIN TO DIVERGE BY AROUND
72HRS...WITH THE NAM TRENDING TOWARD A FLATTER...MORE PROGRESSING
PATTERN AND THE GFS TRENDING TOWARD A MORE AMPLIFIED...SLOWER
PATTERN. THE 00Z GFS RUN IS QUITE SIMILAR TO THE 00Z ECMWF...SO
HAVE FOLLOWED THE GFS/ECMWF SOLUTION FOR FRIDAY EVENING THROUGH
SUNDAY. BASED ON THE LATEST GFS/ECMWF...HAVE MADE SOME ADJUSTMENT
TO THE PCPN FIELDS FOR THE WEEKEND. GENERALLY...THE IDEA HAS BEEN
TO BRING PCPN INTO THE CWA FOR THE WEEKEND...BUT...AS USUAL FOR
LATE FALL...PCPN TYPE HAS BEEN THE BIG QUESTION. SO WHILE THE
TEMPTATION IS THERE TO INCREASE POPS TO LIKELY OR EVEN
CATEGORICAL...WILL NOT GET TOO BOLD YET AND MAINTAIN HIGHER END
CHANCE. THE MAIN THING HOLDING BACK FROM INCREASING POPS TOO MUCH
IS THAT THERE ARE DIFFERENCES IN THE LATEST RUNS ON THE TRACK OF
THE MAIN WEATHER MAKER. MODEL CONSISTENCY IN THE DAYS 3-5 PERIOD
IS ENCOURAGING...BUT SINCE THERE ARE STILL SIGNIFICANT RUN TO RUN
DIFFERENCES IN THE GFS...WILL NOT GET TOO BOLD. THE MAIN
DIFFERENCE INTRODUCED TONIGHT IS THAT THE TRACK OF THE MAIN
SURFACE LOW IS MUCH FURTHER NORTH TONIGHT THAN WAS SEEN LAST
NIGHT. THE LATEST TRACK...THROUGH KANSAS...NRN MISSOURI...NRN
ILLINOIS AND THROUGH LOWER MICHIGAN...WOULD INDICATE LESS
POTENTIAL FOR SNOW AND MORE POTENTIAL FOR FREEZING RAIN...SLEET
AND A SLOPPY WINTRY MIX. HAVE TRIED TO CONVEY THIS IDEA IN THE
LATEST WEATHER GRIDS FOR THE PERIOD FROM SATURDAY MORNING THROUGH
SUNDAY NIGHT. THIS PERIOD WILL NEED TO BE CLOSELY MONITORED OVER
THE NEXT FEW DAYS...FOR POTENTIAL HEADLINES FOR THE UPCOMING
WEEKEND. BEYOND SUNDAY NIGHT...HAVE NOT MADE ANY SIGNIFICANT
ADJUSTMENT TO THE GOING FORECAST.
KREIN
&&
.AVIATION...
1151 AM CST
FOR THE 18Z TAFS...MAIN FOCUS ON GUSTY WINDS AND TIMING OF COLD
FRONTAL PASSAGE THIS EVENING.
LATEST SURFACE ANALYSIS DEPICTS TROUGH/COLD FRONT FROM NORTHWEST
WISCONSIN SOUTH ACROSS EASTERN IOWA. RELATIVELY TIGHT SURFACE
PRESSURE GRADIENT AHEAD OF THIS TROUGH...WITH 5+ MB/3HR PRESSURE
FALLS ACROSS THE WESTERN LAKES. THIS HAS RESULTED IN STRONG WIND
FIELD THIS MORNING...ESPECIALLY ABOVE THE SURFACE WHERE MORNING
ACARS SOUNDINGS HAVE BEEN INDICATING DEEP LAYER OF 50+ KNOT SOUTH
FLOW ABOVE ABOUT 2000 FEET AGL. RATHER DEEP LOW LEVEL INVERSION
HAS KEPT THINGS UNDER CONTROL AT GROUND LEVEL...WITH GUSTS
OCCASIONALLY INTO THE 20-25 KNOT RANGE. WEAK WARM FRONT TO LIFT
ACROSS TERMINAL SITES NEXT FEW HOURS SHOULD HELP INCREASE MIXING
AND PRODUCE MORE FREQUENT GUSTS...THOUGH GRADIENT ALSO WEAKENING
ESPECIALLY LATER THIS AFTERNOON AS BEST PRESSURE FALLS NOW
PROPAGATING OFF TO THE NORTHEAST AND SURFACE TROUGH APPROACHING.
THUS MAY EVEN LOSE GUSTS FOR A TIME THIS EVENING IN WEAKEST
GRADIENT JUST AHEAD OF THE FRONT ITSELF. SHORT RANGE MODEL
GUIDANCE IN PRETTY GOOD AGREEMENT WITH FROPA AROUND 01Z AT KRFD
AND 03-04Z ACROSS CHICAGO TERMINALS. WINDS GRADUALLY VEERING FROM
ABOUT 190 TO 240 DEG AHEAD OF FRONT...THEN SHIFTING 280-290 DEG
WEST NORTHWEST WITH FROPA. WINDY CONDITIONS RETURN THEN WITH LOW
LEVEL COLD ADVECTION...INCREASING GRADIENT AS TROUGH AXIS MOVES
THROUGH...AND DEEPENING OF LOW ACROSS LAKE SUPERIOR THIS EVENING
EXPECTED TO INCREASE WINDS AND DEPTH OF MIXED LAYER POST FRONTALLY
WITH GUSTS RISING BACK INTO THE 25-30 KNOT RANGE OVERNIGHT.
AS FOR CIGS/VIS...ISENTROPIC UPGLIDE PRODUCING GRADUALLY LOWERING
VFR CIGS THIS AFTERNOON AS DRY LOW LEVEL AIR MOISTENS FROM ABOVE.
WRF 290 KELVIN ISENTROPIC SURFACE DEPICTS THIS WELL WITH
CONDENSATION PRESSURE DEFICITS RAPIDLY DECREASING 21-00Z PERIOD. WRF
OMEGA/DIV-Q FIELDS INDICATE MOST FOCUSED LIFT OCCURS BY EARLY
EVENING WITH APPROACH OF MID LEVEL TROUGH AXIS...WITH POTENTIAL
FOR SPRINKLES LATE AFTERNOON/EARLY EVENING HOURS. HAVE MAINTAINED
VCSH FROM PREVIOUS TAFS...AND WHILE OVERALL EXPECT PREVAILING VFR
CONDITIONS HAVE INDICATED SCATTERED LAYER OF 2000-2500 FOOT BASES
DURING PERIOD OF POTENTIAL PRECIP. FORECAST SOUNDINGS/TIME
SECTIONS INDICATE RAPID DRYING OF LOW LEVELS LATE EVENING AS
COLD/DRY LOW LEVEL ADVECTION STRENGTHENS BEHIND FRONT...SUGGESTS
ANY MVFR POTENTIAL TO BE SHORT LIVED.
RATZER
&&
.MARINE...
300 AM CST
A HIGH PRESSURE AREA FROM SOUTHERN ONTARIO TO OHIO WILL MOVE TO THE
ST. LAWRENCE VALLEY AND MID ATLANTIC COAST BY THIS EVENING.
MEANWHILE...A LOW PRESSURE CENTER OVER EASTERN COLORADO WILL TRACK
NORTHEAST TO THE UPPER PENINSULA OF MICHIGAN BY THIS EVENING WHILE
UNDERGOING MODEST DEEPENING. THIS LOW WILL THEN CONTINUE TO WESTERN
QUEBEC BY MIDDAY THURSDAY WHILE CONTINUING TO DEEPEN. DUE TO THE
DEEPENING NATURE OF THIS LOW AS IT APPROACHES THE WESTERN GREAT
LAKES TODAY...SOUTH TO SOUTHWEST WINDS WILL INCREASE TO GALE FORCE
THIS MORNING. WINDS WILL THEN TURN WEST THIS EVENING WITH GALES
PERSISTING THROUGH TONIGHT AS THE LOW DEEPENS OFF TO THE EAST. A
RIDGE OF HIGH PRESSURE WILL BUILD FROM THE NORTHERN PLAINS TO THE
UPPER MISSISSIPPI VALLEY ON FRIDAY...THEN MOVE ACROSS THE SOUTHERN
GREAT LAKES REGION FRIDAY NIGHT AND SATURDAY AS ANOTHER LOW PRESSURE
INTENSIFIES OVER THE CENTRAL PLAINS.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 6 PM CST THIS AFTERNOON FOR LMZ740>745.
GALE WARNING UNTIL 12 PM CST THURSDAY FOR LMZ777-779.
&&
$$
WFO LOT
AREA FORECAST DISCUSSION
NWS CHICAGO IL
530 AM CST WED NOV 28 2007
.DISCUSSION...
336 AM CST
AFTER A BRIEF LULL IN THE ACTIVITY WITH A COOL...CRISP AFTERNOON
YESTERDAY...WEAK WARM ADVECTION HAS BEGUN IN ADVANCE OF THE
DEVELOPING SYSTEMS OVER THE PLAINS. ALL IS GOING ACCORDING TO
PLAN...BASED ON PREVIOUS THINKING...WITH A NRN STREAM SHORT WAVE AND
ASSOCIATED SFC LOW DEEPENING OVER THE DAKOTAS WHILE THE MIDDLE
STREAM SYSTEM DROPS OUT OF COLORADO AND DEEPENS OVER THE WESTERN
PLAINS. TEMPERATURES HAVE RECOVERED SOMEWHAT OVERNIGHT THOUGH THE
LOCAL AREA REMAINS NORTH OF A WARM FRONT EXTENDING FROM NWRN IOWA TO
THE LOWER OHIO VALLEY. HOWEVER...THIS LULL IN THE ACTIVE WEATHER
WILL QUICKLY COME TO AN END TODAY AS THE WARM FRONT LIFTS TO THE
NORTH...ALLOWING TEMPERATURES TO REBOUND INTO MIDDLE 40S TO THE
NORTH AND NEAR 50 FOR THE SRN LOCATIONS OF THE CWA. BUT WITH THE
INCREASED WARM ADVECTION WILL ALSO COME INCREASED MOISTURE AS IS
EVIDENT IN THE LATEST WATER VAPOR SATELLITE IMAGERY. HAVE MADE SOME
SLIGHT ADJUSTMENT TO THE NEAR TERM FORECAST BY INTRODUCING PCPN INTO
THE NWRN PORTIONS OF THE CWA BY EARLY AFTERNOON AND THEN QUICKLY
SPREADING EWD THROUGH THE EVENING AND OVERNIGHT TONIGHT. PCPN TYPE
WILL BE A BIT TRICKY AS THERE WILL BE A RACE BETWEEN COLD ADVECTION
ALOFT AND THE LOW LEVEL WARM ADVECTION IN ADVANCE OF THE DEVELOPING
SYSTEM TO THE EAST. SO HAVE GONE WITH A MIX OF RA/SN INITIALLY FOR
THE NWRN PORTIONS OF THE CWA WITH ALL RAIN FOR THE REMAINDER. FOR
THE REMAINDER OF THE SHORT TERM...THE NAM AND GFS ARE IN QUITE GOOD
AGREEMENT ON HANDLING THE TIMING AND INTENSITY OF THE DEVELOPING NRN
AND MIDDLE STREAM SYSTEMS AND THE SUBSEQUENT PHASING OF THE 2
STREAMS TONIGHT. THE LATEST NAM AND GFS RUNS ARE IN GOOD ENOUGH
AGREEMENT BOTH FOR THE CURRENT RUN AND WITH LAST NIGHT/S SOLUTIONS
THAT FORECAST CONFIDENCE IS RELATIVELY HIGH IN NOT DEVIATING TO FAR
FROM THE NAM12 TRENDS AGAIN TONIGHT. SO WILL EXPECT TO SEE A PERIOD
OF RAIN AND MIXED RA/SN MOVE THROUGH THE CWA THIS AFTERNOON AND EARLY
EVENING BEFORE TAPERING OFF TO LIGHT SNOW AND FLURRIES DURG THE LATE
EVENING HOURS. LOOKING AT ANOTHER BRIEF BREAK IN THE ACTION
THURSDAY AS HIGH PRESSURE RIDGING MOVES ACROSS THE MISSISSIPPI
VALLEY...AND THROUGH THE MIDWEST. A WEAK CLIPPER TRACKING THROUGH
THE UPPER MIDWEST COULD BRING A DUSTING OF LIGHT SNOW TO THE NRN
TIER COUNTIES...BUT EXPECT THAT ANY MORE SUBSTANTIAL SNOW WILL
LIKELY BE CONFINED TO SRN WI...WHERE THE BETTER MID LEVEL FORCING
WILL BE. UNFORTUNATELY...NAM/GFS MODEL SOLUTIONS BEGIN TO DIVERGE
BY AROUND 72HRS...WITH THE NAM TRENDING TOWARD A FLATTER...MORE
PROGRESSING PATTERN AND THE GFS TRENDING TOWARD A MORE
AMPLIFIED...SLOWER PATTERN. THE 00Z GFS RUN IS QUITE SIMILAR TO
THE 00Z ECMWF...SO HAVE FOLLOWED THE GFS/ECMWF SOLUTION FOR FRIDAY
EVENING THROUGH SUNDAY. BASED ON THE LATEST GFS/ECMWF...HAVE MADE
SOME ADJUSTMENT TO THE PCPN FIELDS FOR THE WEEKEND.
GENERALLY...THE IDEA HAS BEEN TO BRING PCPN INTO THE CWA FOR THE
WEEKEND...BUT...AS USUAL FOR LATE FALL...PCPN TYPE HAS BEEN THE
BIG QUESTION. SO WHILE THE TEMPTATION IS THERE TO INCREASE POPS TO
LIKELY OR EVEN CATEGORICAL...WILL NOT GET TOO BOLD YET AND
MAINTAIN HIGHER END CHANCE. THE MAIN THING HOLDING BACK FROM
INCREASING POPS TOO MUCH IS THAT THERE ARE DIFFERENCES IN THE
LATEST RUNS ON THE TRACK OF THE MAIN WEATHER MAKER. MODEL
CONSISTENCY IN THE DAYS 3-5 PERIOD IS ENCOURAGING...BUT SINCE
THERE ARE STILL SIGNIFICANT RUN TO RUN DIFFERENCES IN THE
GFS...WILL NOT GET TOO BOLD. THE MAIN DIFFERENCE INTRODUCED
TONIGHT IS THAT THE TRACK OF THE MAIN SURFACE LOW IS MUCH FURTHER
NORTH TONIGHT THAN WAS SEEN LAST NIGHT. THE LATEST TRACK...THROUGH
KANSAS...NRN MISSOURI...NRN ILLINOIS AND THROUGH LOWER
MICHIGAN...WOULD INDICATE LESS POTENTIAL FOR SNOW AND MORE
POTENTIAL FOR FREEZING RAIN...SLEET AND A SLOPPY WINTRY MIX. HAVE
TRIED TO CONVEY THIS IDEA IN THE LATEST WEATHER GRIDS FOR THE
PERIOD FROM SATURDAY MORNING THROUGH SUNDAY NIGHT. THIS PERIOD
WILL NEED TO BE CLOSELY MONITORED OVER THE NEXT FEW DAYS...FOR
POTENTIAL HEADLINES FOR THE UPCOMING WEEKEND. BEYOND SUNDAY
NIGHT...HAVE NOT MADE ANY SIGNIFICANT ADJUSTMENT TO THE GOING
FORECAST.
KREIN
&&
.AVIATION...DISCUSSION REGARDING 12Z TAFS...
530 AM CDT
RAPID SUCCESSION OF LOW PRES SYSTEMS TO CONTINUE TODAY. SFC HI PRES
THAT BROUGHT CLR SKIES AND LGT WINDS LAST NIGHT IS OFF TO E AND NXT
STORM SYS IS GETTING BETTER ORGANIZED OVER CENTRAL PLAINS STAS THIS
MRNG. THIS LOW IS FCST TO DEEPEN A BIT AS IT MOVES NEWD TOWARD ERN
UPR MI BY THIS EVENING. THIS PROGRESSIVE PATTERN WILL RESULT IN
RATHER LENGTHY TAFS THIS MRNG DUE TO CHGS IN WINDS VEL. SELY SFC
WINDS HAVE ALREADY BEGUN TO INCRS OVR RGN AHEAD OF THIS LOW WITH RFD
GUSTING TO 24 KTS. IN ADDITION...ILX AND DVN 12Z SOUNDINGS BOTH
SHOW LLWS SITUATION WITH WINDS 195 AT 51 KTS AT 1400 AGL OVR
ILX...AND 200 AT 59 KTS AT 1800 AGL OVR DVN. QUICK CHECK OF ACARS
SOUNDINGS AT ORD AND RFD SHOW WINDY CONDS ALF...BUT UNDER LLWS
CRITERIA WITH WINDS 180 AT 34 KTS AT 1400 FT...AND 41 KTS AT 2100 FT
OVR ORD. HAVE RECIEVED NO PIREPS REFERENCING LLWS ENCOUNTERS THUS
FAR. THEREFORE...HAVE OPTED TO NOT INCLUDE LLWS IN 12Z TAFS...BUT
BE ADVISED IT IS QUITE WINDY AOA 2 THSD FT. STGR WINDS TO W AND S
WILL LIKELY OVERSPREAD NRN IL/NWRN IND THRU 15Z...BUT SFC MIXING
WILL ALSO BE INCRSG WITH TIME AS WELL. WINDS TO BCM MORE SWLY WITH
TIME TDY AS LOW TRACKS NEWD TO W OF RGN THIS AFTN. MOST LOCATIONS
EXPECTED TO HAVE FQT GUSTS ARND 30 KTS BY NOON.
FROPA TO OCCUR ERLY THIS EVENING...WITH WIND SHIFT TO WNW AND SOME
DCRS IN WIND SPEED.
GLFMEX STILL EFFECTIVELY BLOCKED BY HI PRES RIDGE OVR GULF STAS...SO
MEAGER AMT OF LLVL MOISTURE AVBL TO THIS SYS. MAY SEE A FEW LGT
SHWRS WITH FROPA...BUT OVERALL LOOKING FOR VFR CIGS/VIS THRU
PERIOD.
MERZLOCK
&&
.MARINE...DISCUSSION REGARDING 300 AM CST ISSUANCE...
300 AM CST
A HIGH PRESSURE AREA FROM SOUTHERN ONTARIO TO OHIO WILL MOVE TO THE
ST. LAWRENCE VALLEY AND MID ATLANTIC COAST BY THIS EVENING.
MEANWHILE...A LOW PRESSURE CENTER OVER EASTERN COLORADO WILL TRACK
NORTHEAST TO THE UPPER PENINSULA OF MICHIGAN BY THIS EVENING WHILE
UNDERGOING MODEST DEEPENING. THIS LOW WILL THEN CONTINUE TO WESTERN
QUEBEC BY MIDDAY THURSDAY WHILE CONTINUING TO DEEPEN. DUE TO THE
DEEPENING NATURE OF THIS LOW AS IT APPROACHES THE WESTERN GREAT
LAKES TODAY...SOUTH TO SOUTHWEST WINDS WILL INCREASE TO GALE FORCE
THIS MORNING. WINDS WILL THEN TURN WEST THIS EVENING WITH GALES
PERSISTING THROUGH TONIGHT AS THE LOW DEEPENS OFF TO THE EAST. A
RIDGE OF HIGH PRESSURE WILL BUILD FROM THE NORTHERN PLAINS TO THE
UPPER MISSISSIPPI VALLEY ON FRIDAY...THEN MOVE ACROSS THE SOUTHERN
GREAT LAKES REGION FRIDAY NIGHT AND SATURDAY AS ANOTHER LOW PRESSURE
INTENSIFIES OVER THE CENTRAL PLAINS.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 6 PM CST THIS AFTERNOON FOR LMZ740>745.
GALE WARNING UNTIL 12 PM CST THURSDAY FOR LMZ777-779.
&&
$$
WFO LOT
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
422 PM EST WED NOV 28 2007
.SHORT TERM...THROUGH TONIGHT
DEEPENING AREA OF LOW PRESSURE CURRENTLY MOVING ACROSS WESTERN LAKE
SUPERIOR WILL TRACK ACROSS ONTARIO TONIGHT...DRAGGING A COLD FRONT
THROUGH SOUTHEAST MICHIGAN AFTER MIDNIGHT. FORCING AND MOISTURE WILL
NOT BE TOO ABUNDANT WITH THIS SYSTEM...WITH ONLY WEAK MID-LEVEL FGEN
AND SOME RIGHT ENTRANCE REGION FORCING AVAILABLE. AS A RESULT...QPF
AMOUNTS ARE EXPECTED TO BE FAIRLY LIGHT AND PRECIPITATION
SHORT-DURATION.
TRICKY FORECAST AS FAR AS PRECIPITATION TYPE IS CONCERNED.
TEMPERATURES THIS AFTERNOON HAVE STRUGGLED TO CLIMB INTO THE LOW/MID
30S...DESPITE SOUTHERLY FLOW AND THE STRONG WARM AIR ADVECTION THAT
HAD BEEN ADVERTISED BY THE MODELS. ACARS SOUNDINGS FROM DTW SHOW A
STRENGTHENING INVERSION BUILDING ABOVE 950 MB...AND SINCE AVAILABLE
ACARS DATA FROM TODAY BEARS A STRONG RESEMBLANCE TO FORECAST NAM
BUFR SOUNDINGS...WILL LEAN TOWARDS THESE TO FORECAST PRECIP TYPE
TONIGHT.
FORECAST IS FOR A FEW RAIN/SNOW SHOWERS TO AFFECT THE TRI-CITES AND
THUMB BY EARLY THIS EVENING...WITH PRECIP SPREADING TO THE REST OF
LOWER MICHIGAN AFTER 7 PM. AFTER 7 PM...PRECIP TYPE SHOULD CHANGE TO
ALL SNOW ACROSS THE TRI-CITIES AND THUMB...WITH A RAIN/SNOW MIX
EXPECTED FROM THERE SOUTHWARD TO DETROIT...AND RAIN SHOWERS FROM
DETROIT SOUTHWARD. PRECIP WILL CHANGE TO ALL SNOW AFTER MIDNIGHT AS
THE COLD FRONT COMES THROUGH. ACCUMULATIONS ARE EXPECTED TO BE
LIGHT...IF ANY...WITH MAXIMUM ACCUMULATION OF AROUND AN INCH
EXPECTED ACROSS THE THUMB AND TRI-CITIES. CONCERNED THAT IF WE GET
ENOUGH WARM AIR ADVECTION THIS EVENING AHEAD OF THE FRONT...IT COULD
THROW ALL THIS OFF THOUGH. TEMPERATURES WILL REMAIN RELATIVE MILD
TONIGHT...MID TO UPPER 20S...WITH INCREASED WINDS AND MOISTURE.
&&
.LONG TERM...THURSDAY THROUGH TUESDAY
MID LEVEL MOISTURE QUICKLY STRIPS AWAY DURING THE DAY ON THURSDAY AS
HIGH PRESSURE BUILDS INTO THE OHIO VALLEY. HAVE LEFT A LOW CHANCE OF
LIGHT SNOW SHOWERS ACROSS THE NORTHERN CWA WHERE MOISTURE WILL BE A
LITTLE DEEPER...WHILE AREAS TO THE SOUTH SHOULD ONLY SEE A FEW
FLURRIES. COLD AIR ADVECTION CONTINUES THROUGH THE DAY WITH 850MB
TEMPERATURES FALLING TO AS LOW AS 15C IN THE NORTH AND WILL EXPECT
TEMPERATURES TO ONLY REBOUND A FEW DEGREES...IF AT ALL...TO NEAR
30.
POLAR VORTEX NOW DIVING SOUTH INTO NORTHERN MANITOBA AND
SASKATCHEWAN WILL SWING THROUGH THE GREAT LAKES REGION BY NOON ON
FRIDAY. A QUICK BUT STRONG SHOT OF MID LEVEL FRONTOGENESIS IS
EXPECTED TO PASS OVER LOWER MICHIGAN CAUSING SCATTERED SNOW SHOWERS
FROM LATE THURSDAY NIGHT INTO FRIDAY MORNING. ALTHOUGH MODELS ONLY
INDICATING .05 QPF OR LESS...THINK THERE IS A POSSIBILITY THAT
THIS STORM MAY BE OVERLY EFFICIENT AS A JET STREAK AND GOOD UPPER
LEVEL DIVERGENCE PASS OVERHEAD. WOULD NOT BE SURPRISED TO SEE SOME
MINOR ACCUMULATIONS...MAYBE UP TO AN INCH...AS THIS SYSTEM PASSES.
THE FORECAST BECOMES INCREASINGLY DIFFICULT AS WE HEAD INTO THIS
WEEKEND. LOW PRESSURE WILL DEVELOP OVER THE ROCKIES...TRACKING
NORTHEAST TOWARDS THE GREAT LAKES REGION BY SUNDAY NIGHT. MODELS
HAVE COME INTO BETTER AGREEMENT...WITH NEARLY ALL 12Z RUNS SHOWING A
RAPIDLY DEEPENING SURFACE CYCLONE TRACKING ACROSS LOWER MICHIGAN
SUNDAY NIGHT. HOWEVER...BASED ON A WATER VAPOR ANALYSIS
...INITIALIZATION ERRORS CONTINUE ON THE 00Z AND 12Z/28TH CYCLES
INCLUDING BEING TOO PROGRESSIVE WITH THE TROUGH CURRENTLY OVER THE
WESTERN UNITED STATES...NOT ENOUGH RIDGING AT 130 W...AND TOO WEAK
ON THE TROUGH NEAR 140W. THESE INITIALIZATION ERRORS REQUIRE US TO
LEAVE ROOM FOR ADJUSTMENT IN THE STORM TRACK WHICH WILL
SIGNIFICANTLY EFFECT BOTH PRECIPITATION TYPES AND AMOUNTS.
00Z/12Z/28 GFS/ECMWF AND 12Z/28 UKMET ARE IN VERY GOOD AGREEMENT
BRINGING THE SURFACE LOW ACROSS LOWER MICHIGAN SUNDAY
NIGHT...WHILE THE 00Z/27/28 UKMET HAS SHOWN THE SYSTEM TRACKING
ACROSS NORTHWEST OHIO. A VERY COLD AIRMASS WILL BE REINFORCED OVER
THE REGION BEHIND A COLD FRONT ON THURSDAY AND AM SOMEWHAT
SKEPTICAL THAT THE SURFACE LOW WILL BE ABLE TO LIFT THE LOW LEVEL
BAROCLINIC ZONE FAR ENOUGH NORTH TO SUPPORT A STORM TRACK INTO
LOWER MICHIGAN...LENDING CREDIBILITY TO THE UKMET SOLUTION. THESE
DIFFERENCES IN STORM TRACK ARE THE DIFFERENCE BETWEEN ACCUMULATING
SNOW AND POSSIBLY FREEZING RAIN SATURDAY NIGHT...FOLLOWED BY RAIN
SUNDAY...THEN CHANGING BACK TO LIGHT SNOW SHOWERS BEHIND THE COLD
FRONT SUNDAY NIGHT. THE OTHER SCENARIO WOULD PLACE US IN THE COLD
SECTOR BUT WOULD NOT BRING PRECIPITATION IN UNTIL SUNDAY/SUNDAY
NIGHT. STRONG WINDS ARE EXPECTED AS THIS STORM SYSTEM RAPIDLY
DEEPENS OVER THE REGION WITH MOST MODELS SHOWING THE CENTRAL
PRESSURE FALLING TO AROUND 984MB BY 12Z MONDAY.
FOR NOW HAVE INCREASED POPS FROM SATURDAY NIGHT THROUGH SUNDAY NIGHT
AND ADDED IN A MENTION OF FREEZING RAIN ACROSS OUR NORTHERN CWA FOR
SATURDAY NIGHT. ACCUMULATING SNOW IS POSSIBLE SATURDAY NIGHT OR
SUNDAY NIGHT WITH SOME IMPACT TO TRAVEL POSSIBLE. REFINEMENTS
WILL MADE TO THE FORECAST AS WE HEAD INTO THIS WEEKEND AND GAIN
CONFIDENCE IN THE STORM TRACK AND PRECIPITATION TYPE.
&&
.MARINE...
GALE FORCE WINDS ARE EXPECTED TO AFFECT ALL MARINE AREAS TONIGHT AS
A STRONG COLD FRONT MOVES THROUGH THE GREAT LAKES. SOUTHWESTERLY
WINDS WILL CONTINUE TO INCREASE TONIGHT AHEAD OF THE FRONT...THEN
FLIP TO THE WEST AFTER MIDNIGHT WHEN THE FRONT COMES THROUGH. WIND
GUSTS WILL BE ESPECIALLY STRONG BEHIND THE FRONT LATE TONIGHT AS
STRONG COLD AIR ADVECTION OCCURS OVER THE RELATIVELY WARMER LAKE
WATERS. CONTINUED INTRUSION OF COLD AIR TOMORROW WILL ALLOW GALE
FORCE WIND GUSTS TO CONTINUE INTO THE AFTERNOON...AND HAVE EXTENDED
GALE WARNINGS FOR ALL NEARSHORE WATERS AND LAKE ST CLAIR INTO
TOMORROW.
ANOTHER LOW PRESSURE SYSTEM...POTENTIALLY SIGNIFICANT...IS EXPECTED
TO IMPACT THE GREAT LAKES THIS WEEKEND. ALTHOUGH DETAILS WITH THIS
STORM SYSTEM ARE STILL UNCERTAIN...IT HAS THE POTENTIAL TO GENERATE
VERY STRONG GALE FORCE WINDS OVER ALL MARINE AREAS...PARTICULARLY ON
SUNDAY AND MONDAY. ANYONE WITH PLANS ON LAKE HURON...LAKE ST
CLAIR...OR WESTERN LAKE ERIE SHOULD PAY CLOSE ATTENTION TO THE
FORECAST.
&&
.PREV DISCUSSION...ISSUED 1254 PM EST WED NOV 28 2007
AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH THE AFTERNOON AND EARLY
EVENING BEFORE A LOW PRESSURE SYSTEM AND COLD FRONT MOVE THROUGH
THE WESTERN GREAT LAKES OVERNIGHT. CEILINGS WILL START TO DROP AND
A FEW SHOWERS WILL START TO DEVELOP BETWEEN 01-03Z AS THE FRONT
BEGINS TO APPROACH. MVFR CEILINGS AND VISIBILITIES ARE EXPECTED TO
SETTLE IN AT ALL TAF SITES AFTER 03-05Z. PERIODS OF IFR
VISIBILITIES WILL BE POSSIBLE AT MBS AS THE COLD FRONT MOVES
THROUGH AND PRECIPITATION TYPE TURNS TO SNOW. PRECIPITATION TYPE
WILL BE MORE MIXED AT FNT...DET AND DTW ALLOWING FOR HIGHER
VISIBILITIES. MOST PRECIPITATION AT DET AND DTW WILL BE IN THE
FORM OF RAIN.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
LOW WATER ADVISORY...INNER SAGINAW BAY...UNTIL MIDNIGHT FRIDAY.
GALE WARNING...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON
INCLUDING SAGINAW BAY...UNTIL 1 PM THURSDAY.
GALE WARNING...LHZ361-LHZ362-LHZ363-LHZ462-LHZ463-LHZ464...UNTIL 4
AM FRIDAY.
LAKE ST CLAIR...
GALE WARNING...UNTIL 10 AM THURSDAY.
SMALL CRAFT ADVISORY...UNTIL 7 PM WEDNESDAY.
MI WATERS OF LAKE ERIE...
GALE WARNING...UNTIL 10 AM THURSDAY.
LOW WATER ADVISORY...FROM 4 AM THURSDAY TO 4 PM THURSDAY.
SMALL CRAFT ADVISORY...UNTIL 7 PM WEDNESDAY.
&&
$$
SHORT TERM...HLO
LONG TERM....KEC
MARINE.......HLO
AVIATION.....HLO
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
338 PM EST WED NOV 28 2007
.SYNOPSIS...
A SURFACE RIDGE OF HIGH PRESSURE EXTENDING FROM THE LOWER GREAT
LAKES SOUTH THROUGH MID ATLANTIC STATES WILL MOVE OFFSHORE BY
TUESDAY MORNING...ALLOWING A WEAK COLD FRONT TO SWEEP EAST THROUGH
THE AREA. THIS FRONT WILL BE FOLLOWED BY ANOTHER HIGH PRESSURE
SYSTEM THAT WILL SETTLE OVER THE MID ATLANTIC REGION LATER THURSDAY
INTO FRIDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
BENIGN WEATHER PATTERN WILL PERSIST OVER THE BLACKSBURG FORECAST
AREA THROUGH THE PERIOD AS DRY HIGH PRESSURE GRADUALLY MOVES
OFFSHORE AND AS A COOL FRONT SWEEPS EAST THROUGH THE REGION. SKIES
SHOULD REMAIN MOSTLY CLEAR ACROSS MOST OF THE AREA TONIGHT...AND
THIN CIRRUS ADVECTING IN FROM THE EAST WILL NOT BE SUFFICIENT TO
OFFSET GOOD RADIATIONAL COOLING EVENT. SURFACE WINDS IN MOST
LOCATIONS WILL BECOME LIGHT AND VARIABLE OR CALM AS LOWER ATMOSPHERE
DECOUPLES...AND LOW DEW POINTS SHOULD ASSURE THAT TEMPERATURES FALL
BELOW GUIDANCE.
AN EXCEPTION TO THE ABOVE WILL BE ACROSS HIGHER ELEVATIONS...WHERE
INCREASING GRADIENT WINDS IN WARM AIR ADVECTION PATTERN WILL RESULT
IN TEMPERATURES AT OR ABOVE GUIDANCE.
ANOTHER CONCERN WILL BE RETURN OF SOME LOW LEVEL MOISTURE LATE
TONIGHT INTO THURSDAY MORNING IN EXTREME SOUTHEASTERN AND EASTERN
PORTIONS OF THE BLACKSBURG AREA BEFORE ARRIVAL OF FRONT. MOISTURE
PROFILE APPEARS TO BE TOO SHALLOW FOR THE DEVELOPMENT OF ANY
DRIZZLE...BUT A PERIOD OF OVERCAST CONDITIONS IS NOT OUT OF THE
QUESTION UNTIL PUSHED EAST BY THE FRONT.
COOL FRONT WILL MOVE EAST THROUGH ENTIRE BLACKSBURG FORECAST AREA
BEFORE NOON ON THURSDAY. DOWNSLOPING CONDITIONS WILL CLEAR SKIES OUT
QUICKLY EAST OF THE BLUE RIDGE...BUT SOME UPSLOPE CLOUDS WILL LINGER
INTO EARLY AFTERNOON ACROSS THE NORMALLY FAVORED UPSLOPE AREAS OF
THE WEST. ONCE AGAIN...THE LOWER ATMOSPHERIC FLOW QUICKLY BECOMES
ANTICYCLONIC...AND DEPTH OF MOIST LAYER IS LIMITED...SO NO
MEASURABLE PRECIPITATION EXPECTED IN THE BLACKSBURG FORECAST AREA.
AIRMASS BEHIND THE COOL FRONT IS NOT ALL THAT COLD...AND WITH GOOD
INSOLATION EXPECTED IN MOST LOCATIONS DURING THE DAY...ESPECIALLY IN
DOWNSLOPE AREAS...RELATIVELY MILD AND SIMILAR MET/MAV GUIDANCE
APPEARED TO BE REASONABLE...WITH HIGHS RANGING FROM THE UPPER 40S
ACROSS THE NORTHWESTERN RIDGES TO NEAR 60 EXTREME SOUTHEAST.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
HIGH PRESSURE TO SETTLE IN WITH DRY WRLY FLOW ALOFT...SHOULD
RESULT IN LOW HUMIDITIES AND A COLD OVERNIGHT LOWS. SOME THIN
HIGH CLOUDS COULD DRIFT ACROSS OUT OF THE SW US WITH WEAK
SUBTROPICAL JET DURING THE DAY FRIDAY BUT SHOULD HAVE LITTLE IMPACT
ON HIGH TEMPS. WENT WITH 30-40% SKY COVERAGE AS OPPOSED TO
ESSENTIALLY CLEAR THAT WAS PROVIDED BY GFS GUIDANCE.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
MEDIUM RANGE MODELS GENERALLY REMAIN IN GOOD AGREEMENT LIFTING A
WEAK WARM FRONT ACROSS US LATE ON SATURDAY BUT WITH HEART OF STORM
SYSTEM REMAINING FARTHER WEST THAN EARLIER MODEL RUNS...IN UPPER
MIDWEST...LOOKS LIKE THERE WILL NOT BE SUFFICIENT MSTR ORISENTROPIC
LIFT FOR ANY PRECIP THIS FAR EAST. STILL GOING TO SLOWLY INCREASE
POPS SATURDAY NIGHT INTO SUNDAY FROM SLGT CHC TO CHC BASED ON SOME
LEVEL OF UNCERTAINTY BUT EASED DOWN FROM RAW GFS GUIDANCE SLIGHTLY.
AS FAR AS MAIN FRONTAL SYSTEM FOR LATER IN THE WEEKEND...MODELS
ALSO IN PRETTY GOOD AGREEMENT WITH THE TIMING OF THE FRONTAL
PASSAGE BEING SUNDAY NIGT OR EARLY MONDAY. 12Z GFS STILL THE
FASTEST SOLN BUT ONLY BY ABOUT 6 HRS. ESSENTIALLY WENT WITH GFS
TIMING ON FRONTAL PASSAGE...WITH HIGHEST POPS SUNDAY NIGHT. WENT A
BIT WARMER THAN GFS GUIDANCE FOR LOWS AHEAD OF FRONT...ESPECIALLY
SUNDAY MORNING AND MONDAY MORNING. GUSTY AND TURNING MUCH COLDER
AGAIN BEHIND FRONT FRO MONDAY NIGHT AND TUES. SOME SNOW SHOWERS
LINGERING IN NW MTNS WITH NW FLOW...HAD TO LINGER SOME SLGT CHC
POPS A LITTLE LONGER BEHIND FRONT THAN WHAT GFS GUIDANCE WAS
GIVING...ESPECIALLY GIVEN ANOTHER REINFORCING S/WV PROGGED TO COME
THRU. NOT CONFIDENT IN GOING ANY HIGH THAN SLIGHT CHC POPS FOR THE
UPSLOPE SNOW INTO TUESDAY YET...BUT IF MODELS REMAIN CONSISTENT
WITH THIS CONTINUED CAA...IT WILL PROBABLY NEED TO BE INCREASED.
SOME SLIGHT MODERATION POSSIBLE BY MID WEEK AS FLOW BECOMES MORE
ZONAL...BUT PLENTY OF COLD AIR REMAINS UP IN CANADA AND IF LARGE
SCALE FLOW BUCKLES A LITTLE MORE COLD AIR CAN EASILY CONTINUE TO
PUSH ON IN.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
VFR WEATHER WITH MAINLY UNRESTRICTED CONDITIONS EXPECTED AT ALL
BLACKSBURG TERMINAL FORECAST POINTS FOR AT LEAST THE NEXT SEVERAL
DAYS. SURFACE HIGH PRESSURE WILL GRADUALLY MOVE OFFSHORE
TONIGHT...ALLOWING A COOL FRONT TO SWEEP EAST THROUGH THE AREA
THURSDAY MORNING. ATMOSPHERE WILL REMAIN QUITE DRY WITH THIS
SYSTEM...SO OTHER THAN SOME SCATTERED TO BROKEN POST FRONTAL
STRATOCUMULUS IN UPSLOPE AREAS OF SOUTHEASTERN WEST VIRGINIA LATER
THURSDAY MORNING UNTIL MID AFTERNOON...OCCASIONAL CIRRUS WILL BE
THE ONLY CLOUDS IN THE SKY.
DECOUPLING OF BOUNDARY LAYER UNDER LINGERING RIDGE AXIS TONIGHT
WILL ALLOW FOR WINDS TO GO CALM OR VARIABLE AT 3 KNOTS OR LESS
UNDER A COOL DRAINAGE WIND AS WINDS JUST OFF THE DECK INCREASE TO
35 KNOTS AS PRESSURE GRADIENT TIGHTENS AHEAD OF APPROACHING COOL
FRONT. THIS WILL RESULT IN THE DEVELOPMENT OF SOME WIND SHEAR AT
ALL TERMINAL FORECAST POINTS TONIGHT INTO THE TIME OF FRONTAL
PASSAGE ON THURSDAY IN 14-16Z TIME FRAME.
ANOTHER DRY COOL FRONT IS EXPECTED TO PASS EAST THROUGH THE AREA
FRIDAY AFTERNOON OR EVENING...WITH NO WEATHER IMPACT TO AIRCRAFT
OPERATIONS EXPECTED. COOL FRONT WILL THEN STALL BEFORE LIFTING
BACK AS A WARM FRONT THROUGH THE MID ATLANTIC REGION SATURDAY
AFTERNOON...POSSIBLY BRINGING A CEILING OF MID AND HIGH LEVEL
CLOUDS BACK INTO THE AREA. HOWEVER...ANY WEATHER INDUCED
RESTRICTIONS TO AIRCRAFT OPERATIONS ASSOCIATED WITH THIS FRONT
SHOULD REMAIN WELL NORTH OF THE BLACKSBURG AREA THROUGH AT LEAST
SATURDAY BEFORE BETTER DYNAMICS AND ASSOCIATED FORCING BEGINS
TO ARRIVE FROM THE WEST ON SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...WERT
NEAR TERM...WERT
SHORT TERM...SK
LONG TERM...SK
AVIATION...WERT
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1238 PM EST WED NOV 28 2007
.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE AREA TONIGHT AND WEDNESDAY.
A WEAK COLD FRONT WILL MOVE THROUGH THE REGION THURSDAY...WITH
HIGH PRESSURE RETURNING AGAIN FOR FRIDAY AND SATURDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A RIDGE OF HIGH PRESSURE AT THE SURFACE WILL REMAIN OVER THE LOWER
GREAT LAKES SOUTH THROUGH MID ATLANTIC REGION TODAY...KEEPING THE
BLACKSBURG FORECAST AREA UNDER CLEAR/MOSTLY CLEAR SKIES...LIGHT WINDS
AND SEASONAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES. 15Z LAMP/LAV
GUIDANCE AND CURRENT SURFACE OBSERVATIONS INDICATE THAT CURRENT
SET OF GRIDS STILL LOOKS GOOD FOR AFTERNOON PERIOD...SO ONLY MADE
A FEW MINOR TWEAKS TO HOURLY TEMPERATURES AND DEW POINTS INTO
EARLY AFTERNOON TO REFLECT CURRENT 2-METER TEMPERATURE PROFILES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
A FAST MOVING TROF COMING OUT OF THE ROCKIES AND NORTHERN PLAINS
TONIGHT WILL BRING A COLD FRONT INTO THE SOUTHERN APPALACHIANS EARLY
THURSDAY MORNING THEN QUICKLY OUT OF THE REGION BY THURSDAY AFTN.
THE FRONT WILL HAVE LIMITED MOISTR ASSOCIATED WITH IT...AND OTHER
THAN SOME SCTD SHOWERS OVER THE WESTERN SLOPES THURSDAY
MORNING...THE FRONT WILL MAINLY BE A WIND PRODUCER. REMOVED THE
CHANCE OF SNOW IN THE WEST WITH THE FRONT AS WARM AIR ADVECTION
AHEAD OF THE FRONT WILL KEEP TEMPS ABOVE THE THRESHOLD FOR SNOW.
SOME MODELS ARE PRODUCING SOME VERY LIGHT PCPN OVER THE VA/NC
PIEDMONT THURSDAY MORNING AS LOW LEVEL MOISTR CRNTLY OFF THE
SOUTHEAST U.S. COAST IS ADVECTED NORTH AHEAD OF THE FRONT...ALTHOUGH
CLOUDS ARE A GOOD BET IN OUR SOUTHEAST COUNTIES THURSDAY
MORNING...THE BEST CHANCE OF PCPN WILL BE EAST OF OUR CWA. WINDS
WILL DIE DOWN THURSDAY NIGHT AS HIGH PRESSURE QUICKLY BUILDS BACK IN
FROM THE WEST. THE HIGH WILL BRING DRY/TRANQUIL WEATHER FOR FRIDAY
WITH NEAR NORMAL TEMPS...AFTER A COLD START IN THE WEST FRIDAY
MORNING.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
LR MODELS HAVE COME INTO BETTER AGREEMENT WITH THIS WEEKENDS SYSTEM.
HOWEVER...THERE STILL REMAINS SOME P TYPE CONCERNS IN THE SHELTERED
MOUNTAIN VALLEYS OF SE WEST VA AND WESTERN VA. H85 WARM PUNCH DOES
SEEM TO MOVE IN FAST ENOUGH TO PREVENT ANY ISSUES...AND ALTHOUGH
HIGH PRESSURE DOES SET UP FARTHER NORTH THAN YESTERDAYS RUNS...IT IS
NOT OF ARCTIC ORIGIN...AS IT TRACKS THROUGH THE UPPER OHIO VALLEY
BEFORE ARRIVING IN NEW ENGLAND. STILL THOUGH WILL KEEP AN EYE ON
GREENBRIER.
STRONG COLD FRONT IS PROGGED TO CROSS NEAR 12Z MONDAY...BUT AT THIS
TIME FRAME...CAN PROBABLY TACK ON ANOTHER 6 TO 12 HOURS BEFORE IT
GETS THROUGH THE CWA. THIS CAUSES A TON OF ISSUES WITH
MOSGUIDE...CONSIDERING IT IS COMPOSED OF PREVIOUS MORE HIGHLY
POLLUTED GFS RUNS...THUS IT SEEMS WAY TOO COLD BOTH SAT NIGHT AND
SUNDAY NIGHT. MIN TEMPS DO NOT MATCH UP AT ALL WITH +6 AN +8C AT H85
ON LATEST GFS RUN BY 12Z SUNDAY. THUS...PLAYED MIN T GRID HIGH
ENOUGH ABOVE MOSGUIDE SO THERE WOULDNT BE ANY P TYPE ISSUES IN WX
GRIDS. BUST POTENTIAL ON TEMPS SUN NIGHT IS HUGE...AND HAVE A
FEELING WE WILL BE RAISING THEM WITH EACH NEW RUN. NEXT TUESDAY
LOOKS TO BE THE COLDEST DAY OF THE SEASON THUS FAR WITH MAX
TEMPS...AND GFS AND ECMWF SEEM TO BE BUILDING HEIGHTS BACK NORTH TOO
QUICKLY FOR THE REST OF THE WEEK. STILL LOOKS LIKE A MORE WINTERLIKE
PATTERN THROUGH NEXT WEEK AND NEXT WEEKEND.
&&
.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
VFR WEATHER WITH MAINLY UNRESTRICTED CONDITIONS EXPECTED AT ALL
BLACKSBURG TERMINAL FORECAST POINTS FOR AT LEAST THE NEXT SEVERAL
DAYS. SURFACE HIGH PRESSURE WILL GRADUALLY MOVE OFFSHORE
TONIGHT...ALLOWING A COOL FRONT TO SWEEP EAST THROUGH THE AREA
THURSDAY MORNING. ATMOSPHERE WILL REMAIN QUITE DRY WITH THIS
SYSTEM...SO OTHER THAN SOME SCATTERED TO BROKEN POST FRONTAL
STRATOCUMULUS IN UPSLOPE AREAS OF SOUTHEASTERN WEST VIRGINIA LATER
THURSDAY MORNING UNTIL MID AFTERNOON...OCCASIONAL CIRRUS WILL BE
THE ONLY CLOUDS IN THE SKY.
DECOUPLING OF BOUNDARY LAYER UNDER LINGERING RIDGE AXIS TONIGHT
WILL ALLOW FOR WINDS TO GO CALM OR VARIABLE AT 3 KNOTS OR LESS
UNDER A COOL DRAINAGE WIND AS WINDS JUST OFF THE DECK INCREASE TO
35 KNOTS AS PRESSURE GRADIENT TIGHTENS AHEAD OF APPROACHING COOL
FRONT. THIS WILL RESULT IN THE DEVELOPMENT OF SOME WIND SHEAR AT
ALL TERMINAL FORECAST POINTS TONIGHT INTO THE TIME OF FRONTAL
PASSAGE ON THURSDAY IN 14-16Z TIME FRAME.
ANOTHER DRY COOL FRONT IS EXPECTED TO PASS EAST THROUGH THE AREA
FRIDAY AFTERNOON OR EVENING...WITH NO WEATHER IMPACT TO AIRCRAFT
OPERATIONS EXPECTED. COOL FRONT WILL THEN STALL BEFORE LIFTING
BACK AS A WARM FRONT THROUGH THE MID ATLANTIC REGION SATURDAY
AFTERNOON...POSSIBLY BRINGING A CEILING OF MID AND HIGH LEVEL
CLOUDS BACK INTO THE AREA. HOWEVER...ANY WEATHER INDUCED
RESTRICTIONS TO AIRCRAFT OPERATIONS ASSOCIATED WITH THIS FRONT
SHOULD REMAIN WELL NORTH OF THE BLACKSBURG AREA THROUGH AT LEAST
SATURDAY BEFORE BETTER DYNAMICS AND ASSOCIATED FORCING BEGINS
TO ARRIVE FROM THE WEST ON SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...WERT
SHORT TERM...KM
LONG TERM...KM
AVIATION...WERT
AREA FORECAST DISCUSSION
NWS SEATTLE WA
925 AM PST WED NOV 28 2007
.SYNOPSIS...A LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT WILL
PASS THROUGH WESTERN WASHINGTON TONIGHT. SNOW LEVELS BE AGAIN BE
LOW WITH LIGHT SNOW POSSIBLE ON THE THE HIGHER HILLS IN THE
LOWLANDS...MAINLY NORTH AND EAST OF SEATTLE AND ALSO ALONG THE
SOUTHWEST PORTION OF HOOD CANAL. SHOWERS WILL TAPER OFF THURSDAY
EVENING WITH BELOW NORMAL TEMPERATURES ACROSS THE AREA. COLD
WEATHER WILL PERSIST THROUGH SATURDAY WITH A CHANCE OF RAIN OR SNOW.
A STRONG WARM FRONT WILL BRING WARMER...WET AND POSSIBLY WINDY
WEATHER BACK TO THE AREA SUNDAY NIGHT THROUGH TUESDAY.
&&
.SHORT TERM...THE MAIN PROBLEM OF THE DAY IN THE SHORT TERM CONCERNS
THE POSSIBILITY OF LOWLAND SNOW TONIGHT AS A LOW PRESSURE
SYSTEM...NOW DEVELOPING NEAR 50N/132W...DRIVES ESE. LATEST 12Z
GUIDANCE SUGGESTS THAT THE LOW WILL MOVE ESE ALONG THE SOUTH SLOPES
OF THE OLYMPICS TO JUST SOUTH OF SEATAC THEN INTO EASTERN
WASHINGTON.
THE AIR MASS IS NOT OVERLY COOL AT THIS POINT WITH SURFACE
TEMPERATURES IN THE UPPER 30S TO MID 40S. ACARS FREEZING LEVELS FROM
FLIGHTS IN AND OUT OF SEATAC THIS MORNING ARE NEAR 2500 FEET.
HOWEVER GUIDANCE INSISTS THAT FREEZING LEVELS WILL FALL TO BELOW
1000 FEET THIS EVENING AS PRECIPITATION RATES INCREASE WITH THE
APPROACHING FRONT AND LOW. LOW LEVEL THICKNESSES AND 925 MB
TEMPERATURES SUPPORT THE IDEA THAT ONCE PCPN GETS
GOING...PRECIPITATION WILL CHANGE TO SNOW ON HILLTOPS AND ALONG THE
HOOD CANAL. ACARS SOUNDINGS FROM VANCOUVER BC ALREADY SHOW FREEZING
LEVELS FALLING TO AROUND 1000-1500 FT AS FLOW BACKS AROUND TO NELY.
THAT BEING SAID...THE 12Z NAM12 AND ITS ASSOCIATED MM5 SOLUTION FROM
UNIVERSITY OF WASHINGTON SHOW PRECIPITATION AS SNOW STARTING AROUND
THIS AFTERNOONS COMUTE EVERETT SOUTHWARD...AND FOCUSES SOME ADVISORY
LEVEL AMOUNTS SEATTLE SOUTHWARD OVERNIGHT WITH SNOW CONTINUING OVER
THE SW INTERIOR THU MORNING. A QUICK LOOK AT THE GFS AND ITS
ASSOCIATED MM5 SOLUTION ALSO INDICATE A SHIFT TO THE SOUTH BUT
OVERNIGHT. IS THE 12Z RUN A REFINEMENT OF THE LOW TRACK OR A FLIP
FLOP. DONT KNOW AT THIS POINT. THE SPS WAS REFRESHED THIS MORNING. I
WILL LIKELY REFRESH IT AGAIN BY NOON AFTER LOOKING AT THE 4 KM MM5
SOLUTION AND THE NEW ECMWF. WILL LIKELY AWAIT ISSUING ANY ADVISORIES
OR WARNINGS UNTIL IT IS CLEAR WHERE PRECIPITATION WILL BE HEAVIEST.
STAY TUNED. WILL LIKELY NEED TO ISSUE A SNOW ADVISORY FOR THE
MOUNTAINS FOR TONIGHT AS THE SYSTEM PASSES.
AFTER THIS SYSTEM GOES BY...A MODIFIED ARCTIC BOUNDARY STAYS STALLED
OVER THE AREA THROUGH THUR AND POSSIBLY INTO FRI OR SAT. THIS MAY
KEEP CONDITIONS CLOUDY AND COLD...LOWS 25-30 AND HIGHS 35-40...WITH
A CHANCE OF SHOWERS IN THE FORM OF SN. LIGHT AMOUNTS THOUGH.
CURRENT FORECASTS LOOK OKAY AT THIS POINT. NO UPDATES ARE PLANNED AT
THIS TIME. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...FOR THE
WEEKEND...BOTH GFS AND THE EUROPEAN MODEL SHOWS AN EXPANSIVE UPPER
LEVEL TROUGH ACROSS WESTERN CANADA WITH A WEAK SURFACE BOUNDARY
LYING ACROSS WASHINGTON. WITH COOLER AIR STILL IN PLACE...MAY
CONTINUE TO SEE A CHANCE OF RAIN OR SNOW ACROSS THE AREA. THEN...BY
SUNDAY MORNING A DEEP SURFACE LOW OVER THE CENTRAL PACIFIC WILL
BRING A WARM FRONT UP THROUGH THE AREA. THIS WILL BRING WARMER BUT
WETTER WEATHER TO THE AREA...WITH MORE SNOW POSSIBLE NORTH. BY
MONDAY...PRESSURE GRADIENTS WILL REALLY TIGHTEN AS BOTH GFS AND EURO
SHOW A DEEP 944MB SURFACE LOW NEAR 50N/140W. THIS SYSTEM WILL HEAD
NORTH NEAR THE QUEEN CHARLOTTE ISLANDS MON EVENING WITH VERY WET AND
WINDY WEATHER ACROSS WEST WASH. 33
&&
.AVIATION...AN UPPER TROF OFFSHORE WILL MOVE ACROSS THE AREA
TONIGHT. MODERATELY STRONG WLY FLOW ALOFT OVER THE REGION WILL
BECOME LIGHT NW OVERNIGHT. A WEAK WMFNT OFF THE COAST WILL MOVE
ONSHORE LATE TODAY AND THEN NEARLY DISSIPATE AS IT LIFTS NEWD ACROSS
WRN WA. THE FAST MOVING CDFNT WILL MOVE ONSHORE EARLY THIS EVENING
AND DISSIPATE AS IT CROSSES THE CASCADES TONIGHT. LOW LEVEL SLY FLOW
BECOMING NLY OVERNIGHT. THE STABLE AIR MASS WILL BECOME MOIST DURING
THE DAY. BY 21Z...ANTICIPATE PREVAILING BASES OF 1-3K FT MSL WITH
MERGING LAYERS TO 20K FT MSL ACROSS THE AREA.
AT KSEA...GENERALLY VFR CONDITIONS TIL ABOUT 18Z...THEN CIGS
LOWERING TO NEAR 015. -RA WILL DEVELOP AFTER 19Z BUT THERE COULD BE
A FEW SPRINKLES BEFORE THEN. WINDS WILL BE SE 4-8 KNOTS...BECMG SLY
8-12 KNOTS AFTER 00Z. THE REMNANTS OF THE WMFNT WILL MOVE ACROSS
THE SITE ABOUT 01Z...WITH THE CDFNT PASSAGE EXPECTED ABOUT 06Z.
&&
.MARINE...A WEAK WARM FRONT ABOUT 115 NM W OF THE WASHINGTON COAST
WILL MOVE ONSHORE LATE TODAY. A FAST MOVING COLD FRONT ABOUT 270 NM
OFFSHORE WILL MOVE ACROSS THE COASTAL WATERS LATER THIS AFTERNOON
AND THE INLAND WATERS THIS EVENING. NORTHERLY FLOW WILL DEVELOP
OVERNIGHT THROUGH FRI IN RESPONSE TO HIGHER PRES OVER BRITISH
COLUMBIA AND LOWER PRES OVER OREGON.
LOOKING FURTHER AHEAD...A STRONG WARM FRONT IS EXPECTED TO MOVE
ACROSS THE AREA SOMETIME SUNDAY. THERE IS A POTENTIAL FOR STORM
FORCE WINDS OVER THE COASTAL WATERS AND THE WEST ENTRANCE TO THE
STRAIT...WITH GALE FORCE WINDS POSSIBLE OVER THE REMAINING
WATERS...AHEAD OR BEHIND THE FRONT.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY ALL WATERS.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION...CORRECTION
NWS LA CROSSE WI
432 AM CST WED NOV 28 2007
.SHORT TERM...TODAY THROUGH FRIDAY
MAIN FORECAST CONCERNS FOR THIS PERIOD WERE SNOW CHANCES TODAY AND
FRIDAY AND WINDS THROUGH THURSDAY.
08Z SURFACE ANALYSIS SHOWED LOW PRESSURE OVER KANSAS WITH WARM FRONT
EXTENDING FROM EAST CENTRAL NEBRASKA THROUGH SOUTHERN IOWA AND INTO
CENTRAL ILLINOIS. AHEAD OF THE FRONT...IR SATELLITE SHOWED CLOUDS
DEVELOPING ACROSS THE FORECAST AREA AND SURFACE OBSERVATIONS DID
INDICATE SNOW IN NORTHEAST MINNESOTA.
IN THE NEAR TERM...QUESTION IS HOW FAR SOUTH THE PRECIPITATION WILL
GET TODAY AND WHEN IT WILL BEGIN. 00Z MODELS CONTINUE TO HAVE
GREATEST AMOUNT OF MOISTURE ALONG WITH BETTER QG CONVERGENCE OVER
NORTHERN WISCONSIN. THEY ALSO HAVE A MIXTURE OF OPINION ON WHEN
SATURATION WILL OCCUR. NAM HAS ALL QPF STAYING NORTH OF THE FORECAST
AREA WHILE GFS BRINGS MEASURABLE PRECIPITATION DOWN INTO IOWA AND
NORTHERN ILLINOIS. 28/03Z SREF HAD GREATER PROBABILITIES FOR QPF OVER
NORTHERN WISCONSIN AND TAPERING OFF GOING SOUTH ALONG THE COLD FRONT.
DID TRIM PRECIPITATION CHANCES BACK ON THE SOUTHERN PART OF THE
FORECAST AREA WITH THE THOUGHTS THAT SATURATION HAS SMALL CHANCES OF
OCCURRING THAT FAR SOUTH. TIMING OF FRONTAL PASSAGE LOOKS GOOD AROUND
18Z. WITH THIS...WINDS WILL SWITCH TO THE NORTHWEST AND AS LAPSE
RATES WILL BE STEEP ALONG WITH A STRONG PRESSURE GRADIENT...WINDS
WILL BE GUSTY.
NEXT ISSUE IS SNOW CHANCES THURSDAY NIGHT INTO FRIDAY WITH COLD
FRONTAL PASSAGE. MODELS DO INDICATE SOME ISENTROPIC LIFT...HOWEVER QG
CONVERGENCE IS MINIMAL AND THERE ARE TIMING DIFFERENCES BETWEEN
MODELS. RIGHT NOW NAM SEEMS TO BE THE OUTLIER AS IT IS A SLOWER
SOLUTION...SO FOR NOW WENT WITH THE OTHER MODELS...WHICH HAD SUPPORT
BY THE SREF AND HAVE SMALL SNOW CHANCES THURSDAY NIGHT.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
A LOW PRESSURE SYSTEM WILL DEVELOP OVER THE SOUTHERN ROCKIES AHEAD OF
A SHORTWAVE TROUGH IN THE WESTERN CONUS FRIDAY NIGHT. 28/00Z GFS AND
ECMWF START BRINGING PRECIPITATION INTO THE FORECAST AREA SATURDAY
MORNING...THEREFORE ADDED SNOW CHANCES FOR THAT TIME FRAME. IF MODELS
CONTINUE ON THIS TREND...THIS LOW PRESSURE SYSTEM MAY BE EAST OF THE
AREA SOONER THAN CURRENT FORECAST INDICATES THEREFORE WILL NEED TO BE
WATCHED BY FOLLOWING SHIFTS. ALSO...WITH MODELS TRYING TO BRING
WARMER AIR NORTH...PRECIPITATION TYPE MAY NEED TO BE WATCHED...
HOWEVER KEPT IT AS SNOW FOR NOW.
&&
.AVIATION...THROUGH TONIGHT
WE ARE CONTINUING TO MONITOR A LOW PRESSURE SYSTEM MOVING OUT OF THE
CENTRAL PLAINS EARLY THIS MORNING. THE GFS CONTINUES TO BE THE ONLY
MODEL THIS MORNING TO SHOW ANY PRECIPITATION ACROSS THE TAF SITES
TODAY. RIGHT NOW...IT IS NOT VERIFYING TOO WELL WITH ITS 06Z TO 12Z
PRECIPITATION. AS A RESULT...I AM STILL NOT CONVINCED THAT WE WILL
SEE MORE THAN SPRINKLE OR FLURRIES WITH THIS SYSTEM. I AM ALSO
BEGINNING TO HAVE SOME DOUBTS ON THE MVFR CEILINGS FOR TODAY. IT
APPEARS THAT BOTH THE NAM/WRF AND GFS ARE A BIT TOO SATURATED AT 925
MB SINCE THERE ARE NO CLOUDS LOWER THAN 8000 FEET RIGHT NOW AND WE
SHOULD ALREADY BE SEEING MVFR CEILINGS ACROSS WESTERN IOWA. HOWEVER
SINCE THEY CONTINUE TO STILL SHOW UP IN THE BUFKIT SOUNDINGS AND
THEY ARE CURRENTLY IN THE TAFS...I AM NOT PLANNING ON MAKING ANY
CHANGES AT THIS TIME. HOWEVER IF THE TAMDAR AND 12Z UPPER AIR
SOUNDINGS SHOW LIMITED MOISTURE LATER ON THIS MORNING...I MAY CHANGE
MY MIND.
AS A COLD FRONT MOVES THROUGH THE REGION THIS AFTERNOON...THE WINDS
WILL SHIFT TO THE WEST AND NORTHWEST AND INCREASE INTO THE 15 TO
25 KNOT RANGE BY LATE THIS AFTERNOON AND CONTINUE THROUGH THE NIGHT.
THERE MAY BE EVEN BE SOME WIND GUSTS UP TO 30 KNOTS FROM TIME TO
TIME.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT AND LONG TERM - BROOKS
AVIATION - BOYNE
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
414 AM CST WED NOV 28 2007
.SHORT TERM...TODAY THROUGH THURSDAY...
CONCERNS THIS MORNING ON CURRENT HEADLINE AND DEVELOPING SNOW. WAA
PATTERN WELL IN PLACE...WITH 50 KT LLVL JET POINTED INTO CENTRAL
WI. THOUGH AT THE SURFACE...DRY AIRMASS HARD TO OVERCOME. LAST
AVAILABLE TAMDAR SOUNDINGS SHOW VERY DRY BELOW 800MB. LIGHT SNOW
JUST BEGINNING TO BREAK OUT IN NW WISCONSIN.
MODELS FAIRLY SIMILAR WITH TROF MOVING THROUGH NORTHERN
PLAINS...SHIFTING EAST THROUGH WI THIS EVENING. DYNAMICS ENOUGH
FOR LIGHT SNOW OVER ENTIRE AREA...ONLY CHANGE TO POPS IS LATER
START EAST CENTRAL. SOME FRONTOGENETIC FORCING FAR NORTH/U.P.
CONCERN IS AVAILABLE MOISTURE. AM NOT CONVINCED WILL MEET SNOW
AMOUNTS ADVERTISED IN CURRENT ADVISORY. ACTUALLY LOWERED INTO 1 TO
3 INCH RANGE OVER THE NORTH. WILL LET ADVISORY RUN AND NOT CONFUSE
PUBLIC WITH SNOW STILL IN FORECAST. THINK EVAPORATIVE COOLING WILL
KEEP THINGS ALL SNOW OVER THE SOUTH THIS AM...SOUNDINGS SHOW SOME
INDICATION FOR MIX EARLY AFTERNOON...THOUGH STAYED WITH SNOW IN
COORDINATION WITH SURROUNDING OFFICES.
ATTENTION THEN TURNS TO LES POTENTIAL TONIGHT AND THU. SIG
INSTABILITY AVAILABLE...THOUGH WINDS MUCH TOO WEST AND INVERSION
HEIGHTS ONLY AROUND 4K. WILL STAY WITH CURRENT CHANCE CATEGORIES
WITH NO SIG ACCUMULATION EXPECTED ATTM.
TEMPERATURES BEGINNING TO CLIMB...WITH CLOUDS AND PCPN STAYED ON
LOWER SIDE OF GUIDANCE TODAY.
.LONG TERM...THURSDAY NITE THRU TUESDAY. FORECAST FOCUS ON A
SIGNIFICANT WINTER STORM THIS WEEKEND.
FORECAST ISSUES BEGIN FAIRLY EARLY AS THE MODELS INDICATE A CHANCE
FOR SOME PRECIP ACROSS PORTIONS OF THE CWA LATE THURSDAY NITE AND
INTO EARLY FRIDAY MORNING. DEPITE THE PROXIMITY OF THE PRECIP
CLOSE TO THE CWA WILL OPT TO KEEP THESE PERIODS DRY AS THE BEST
FORCING REMAINS TO THE SOUTH OF THE CWA. GIVEN THE FRESH SNOW
EXPECTED ACROSS MUCH OF THE CWA TEMPERATURES WILL BE FAIRLY COLD
THURSDAY AND FRIDAY NITE.
THE MODELS ARE COMING MORE IN LINE WITH A SOLUTION FOR THE STORM
SYSTEM DURING THE WEEKEND. THE ECMWF HAS COME IN LINE WITH THE
GFS/CANADIAN MODELS IN PUSHING SNOW INTO THE CWA EARLIER ON
SATURDAY. THEREFORE WILL INTRODUCE SNOW INTO THE FORECAST STARTING
ON SATURDAY GIVEN THE MODEL CONSENSUS. THE BULK OF THE SNOW LOOKS
TO FALL SATURDAY AFTERNOON AND SATURDAY NITE AS THE LOW MOVES
TOWARDS NORTHERN ILLINOIS. ALTHOUGH ADDITIONAL SNOW IS EXPECTED
SUNDAY AS THE LOW MOVES INTO SOUTHERN MICHIGAN...THE AMOUNTS WILL BE MUCH
LOWER THAN THE SATURDAY PERIODS. SUNDAY NITE GETS INTERESTING AS
THE ECMWF/CANADIAN MODELS DEEPEN THE LOW ACROSS THE NORTHERN
GREAT LAKES WITH CONTINUED CHANCES FOR ADDITIONAL SNOWFALL ACROSS
THE EASTERN PORTION OF THE CWA...WHILE THE GFS EXITS THE SYSTEM
OUT OF THE REGION RATHER QUICKLY. GIVEN LOW PRESSURE SYSTEMS TEND
TO DEEPEN OVER THE RELATIVELY WARM GREAT LAKES WILL LEAN TOWARDS
THE ECMWF/CANADIAN SOLUTIONS AND MAINTAIN CHANCY POPS SUNDAY NITE.
AT THIS POINT 6 INCHES OR MORE OF SNOW LOOKS TO BE A FAIRLY GOOD
BET ACROSS THE CWA FROM SATURDAY TO SUNDAY NITE...WITH THE BEST
CHANCE FOR HIGHER AMOUNTS ACROSS THE SOUTHERN AND EASTERN PORTION
OF THE CWA. WILL ADJUST WORDING IN THE HAZARDOUS WEATHER OUTLOOK
TO REFLECT THIS NEW INFORMATION.
LAKE EFFECT SNOW WILL CONTINUE THE SNOW CHANCES ACROSS PORTIONS OF
NORTH CENTRAL WISCONSIN MONDAY AND TUESDAY. HOWEVER THE WIND
DIRECTION MAY BE A BIT TOO WESTERLY FOR ADDITIONAL SIGNIFICANT
ACCUMULATIONS ONCE THE SYNOPTIC SNOW HAS PASSED TO THE EAST.
TEMPERATURES WILL COOL OFF AS THE LOW MOVES OUT OF THE
REGION...WITH WELL BELOW TEMPERATURES WITH A FRESH SNOW PACK.
&&
.AVIATION...LOWERING CIGS THIS AM WITH SNOW DEVELOPING OVER THE
AREA. CIGS RHI DROPPING TO MFVR EARLY...TEMPORARILY INTO IFR RANGE
IN SNOW...AUW AND GRB DROPPING TO MVFR BY MID TO LATE MORNING WITH
SNOW DEVELOPING AROUND NOON. STRONG LOW LEVEL SOUTHWEST FLOW MAY LEAD
TO LLVL WINDSHEAR THIS AM.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
SNOW ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ005-010>012.
&&
$$
TE/KURIMSKI
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