FXUS61 KGYX 090941
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
441 AM EST WED DEC 9 2009
.SYNOPSIS...
LOW PRESSURE OVER THE MIDWEST WILL MOVE NORTHEAST TODAY AND
TONIGHT AS A SECONDARY LOW DEVELOPS OFF THE MID ATLANTIC COAST AND
TRAVELS NORTHEAST THROUGH THE GULF OF MAINE. THE COASTAL LOW WILL
MOVE OVER THE CANADIAN MARITIMES THURSDAY AND REMAIN THERE THROUGH
FRIDAY. HIGH PRESSURE WILL BUILD SOUTH OF THE REGION THURSDAY AND
FRIDAY. LOW PRESSURE SYSTEMS WILL APPROACH THE REGION FROM THE
WEST AND THE SOUTH SUNDAY AND MOVE EAST OF THE REGION SUNDAY
NIGHT. A RIDGE OF HIGH PRESSURE WILL CROSS THE AREA MONDAY AND
TUESDAY FOLLOWED BY ANOTHER CHANCE OF PRECIPITATION FOR WEDNESDAY.
&&
.NEAR TERM /THROUGH TODAY/...
HERE WE GO...
OVERALL FORECAST PHILOSOPHY HAS NOT CHANGED MUCH AS THE SCENARIO
STARTS TO UNFOLD. SNOW IS SPREADING NORTHEAST EARLY THIS MORNING
IN THE STRONG WARM AIR ADVECTION...AND THIS WILL OVERSPREAD THE
REGION THROUGH THE MID MORNING HOURS. STARTING TO SEE SOME
REFLECTION OF DEVELOPING 850-700 MB FRONTOGENETIC FORCING ACROSS
SOUTHEAST NEW YORK AND NORTHERN NEW JERSEY. AS THIS FORCING RACES
NORTHEAST THIS MORNING...WOULD EXPECT THIS TO ENHANCE PRECIPITATION
RATES BY MID TO LATE MORNING.
GIVEN THE STRENGTH OF THE FRONTOGENETIC FORCING...WOULD EXPECT SNOW
TO FALL HEAVILY AT TIMES THIS MORNING INTO THE AFTERNOON. DURING
THIS PERIOD...SNOWFALL RATES OF 1 TO 2 INCHES ARE EXPECTED...WITH
THE BEST BANDING ACROSS SOUTHERN NEW HAMPSHIRE THIS MORNING...THEN
ACROSS WESTERN MAINE LATE MORNING AND THIS AFTERNOON.
THE AFFECT OF WARMING IN THE BOUNDARY LAYER MAY BECOME PROBLEMATIC
ACROSS THE NEW HAMPSHIRE COAST AND THE SOUTHWEST MAINE COAST. WITH
THE COASTAL FRONT DEVELOPING...THIS WILL MITIGATE THE WARMING...AND
ALLOW PRECIPITATION TO STAY SNOW LONGER. WITH THE POTENTIAL FOR AS
MUCH AS 2 INCHES AN HOUR FOR FEW HOURS THIS MORNING...HAVE OPTED
TO UPGRADE THESE AREAS TO WINTER STORM WARNINGS.
ELSEWHERE...THE BEST BANDING OF SNOW SHOULD OCCUR WHERE UPSLOPING
WINDS INTERSECT THE TERRAIN. IN THESE AREAS...THE ENHANCEMENT WILL
BE IN MORE OR LESS THE SAME LOCATION AS THE MAXIMUM SNOW GROWTH...AND
HAVE INDICATED THE HIGHEST SNOW AMOUNTS FROM NORTH OF KCON THROUGH
EASTERN NEW HAMPSHIRE THROUGH THE FOOTHILLS. EXPECTING A BIT LESS
FOR THE MOUNTAINS DURING THE DAY...AND SHADOWING WILL OCCUR ALONG
THE CONNECTICUT RIVER VALLEY.
THE COASTAL FRONT HAS THE BEST CHANCE OF IMPINGING ALONG THE MID
COAST OF MAINE. THIS MEANS THIS AREA HAS THE BEST CHANCE OF SEEING
A CHANGE TO RAIN AS SURFACE TEMPERATURES GET ABOVE FREEZING.
HOWEVER...THE STRONG VERTICAL MOTION WILL LIKELY OVERCOME WARMING
AND ALLOW AREAS NORTH OF ROUTE ONE TO SEE MORE THAN 6 INCHES OF
SNOW.
THE POSITION OF THE COASTAL FRONT WILL ALSO DICTATE THE STRENGTH
OF SURFACE WINDS. THE MOST CONCERN IS FOR THE MID COAST OF MAINE...
WHERE THE COASTAL FRONT HAS THE BEST CHANCE OF MAKING IT INLAND.
MODEL SOUNDINGS AT KRKD SHOW 70 KNOTS WINDS AT THE TOP OF THE
INVERSION CLOSE TO 0000 UTC THURSDAY.
THE MORE PROBLEMATIC AREA WILL BE FROM PORTLAND TO WISCASSET. THE
EXPECTED POSITION OF THE COASTAL FRONT WOULD KEEP THE HIGHEST
WINDS JUST ABOVE THE INVERSION. THE BEST SURFACE GRADIENT IS FROM
MID AFTERNOON THROUGH EARLY EVENING...AND WINDS FROM THE SURFACE
LOW MAY BE ENOUGH FOR GUSTS TO 45 MPH. WILL HAVE TO WATCH TRENDS
TO SEE IF THE COASTAL FRONT GETS CLOSER.
OVERALL...THE COLDER NAM MODEL WAS FAVORED FOR THE FORECAST THIS
MORNING.
&&
.SHORT TERM /TONIGHT/...
THE BEST LIFT SHOULD EXIT IN THE EVENING HOURS...AS AN OCCLUDED
FRONT EXITS THE REGION. THE STRONGEST WINDS AHEAD OF THE FRONT
WILL OCCUR ACROSS THE EVENING...AS THE MIXED LAYER INCREASES TO
ITS HIGHEST. AFTER THIS...WINDS DROP OFF FAIRLY QUICKLY BEHIND THE
FRONT AS THE GRADIENT LAGS. THE LOW LEVELS REMAIN MOIST IN THE
WAKE OF THE SURFACE LOW...SO A MENTION OF LIGHT PRECIPITATION WAS
CONTINUED.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
A PERSISTENT NORTHWEST FLOW WILL DEVELOP ACROSS THE REGION THURSDAY
AND FRIDAY AS THE PRESSURE GRADIENT BETWEEN THE LOW TO THE NORTHEAST
AND HIGH TO THE SOUTH REMAINS RATHER TIGHT. THIS WILL LEAD TO
CLOUDS AND THE THREAT OF SNOW SHOWERS IN THE MOUNTAINS...ESPECIALLY
IN UPSLOPE AREAS...WITH PARTLY CLOUDY SKIES TO THE SOUTH. TEMPERATURES
WILL REMAIN RATHER COLD AS COLD AIR FUNNELS DOWN FROM CENTRAL CANADA.
WINDS WILL BE GUSTY BOTH THURSDAY AND FRIDAY AFTERNOONS AS COLD
ADVECTION COMBINED WITH DAYTIME HEATING WILL MIX DOWN SOME STRONG
GUSTS.
AREAS OF LOW PRESSURE APPROACH THE REGION SUNDAY FROM BOTH THE
WEST AND SOUTH. TOO EARLY TO KNOW IF THESE SYSTEMS WILL PHASE.
LATEST GFS KEEPS THESE SYSTEMS SEPARATE AND WOULD EXPECT MINIMAL
IMPACTS IF THIS IS THE CASE. AT THIS TIME WILL JUST MENTION
CHANCE OF SNOW IN FORECAST. HIGH PRESSURE WILL FOLLOW THESE
SYSTEMS WITH REINFORCEMENT OF COLD AIR FOR MONDAY AND TUESDAY.
TIMING OF NEXT SHORT WAVE WILL BRING IT THROUGH AREA NEXT
WEDNESDAY.
&&
.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
IN THE NEAR TERM /TODAY/...GENERALLY VFR CONDITIONS EARLY THIS
MORNING (THOUGH KPSM HAS JUST DROPPED TO MVFR AS THE INVERSION
DROPS NEAR THE COAST IN THE NORTHEAST SURFACE WIND. SNOW IS NOW AS
CLOSE AS SOUTHWEST VERMONT AND CENTRAL MASSACHUSETTS...AND WOULD
EXPECT CONDITIONS TO DROP TO IFR WITH THE DEVELOPMENT OF SNOW.
THIS SHOULD OCCUR BETWEEN 1100 AND 1400 UTC FROM WEST TO EAST.
AS THE BEST LIFT AHEAD OF THE WARM FRONT OCCURS THIS MORNING INTO
THE AFTERNOON...LIFR CONDITIONS WILL DEVELOP IN HEAVY SNOW. MIXING
WITH RAIN COULD OCCUR AT KPSM AND KPWM AFTER 1800 UTC...AND MIXING
WITH -FZRA COULD OCCUR AT KCON AND KLEB.
CLOSE TO THE COAST...WINDS WILL INCREASE QUICKLY THIS AFTERNOON AS
SURFACE LOW PRESSURE DEVELOPS ON A WARM FRONT. KPSM AND KPWM COULD
SEE EAST WINDS GUST TO 35 KNOTS THIS AFTERNOON AND THIS EVENING
BEFORE THE PASSAGE OF THE LOW.
IN THE SHORT TERM /TONIGHT/...LIFR CONDITIONS ARE EXPECTED THIS
EVENING IN THE WAKE OF THE SURFACE LOW AND PASSAGE OF AN OCCLUDED
FRONT. THE PASSAGE OF THE FRONT SHOULD MARK THE END OF THE GUSTY
WINDS. AS WINDS BECOME WEST BEHIND THE FRONT...CONDITIONS MAY
IMPROVE TO IFR AND POSSIBLE MVFR AT KPWM AND KPSM AFTER 0800 UTC
THURSDAY.
LONG TERM...MOSTLY VFR CONDITIONS EXPECTED WITH SOME MVFR
CONDITIONS POSSIBLE IN THE MOUNTAINS IN SNOW SHOWERS. NORTHWEST
WINDS WILL BE GUSTY THURSDAY AND FRIDAY...ESPECIALLY DURING THE
AFTERNOONS. THERE IS A MINIMAL CHANCE THAT IFR CONDITIONS COULD
DEVELOP SUNDAY IN SNOW.
&&
.MARINE...
IN THE NEAR TERM /TODAY/...WINDS ARE INCREASING IN THE GRADIENT
WELL AHEAD OF THE WARM FRONT ACROSS THE MID ATLANTIC STATES...AS
SURFACE HIGH PRESSURE EXITS THE WATERS THIS MORNING. ALREADY SEEING
INDICATIONS OF LOW PRESSURE DEVELOPING ON THE FRONT ACROSS THE MID
ATLANTIC AS WELL.
THE STRONGEST GRADIENT AHEAD OF THE WARM FRONT IS ACROSS WESTERN
PENNSYLVANIA AND WEST VIRGINIA EARLY THIS MORNING...SO THE TIMING
OF THE STRONGER WINDS WAS BACKED UP A BIT. HOWEVER...NOT MUCH
CHANGE IN THE FORECAST PHILOSOPHY AS THE SECONDARY LOW PRESSURE
SYSTEM BECOMES THE MAIN DRIVER OF THE SURFACE WINDS. EXPECTING A
COASTAL FRONT TO DEVELOP THIS MORNING...AND THIS COULD BE THE KEY
TO THE WIND FORECAST FOR THE SOUTHERNMOST WATERS THIS AFTERNOON AND
EVENING.
THE COASTAL FRONT...AS AN EXTENSION OF THE WARM FRONT TO THE
SOUTH...MAY TEND TO KEY WINDS MORE NORTHEAST FOR ANZ154 AND CASCO
BAY (AS IT TYPICAL IN THIS TYPE OF SITUATION). THIS WOULD LOWER
THE INVERSION...AND KEEP THE STRONGEST WINDS ABOVE THE SURFACE.
FOR THIS REASON...THE GALE WARNING WAS KEPT IN PLACE...MAINLY FOR
THE PASSAGE OF THE SURFACE LOW.
FOR EASTERN WATERS...THE COASTAL FRONT IS MORE LIKELY TO INTRUDE...
AND THE BEST GRADIENT WILL BE FROM MID AFTERNOON THROUGH EARLY
EVENING. MODEL SOUNDINGS SHOW 55 KNOT WINDS AT THE TOP OF THE
INVERSION...AND THIS COULD MIX DOWN AS WINDS BECOME MORE EAST TO
PERHAPS SOUTHEAST. THE STORM WARNING WAS EXTENDED TO ANZ152 AND TO
PENOBSCOT BAY (WHERE THE STRONGEST GUSTS SHOULD BE AT THE MOUTH OF
THE BAY). WOULD EXPECT SEAS TO JUMP THIS AFTERNOON AS THE WINDS
INCREASE WITH THE APPROACH OF THE SURFACE LOW IN ALL WATERS.
IN THE SHORT TERM /TONIGHT/...AS THE SURFACE LOW PASSES THIS EVENING...
THE BEST GRADIENT WILL BE DURING THE EVENING HOURS ACROSS CENTRAL
AND EASTERN WATERS. MODEL SOUNDINGS SHOW THE BEST MIXING POTENTIAL
DURING THIS EVENING. AFTER THE PASSAGE OF THE SURFACE LOW (AND
ASSOCIATED OCCLUSION)...WOULD EXPECT TO SEE WINDS SHIFT TO THE
WEST AND DROP OFF AS THE GRADIENT RELAXES.
AS THE SURFACE GETS FURTHER AWAY AND DEEPENS AS IT HEADS TO THE
MARITIMES...THE GRADIENT TIGHTENS ONCE AGAIN. MODEL SOUNDINGS
SUGGEST THAT THE MIXED LAYER COULD ALLOW ACCESS TO 40 TO 45 KT
WINDS AT THE TOP OF THE INVERSION. THIS COULD BRING WINDS BACK TO
GALE BY LATE TONIGHT FROM THE WEST.
LONG TERM...NORTHWEST WINDS WILL REMAIN STRONG AND GUSTY THURSDAY
THROUGH SATURDAY AS THE PRESSURE GRADIENT REMAINS TIGHT AND COLDER
AIR PUSHES INTO THE REGION. SEAS ARE EXPECTED TO REMAIN ABOVE SCA
CRITERIA THROUGH SATURDAY WITH SEAS INCREASING OFFSHORE. WINDS WILL
DIMINISH AND SEAS WILL SUBSIDE EARLY SUNDAY AS HIGH PRESSURE MOVES
OFF THE COAST. WINDS AND SEAS COULD INCREASE AGAIN LATE SUNDAY AS
LOW PRESSURE MOVES OFFSHORE SOUTH OF THE REGION.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR MEZ018-
023.
WINTER STORM WARNING FROM 9 AM THIS MORNING TO 1 AM EST
THURSDAY FOR MEZ007>009-012>014-019>022-024>028.
HIGH WIND WARNING FROM 1 PM THIS AFTERNOON TO 10 PM EST THIS
EVENING FOR MEZ022-026>028.
WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 10 PM EST THIS
EVENING FOR MEZ024-025.
NH...WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR
NHZ001>010-013-014.
MARINE...GALE WARNING FROM 7 AM THIS MORNING TO 3 AM EST THURSDAY FOR
ANZ153-154.
STORM WARNING FROM 7 AM THIS MORNING TO 3 AM EST THURSDAY FOR
ANZ150>152.
&&
