FXUS61 KGYX 080925
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
425 AM EST TUE DEC 8 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD EAST ACROSS THE AREA TODAY THEN EXIT INTO
THE MARITIMES TONIGHT. A WARM FRONT EXTENDING FROM LOW PRESSURE
OVER THE GREAT LAKES WILL APPROACH THE REGION WEDNESDAY MORNING. A
SECOND AREA OF LOW PRESSURE WILL DEVELOP ON THE WARM FRONT AND
BRING THE THREAT OF HEAVY SNOW AND STRONG WINDS ALONG THE COAST
WEDNESDAY AND WEDNESDAY. THE SECOND LOW WILL TRACK NORTHEAST INTO
THE MARITIMES AS HIGH PRESSURE BUILDS EAST FOR THURSDAY AND
FRIDAY. GUSTY WEST TO NORTHWEST WINDS WILL BRING THE COLDEST AIR
OF THE SEASON INTO NORTHERN NEW ENGLAND FOR THE WEEKEND. LOW
PRESSURE MAY APPROACH THE REGION EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 9 AM THIS MORNING/...
1017 MILLIBAR LOW WAS SITUATED WELL EAST OF CAPE COD WITH WEAK
TROUGH EXTENDING NORTHWEST INTO THE MIDCOAST OF MAINE. A 1028
MILLIBAR HIGH WAS CENTERED OVER SOUTHEAST OHIO. SOME LIGHT SNOW
SHOWERS CONTINUE VCNTY OF THE TROUGH IN MID COAST SECTIONS OF
MAINE AS WELL AS ACROSS THE HIGHER TERRAIN IN UPSLOPE FLOW.
ELSEWHERE...SKIES HAD BRIEFLY BROKE OUT OVER SOUTHERN AND WESTERN
SECTIONS BEHIND THE EXITING SHORT WAVE EVIDENT ON WATER VAPOR
IMAGERY...BUT ONLY TO FILL IN WITH LOW CLOUDS AND FOG.
&&
.SHORT TERM /9 AM THIS MORNING THROUGH 6 AM WEDNESDAY/...
ANY LEFTOVER FLURRIES SHOULD END ALONG THE MID COAST AND ACROSS THE
HIGHER TERRAIN THIS MORNING AS THE SURFACE HIGHS BUILDS EASTWARD.
OUTSIDE OF SOME LINGERING LOW CLOUDS ACROSS THE HIGHER TERRAIN...
SHOULD SEE A GOOD DEAL OF LATE MORNING AND AFTERNOON SUNSHINE ACROSS
THE REMAINDER OF THE AREA. A BLEND OF MET/MAV VALUES YIELDS HIGHS
MAINLY IN THE 30S. TEMPERATURES DROP OFF QUICKLY AFTER DUSK GIVEN
LIGHT WINDS AND MAINLY CLEAR SKIES TO START. SHOULD SEE READINGS
STABILIZE...AND EVEN RISE A FEW DEGREES AFTER 05Z AS CLOUDS SPREAD
RAPIDLY NORTHEAST IN DEVELOPING OVERRUNNING PATTERN. GIVEN THE DRY
AIR INITIALLY IN PLACE...I CONFINED CHANCE POPS TO AREAS SOUTH OF
A /KLEB/ LEBANON TO /KSFM/ SANFORD LINE AFTER MIDNIGHT IN A
COMPROMISE OF THE SLOWER NAM AND MORE PROGRESSIVE GFS SOLUTIONS.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
THE MAIN EVENT OCCURS WEDNESDAY AND WEDNESDAY NIGHT. MODELS ARE
IN FAIRLY GOOD AGREEMENT WITH THE OVERALL SYNOPTIC PATTERN FOR
WEDNESDAY AND WEDNESDAY NIGHT...AND CONFIDENCE IS INCREASING FOR A
HIGH IMPACT EVENT WITH REGARD TO SNOW AND WIND.
OVERRUNNING WILL BE IN PROGRESS WEDNESDAY MORNING...AS 850 MB
WINDS OF 40 TO 50 KNOTS WILL BE RUNNING OVER A SURFACE WARM FRONT
SOUTH OF THE REGION. 850-700 MB FRONTOGENETIC FORCING WILL INCREASE
IN THE WARM AIR ADVECTION...STRETCHING FROM NORTHEAST VERMONT
THROUGH NEW HAMPSHIRE INTO WESTERN MAINE WEDNESDAY MORNING. THE
COLUMN WILL BE COLD ENOUGH FOR THE PRECIPITATION TO START AS SNOW
IN ALL AREAS...AND IT SPREADS NORTHEAST INTO EASTERN ZONES BY MID
TO LATE MORNING.
AS THE FRONTOGENETIC FORCING INCREASES...MOISTURE SHOULD BE PUSHED
INTO THE MAXIMUM SNOW GROWTH REGION...AND THE SNOW SHOULD BECOME
HEAVY AT TIMES DURING THE LATE MORNING HOURS. BANDED SNOW IS POSSIBLE
DURING THIS TIME...AND SNOWFALL RATES COULD REACH 1 TO 2 INCHES AN
HOUR. MODELS APPEARS TO HAVE BACKED OFF SOME OF THE AMOUNT OF
WARMING IN THE LOWER TO MID LEVELS DURING THIS TIME WHEN COMPARED
TO EARLIER RUNS...AND THIS SHOULD MAINTAIN THE ABILITY TO MAKE
SNOWFLAKES FOR MOST OF THE AREA INTO THE MID AND LATE AFTERNOON.
THE FIRST PHASE CHANGE PROBLEM WILL LIKELY BE NEAR THE COAST. THE
OCEAN IS STILL WARM (FOR THE TIME OF YEAR)...AND THE LOW LEVEL
TRAJECTORY COULD RESULT IN WARMING IN THE BOUNDARY LAYER. THIS
SHOULD OCCUR FIRST ALONG THE NEW HAMPSHIRE SEACOAST AND ACROSS
COASTAL YORK COUNTY. THE TRANSITION MAKE TAKE LONGER FURTHER UP
THE COAST...WHERE STRONG VERTICAL MOTION MAY BE ABLE TO OVERCOME
THE BOUNDARY LAYER WARMING.
FURTHER INLAND...THE WARMING IN THE LOWER TO MID LEVELS MAY TAKE
QUITE A BIT LONGER (AND PERHAPS NOT UNTIL THE HEAVIEST PRECIPITATION
ENDS ACROSS THE MOUNTAINS AND FOOTHILLS). AGAIN...THE TRANSITION
WILL BE SLOWED AS STRONG VERTICAL MOTION MAY BE ABLE TO OVERCOME
ANY BOUNDARY LAYER WARMING. THE BEST FRONTOGENETIC FORCING AND LOW
LEVEL FLOW MAY NEARLY COINCIDE...EXTENDING FROM NEAR KCON THROUGH
THE FOOTHILLS OF NEW HAMPSHIRE AND WESTERN MAINE. IN THESE AREAS...
MORE THAN 6 INCHES APPEARS FAIRLY LIKELY...SO A WINTER STORM
WATCH WAS ISSUED.
WINTER STORM WATCHES WERE ALSO ISSUED FOR ALL AREAS EXCEPT COASTAL
YORK AND COASTAL ROCKINGHAM COUNTIES. INTERIOR SOUTHEAST NEW HAMPSHIRE
MAY ALSO HAVE A BOUNDARY LAYER ISSUE...BUT THIS MAY NOT OCCUR UNTIL
MOST OF THE PRECIPITATION HAS ALREADY FALLEN. THIS COULD ALSO BE
THE CASE FOR THE MID COAST...AND THAT IS THE REASON THE MID COAST
WAS INCLUDED IN THE WATCH AS WELL.
MODELS HAVE BEEN INDICATING THE GRADIENT AHEAD OF THE WARM FRONT
(OR OCCLUSION BY THIS POINT) WEDNESDAY AFTERNOON COULD TIGHTEN
ENOUGH FOR STRONG WINDS FOR A FEW RUNS. MODEL SOUNDINGS AT KRKD
SHOW THE POTENTIAL FOR 45 KNOTS OF WINDS IN THE BOUNDARY LAYER
NEAR 0000 UTC THURSDAY...AS WELL AS WINDS NEAR 60 KNOTS JUST ABOVE
THE INVERSION.
SINCE MODELS HAVE PLACED THE HEART OF THE LOW LEVEL JET (NEAR 70
KNOTS AT 925 MB) ACROSS THE MID COAST IN THE AFTERNOON AND EVENING
HOURS...A HIGH WIND WATCH WAS ISSUED FOR THESE AREAS. COULD BE
THAT COASTAL NEW HAMPSHIRE AND YORK COUNTIES MAY SEE WINDS GUST TO
NEAR 45 MPH...AND EVENTUALLY A WIND ADVISORY MAY BE NEEDED THERE.
MAY ALSO NEED WIND ADVISORIES FOR PORTIONS OF INTERIOR CENTRAL
MAINE...BUT THIS IS STILL PROBLEMATIC. IF THE BOUNDARY LAYER DOES
NOT WARM...THE STRONGEST WINDS WOULD BE SHUNTED OVER THE COLD AIR
IN PLACE. THIS IS THE REASON THESE ZONES WERE NOT INCLUDED IN THE
HIGH WIND WATCH.
BOUNDARY LAYER WINDS WILL DICTATE HIGH TEMPERATURES WEDNESDAY.
ACCEPTED THE WARMER GFS MOS NUMBERS NEAR THE COAST...WHERE THE
BEST CHANCE OF WARMING WILL OCCUR. ELSEWHERE...USED A BLEND OF MOS
NUMBERS FOR HIGHS.
FOR WEDNESDAY NIGHT...THE BEST WARM AIR ADVECTION ENDS IN THE
EARLY EVENING AHEAD OF THE SHORT WAVE DRIVING EVERYTHING ALONG.
AFTER THE SHORT WAVE PASSES...THE AIRMASS WILL LOSE ITS ABILITY TO
MAKE SNOWFLAKES...AND ALL AREAS SHOULD SEE THE PRECIPITATION CHANGE
TO RAIN. OVER THE COASTAL PLAIN...THIS MAY BE PLAIN RAIN. FURTHER
INLAND...LIGHT FREEZING RAIN IS POSSIBLE (WHICH IS TYPICAL AT THE
END OF WARM AIR ADVECTION INDUCED PRECIPITATION EVENTS).
THE STRONGEST WINDS WILL OCCUR BEFORE 0400 UTC ACROSS THE MID
COAST. MODELS SOUNDINGS SHOW THE POTENTIAL FOR WIND GUSTS TO 55
MPH AHEAD OF AN OCCLUDED FRONT. BEHIND THE FRONT...WINDS SHOULD
DROP OFF FAIRLY QUICKLY. SINCE THE COLD AIR ADVECTION BEHIND THE
SYSTEM DOES NOT RUSH IN...TEMPERATURES MAY NOT MOVE MUCH FROM
EARLY EVENING READINGS.
AN UPSLOPE/DOWNSLOPE PATTERN SHOULD DEVELOP THURSDAY...BUT THE
FLOW WILL BE MORE WEST TO EAST. THIS MAY RESULT IN LESS SUNSHINE
NEAR THE COAST THAN WOULD NORMALLY BE EXPECTED IN THIS PATTERN.
CONVERSELY...THE AIRMASS MAY NOT HAVE ENOUGH MOISTURE FOR MUCH
UPSLOPE DURING THIS PERIOD AS WELL. IN ANY EVENT...THE GRADIENT
SUPPORTS GUSTY WINDS THURSDAY...AND MODEL SOUNDINGS SUGGEST 45
KNOTS MAY BE AVAILABLE AT THE TOP OF THE INVERSION. THERE IS A LOW
PROBABILITY THAT WINDS COULD GUST TO NEAR ADVISORY LEVELS...BUT
THIS WAS NOT FOLLOWED FOR NOW.
A COLD CYCLONIC FLOW FOLLOWS FOR FRIDAY AND SATURDAY WITH THE
COLDEST AIR OF THE SEASON. THE 0000 UTC GFS AND ECMWF SHOW THE
POTENTIAL FOR A STORM TO PASS SOUTHEAST OF THE BENCHMARK SUNDAY
NIGHT AND MONDAY MORNING.
&&
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
SHORT TERM /THROUGH 11Z WEDNESDAY/...AREAS OF EARLY MORNING MVFR
IN FOG WITH LOCALLY IFR CONDITIONS...IMPROVING TO VFR THROUGHOUT
BY 14Z.
LONG TERM...CONDITIONS SHOULD DROP QUICKLY TO LIFR WITH THE
DEVELOPMENT OF SNOW WEDNESDAY MORNING (BETWEEN 1000 UTC AND 1500
UTC FROM WEST TO EAST). LIFR CONDITIONS ARE EXPECTED TO CONTINUE
THROUGH LATE WEDNESDAY NIGHT...AS LOW PRESSURE PULLS AWAY AND A
DOWNSLOPE FLOW HELPS TO SCOUR OUT LOW LEVEL MOISTURE.
WINDS MAY BECOME AN ISSUE FOR KPSM...KPSM AND KAUG LATE WEDNESDAY
MORNING INTO WEDNESDAY EVENING. RIGHT NOW...GUSTS TO 35 TO 40
KNOTS FROM THE NORTHEAST ARE POSSIBLE DURING THIS PERIOD...WITH
KPWM STANDING THE BEST CHANCE OF SEEING THE HIGHER GUSTS.
VFR CONDITIONS ARE EXPECTED THURSDAY AND FRIDAY AS DOWNSLOPING IN
THE WAKE OF THE LOW SCOURS THE REMAINING LOW LEVEL MOISTURE. WEST
WINDS COULD GUST TO 35 KNOTS THURSDAY AT ALL TERMINALS. VFR
CONDITIONS ARE THEN EXPECTED INTO SATURDAY.
&&
.MARINE...
SHORT TERM /THROUGH TONIGHT/...WINDS AND SEAS REMAIN BELOW SMALL
CRAFT THRESHOLD AS HIGH PRESSURE BUILDS EAST AND CRESTS ACROSS THE
WATERS THIS EVENING. THEN...WINDS AND SEAS BEGIN TO INCREASE QUICKLY
TOWARDS THE END OF THE PERIOD.
LONG TERM...THE OVERALL PATTERN FOR THE UPCOMING STORM IS COMING
INTO BETTER FOCUS. THE GRADIENT SHOULD INCREASE FAIRLY QUICKLY
WEDNESDAY MORNING...REACHING GALE FORCE IN ALL WATERS BY LATE
MORNING. THE BEST GRADIENT SHOULD BE OVER THE WATERS FROM MID
AFTERNOON INTO EARLY EVENING...AS LOW PRESSURE FORMS ON A WARM
FRONT SOUTH OF THE WATERS AND TRACKS NORTHEAST. MODELS ARE SHOWING
55 TO 70 KNOT WINDS JUST ABOVE THE INVERSION DURING THIS TIME.
FOR NOW...KEPT WINDS JUST BELOW STORM FORCE...SINCE THE DEPTH OF
THE MIXED LAYER IS STILL IN QUESTION. MODEL SOUNDINGS FOR
APPLEDORE ISLAND SHOW WINDS NEAR STORM FORCE IN THE BOUNDARY LAYER
IN THE BEST GRADIENT AHEAD OF THE SURFACE LOW. LATER FORECASTS MAY
HAVE TO ADDRESS THE POTENTIAL.
AS THE SURFACE LOW PASSES (AT ABOUT THE SAME TIME AS THE OCCLUSION
IS SKIPS ALONG)...SURFACE WINDS SHOULD DROP SIGNIFICANTLY DURING
THE LATE EVENING HOURS WEDNESDAY. IN FACT...THE GRADIENT MAY DROP
ENOUGH TO ALLOW WINDS TO DROP BELOW SMALL CRAFT LIMITS...ESPECIALLY
OVER THE BAYS. HOWEVER...THIS WILL BE SHORT LIVED...AS THE SURFACE
LOW DEEPENS AS IT TRACKS FOR THE MARITIMES.
STRONG SURFACE HIGH PRESSURE WILL BUILD EAST FROM THE OHIO VALLEY
LATE WEDNESDAY NIGHT AND THURSDAY. THE GRADIENT BETWEEN THE TWO
SHOULD SUPPORT GALE FORCE WINDS DEVELOPING THURSDAY MORNING. MODEL
SOUNDINGS ALSO SHOW A MIXED LAYER DEEP ENOUGH TO SUPPORT GALE
FORCE GUSTS. THE PATTERN BECOMES NEARLY STATIONARY...WHICH MEANS
GALE FORCE WINDS ARE POSSIBLE RIGHT INTO FRIDAY.
&&
.TIDES/COASTAL FLOODING...
WE HAVE JUST PASSED THE HIGHEST ASTRONOMICAL TIDES OF THE MONTH
LAST WEEK...AND THEY CONTINUE TO FALL. WHILE THE TIDE WEDNESDAY
AFTERNOON IN PORTLAND IS 9.4 FT...THE COMBINATION OF A STORM SURGE
PRODUCED BY STRONG PRESSURE FALLS AND BUILDING SEAS MAY RESULT IN
SPLASHOVER. RIGHT NOW...COASTAL FLOODING IS NOT EXPECTED BECAUSE
THE ASTRONOMICAL TIDE IS LOW.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING
FOR MEZ018.
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE
WEDNESDAY NIGHT FOR MEZ007>009-012>014-019>022-024>028.
HIGH WIND WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR MEZ024>028.
NH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING
FOR NHZ001>010-013.
MARINE...GALE WARNING FROM 7 AM WEDNESDAY TO 3 AM EST THURSDAY FOR
ANZ150>154.
&&
$$
