FXUS61 KBOX 251323
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
823 AM EST WED NOV 25 2009
.SYNOPSIS...
LOW PRESSURE WILL MOVE INTO THE MARITIMES TODAY WILL WEAKEN AS WEAK
HIGH PRESSURE BUILDS ACROSS NEW ENGLAND. LOW PRESSURE OVER THE GREAT
LAKES WILL REDEVELOP ALONG THE MID ATLC COAST THURSDAY AND INTENSIFY
AS IT TRACKS TO NEAR NANTUCKET EARLY FRIDAY. THIS STORM WILL MOVE
NORTH THROUGH THE MARITIMES FRIDAY NIGHT AND SATURDAY BRINGING STRONG
NORTHWEST WINDS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
N/NE LOW LEVEL JET WILL WEAKEN THIS MORNING AS WEAK SFC RIDGING
DEVELOPS. HOWEVER...LIGHT NE FLOW AND ABUNDANT LOW LEVEL MOISTURE
TRAPPED BELOW THE INVERSION WILL RESULT IN MOCLDY SKIES AND CANT
RULE OUT AREAS OF DRIZZLE THIS MORNING...ESPECIALLY IN THE COASTAL
PLAIN.
ONE SHORTWAVE EJECTING NE FROM THE MIDWEST MEAN TROF WILL REACH THE
EASTERN GT LAKES LATE TODAY WITH UPPER JET MOVING INTO SNE FROM THE
WEST. BEST QG FORCING REMAINS NORTH AND WEST OF SNE BUT ENOUGH
FORCING TO BRING IN CHC SHOWERS TO W ZONES LATE TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
MID LEVEL SHORTWAVE QUICKLY MOVES NE INTO CANADA THIS EVENING BUT
UPPER JET DYNAMICS AND A PERIOD OF QG FORCING MAY RESULT IN A FEW
SHOWERS MOVING EWD ACROSS SNE AND HAVE CHC POPS TONIGHT FOR ALL BUT
E MA WHERE SLIGHT CHC POPS. LOW LEVELS REACH NEAR SATURATION
TONIGHT SO LOW CLOUDS...FOG AND AREAS OF DRIZZLE ALSO LIKELY.
THU...NAM/GFS SHOW SIGNIFICANT DIFFERENCES IN LOW LEVEL MOISTURE
PROFILE WHICH MAKES FOR AN UNCERTAIN CLOUD FORECAST. NAM SCOURS OUT
THE LOW LEVEL MOISTURE AND BRINGS SUNSHINE TO SNE...WHILE GFS LOCKS
IN THE LOW LEVEL MOISTURE AND MAINTAINS CLOUDY SKIES. LIGHT
EASTERLY TRAJECTORY WOULD SUPPORT MORE CLOUDS AND LIMIT MIXING SO WE
ARE LEANING TOWARD THE CLOUDIER GFS.
COASTAL LOW BEGINS TO TAKE SHAPE OFF THE MID ATLC COAST THU AS
AMPLIFICATION OF THE MID LEVEL TROF RESULTS IN COUPLED JET STRUCTURE
OFF THE COAST. THE STORM WILL BE FAR ENOUGH SOUTH TO KEEP RAIN
SHIELD OFFSHORE THROUGH THE DAY THU...BUT CANT RULE OUT AREAS OF
DRIZZLE WITH LOW LEVEL MOISTURE TRAPPED BELOW MID LEVEL SUBSIDENCE
INVERSION AND WEAK LOW LEVEL ISENTROPIC LIFT. FOR TEMPS...LOWERED
MAV GUIDANCE A FEW DEGREES WITH EXPECTATION OF CLOUD COVER.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
THE 00Z MODELS ARE IN FAIR AGREEMENT THROUGH SATURDAY...BUT THERE
REMAIN DIFFERENCES THAT COULD HAVE AN IMPACT ON SENSIBLE WEATHER.
A STRONG UPPER LOW WILL MOVE FROM THE GREAT LAKES AND TOWARD THE
NORTHEAST THURSDAY NIGHT. THIS WILL CONTINUE TO AID IN SURFACE
CYCLOGENESIS OFF THE MID ATLANTIC COAST THURSDAY NIGHT...WITH SURFACE
LOW PRESSURE PROBABLY MOVING TO A POSITION NEAR OR JUST EAST OF
NANTUCKET 12Z FRIDAY. SYNOPTIC SCALE ASCENT WILL INCREASE AS THURSDAY
NIGHT PROGRESSES...AND THIS WILL RESULT IN INCREASING COVERAGE OF
RAIN. THEREFORE...HAVE CHANCE POPS EARLY IN THE THURSDAY NIGHT
PERIOD...INCREASING TO CATEGORICAL AFTER MIDNIGHT.
THE FRIDAY AND FRIDAY NIGHT FORECAST REMAINS A BIT TRICKY AT THIS
TIME AS POPS WILL BE GOVERNED BY THE ULTIMATE TRACK AND STRENGTH OF
THE MID AND UPPER LEVEL LOW. IF THIS LOW TRACKS APPROXIMATELY FROM
EASTERN PA INTO NORTHERN NEW ENGLAND/QUEBEC...THEN HIGH POPS WILL BE
SHORT LIVED AS DRY SLOTTING WILL AFFECT SNE...ESPECIALLY THE EASTERN
HALF. THE 00Z OPERATIONAL GFS AND 03Z SREF ARE TWO MAIN SUPPORTERS OF
THIS SOLUTION. IF THIS PANS OUT...FRIDAY MAY NOT ACTUALLY BE ALL THAT
BAD OF A DAY EXCEPT FOR SOME SHOWERS IN THE MORNING. BREAKS OF SUN
WOULD ALSO LIKELY RESULT...ESPECIALLY ON THE COASTAL PLAIN...ALLOWING
FOR A WARMER SCENARIO THAN CURRENTLY FORECAST.
ON THE OTHER HAND...YOU HAVE THE 12Z AND 00Z OPERATIONAL ECMWF WHICH
IS MORE AMPLIFIED AND FURTHER SOUTH/SOUTHEAST WITH THE MID/UPPER LOW
FRIDAY AND FRIDAY NIGHT. THIS SOLUTION WOULD ALLOW FOR BETTER INFLOW
AND MOISTURE CONVERGENCE AND THEREFORE MORE WIDESPREAD HEAVIER PRECIP
FRIDAY AND FRIDAY NIGHT. IN ADDITION...THE 00Z ECMWF WOULD PROBABLY
ALLOW FOR ACCUMULATING SNOW FOR HIGHER TERRAIN LOCATIONS IN THE
INTERIOR FRIDAY NIGHT.
THE 00Z NAM AND GFS ENSEMBLE ARE SOMEWHERE IN THE MIDDLE OF THESE
SOLUTIONS. A COMPROMISE IS IN ORDER GIVEN THE CURRENT DIFFERENCES.
THEREFORE...WE ARE NOT QUITE SOLD ON CUTTING OFF POPS AS ABRUPTLY AS
THE GFS SOLUTIONS...BUT ON THE OTHER HAND NOT GOING AS GUNG HO AS THE
ECMWF FOR FRIDAY AND FRIDAY NIGHT. AS SUCH...WE WILL GO WITH
CATEGORICAL POPS FOR RAIN THROUGH FRIDAY MORNING...THEN SLOWLY TAPER
THEM BACK FRIDAY AFTERNOON THROUGH FRIDAY NIGHT. NO HIGHER THAN HIGH
CHANCE FRIDAY NIGHT FOR NOW. THE ECMWF LOOKS A BIT TOO ROBUST RIGHT
NOW.
AS FAR AS WEATHER GOES...WILL GRADUALLY TRANSITION RAIN SHOWERS OVER
TO SNOW SHOWERS FRIDAY EVENING IN THE HIGHER TERRAIN...WITH EVEN A
CHANCE OF SNOW SHOWERS FOR COASTAL LOCATIONS AS THE NIGHT WEARS ON.
WOULDN/T BE COMPLETELY SHOCKED TO SEE SOME MINOR SNOW ACCUMS FRIDAY
NIGHT...ESPECIALLY ACROSS THE HIGHER TERRAIN. IN ANY CASE...WENT DRY
SATURDAY AND SATURDAY NIGHT AS LOW PULLS AWAY.
WINDS WILL BE AN ISSUE FRIDAY NIGHT THROUGH SATURDAY NIGHT AS THE LOW
REALLY WINDS UP TO OUR NORTHEAST. WOULDN/T BE SURPRISED IF WE NEEDED
A WIND ADVISORY FOR A GOOD PORTION OF THE CWA ON SATURDAY...PERHAPS
STARTING AS EARLY AS FRIDAY NIGHT AS LOW LEVELS BECOME WELL MIXED.
THE NEXT CHANCE OF PRECIPITATION WILL PROBABLY COME MIDWEEK...BUT
DETAILS ARE IMPOSSIBLE TO IRON OUT AT THIS TIME.
MAX TEMPERATURES DURING THE PERIOD WILL LIKELY AVERAGE AROUND OR
ABOVE NORMAL...EXCEPT FOR SATURDAY WHERE WE THINK THEY WILL BE A GOOD
5F BELOW NORMAL.
&&
.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
MOST TAFS AMENDED AT 13Z TO REFLECT IFR CONDITIONS THROUGHOUT DAY.
HIGH CONFIDENCE ON CIGS/VSBYS ONLY IMPROVING SLIGHTLY LATER THIS
MORNING BEFORE LOWERING AGAIN LATE THIS AFTERNOON OR THIS EVENING.
12Z CHH SOUNDING SHOWS PRONOUNCED LOW LEVEL INVERSION WITH LIGHT N/NE
WINDS WHICH WILL KEEP LOW CLOUDS/FOG LOCKED IN. SATELLITE LOOP SHOWS
HIGH CLOUD SHIELD ALREADY OVERSPREADING SOUTHERN NW ENGLAND WHICH
WILL PREVENT ANY SUNSHINE FROM HELPING TO BURN OFF LOW CLOUDS.
KBDL...SMALL CHANCE CONDITIONS COULD IMPROVE TO MVFR 16Z-21Z.
KBOS...VSBY SHOULD IMPROVE TO 4-5SM AROUND 16Z BUT CIGS SHOULD REMAIN
005-008. SMALL CHANCE CIGS COULD LIFT TO OVC012 16Z-21Z BUT THAT DOES
NOT APPEAR LIKELY AT THIS TIME. CIGS/VSBYS COULD LOWER A BIT SOONER
THIS EVENING THAN INDICATED IN TAF /PERHAPS AS EARLY AS 00Z THU/ AND
WILL REVISIT THAT WITH SCHED 15Z AMD.
TONIGHT...WIDESPREAD IFR/LIFR CONDITIONS EXPECTED TO REDEVELOP.
THURSDAY...IFR IN THE MORNING SHOULD IMPROVE TO MVFR IN THE COASTAL
PLAIN AND VFR IN THE CT VALLEY. LOW CONFIDENCE FORECAST AS THERE ARE
SIGNIFICANT DIFFERENCES IN LOW LEVEL MOISTURE PROFILE BETWEEN
NAM/GFS. GIVEN LIGHT WIND FLOW WITH EASTERLY TRAJECTORY WE WILL LEAN
TOWARD MORE PESSIMISTIC GFS.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...
THU NIGHT AND FRI...WIDESPREAD MVFR/IFR CIGS AND VSBYS IN SHOWERS.
FRI NIGHT AND SAT...IMPROVEMENT TO VFR FORESEEN LATE. STRONG SURFACE
WINDS WITH W WIND GUSTS 35-40 KT AND ASSOCIATED MECHANICAL
TURBULENCE.
SUN...VFR WITH DIMINISHING WINDS.
&&
.MARINE...
WINDS ARE DIMINISHING EARLY THIS MORNING WITH GUSTS DOWN TO 20-25
KT. WILL END SCA FOR THE NEARSHORE WATERS BY 12Z BUT THE SCA WILL
CONTINUE THROUGH TONIGHT FOR OUTER WATERS DUE TO SEAS. 8-10 FT SEAS
EASTERN WATERS WILL SLOWLY SUBSIDE BUT WILL REMAIN ABOVE 5 FT OVER
ALL OUTER WATERS THROUGH TONIGHT...AND PROBABLY INTO THU SO SCA WILL
LIKELY NEED TO BE EXTENDED.
LIGHT EASTERLY WINDS EXPECTED FROM LATE TODAY INTO THU.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...
THU NIGHT AND FRI...NE WINDS INCREASE THEN SHIFT TO W LATE FRIDAY.
FRI NIGHT AND SAT...W WINDS STRENGTHEN TO GALE FORCE BEHIND THE
DEPARTING LOW WHICH WILL INTENSIFY ACROSS THE CANADIAN MARITIMES.
W WINDS COULD GUST TO 40 KT OR MORE.
SUN...DIMINISHING W WINDS WITH LINGERING GUSTS OF SCA LEVELS.
PERSISTENT ONSHORE FLOW AND 6 TO 8 FOOT EAST SWELLS COULD LEAD TO
MINOR BEACH EROSION ACROSS THE EASTERN MASSACHUSETTS COAST. WE COULD
SEE A SURGE OF 1.0 TO 1.5 FT DURING THE TIMES OF HIGH TIDE THURSDAY
NIGHT THROUGH FRIDAY BUT ASTRONOMICAL TIDES ARE QUITE LOW.
&&
.CLIMATE...
IT IS INTERESTING TO NOTE THAT BOSTON/S LOGAN AIRPORT HAS NOT GOTTEN
DOWN TO THE FREEZING MARK SO FAR THIS SEASON. THE LATEST IN THE
SEASON THAT BOS HAS GONE WITHOUT HITTING 32F WAS DEC 2ND 1975. IT/S
POSSIBLE WE BREAK THAT RECORD...BUT IT WILL BE CLOSE SUNDAY
NIGHT...AND NOT COMPLETELY OUT OF THE QUESTION SATURDAY NIGHT...BUT
LOWER PROBABILITY THEN.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ250-251-
254>256.
&&
$$
SYNOPSIS...KJC/EKSTER
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...EKSTER
AVIATION...KJC/EKSTER/JWD
MARINE...KJC/EKSTER
CLIMATE...
