000
FXUS61 KBOX 211856
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
156 PM EST SAT NOV 21 2009

.SYNOPSIS...
HIGH PRESSURE WILL MOVE FROM THE GREAT LAKES INTO SOUTHEAST CANADA
TONIGHT...THEN MOVE EAST OF NOVA SCOTIA MONDAY. A WEAK LOW PRESSURE
WILL APPROACH SOUTHERN NEW ENGLAND FROM THE SOUTH MONDAY NIGHT AND
TUESDAY. WEAK HIGH PRESSURE WILL PROBABLY RESULT IN A DRY
THANKSGIVING...BEFORE A POSSIBLE COASTAL STORM ON FRIDAY.

.NEAR TERM /THROUGH TONIGHT/...
HIGH CLOUDS CONTINUE TO STREAM ACROSS SOUTHERN NEW ENGLAND...WITH
THE THICKEST CLOUDS NOW ACROSS CAPE COD AND THE ISLANDS. FARTHER
WEST...PLENTY OF CLOUDS FROM THE GREAT LAKES BANKED UP AGAINST THE
WEST SLOPES OF THE BERKSHIRES. WITH WINDS SHIFTING TO THE NORTH AND
REMAINING FAIRLY LIGHT...DO NOT EXPECT THESE CLOUDS TO SPILL OVER THE
BERKSHIRES INTO SOUTHERN NEW ENGLAND.

USED A BLEND OF MOS GUIDANCE FOR TEMPERATURES TONIGHT.

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
HIGH PRESSURE REMAINS ACROSS NORTHERN NEW ENGLAND AND SOUTHEAST
CANADA. THIS SHOULD MEAN ANOTHER MOSTLY SUNNY DAY...BUT THIS TIME
WITH ONSHORE WINDS BY AFTERNOON. THESE ONSHORE WINDS COULD LEAD
MARINE STRATUS LATE IN THE DAY INTO SUNDAY NIGHT...PARTICULARLY SOUTH
AND EAST OF I-95 IN MA AND RI. GIVEN THE EXPECTED TIMING OF THE WIND
SHIFT THOUGH...THINKING THIS MAY BE MORE OF A CONCERN SUNDAY NIGHT.

MOS TEMPERATURES LOOK REASONABLE ONCE AGAIN...SO USED A BLEND OF THE
MAV/MET GUIDANCE.

.LONG TERM /MONDAY THROUGH FRIDAY/...
CONFIDENCE IS BELOW AVERAGE DURING THIS PERIOD DUE TO SPREAD IN
MODEL SOLUTIONS AS WELL AS SOME RUN TO RUN DISCONTINUITY.

SEEING TENDENCY FOR VARIOUS MEDIUM RANGE MODELS TO PROJECT
MEASURABLE RAIN FOR MON NIGHT THRU TUE...AND THIS IS SUPPORTED BY
SREF PROBABILITIES. NOTICED THAT 00Z ECMWF IS WETTER THAN ITS PRIOR
RUN. THERE ARE TIMING AND QPF VARIATIONS AMONG THE MODELS.
THUS...HAVE NOT TRIED TO BE TOO PRECISE ON TIMING OF ONSET AND
ENDING OF POPS AND HAVE CAPPED AT HIGH CHANCE FOR NOW. SUSPECT MOST
LOCATIONS WILL GET MEASURABLE SOMETIME IN THE MON NIGHT TO TUE NIGHT
TIME FRAME BUT CANNOT PIN THE TIMING DOWN ANY BETTER. THE GLOBAL GEM
STILL LOOKS TOO ROBUST GIVEN THAT THIS SYSTEM IS ASSOCIATED WITH A
DAMPENING SHORT WAVE TROF MOVING INTO THE LONG WAVE RIDGE POSITION.
HOWEVER...AS WEAK AS SYSTEM IS...DOES LOOK LIKE DECENT OVERRUNNING
WITH A SUBTROPICAL MOISTURE SOURCE. AS FAR AS TIMING...AM SUSPICIOUS
THAT DRY LOW LEVEL AIR ASSOCIATED WITH MODERATELY STRONG HIGH PRES
CENTERED OVER NOVA SCOTIA AT THE OUTSET MAY DELAY THE SPREAD OF RAIN
INTO SOUTHWEST NH AND NORTHEAST MA MON NIGHT.

WED IS A LITTLE COMPLICATED WITH VIGOROUS NEGATIVE TILT SHORT WAVE
TROF ROTATING THROUGH THE GREAT LAKES. SOUTHERN NEW ENGLAND IS
FAIRLY WELL EAST OF SIGNIFICANT DYNAMICS. GFS DEPICTS SE FLOW THAT
COULD IN ITSELF CONTRIBUTE TO LOW CLOUDS AND DRIZZLE WHEREAS THE
ECMWF SHOWS LESS RH AND FLAT GRADIENT AMIDST WEAK SURFACE RIDGE.
HAVE GONE WITH SLIGHT CHANCE TO CHANCE POPS. TEMPERATURES MAY BE
TRICKY FOR WED GIVEN WARM AIR MASS ALOFT WITH 8C 850 MB
TEMPERATURES BUT INVERSION MAY PREVENT REALIZING THE RELATIVE WARMTH
AT THE SURFACE. IF GET ENOUGH SUN...THEN WED MAX TEMPERATURES MAY
END UP CONSIDERABLY HIGHER THAN CURRENTLY FORECAST.

THANKSGIVING DAY CURRENTLY LOOKS DRY WITH PERHAPS A SUNNY START
BEFORE INCREASING CLOUDS DURING THE AFTERNOON AHEAD OF THE NEXT
SYSTEM. A VIGOROUS SHORT WAVE TROF HELPS INITIATE A COASTAL LOW BUT
AGAIN MEDIUM MODELS NOT IN GOOD AGREEMENT IN HANDLING THIS SYSTEM
WITH REGARD TO INTENSITY AND TRACK. HAVE GONE WITH CHC POPS THU
NIGHT AND FRI. AIR MASS MAY COOL SUFFICIENTLY TOWARD BACK PART OF
STORM TO CAUSE PTYPE UNCERTAINTY. POTENTIAL FOR RAIN TO MIX WITH OR
CHANGE TO SNOW OVER THE HIGHER ELEVATIONS OF OUR NW ZONES ON FRI BUT
CONFIDENCE OF THIS ACTUALLY OCCURRING IS CURRENTLY LOW.

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...

TONIGHT...VFR. PATCHY FOG WITH BRIEF MVFR CIGS/VSBYS LATE AT NIGHT
IN THE NORMALLY SUSCEPTIBLE VALLEYS.

SUNDAY...VFR. MAY SEE PATCHY VFR TO LOCAL MVFR CIGS ALONG THE COAST
DURING THE LATE MORNING AND AFTERNOON.

SUNDAY NIGHT...VFR MOST LOCATIONS. GREATER RISK OF MVFR CIGS ALONG
THE EAST COAST AND SOUTH AND EAST OF A LINE FROM KBOS-KPVD.
CONFIDENCE ON THIS IS NOT HIGH AT THIS TIME.

OUTLOOK /MONDAY THROUGH WEDNESDAY/...

MON THRU WED...VFR MON BECOMING MVFR WITH AREAS IFR IN RAIN AND FOG
MON NIGHT THROUGH TUE NIGHT. MVFR CIGS MAY PERSIST INTO WED.

.MARINE...
HIGH PRES BUILDING N OF THE WATERS TONIGHT. WINDS GRADUALLY SHIFTING
N TONIGHT...THEN NE SUNDAY INTO SUNDAY NIGHT. SEAS BELOW 5 FT TONIGHT
INTO EARLY SUNDAY. DO EXPECT SEAS TO BUILD OVER 5 FT ACROSS THE OUTER
COASTAL WATERS SUNDAY AFTERNOON INTO SUNDAY NIGHT ONCE NE WINDS GET
ESTABLISHED. THERE IS STILL A QUESTION ABOUT STRENGTH OF THESE
WINDS...WHICH WILL BE ENTIRELY DEPENDENT UPON THE APPROACH OF A LOW
PRESSURE FROM THE MID ATLANTIC COAST.

OUTLOOK /MONDAY THROUGH WEDNESDAY/...

PERSISTENT E GRADIENT WITH CONSIDERABLE FETCH WILL LIKELY KEEP SEAS
NEAR OR ABOVE 5 FT EXPOSED COASTAL WATERS MON NIGHT THRU WED MORNING AND
MAY BE STRONG ENOUGH TO MEET SCA WIND THRESHOLDS OVER MOST OF WATERS.
RESPITE LIKELY LATE WED THRU THU BEFORE RISK OF POTENT COASTAL LOW PRES
SYSTEM TOWARD END OF WEEK.

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.

SYNOPSIS...BELK/THOMPSON
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...THOMPSON
AVIATION...BELK/THOMPSON
MARINE...BELK/THOMPSON