FXUS61 KBOX 112031
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
331 PM EST FRI DEC 11 2009
.SYNOPSIS...
LARGE LOW PRES OVER SE CANADA WILL CONTINUE TO GENERATE BLUSTERY AND
UNSEASONABLY COLD WEATHER ACROSS SOUTHERN NEW ENGLAND INTO SAT. A
WEAK WAVE OF LOW PRES WILL MOVE S OF SOUTHERN NEW ENGLAND SUN
AFTERNOON AND EVENING...BRINGING A PERIOD OF RAIN AND OR SNOW TO THE
REGION. WEAK HIGH PRES FOLLOWS MON PROVIDING DRY AND SEASONABLE
TEMPS. ANOTHER COLD FRONT SHOULD MOVE ACROSS THE REGION LATE TUE
BRINGING MUCH COLDER AIR TO THE REGION WED AND THU.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
WIND SPEEDS REMAINING BELOW WIND ADVISORY LEVELS THIS AFTERNOON. KBOX
88D SHOWING SOME ECHOES...BUT ALL SURFACE OBSERVATION INDICATE THIS
IS VIRGA. WITH DEW POINTS IN THE SINGLE DIGITS AND THE MAIN MID
LEVEL TROUGH TO OUR EAST BY THIS EVENING...DO NOT THINK A MENTION OF
SNOW SHOWERS OR FLURRIES IS WARRANTED. GUSTY WEST WINDS CONTINUE
THROUGH TONIGHT.
MAV GUIDANCE TEMPERATURES ARE TOO HIGH THE REST OF THIS AFTERNOON...
BUT LOOK REASONABLE TONIGHT. MET GUIDANCE TEMPERATURES ARE IN MUCH
BETTER AGREEMENT WITH LATEST OBSERVATIONS. FOLLOWING THE MET GUIDANCE
FOR THE REMAINDER OF THIS AFTERNOON...THEN USED A BLEND WEIGHT MORE
TOWARD THE NAM OVERNIGHT.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
HIGH PRESSURE EXPECTED TO MOVE EAST THROUGH THE MID ATLANTIC STATES
DURING THE DAY SATURDAY. THE SURFACE RIDGE SHOULD CREST ACROSS NEW
ENGLAND SATURDAY NIGHT. EXPECTING NEAR NORMAL TO BELOW NORMAL
TEMPERATURES SATURDAY AND SATURDAY NIGHT. MET GUIDANCE LOOKS TO BE
HANDLING THE COLDER AIR BETTER SATURDAY...SO LEANED IN THAT
DIRECTION. A BLEND OF THE GFS AND NAM LOOKS GOOD SATURDAY NIGHT. WIND
SHOULD DIMINISH LATE SATURDAY INTO SATURDAY NIGHT.
BOTH MET AND MAV GUIDANCE EXHIBITING TYPICAL HIGH BIAS IN DEW POINTS
IN A WELL-MIXED WEST TO NORTHWEST FLOW. WILL UNDERCUT THIS GUIDANCE
SATURDAY.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
SUNDAY....WILL SEE SOME MODERATION IN TEMPERATURES SUNDAY AS HIGH
PRESSURE SLIPS EAST OF THE AREA AND WINDS SHIFT TO THE SOUTH. A WARM
FRONT AND WEAK INVERTED TROUGH WILL APPROACH THE AREA FROM THE
SOUTHWEST DURING THE AFTERNOON. NOTING INCREASING WARM AIR ADVECTION
AND THE DEVELOPMENT OF A SOUTHERLY LOW LEVEL JET ACROSS THE WESTERN
ZONES DURING THE AFTERNOON HOURS. THIS OCCURS AS A WAVE OF LOW
PRESSURE FORMS ALONG THE MID ATLANTIC COAST BY EVENING. SOME TIMING
ISSUES EXIST BETWEEN THE SLOWER NAM/RGEM AND MORE PROGRESSIVE
GFS/ECMWF BUT THE DIFFERENCES ARE FAIRLY MINOR.
OVERALL HAVE INCREASED POPS SUNDAY AFTERNOON TO LIKELY ACROSS THE
CENTRAL AND WEST...CHANCE POPS FURTHER EAST. THE COMBINATION OF
SUBZERO H85 TEMPS GENERALLY NORTH OF THE CT/RI BORDER AND INCREASING
ISENTROPIC LIFT...SHOULD ALLOW FOR A FEW HOURS OF SNOW TO BEGIN THIS
EVENT ACROSS THE INTERIOR. ALONG THE COAST BOUNDARY LAYER TEMPS WILL
BE TOO WARM AND THIS WILL FAVOR ALL RAIN.
SUNDAY NIGHT...INCREASING WARM AIR ADVECTION EXPECTED AS THE
INVERTED TROUGH STRENGTHENS. THE GFS FEATURES A DEEPENING UPPER
LEVEL TROUGH AND SURFACE LOW TO THE SOUTH OF LONG ISLAND DURING
THE EVENING WHILE THE NAM/ECMWF AND RGEM TAKE A FEW HOURS LONGER.
GOOD MODEL CONSENSUS SO HAVE BOOSTED POPS TO CATEGORICAL ACROSS
MUCH OF THE AREA WITH LIKELY POPS NORTH. PRECIPITATION SHOULD CHANGE
TO RAIN ACROSS MUCH OF THE AREA EXCEPT PERHAPS THE FAR INTERIOR
NORTHWEST WHERE THERMAL PROFILES ARE A BIT MORE MARGINAL. THERE
COULD BE AN ADVISORY LEVEL SNOWFALL ACROSS INTERIOR NORTHWEST
MASSACHUSETTS AND SOUTHWESTERN NH BEFORE PRECIPITATION TAPERS OFF
BY DAYBREAK. CURRENTLY BEST OMEGA APPEARS TO BE BELOW THE DENDRITIC
SNOW GROWTH REGION. POPULATED SLIGHTLY COLDER NAM THICKNESSES AND
GFS QPF AMOUNTS TO DERIVE SNOWFALL TOTALS.
MONDAY THROUGH TUESDAY...MONDAY SHOULD FEATURE DRY CONDITIONS AS
THE FORECAST AREA WILL BE SITUATED IN BETWEEN WEATHER SYSTEMS. HAVE
CHANCE POPS MENTIONED FOR TUESDAY AND TUESDAY NIGHT AS A COLD FRONT
CROSSES THE AREA. GENERALLY FOLLOWED THE GFS/CANADIAN GGEM SOLUTIONS.
WEDNESDAY THROUGH THURSDAY...ARCTIC AIR SPREADS ACROSS THE REGION.
USED A BLEND OF RAW 2M AND MOSGUIDE TEMPERATURES FOR HIGHS AND
FOLLOWED MOSGUIDE FOR LOWS. DRY CONDITIONS EXPECTED TO PREVAIL WITH
THE EXCEPTION OF PERHAPS A FEW SCATTERED SNOW SHOWERS AND FLURRIES
ACROSS THE INTERIOR HIGH TERRAIN AS LAKE MOISTURE ADVECTS DOWNWIND.
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
VFR FOR MOST OF THIS PERIOD. ISOLD -SHSN COULD BRIEFLY RESULT IN MVFR
VSBY NORTH OF KBOS-KORH-KPSF.
OUTLOOK /SATURDAY NIGHT THROUGH TUESDAY/...
SUNDAY...VFR TO START THEN MVFR IN -RA SOUTHWEST/-SN NORTHWEST AS AN
INVERTED TROUGH APPROACHES THE AREA IN THE AFTERNOON.
SUNDAY NIGHT...MVFR CEILINGS/VSBYS IN -RA WITH -SN WELL NORTHWEST AS
AN INVERTED TROUGH CROSSES THE AREA.
MONDAY...VFR BUT PERHAPS MVFR CEILINGS EARLY ACROSS THE CAPE AND
ISLANDS.
TUESDAY...MVFR IN SCT -SHRA/-SHSN AS A COLD FRONT APPROACHES.
&&
.MARINE...
STILL EXPECTING GUSTY WINDS ACROSS THE WATERS TONIGHT INTO SATURDAY.
HAVE DROPPED THE GALE WARNING IN NARRAGANSETT BAY...WHERE THE NOAA
PORTS DATA INDICATE WINDS BELOW 34 KT FOR THE VAST MAJORITY OF THE
BAY. ELSEWHERE...WILL CONTINUE THE GALE WARNING INTO EARLY SATURDAY
MORNING. WITH A HIGH PRESSURE MOVING INTO THE MID ATLANTIC STATES
DURING THE DAY...ADJUSTED THE TIMING OF THE GALE WARNING. WILL LIKELY
NEED TO ISSUE SMALL CRAFT ADVISORIES ONCE THE GALE WARNINGS ARE DONE
FOR AT LEAST A PORTION OF SATURDAY. WINDS DIMINISH SATURDAY NIGHT...
BUT ROUGH SEAS SHOULD CONTINUE ACROSS THE OUTER COASTAL WATERS
THROUGH MOST OF SATURDAY NIGHT.
OUTLOOK /SUNDAY THROUGH TUESDAY/...
SUNDAY...WINDS AND SEAS EXPECTED TO BE BELOW SCA CRITERIA. S WINDS
COULD GUST UP TO 20 KT ALONG THE S COAST DURING THE AFTERNOON
SUNDAY NIGHT...COASTAL LOW PRESSURE DEVELOPING OFF THE MID ATLANTIC
COAST WILL CAUSE SHIFTING WINDS TO E THEN N OVERNIGHT. SEAS MAY
BUILD UP TO 5 FEET ACROSS THE OUTER WATERS.
MONDAY...A SMALL CRAFT ADVISORY POSSIBLE FOR N WINDS GUSTING UP TO
25 KT ACROSS THE OUTER WATERS AND SEAS UP TO 6 FT.
TUESDAY...A SMALL CRAFT ADVISORY MAY BE NEEDED. SHIFTING WINDS TO
SOUTHWEST AHEAD OF A COLD FRONT. WINDS COULD GUST TO 20 TO 25 KT AND
SEAS MAY BUILD UP TO 5 FEET LATE.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...GALE WARNING UNTIL 11 AM EST SATURDAY FOR ANZ231-232-250-251-
254>256.
GALE WARNING UNTIL 5 AM EST SATURDAY FOR ANZ230-233>235-237.
SMALL CRAFT ADVISORY UNTIL 1 PM EST SATURDAY FOR ANZ236.
&&
$$
SYNOPSIS...BELK/STRAUSS
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...STRAUSS
AVIATION...BELK/STRAUSS
MARINE...BELK/STRAUSS
