FXUS61 KBOX 050043
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
743 PM EST FRI DEC 4 2009
.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL ACROSS THE REGION TONIGHT. LOW
PRESSURE NEAR THE CAROLINAS EARLY SATURDAY WILL INTENSIFY AS IT
PASSES ABOUT 120 MILES SE OF NANTUCKET SATURDAY NIGHT. HIGH PRESSURE
WILL FOLLOW SUNDAY INTO MONDAY. A WEAK LOW PRESSURE PASSES NORTH OF
OUR AREA LATE MONDAY INTO MONDAY NIGHT...BUT THEN ANOTHER
POTENTIALLY STRONG LOW PRESSURE SYSTEM AFFECTS SOUTHERN NEW ENGLAND
MIDWEEK.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
INCREASING HIGH CLOUDS AND SOME STRATOCUMULUS FILTERED ACROSS THE
AREA THIS AFTERNOON. CLOUDS WILL CONTINUE TO INCREASE AND THICKEN
OVERNIGHT. DUE TO THE INCREASING CLOUD COVER...FORECASTED
TEMPERATURES SLIGHTLY MILDER THAN MAV/MET MOS GUIDANCE.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
SATURDAY AND SATURDAY NIGHT...A SIGNIFICANT PRECIPITATION EVENT IS
EXPECTED TO DEVELOP ACROSS THE AREA SATURDAY AFTERNOON AND CONTINUE
OVERNIGHT BEFORE TAPERING OFF BY DAYBREAK.
IN GENERAL MODELS APPEAR TO BE INTENSIFYING THE LOW MORE QUICKLY
OVER SOUTHEASTERN NEW ENGLAND AND TRENDING THE TRACK CLOSER TO THE
COAST...WITH THE SURFACE TRACK JUST SOUTHEAST OF THE 40N AND 70W
BENCHMARK POSITION BY 06Z SUNDAY. THE 12Z GFS MADE A JUMP FURTHER
WEST WITH THE TRACK...WHILE THE 12Z NAM IS A BIT FURTHER EAST AND
MORE REFLECTIVE OF THE OVERALL ENSEMBLE MEAN. SO GENERALLY FAVORED A
50/50 BLEND OF THE NAM/GFS. THE DIFFERENCE IS THAT THE NAM IS
INITIALLY A BIT MILDER WITHIN THE BOUNDARY LAYER THAN THE GFS AND
ALSO THE POSITION OF THE BEST MID LEVEL FRONTOGENETIC FORCING AND
BANDING DIFFERS WITHIN THE DEFORMATION ZONE.
INITIALLY SATURDAY AFTERNOON...1000-850MB AND 850-700MB THICKNESSES
SUPPORT SNOW EXCEPT SOUTHEAST OF INTERSTATE 95. PRECIPITATION IS
EXPECTED TO BE LIGHT...BUT INCREASE IN INTENSITY DURING THE
AFTERNOON. THIS WILL AID IN COOLING THE VERTICAL COLUMN. THE MAIN
BULK OF PRECIPITATION IS EXPECTED TO FALL BETWEEN 00Z AND 06Z
WITH THE VERTICAL COLUMN CONTINUING TO COOL BEFORE PRECIPITATION
ENDS BY 12Z.
SNOW GROWTH LOOKS FAVORABLE I95 WEST TO I84 AND NORTH THROUGH
WORCESTER COUNTY WITH FAIRLY STRONG OMEGA WITHIN THE DENDRITIC
SNOW GROWTH REGION CENTERED FROM 00Z THROUGH 06Z SUNDAY.
REGARDING THE LATEST TRENDS...THE 15Z SREFS HAVE INCREASED THE CHANCE
OF SNOW AMOUNTS GREATER THAN OR EQUAL 4 INCHES ACROSS THE HIGHER TERRAIN
OF NORTHERN RHODE ISLAND...WORCESTER COUNTY AND THE METROWEST AND NORTH
SHORE AREAS OF BOSTON AS WELL AS PORTIONS OF SOUTHERN NEW HAMPSHIRE.
THERE IS A LOW PROBABILITY OF WARNING CRITERIA AMOUNTS THE HIGH
TERRAIN DEPENDING HOW QUICKLY THE RAIN CHANGES OVER TO SNOW. ALSO
GIVEN THE HEAVY WET CONSISTENCY OF THE SNOW AND PROGRESSIVE NATURE
OF THE EVENT...MORE CONFIDENT IN AN ADVISORY WITH 2 TO 5 INCH
AMOUNTS ACROSS THE INTERIOR. NOT ENOUGH CONFIDENCE TO ISSUE A WATCH.
IT IS MAINLY A THIRD PERIOD EVENT SO WILL HIGHLIGHT THIS IN THE
HAZARDOUS WEATHER OUTLOOK.
WIND: THE NAM/GFS BOTH DEVELOP A STRONG 50-55KT LOW LEVEL NE JET BY
06Z SUNDAY AS THE LOW INTENSIFIES ACROSS COASTAL SECTIONS. A WIND
ADVISORY MAY BE NECESSARY ACROSS PORTIONS OF SOUTHEAST COASTAL NEW
ENGLAND SATURDAY NIGHT. SOME MINOR BEACH EROSION IS POSSIBLE
SATURDAY NIGHT AND EARLY SUNDAY.
PRECIPITATION: USED A BLEND OF MORE CONSERVATIVE 12Z RGEM/SREF AND
HEAVIER 12Z GFS QPF AMOUNTS.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
SUNDAY...MODELS IN GOOD AGREEMENT ON LOW PRESSURE CENTER OFF THE
COAST OF NOVA SCOTIA FOR 12Z SUN...PULLING TO THE NORTHEAST. IN ITS
WAKE HIGH PRESSURE WILL BUILD INTO THE AREA. STILL A TIGHT GRADIENT
TO START ACCOMPANIED BY COLD AIR ADVECTION AND NAM/GFS GUIDANCE
INDIATING STRONG WIND GUSTS OVER THE CAPE AND ISLANDS...INDICATING
THE POTENTIAL FOR ADVISORY CRITERIA GUSTS IN THE MORNING. OTHERWISE
DRIER AIR MOVING INTO SOUTHERN NEW ENGLAND BRINGING SUNSHINE.
SUN NIGHT...HIGH PRESSURE CROSSES THROUGH THE AREA WITH DRY
CONDITIONS.
MON AND MON NIGHT...MODEL DISCREPANCIES EXIST REGARDING POTENTIAL
FOR A WEAK LOW PASSING TO OUR NORTH DURING THIS TIMEFRAME. GFS AND
SREF HAVE DIFFERENCES IN TIMING BUT ARE MOST ROBUST WITH IT...EVEN
THEN QPF AMOUNTS ARE LIGHT. GGEM/ECMWF ARE QUITE A BIT WEAKER. WILL
GO WITH A MODEL COMPROMISE HERE AND KEEP POPS TO CHANCE IN FAR
NORTHERN PORTION OF THE AREA MON AND MON NIGHT...ELSEWHERE SLIGHT
CHANCE. THIS IS CLOSE TO THE PREVIOUS FORECAST. THERMAL PROFILES
SHOW POTENTIAL FOR A PRECIP TYPE OF LIGHT SNOW IN SOUTHERN NH AND
NORTHERN MA...BUT AT THIS TIME WOULD EXPECT NO MORE THAN A DUSTING.
TUESDAY...BRIEF VISIT BY HIGH PRESSURE.
MODELS SHOW A VIGOROUS SOUTHERN STREAM SYSTEM TRACKING FROM THE
SOUTHERN PLAINS TUESDAY NIGHT...INTO THE GREAT LAKES OR OHIO VALLEY
REGION WEDNESDAY. FOR THIS FAR OUT...GFS/ECMWF/GGEM SURFACE FEATURES
ARE NOT ALL THAT DIFFERENT...THOUGH UPPER TROUGH IS DEEPER IN GGEM.
TYPICALLY WE/D STAY AT A HIGH CHANCE POP THIS FAR IN THE
EXTENDED...BUT EVEN GEFS INDICATING AROUND AN INCH QPF AND NEAR 100
PERCENT CHANCE OF MEASURABLE PRECIP. SO WILL GO WITH LIKELY POPS
FOR THE WEDNESDAY TIMEFRAME. IF PRECIP BEGINS TUE NIGHT THERE IS THE
POTENTIAL FOR LIGHT SNOW...THEN GFS SURFACE TEMPS/THICKNESSES
SUPPORT PTYPE OF SNOW INTO WED MORNING...THEN A CHANGEOVER TO RAIN.
COULD SEE SOME ACCUMULATING SNOWS PRIOR TO CHANGEOVER PARTICULARLY
IN THE FAR INTERIOR.
POTENTIAL EXISTS FOR STRONG WINDS AS MODELS CONTINUE TO SHOW A 60 TO
70 KT LOW LEVEL JET EXTENDING INTO THE AREA.
LINGERING SHOWERS POSSIBLE ON THURSDAY WITH WRAP AROUND MOISTURE
FROM SYSTEM. STRONG W/NW WINDS BEHIND THE LOW AS IT PULLS INTO CANADA.
HIGH PRESSURE SHOULD BRING DRY CONDITIONS AND DIMINISHING WINDS FOR
FRIDAY.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
THROUGH TONIGHT...VFR WITH LIGHT W WINDS...BECOMING GENERALLY NE
TOWARD DAYBREAK SAT. CIGS AOA 9KFT DEVELOPING TONIGHT.
SATURDAY...MVFR CIGS SPREADING S TO N DURING THE 16Z TO 20Z TIME
FRAME WITH RAIN SHOWERS DEVELOPING AN HOUR OR 2 AFTER MVFR CIGS
DEVELOP /DOWNWARD SATURATING FM PCPN ALOFT/. CONDS LOWER FURTHER IN
THE AFTN...TO IFR CONDITIONS EARLY EVENING. LATE AFTERNOON PRECIP
GENERALLY -RA IN TAF LOCATIONS BUT MIX/CHANGEOVER TO -SN W OF BOS/PVD
PRIOR TO 00Z. THERE IS A CHANCE FOR A NARROW BAND OF 1/4 TO 1/2 SM
S/S+ SOMEWHERE CENTRALLY ARCED ROUGHLY NEAR OR JUST SE OF LWM-ORH-HFD
IN THE LATE AFTN. DETAILS TO BE DETERMINED FROM LATER MODEL RUNS.
WINDS LATE SAT AFTN N-NE G10-20KTS ALL AIRPORTS.
SAT NIGHT...IFR CONDITIONS IN SNOW DURING THE EVENING IN THE WEST AND
PAST MIDNIGHT COAST WITH ASSOCIATED LOWER VSBYS. NNE GUSTS 25-35 KTS
LIKELY CC AND THE ISLANDS.
OUTLOOK /SUNDAY THROUGH THURSDAY/...
SUN...MVFR CIGS POSSIBLE EARLY BOS/HYA VICINITY...THEN VFR.
MON...VFR...MVFR POSSIBLE AT NIGHT IN SCTD -SHRA/-SHSN.
TUE...VFR.
WED...POSSIBLE IFR AND STRONG WINDS.
THU...POSSIBLE MVFR AND STRONG WINDS.
&&
.MARINE...
TONIGHT...A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CONTINUES ACROSS
THE SOUTHEASTERN WATERS FOR LINGERING S SWELL.
SATURDAY AND SATURDAY NIGHT...A GALE WATCH HAS BEEN POSTED ACROSS
MOST OF THE COASTAL WATERS SATURDAY EVENING THROUGH EARLY SUNDAY
MORNING. NE TO N WINDS SHOULD INCREASE TO 25 TO 35 KT WITH HIGHER
GUSTS POSSIBLE. THERE IS A LOW PROBABILITY OF STORM FORCE WIND GUSTS
ACROSS THE EASTERN WATERS.
OUTLOOK /SUNDAY THROUGH THURSDAY/...
GLW CONDITIONS WOULD THEN CONTINUE INTO EARLY SUNDAY...THEN WINDS
DIMINISH AS LOW PULLS FURTHER TO THE NE. ROUGH SEAS WILL LIKELY LAST
INTO SUNDAY NIGHT IN THE OUTER WATERS. LIGHTER WINDS AND FLAT SEAS
EXPECTED MON AS HIGH PRESSURE BUILDS OVER NEW ENGLAND.
THERE IS A CHANCE FOR SCA CONDITIONS MON NIGHT INTO TUE AS A LOW
PRESSURE SYSTEM TRACKS NORTH OF THE WATERS.
GALE FORCE WINDS ARE POSSIBLE WED INTO THU AS A STRONG LOW PRESSURE
TRACKS FROM THE SOUTEHRN PLAINS TO THE GREAT LAKES...AND ON TO NOVA
SCOTIA.
&&
.TIDES/COASTAL FLOODING...
COASTAL FLOODING: AGAIN THIS WILL BE A PROGRESSIVE EVENT. HOWEVER A
ONE TO PERHAPS ONE AND ONE HALF FOOT SURGE MAY OCCUR AROUND THE TIME
OF SUNDAY MORNING HIGH TIDE ALONG WITH WAVES INCREASING TO 9 TO 13
FT. THIS COULD LEAD TO SOME MINOR SPLASHOVER SATURDAY NIGHT AND EARLY
SUNDAY PARTICULARLY ACROSS THE CAPE AND ISLANDS.
&&
.CLIMATE...
BOSTON/S LOGAN AIRPORT HAS NOT FALLEN TO THE FREEZING MARK SO FAR
THIS SEASON. THE RECORD LATEST IN THE SEASON THAT BOSTON HAS
RECORDED ITS FIRST 32F WAS DEC 2ND 1975. AS OF TODAY...THIS RECORD
HAS BEEN BROKEN. AVERAGE FIRST DATE OF 32 IN BOSTON IS AROUND
NOVEMBER 4TH. CURRENT FORECAST SUGGESTS THAT THE MINIMUM AT LOGAN
MAY NOT FALL TO BELOW FREEZING UNTIL EARLY SUNDAY MORNING.
RECORD WARMEST DAILY MINIMUMS SET 12/3/09
BOSTON 50
PROVIDENCE 51
WINDSOR LOCKS CT 46
ISSUED A PUBLIC INFORMATION STATEMENT SUMMARIZING
CLIMATOLOGICAL AUTUMN 2009.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...GALE WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING FOR
ANZ231>235-237-250-251-254>256.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM EST THIS
EVENING FOR ANZ235-254>256.
&&
$$
SYNOPSIS...NMB
NEAR TERM...STRAUSS
SHORT TERM...STRAUSS
LONG TERM...NMB
AVIATION...DRAG/STRAUSS/NMB
MARINE...STRAUSS/NMB
TIDES/COASTAL FLOODING...
CLIMATE...
