000
FXUS61 KBOX 061806
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
106 PM EST MON FEB 6 2012

.SYNOPSIS...
A WARM FRONT MOVES NORTHEAST OF NEW ENGLAND BRINGING A MILD WEST
TO SOUTHWEST WIND. A COLD FRONT WILL SLIDE ACROSS SOUTHERN NEW
ENGLAND ON TUESDAY. HIGH PRESSURE THEN BUILDS FROM CANADA ON
WEDNESDAY. LOW PRESSURE MOVING OUT OF THE SOUTHERN PLAINS MAY
BRING PRECIPITATION OUR WAY WEDNESDAY NIGHT AND THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1 PM UPDATE...
MAIN BULK OF THE FORECAST CONTINUES TO BE ON TRACK. HAVE UPDATED
THE FORECAST TO ACCOUNT FOR CURRENT TRENDS. UPPER LEVEL CLOUDS
HAVE DISSIPATE THIS MORNING LEADING TO A SUNNY DAY ACROSS SOUTHERN
NEW ENGLAND. TEMPERATURES HAVE INCREASED SIGNIFICANTLY OVER THE
PAST FEW HOURS...AND THIS TREND WILL CONTINUE AS THE SUN ANGLE
CONTINUES TO INCREASE. EXPECT TEMPS TO REACH IN THE MID 40S TO LOW
50S ACROSS THE REGION. WINDS WILL CONTINUE TO BE OUT OF THE
SOUTHWEST AND BE QUITE GUSTY AT TIMES AS THE 850MB JET OF 35KTS
MIXES DOWN. BELIEVE WINDS WILL REMAIN AROUND 15-20KTS WITH GUSTS
AROUND 25 KTS WITH A FEW 30KTS OCCURRING...ESP ACROSS THE CAPE AND
ISLANDS. IN FACT...KACK REPORTED A GUST OF 35KTS...JUST SHY OF ADV
CRITERIA. THIS SHOULD CONTINUE OVER THE NEXT FEW HOURS UNTIL THE
PRESSURE GRADIENT BEGINS TO LAX AND THE SUN SETS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
TONIGHT...
COLD FRONT APPROACHES FROM THE NORTH...REACHING THE ST LAWRENCE
VALLEY AROUND MIDNIGHT AND SOUTHERN/CENTRAL VT/NH TOWARD MORNING.
TEMPERATURES THIS MORNING UPSTREAM JUST SOUTH OF THE FRONT ARE
25-35...WHICH IS A GOOD ESTIMATE OF WHERE OUR MIN TEMPS WILL BE
TONIGHT. CROSS SECTIONS SHOW SOME INCREASING MOISTURE BELOW 850
MB...BUT ALL OF THE LIFT IS HIGH ABOVE AND IN DRY AIR. THIS MEANS
SOME INCREASE IN CLOUDS LATE AT NIGHT...BUT NO PRECIPITATION IS
EXPECTED.

TUESDAY...
THE COLD FRONT WILL CROSS SOUTHERN NEW ENGLAND. MODEL CONSENSUS
HAS THE FRONT APPROACHING THE SOUTH COAST BY 18Z...THEN OFF THE
COAST DURING THE AFTERNOON. SHALLOW MOISTURE BUT LITTLE LIFT SO
EXPECT SOME CLOUDS. COULD BE SCATTERED FLURRIES IN THE HIGHER
TERRAIN BUT MOST PLACES WILL HAVE NO PRECIPITATION.

COLD ADVECTION IN THE AFTERNOON WILL AID IN DEEPER MIXING. BOTH
NAM AND GFS SHOW MIXING TO 900 MB. TEMPS AT THAT LEVEL ARE
FORECAST AT -2C TO -5C...AND MIXING THOSE TEMPS TO THE SURFACE
WOULD BRING MAX TEMPS IN THE 40S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
HIGHLIGHTS...
  * QUIET WEATHER EXPECTED THROUGH TUE
  * LIGHT SNOW POSSIBLE OVER PORTIONS OF THE S COAST WED

OVERVIEW AND MODEL PREFERENCES...
06/00Z LONG RANGE MODEL SUITE AGREEMENT GETTING BETTER WITH THIS
RUN. OVERALL FORECAST CONFIDENCE IS HIGHER NOW THROUGH THE
UPCOMING WEEKEND. THIS IS PRIMARILY DUE TO THE FACT THAT GUIDANCE
IS NOW HANDLING A DEEPENING/DIGGING HUDSON BAY VORTEX AND THE
SUBSEQUENT BREAK DOWN OF WRN CANADA RIDGE BETTER THAN PREVIOUS
RUNS. SATELLITES AND A FEW SFC OBSERVING STATIONS NOW BEGINNING TO
SAMPLE STRONG SHORTWAVE ENERGY THAT WILL START THIS DIGGING
PROCESS THROUGH NORTHERN ALBERTA AND SASKATCHEWAN. IN ESSENCE THE
PERIOD WILL BE MARKED BY THE TRANSITION FROM DRY NW FLOW TO
MOIST/WARM SW FLOW AS THE BASE OF THE TROF ASSOCIATED WITH THE
VORTEX SINKS TO THE GREAT LAKES. THIS TROF WILL THEN MIGRATE E AS
ENERGY WRAPS INTO THE BASE INTO THE WEEKEND. GIVEN THAT OPNL AND
ENSEMBLE FORECAST MEMBERS ARE IN GENERALLY GOOD AGREEMENT
TEMPORALLY AND SPATIALLY /GENERALLY ONLY 6 HOURS DIFFERENCE LATE
IN THE PERIOD/...WILL CONTINUE TO USE ECMWF/GFS BLEND. THE BIGGEST
DIFFERENCE LAY IN THE DEPTH OF THE TROF...THUS THE NATURE OF THE
POTENTIAL COLD THIS TROF COULD PRODUCE. GFS IS COLDEST AND DEEPEST
WITH H5 516DM CONTOURS NOSING INTO SRN NH AND NRN MA...ECMWF ONLY
ALLOWS 528DM LINE TO DIP THIS FAR. SPLITTING THE DIFFERENCE HERE
IS PROBABLY BEST AS THERE IS TIME TO SORT THIS OUT AND EITHER
MODEL COULD BE TOO AMPLIFIED GIVEN THE NATURE OF THE WINTER THUS
FAR. ALSO THERE HAS BEEN A MODEL BIAS MODELS THIS WINTER WITH EACH
MODEL TRYING TO BRING IN ARCTIC AIRMASSES LATE IN THE RUN.

DETAILS...

TUE NIGHT INTO WED NIGHT...
WEAKENING COLD FRONT WILL GRADUALLY BE SHIFTING S OF THE
AREA...ALTHOUGH IT STALLS GENERALLY FROM ABOUT THE DC METRO AREA
NE TO JUST S OF THE BENCHMARK. AT THIS POINT WITH A SECOND ROUND
OF CAA AND W FLOW ALOFT...MOSTLY JUST A FEW REMAINING CLOUDS TO
CONTEND WITH OVERNIGHT TUE NIGHT. RIDGE OF HIGH PRES THEN SETS UP
AGAIN OVER PORTIONS OF NRN VT AND NH. THE KEY FOR THE PERIOD WILL
BE A WEAK WAVE PROGGED TO MOVE ALONG THE STALLED BAROCLINIC ZONE
TO THE S DURING THE DAY WED. SRN STREAM FLOW IS GENERALLY
SWLY...SO THERE LOOKS TO BE A BIT MORE MOISTURE ASSOCIATED WITH
THIS WAVE. LLVL FGEN IS WEAK...CLOSELY ASSOCIATED WITH THE FRONT
AND THE WAVE ITSELF. ALTHOUGH THERE IS SOME WEAK DEFORMATION WITH
THE H85 TO H7 OPEN WAVE PASSING OVER SOUTHERN NEW ENGLAND DURING
THE DAY. THEREFORE...COULD SEE SOME PRECIP /WITH THE COLUMN COOL
ENOUGH TO AT FOR SNOW BEFORE A POSSIBLE CHANGEOVER LATER IN THE
DAY/ OVER PORTIONS OF CT...RI...AND SE MA WITH A SHARP CUTOFF
SOMEWHERE OVER CENTRAL MA. AREAS N OF THE MA PIKE LIKELY TO SEE
LITTLE TO NO PRECIP FROM THIS FEATURE. DEPENDING ON THE FINAL
ORIENTATION OF THE STALLED FRONTAL BOUNDARY /ECMWF IS MUCH CLOSER
TO THE CAPE AND ISLANDS/ RAIN/SNOW SHOWERS MAY LINGER INTO THE
EARLY OVERNIGHT HOURS WED NIGHT PARTICULARLY OVER SE MA. QPF IS
EXPECTED TO BE LIGHT GIVEN THE WEAK DYNAMICS SO LITTLE SNOW/RAIN
ACCUMULATION IS EXPECTED.

COLUMN GRADUALLY COOLS THROUGH THE PERIOD WITH H92 TEMPS SETTLING
CLOSE TO -6C...THIS SHOULD YIELD TEMPS SLIGHTLY ABOVE NORMAL FOR
THIS TIME OF YEAR. CLOUD COVER WITH THE STALLED FRONT AND INCOMING
WAVE COULD NARROW DIURNAL TREND...KEEPING HIGHS CLOSER TO NORMAL
AND LOWS A BIT WARMER. THIS MAY ALSO BE ENOUGH TO KEEP LLVLS
CONDITIONED FOR ALL SNOW IN THE SRN PORTIONS OF THE FA. WILL HAVE
TO MONITOR THIS IN THE NEXT 48 HOURS.

THU THROUGH FRI...
LONGWAVE TROF BEGINS TO DIG TOWARD SRN NEW ENGLAND FROM THE GREAT
LAKES DURING THIS PERIOD. AS A RESULT H5 CONFLUENT FLOW DEVELOPS
OVER THE AREA...AND GRADUALLY SHIFTS MORE SWLY AS THE TROF
APPROACHES. THIS CONFLUENCE ALLOWS FOR WEAK LLVL RIDGING TO
DEVELOP...SO GENERALLY DRY WX EXPECTED WITH WARMING RETURN FLOW.
H92 TEMPS REBOUND CLOSE TO 0C...SO TEMPS PROGGED TO BE GENERALLY
ABOVE NORMAL THROUGH THE PERIOD.

THIS COMING WEEKEND...
LOW PRES ASSOCIATED WITH THE STRONG TROF IS EXPECTED TO PASS WELL
N OF THE REGION...ALTHOUGH IT WILL DRAG A REASONABLY ROBUST COLD
FRONT THROUGH THE AREA FRI NIGHT INTO SAT. CROSS SECTIONS REVEAL
THAT THIS FRONT HAS A STRONG LLVL THETA-E GRADIENT AND REASONABLE
MOISTURE TO WORK WITH....THEREFORE THIS SHOULD BRING PRECIP TO
ALMOST ALL AREAS DURING THE OVERNIGHT AND EARLY SAT TIMEFRAME.
COLUMN HAS HAD A CHANCE TO SUFFICIENTLY WARM AHEAD OF THE
FRONT...SO IT SHOULD BEGIN AS ALL RAIN. HOWEVER...WILL NEED TO
MONITOR THE SPEED WITH WHICH THE COLD AIR IS ABLE TO MOVE IN
BEHIND THE FRONT CONSIDERING THIS FRONT SHOWS MOSTLY ANAFRONT
CHARACTERISTICS...SO SOME SNOW IS STILL POSSIBLE.

THE BASE OF THE TROF BEGINS TO SINK OVER SUN INTO MON WITH COLD
HIGH PRES. ATTM...SOUNDINGS SUGGEST TEMPS WELL BELOW
NORMAL....ALTHOUGH...AS MENTIONED IN THE OVERVIEW...THIS COULD BE
AN OVER-AMPLIFICATION BIAS THAT MODELS HAVE SUGGESTED SEVERAL TIMES
THIS SEASON. IN EITHER CASE DRY WX RETURNS.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
FORECASTER CONFIDENCE LEVELS...
  LOW...LESS THAN 30 PERCENT
  MODERATE...30 PERCENT TO 60 PERCENT
  HIGH...GREATER THAN 60 PERCENT

TODAY...
VFR. HIGH CONFIDENCE. EXPECT MOSTLY SUNNY SKIES WITH SOUTHWESTERLY WINDS
GUSTING UP TO 20-25 KT THROUGH THE REST OF THE AFTERNOON. A FEW
GUSTS TO 30 KT POSSIBLE OVER CAPE AND ISLAND TERMINALS.

TONIGHT...
VFR. HIGH CONFIDENCE. WINDS WILL BEGIN TO SWITCH TO THE WEST AS A
COLD FRONT APPROACHES THE REGION. CIGS OF 3000 TO 400O FT ARE
POSSIBLE ESPECIALLY OVER THE NORTHWESTERN TERMINALS AS THE FRONT
MOVES CLOSER.

TOMORROW...
VFR. MODERATE CONFIDENCE. COLD FRONT WILL MOVE THROUGH THE REGION
ALLOWING THE POTENTIAL FOR CLOUDS TO BE AROUND 3000 AND 5000 FEET
ESPECIALLY DURING THE MORNING. WINDS WILL SWITCH FROM THE WEST TO
THE NORTHWEST AROUND 12-15Z AS FRONT PASSES THROUGH.

KBOS TERMINAL...
HIGH CONFIDENCE VFR. WSW WINDS TODAY WITH GUSTS 20 TO 25 KT
THROUGH THE AFTERNOON WITH MOSTLY CLEAR SKIES TODAY. A COLD FRONT
CROSSES THE AREA TOMORROW MORNING WITH A FEW LOW VFR CIGS
POSSIBLE AND WINDS SHIFTING THE NW INTO THE DAY.

TUESDAY NIGHT...
MODERATE TO HIGH CONFIDENCE VFR.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...

WEDNESDAY INTO WEDNESDAY NIGHT...
MODERATE CONFIDENCE VFR. LOW CONFIDENCE MVFR/IFR CONDITIONS IN A
MIX OF SNOW AND RAIN OVER TERMINALS IN CT/RI AND SE MA.

THURSDAY AND FRIDAY...
MODERATE CONFIDENCE VFR.

&&

.MARINE...
TODAY...
HIGH PRESSURE MOVES SOUTH OF THE WATERS...BRINGING A WEST TO
SOUTHWEST WIND TO THE WATERS. PRESSURE GRADIENT AND LOW LEVEL
WINDS ALOFT WILL BE SUFFICIENT TO BRING FREQUENT 25 KNOT GUSTS TO
THE WATERS...AND THE STEADY WIND WILL BE ENOUGH TO BUILD SEAS ON
THE OUTER WATERS TO 5-7 FEET. PARTS OF RI SOUND MAY ALSO REACH 5
FEET. A SMALL CRAFT ADVISORY CONTINUES FOR ALL WATERS WITH
CRITERIA EXPECTED TO BE REACHED TODAY.

TONIGHT...
WINDS WILL DIMINISH ON ALL WATERS...BUT REMAIN NEAR 25 KNOTS ON
THE OUTER WATERS AND ON NANTUCKET SOUND....AND POSSIBLY CAPE COD
BAY. SEAS WILL ALSO SUBSIDE...BUT MAY REMAIN AT OR ABOVE 5 FEET ON
THE SOUTHERN AND SOUTHEAST WATERS. SMALL CRAFT ADVISORIES WILL COME
DOWN PIECE-BY-PIECE AS CONDITIONS RELAX.

TUESDAY...
A COLD FRONT WILL MOVE ACROSS THE WATERS DURING THE DAY...TURNING
WINDS FROM WEST TO NORTHWEST. WINDS WILL CONTINUE TO
DIMINISH...BUT WITH 20 KNOT GUSTS STILL POSSIBLE. SEAS WILL ALSO
SUBSIDE...BUT WITH 5 FOOT SEAS FOR A PART OF THE MORNING AND
AFTERNOON ON THE SOUTHERN AND SOUTHEAST OUTER WATERS. EXPECT SMALL
CRAFT ADVISORIES TO LINGER ON THESE OUTER WATERS FOR AT LEAST A
PART OF THE DAY.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...

TUE NIGHT INTO THU...
GENERALLY WEAK FLOW THROUGH THE PERIOD WILL KEEP WIND GUSTS AND
SEAS BELOW SCA THRESHOLDS. SOME RAIN SHOWERS ARE POSSIBLE
ESPECIALLY OVER THE SOUTHERN WATERS WED INTO WED NIGHT.

THU NIGHT INTO FRI...
A COLD FRONT WILL APPROACH THE WATERS DURING THIS PERIOD WITH
INCREASING SW WINDS. GUSTS MAY REACH 25 TO 30 KT. SEAS WILL ALSO
BUILD IN SW SWELL...REACHING 5 TO 6 FT ESPECIALLY OVER THE OUTER
WATERS.  SCA MAY BE NEEDED.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EST TUESDAY FOR ANZ231>234.
     SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ230.
     SMALL CRAFT ADVISORY UNTIL 9 PM EST THIS EVENING FOR ANZ236-
     251.
     SMALL CRAFT ADVISORY UNTIL 8 AM EST TUESDAY FOR ANZ235-237.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST TUESDAY FOR ANZ250.
     SMALL CRAFT ADVISORY UNTIL 5 PM EST TUESDAY FOR ANZ254-255.
     SMALL CRAFT ADVISORY UNTIL 3 PM EST TUESDAY FOR ANZ256.

&&

$$
SYNOPSIS...WTB/DOODY
NEAR TERM...WTB/DOODY/DUNTEN
SHORT TERM...WTB
LONG TERM...DOODY
AVIATION...DOODY/DUNTEN
MARINE...WTB/DOODY

NWS RAHNWS Office Area Forecast Discussion