Area Forecast Discussion
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000
FXUS61 KBOX 211154
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
654 AM EST SUN DEC 21 2014

.SYNOPSIS...
AN AREA OF SNOW SHOWERS WILL AFFECT AREAS MAINLY SOUTH OF THE MA
TURNPIKE THIS MORNING...EXCEPT IT WILL BE MILD ENOUGH FOR RAIN
SHOWERS ACROSS THE FAR SOUTHEAST NEW ENGLAND COAST. WEAK LOW
PRESSURE WILL PASS SOUTH OF NEW ENGLAND BRINGING ANOTHER PERIOD OF
PRECIPITATION MONDAY NIGHT AND TUESDAY. A MUCH STRONGER STORM
PASSING WEST OF NEW ENGLAND WILL BRING HEAVY RAINFALL...GUSTY
WINDS AND COASTAL FLOODING CONCERNS TO THE REGION WEDNESDAY AND
WEDNESDAY NIGHT. DRY BUT VERY WINDY CONDITIONS FOLLOW FOR
CHRISTMAS DAY.

&&

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

700 PM UPDATE...

VERY LITTLE CHANGES TO THE FORECAST AS OVERALL TREND IS ON TRACK
FOR THIS MORNING. RADAR ECHOES LOOK A LITTLE DECEIVING AS SNOW HAS
SPREAD ACROSS A GOOD PORTION OF SOUTHERN NEW ENGLAND PER OBS.
ANTICIPATE MORE WIDE SPREAD BUT LIGHT SNOW OVER THE NEXT HOUR OR
TWO OUTSIDE OF THE COASTAL FRONT...WHICH IS DRAPED OVER GHG-TAN-
UUU.

PREVIOUS DISCUSSION...

APPROACHING SHORTWAVE HAS ALLOWED AN AREA LIGHT SNOW SHOWERS TO
EXPAND SOUTH OF THE MA TURNPIKE VERY EARLY THIS MORNING...BUT A FEW
SNOW SHOWERS DID EXTEND INTO NORTHERN MA.  RADAR IMAGERY ACTUALLY
OVER SHOOTING SOME OF THE ACTIVITY ACROSS NORTHERN CT...BASED ON
OBSERVATIONS.  THE RAIN/SNOW LINE RUNS ROUGHLY FROM NEWPORT...TO
TAUNTON AND JUST NORTH OF MARSHFIELD.  OVERALL...DO NOT EXPECT MUCH
CHANGE IN THE RAIN/SNOW LINE THIS MORNING BASED ON THERMAL PROFILES
AND POSITIONING OF THE COASTAL FRONT.

MAIN UNCERTAINTY IS JUST HOW MUCH SNOW OCCURS THIS MORNING WITH THE
SHORTWAVE MOVING ACROSS CT.  GIVEN THE TRACK OF THE SHORTWAVE...BEST
FORCING WILL BE LOCATED SOUTH OF THE MA TURNPIKE AND ESPECIALLY
ACROSS NORTHERN CT/RI.  WE WILL FORECAST 1 TO 2 INCHES OF SNOW
ACROSS THIS REGION...BUT A FEW ISOLATED 3 INCH AMOUNTS CAN NOT BE
RULED OUT. MEANWHILE...AREAS NORTH OF THE MA TURNPIKE WILL BE
REMOVED FROM THE BEST FORCING...BUT STILL SEE SOME SCATTERED
SHOWERS.  ACCUMS IN THIS AREA LIKELY TO BE A DUSTING TO LESS THAN AN
INCH.

ALSO...SOME OF THE PRECIPITATION CURRENTLY ACROSS SOUTHEAST MA IS
BEING ENHANCED FROM THE COASTAL FRONT.  A LOT OF THIS PRECIP WILL
BE IN THE FORM OF RAIN SHOWERS ACROSS PLYMOUTH AND EVEN INTO
PORTIONS OF BRISTOL COUNTY...POINTS SOUTH AND EAST.  HOWEVER...AT
LEAST THE SLIGHTLY HIGHER TERRAIN OF SOUTHEAST MA SHOULD SEE SNOW
SHOWERS.  WILL HAVE TO KEEP A CLOSE EYE ON IF COASTAL FRONT SHIFTS
SLIGHTLY THIS MORNING.  IT COULD MEAN THE DIFFERENCE BETWEEN AN AREA
GETTING MAINLY RAIN SHOWERS OR PERHAPS AN INCH OR SO OF SNOW.
OVERALL...DO NOT EXPECT THE COASTAL FRONT TO MOVE TOO MUCH THIS
MORNING...BUT JUST A FEW MILES CAN MAKE DIFFERENCE FOR A
PARTICULARLY NEIGHBORHOOD.

BULK OF PRECIPITATION WILL BE THIS MORNING WITH THE SHORTWAVE.
HOWEVER...ENOUGH LOW LEVEL MOISTURE/WEAK LIFT WILL REMAIN THIS
AFTERNOON FOR AT LEAST THIS RISK OF SCATTERED PRECIPITATION AND WILL
MAINTAIN SOME POPS.  HIGH TEMPS MAINLY IN THE 30S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
TONIGHT...

A RATHER CLOUDY AND RAW NIGHT ACROSS SOUTHERN NEW ENGLAND.  WHILE
THERE IS NOT A SIGNIFICANT SHORTWAVE TO TRIGGER A LOT OF
PRECIPITATION...PLENTY OF LOW LEVEL MOISTURE/WEAK SHALLOW LIFT
REMAINS.  THIS MAY BE ENOUGH TO RESULT IN A FEW RAIN/SNOW SHOWER
FROM TIME TO TIME.  PTYPE...WOULD BE MAINLY SNOW SHOWERS EXCEPT TO
THE SOUTHEAST OF A NEWPORT...TO TAUNTON...TO JUST NORTH OF
MARSHFIELD LINE.  AGAIN...MUCH OF THE NIGHT WILL PROBABLY END UP
DRY...BUT JUST THE RISK FOR A FEW RAIN/SNOW SHOWERS.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
HIGHLIGHTS...

* WEAK SHORTWAVE ON MON NIGHT/TUESDAY COULD BRING WINTRY
  MIX/FREEZING RAIN TO THE INTERIOR
* ANOMALOUS SYSTEM ACROSS THE GREAT LAKES WILL BRING HEAVY
  RAIN...GUSTY WINDS AND COASTAL FLOODING CONCERNS AROUND CHRISTMAS
  EVE
* BLUSTERY BUT AIRMASS WILL BE DRYING OUT ON CHRISTMAS DAY

OVERVIEW...

THE MODELS AND ENSEMBLES OFFER A REASONABLY SIMILAR AND PREDICTABLE
LARGER SCALE MID TO UPPER LEVEL PATTERN EVOLUTION FOR MUCH OF THE
UPCOMING WEEK. THIS ACTIVE FLOW REGIME DEVELOPS SEVERAL MID-UPPER
LEVEL TROUGH AND ASSOCIATED/UNSETTLING LEAD SURFACE LOW/FRONTAL
SYSTEMS AND PCPN SWATHS PROGRESS STEADILY ACROSS THE LOWER 48. THE
FIRST AMPLIFIED/DEEP LEAD SYSTEM WORKS ACROSS THE ERN/NERN US INTO
ERN CANADA CHRISTMAS EVE INTO CHRISTMAS ALLOWING FOR A MOIST/WARMED
AIRMASS IN ADVANCE OF FRONTAL APPROACH WITH HEAVIEST LEAD QPF
POTENTIAL OVER NEW ENGLAND. BIGGEST QUESTION IS THE EVOLUTION OF THE
SECONDARY LOW PRESSURE SYSTEM. 00Z GUIDANCE HAS BACKED OFF ON THE
STRENGTH OF THE LOW AND IS HAVING ISSUES ON HOW TO HANDLE ITS
EVOLUTION. THE EC AND GFS HAVE SLOWED DOWN THE SYSTEM SLIGHTLY WITH
THE EC HAVING MORE OF A NEGATIVE TROUGH VS THE GFS. BELIEVE THE
UKMET IS A GOOD COMPROMISE AT IS WAS THE FIRST DETERMINISTIC
GUIDANCE ON TAMPERING DOWN THE FIRST MAIN LOW...WHILE THE CMC IS OUT
TO LUNCH. REGARDLESS THIS IS A VERY ANOMALOUS SYSTEM THAT IS ABOUT 4
STANDARD DEVIATIONS AWAY.

A SECONDARY SYSTEM DEEPENS ACROSS THE FOUR CORNERS ON FRIDAY AND
WITH THE STUBBORN TROUGH OVER THE CENTRAL U.S...IT WILL PUSH A
SYSTEM TOWARDS SOUTHERN NEW ENGLAND BY SUNDAY. THIS SYSTEM MAY
SUPPORT A MODEST SWATH OF OVERRUNNING SNOW OVER SOUTHERN NEW
ENGLAND.

DETAILS...

MONDAY INTO TUESDAY...MODERATE CONFIDENCE.

A WEAK WAVE OF LOW PRESSURE DEVELOPS ALONG THE SOUTHEAST COAST
MONDAY...AND WILL BE ON A DEVELOPING WARM FRONTAL BOUNDARY. THIS LOW
REMAINS WEAK AS THE WARM FRONT MOVES SLOWLY NORTH MONDAY NIGHT INTO
TUESDAY. APPEARS THAT THERE IS DECENT WARM ADVECTION AHEAD OF THIS
WAVE. SEVERAL HI-RES GUIDANCE MODELS SHOW THAT THERE IS THE
POTENTIAL FOR COLD AIR DAMMING ACROSS THE INTERIOR INTO TUESDAY.
BIGGEST QUESTION WILL BE IS THERE ENOUGH MOISTURE FOR PRECIP DURING
THIS TIME FRAME. DUE TO A STRENGTHENING LLJ PROVIDING A GOOD SOURCE OF
LIFT ANTICIPATE PRECIP TO DEVELOP AND OVERSPREAD ACROSS SOUTHERN NEW
ENGLAND. IF THIS PLAYS OUT WITH COLD AIR DAMMING AND WARM AIR
ADVECTION...THEN WE COULD SEE FREEZING RAIN/DRIZZLE ACROSS THE I-91
CORRIDOR LATE MONDAY INTO TUESDAY MORNING. DURING THE DAY ON
TUESDAY...GOOD AMOUNT OF WARM AIR WILL PUSH SURFACE TEMPS ABOVE
FREEZING BY THE LATE MORNING ALLOWING FOR ANY PRECIP TO BE MORE OF
THE LIQUID VARIETY AHEAD OF THE CHRISTMAS EVE STORM. HOWEVER
GUIDANCE IS ALWAYS TOO FAST IN SCOURING TEMPS OUT ESP ACROSS THE CT
VALLEY SO WE WILL NEED TO MONITOR THIS CLOSELY...ESP DUE TO LIGHT
WINDS AND THE HIGH IN EASTERN CANADA. A WINTER WX ADVISORY MAY BE
NEEDED FOR THE LIGHT ICING POTENTIAL.

WE COULD ALSO SEE SOME MINOR COASTAL FLOODING CONCERNS ON TUESDAY. SEE
BELOW FOR MORE DETAILS.

WEDNESDAY INTO THURSDAY...HIGH CONFIDENCE IN SYSTEM LOW CONFIDENCE
ON DETAILS.

ANOMALOUS SYSTEM WILL STRENGTHEN OVER THE GREAT LAKES TUESDAY INTO
WEDNESDAY. A SECONDARY SHORTWAVE WILL ROUND THE DEEP TROUGH AND
DEVELOP A SECONDARY LOW PRESSURE ALONG THE COLD FRONT. THIS
SECONDARY LOW WILL STRENGTHEN AND PASS WEST OF SOUTHERN NEW ENGLAND.
THIS SYSTEM WILL CONTINUE TO DEEPEN AS IT MOVES TOWARDS EASTERN
CANADA SWINGING A COLD FRONT ACROSS THE NORTHEAST.

STRONG SOUTHERLY JET OUT AHEAD OF THE FRONT WITH A GULF MOISTURE
CONNECTION WILL IMPACT SOUTHERN NEW ENGLAND ON CHRISTMAS EVE. THIS
STRONG JET WILL YIELD FOR PCPN IN THE LIQUID VARIETY.  PW ANOMALIES
ARE BETWEEN +4 TO +5 STANDARD DEVIATIONS ABOVE NORMAL WHICH IS QUITE
ANOMALOUS FOR THIS TIME OF YEAR. IN FACT CURRENT PWATS ARE PROGGED
ABOVE 1.6 INCHES WITH MODEL QPF OVER 2 INCHES...AT THE VERY LEAST
COULD SEE URBAN AND POOR DRAINAGE FLOODING. LATEST EC EVEN SHOWS
OVER 2.5 INCHES OF QPF...AND WITH THE TROPICAL CONNECTION AND STRONG
SOUTHERLY FLOW COULD SEE HIGHER AMOUNTS DUE TO TOPOGRAPHY
ENHANCEMENTS. RAINFALL RECORDS MAY FALL IF EVERYTHING FALLS INTO
PLACE.

AHEAD OF THE FRONT...SOUTHERN NEW ENGLAND WILL WARM SECTOR WED INTO
THUR MORNING ALLOWING FOR TEMPERATURES TO BE WELL ABOVE AVERAGE. IN
FACT WE MAY BE CLOSE AT BREAKING RECORD HIGH TEMPS IF TEMPS WARM TO
60F OR ABOVE ON CHRISTMAS EVE. SINCE WE WILL BE IN THE WARM
SECTOR...AND SHOWALTERS CLOSE TO ZERO...ISOLATED THUNDER IS STILL
POSSIBLE.

STRONG LOW LEVEL WINDS WILL ALSO BE A CONCERN ESPECIALLY WEDNESDAY
NIGHT. THE ECMWF SHOWS EAST-SOUTHEAST WINDS 30-40 KNOTS ON WEDNESDAY
INCREASING TO 60-75 KNOTS BY WEDNESDAY NIGHT. STRONG DOWNPOURS MAY
OVERCOME THE LOW LEVEL INVERSION AND BRING STRONG GUSTS OF AT LEAST
30-40 KNOTS ESPECIALLY ALONG THE SOUTH COAST. A WIND ADVISORY MAY BE
NEEDED IN SOME AREAS.

CHRISTMAS DAY...MODERATE CONFIDENCE.

AS THE COLD FRONT PASSES THROUGH EARLY CHRISTMAS DAY...THE WEST
WINDS WILL HELP DRY THE AIRMASS ALLOWING FOR PARTLY SUNNY SKIES.
STRONG CAA ON THURSDAY WILL ALLOW DESCENT MIXING. WINDS IN THE SFC-
850 MB LAYER WILL BE 30-40 KNOTS AND POSSIBLY A LITTLE
HIGHER...WHICH WOULD REQUIRE A WIND ADVISORY FOR MUCH OF THE AREA.

FRIDAY-SUNDAY...LOWER CONFIDENCE

WEAK HIGH PRESSURE BUILDS OVER THE AREA FRIDAY INTO SATURDAY. THE
NEXT SHORTWAVE APPROACHES LATE SATURDAY INTO SUNDAY AND SHOULD BRING
INCREASING CLOUDS FROM WEST TO EAST ALONG WITH A CHANCE OF RAIN OR
SNOW SHOWERS MAINLY IN THE AFTERNOON AND AT NIGHT.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /TODAY AND TONIGHT/...

TODAY AND TONIGHT...MODERATE CONFIDENCE.  MAINLY MVFR CONDITIONS
SOUTH OF THE MA TURNPIKE WITH BORDERLINE VFR TO MARGINAL MVFR CIGS
NORTH OF THE PIKE THROUGH TONIGHT.  AN AREA OF SNOW SHOWERS WILL
EXPAND MAINLY ACROSS AREAS SOUTH OF THE PIKE THIS MORNING...BUT A
FEW SNOW SHOWERS WILL STILL AFFECT NORTHERN MA.  VSBYS/CIGS MAY
BRIEFLY DROP TO IFR LEVELS IN NORTHERN CT/RI/SE MA.  PTYPE WILL BE
RAIN SHOWERS ACROSS MOST OF PLYMOUTH COUNTY AND ONTO THE
CAPE/ISLANDS WITH SNOW SHOWERS NORTH AND WEST.  BULK OF PRECIP THIS
MORNING...BUT A FEW LINGERING RAIN/SNOW SHOWERS STILL POSSIBLE THIS
AFTERNOON AND EVENING.

KBOS TERMINAL...MODERATE CONFIDENCE.  A FEW SNOW SHOWERS POSSIBLE
THIS MORNING BUT BULK OF ACTIVITY SHOULD BE SOUTH OF THE TERMINAL.

KBDL TERMINAL...MODERATE CONFIDENCE.  PERIOD OF SNOW SHOWERS THIS
MORNING MAY DROP AN INCH OR TWO OF SNOW.  MVFR CONDITIONS DOMINATE
TODAY....BUT A BRIEF PERIOD OF IFR CONDITIONS ARE POSSIBLE THIS
MORNING IN SNOW SHOWERS.

OUTLOOK...MONDAY THROUGH THURSDAY...MODERATE CONFIDENCE.

MONDAY...MVFR CIGS CONTINUE IN RI/EASTERN MASS IN MARINE EAST FLOW.
VFR IN THE WEST.

TUESDAY...VFR WITH SCATTERED MVFR IN ANY RAIN/SNOW SHOWERS.

WEDNESDAY...CONDITIONS LOWERING TO IFR IN RAIN/HEAVY RAIN. ISOLATED
THUNDERSTORMS POSSIBLE ESPECIALLY WEDNESDAY NIGHT. EAST-SOUTHEAST
SURFACE WINDS MAY GUST TO 35-45 KNOTS. WINDS AT 2000 FEET AGL WILL
REACH 50-60 KNOTS WEDNESDAY AFTERNOON AND EARLY NIGHT CREATING LOW
LEVEL WIND SHEAR CONCERNS.

CHRISTMAS DAY...WEST WIND GUSTING 30-40 KNOTS. CONDITIONS IMPROVING
TO VFR AS THE WIND BRINGS IN COOLER DRIER AIR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /TODAY AND TONIGHT/...HIGH CONFIDENCE.

HIGH PRESSURE ACROSS QUEBEC WILL RESULT IN NORTHEAST WINDS ACROSS
THE WATERS THAT WILL GUST TO BETWEEN 15 AND 20 KNOTS.  THIS WILL
RESULT IN 2 TO 4 FOOT SEAS.  HOWEVER...NO HEADLINES PLANNED AS
CONDITIONS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS.

OUTLOOK...MONDAY THROUGH THURSDAY...MODERATE CONFIDENCE

MONDAY...EAST TO NORTHEAST WINDS GUSTING AROUND 15 KNOTS OR LESS.
SEAS WILL HOLD AROUND 3-4 FEET...MAY INCREASE TO 5FT IN NORTHEAST
FLOW AS GUIDANCE MAY BE UNDERDONE.

TUESDAY... INCREASING EAST WINDS WITH FREQUENT GUSTS 25 TO 30 KNOTS.
SEAS WILL BUILD TO 5-6 FEET ON THE EXPOSED WATERS.  A SMALL CRAFT
ADVISORY MAY BE NEEDED.

WEDNESDAY...RAIN WILL BE HEAVY AT TIMES PRODUCING POOR VISIBILITY.
INCREASING SOUTHEAST WINDS 20-25 SUSTAINED AND 40 KNOT GUSTS.  WINDS
SHOULD SHIFT TO SOUTH WEDNESDAY NIGHT AND SOUTHWEST TOWARD THURSDAY
MORNING. RAIN WILL TAPER OFF WITH THE WIND SHIFT TO SOUTHWEST. SEAS
WILL CONTINUE TO BUILD WITH 7-11 FEET HEIGHTS ON THE EXPOSED WATERS.
A GALE WARNING WILL BE NEEDED...WITH A LOW PROB OF A FEW STORM FORCE
GUSTS ACROSS THE EASTERN OUTER WATERS.

CHRISTMAS DAY... WEST SOUTHWEST WINDS WILL CONTINUE TO GUST 35-40
KNOTS...SO A CONTINUED GALE WARNING MAY BE NEEDED. SEAS OF 7-15 FEET
ARE POSSIBLE ON THE EXPOSED WATERS...AND 5 FEET IS POSSIBLE ON SOME
OF THE NEARSHORE WATERS.

&&

.TIDES/COASTAL FLOODING...
HIGH ASTRONOMICAL TIDES WILL OCCUR TUESDAY THROUGH THURSDAY. BREAKING
IT DOWN...ON TUESDAY HIGH TIDE AT BOSTON WILL BE 11.6 FT. THERE WILL
BE ONSHORE FLOW DURING THIS HIGH TIDE ALLOWING FOR MINOR SPLASHOVER.
IF WIND GUSTS INCREASE THEN COULD POSSIBLE SEE MINOR COASTAL
FLOODING.

ON WEDNESDAY...WINDS WILL SWITCH TO A MORE SOUTHEASTERLY FLOW DURING
THE DAY AND INCREASE QUICKLY FROM APPROACHING SYSTEM AND DECENT
PRESSURE FALLS. WEDNESDAY AFTERNOON HIGH TIDE IN BOSTON IS 11.7 FT
AND WITH ANY STRENGTH ON THE EASTERLY WIND FLOW WILL PUSH THE TIDE
OVER. RIGHT NOW BELIEVE MINOR COASTAL FLOODING IS POSSIBLE ALONG THE
EAST COASTLINE.

WEDNESDAY EVENING...THE WIND GOES IN A MORE SOUTHERLY DIRECTION AND
THE TIDE WILL BE INCREASE ACROSS THE SOUTH COAST. HIGH TIDE IN
PROVIDENCE WILL BE 5.2 FT. 925 MB LLJ STRENGTHENS TO 50-60 KTS WHICH
COULD PUSH A DECENT SURGE UP ALONG THE SOUTH COAST DURING THE TIME
OF HIGH TIDE. THINKING THAT MINOR COASTAL FLOODING COULD OCCUR BUT
CANNOT RULE OUT MODERATE ALONG THE SOUTH COAST...ESP IF LLJ
STRENGTHENS EVEN MORE.

&&

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

&&

$$
SYNOPSIS...FRANK/DUNTEN
NEAR TERM...FRANK/DUNTEN
SHORT TERM...FRANK
LONG TERM...DUNTEN
AVIATION...FRANK/DUNTEN
MARINE...FRANK/DUNTEN
TIDES/COASTAL FLOODING...STAFF


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