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382
FXUS61 KBOX 312115
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
415 PM EST SAT JAN 31 2015

.SYNOPSIS...
BLUSTERY AND VERY COLD CONDITIONS TONIGHT AND INTO TOMORROW. A
MAJOR WINTER STORM WILL AFFECT THE REGION VERY LATE SUNDAY NIGHT
INTO MONDAY EVENING WITH HEAVY SNOW FOR MANY LOCATIONS. BITTERLY
COLD WIND CHILLS FOLLOW LATER MONDAY NIGHT INTO TUESDAY MORNING.
MODERATING TEMPS WEDNESDAY THEN VERY COLD CONDITIONS WILL RETURN
TOWARD THE END OF THE WEEK. A COASTAL STORM WILL PASS WELL SOUTH
OF NEW ENGLAND LATE IN THE WEEK BUT WILL HAVE TO BE MONITORED.

&&

.NEAR TERM /THROUGH SUNDAY/...

430 PM UPDATE...

FORECAST REMAINS ON TRACK FOR THE REMAINDER OF THE AFTERNOON. LOW
PRESSURE WILL CONTINUE TO DEEPEN AS IT MOVE TOWARDS THE
MARITIMES...ALLOWING FOR THE TIGHT PRESSURE GRADIENT TO CONTINUE.
LATEST OBS AND BUFKIT SOUNDINGS SHOW THAT WIND GUSTS WILL BEGIN TO
SLOWLY SUBSIDE THIS AFTERNOON...AND WITH MANY SITES BELOW ADV
CONDITIONS PLAN ON LETTING THE ADV GO EXCEPT FOR THE CAPE AND
ISLANDS.

TONIGHT...

DEEPENING LOW WILL MOVE WELL TOWARDS THE MARITIMES TONIGHT ALLOWING
FOR WEAK MID-LEVEL RIDGING INTO THE REGION. STILL A DESCENT PRESSURE
GRADIENT OVERNIGHT...ESP ACROSS THE EAST COAST SO ANTICIPATE WIND
GUSTS TO REMAIN UP. HOWEVER ACROSS THE CT VALLEY REGION WINDS LOOK
TO DECOUPLE OVERNIGHT SO EXPECT TEMPS TO DROP WELL INTO THE SINGLE
DIGITS AND MAY BE CLOSE TO ZERO ESP AT ORE. HOWEVER WITH LIGHT
WINDS...WIND CHILL ADV ARE NOT NEEDED. BIGGEST ISSUE WITH THESE
COOLING TEMPS IS THE SKY COVER. AHEAD OF APPROACHING ARCTIC
FRONT...MID TO HIGH LEVEL CLOUDS WILL BE MOVING IN FROM THE NORTH.
THIS MAY LIMIT TEMPS...SO PLAYED THEM A TAD CONSERVATIVE.

TOMORROW...

850MB ARCTIC FRONT WILL PUSH THROUGH THE REGION TOMORROW. HOWEVER
TEMPS WILL BE WARMER THAN TODAY AS 925 MB TEMPS JUMP FROM -13C TO
-8C. EXPECT TEMPS TO WARM INTO THE MID 20S TO PERHAPS THE LOW 30S
ALONG THE COASTAL PLAIN. MID TO HIGH LEVEL MOISTURE WILL BE
INCREASING THROUGHOUT THE DAY WHICH WILL INCREASE CLOUD COVER.
OTHERWISE WINDS WILL BE CALMER AND DRY WEATHER WILL PREVAIL
THROUGH MOST OF THE DAY.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...

HIGHLIGHTS...

* MAJOR WINTER STORM VERY LATE SUN NIGHT INTO MON EVENING
* HEAVY SNOWFALL EXPECTED FOR MUCH OF THE REGION
* BIGGEST UNCERTAINTY SNOWFALL AMTS NEAR SOUTH COAST - PTYPE ISSUES
* BITTERLY COLD AIR LATE MON NIGHT - WIND CHILLS 15 TO 25 BELOW ZERO

DETAILS...

A MAJOR WINTER STORM WILL AFFECT SOUTHERN NEW ENGLAND VERY LATE SUN
NIGHT INTO MONDAY EVENING.  ARCTIC HIGH PRESSURE ACROSS EASTERN
CANADA WILL COMBINED WITH LOW PRESSURE APPROACHING FROM THE WEST.
THE RESULT WILL BE STRONG SOUTHWEST FLOW ALOFT OVER RUNNING THE
ARCTIC DOME AT THE SURFACE.  THEN AS THE LOW DEEPENS...MUCH OF THE
REGION WILL SEE SNOW ON THE BACKSIDE OF THE SYSTEM.  BIGGEST
UNCERTAINTY IS HOW MUCH OF THE REGION TRANSITIONS TO A PERIOD OF
MIXED PTYPE DURING THE MIDDLE OF THE EVENT...CUTTING DOWN ON
POSSIBLE SNOW ACCUMS.

1) TIMING AND UNCERTAINTY

SNOW WILL LIKELY ARRIVE FROM SOUTHWEST TO NORTHEAST VERY LATE SUN
EVENING IN OUR WESTERN ZONES AND AFTER MIDNIGHT ACROSS THE REST OF
THE REGION.  EXTREMELY TIGHT MID LEVEL THERMAL PACKING WILL ALLOW
SNOW TO QUICKLY BECOME HEAVY.  SNOW WILL FALL HEAVY MONDAY MORNING
AT 1 TO 2 INCHES PER HOUR AND SIGNIFICANTLY IMPACT THE AM RUSH HOUR.

THINGS THEN BECOME MORE UNCERTAIN LATER IN THE MORNING AND
AFTERNOON.  THE GFS IS MOST AGGRESSIVE IN SURGING WARM MID LEVEL AIR
TO THE MA PIKE...RESULTING IN A CHANGE TO A PERIOD OF SLEET/FREEZING
RAIN AND EVEN PLAIN RAIN ALONG THE FAR SOUTHEAST NEW ENGLAND COAST.
THE NAM/ECMWF/GGEM APPEAR THE COLDEST KEEPING MOST AREAS HEAVY
SNOW...EXCEPT FOR THE CAPE AND ISLANDS.  THE UKMET APPEARS TO BE IN
BETWEEN THE OTHER SOLUTIONS.  GIVEN THE UNCERTAINTY WILL BLEND THE
MODELS.  RIGHT NOW WERE THINKING TRANSITION AREA MAY GET BRIEFLY
NEAR OR PERHAPS JUST NORTH OF THE THE TAUNTON TO PROVIDENCE
CORRIDOR...BEFORE COLLAPSING SOUTHEAST.

REGARDLESS HOW FAR NORTH THE TRANSITION LINE GETS...MOST AREAS WILL
CHANGE BACK TO SNOW MON EVENING.  GIVEN CLOSED MID LEVEL CENTERS AND
VERY COLD NORTHEAST FLOW...COULD BE SOME OCEAN ENHANCEMENT ACROSS
EASTERN NEW ENGLAND FOR A TIME BEFORE SNOW ENDS.  BULK OF SNOW
SHOULD WIND DOWN AFTER MIDNIGHT ALTHOUGH THE GGEM IS A BIT SLOWER.

2) SNOWFALL ACCUMULATIONS AND HEADLINES

WE ARE PRETTY CONFIDENT IN A HEAVY SNOWFALL FOR MUCH OF THE
REGION...EXCEPT FOR AREAS NEAR THE SOUTH COAST WHERE PTYPE ISSUES
MAYBE MORE PROBLEMATIC.  8 TO 14 INCHES EXPECTED FOR MUCH OF THE
REGION.  HAVE UPGRADED ALL AREAS FROM PROVIDENCE TO TAUNTON
NORTHWARD TO WINTER STORM WARNING/S WITH HIGH CONFIDENCE ON CRITERIA
BEING MET.  AREAS SOUTHEAST OF THAT LINE...THERE IS SOME MORE
UNCERTAINTY ESP CAPE/ISLANDS.  IF A LOT OF MIXING OCCURS THESE AREAS
MAY STRUGGLE TO REACH WARNING CRITERIA...BUT ITS STILL CERTAINLY
POSSIBLE DEPENDING ON MODEL TRENDS.  THEREFORE...WE HAVE HELD THE
WINTER STORM WATCH FOR THE SOUTH COAST AND THE ISLANDS.

3) STRONG WINDS AND BLOWING AND DRIFTING SNOW

NORTHEAST WIND GUSTS OF 35 TO 50 MPH EXPECTED ALONG THE COAST MONDAY
INTO MONDAY NIGHT AS STORM INTENSIFIES AND PRESSURE GRADIENT
INCREASES.  THIS WILL LIKELY RESULT IN POOR VISIBILITY ALONG WITH
BLOWING AND DRIFTING SNOW.  ITS POSSIBLE THAT A FEW LOCATIONS ALONG
THE COAST COULD SEE NEAR BLIZZARD CONDITIONS FOR A VERY SHORT
TIME...BUT STORM DOESN/T SEEM TO WARRANT THOSE TYPE OF HEADLINES.

4) BITTERLY COLD AIR MONDAY NIGHT INTO EARLY TUESDAY MORNING.

TEMPS WILL LIKELY PLUNGE BELOW ZERO TO 5 ABOVE ZERO IN MANY
LOCATIONS BY EARLY TUE MORNING.  THIS WILL RESULT IN WIND CHILLS
VALUES BETWEEN 15 AND 25 BELOW ZERO. WIND CHILL ADVISORIES WILL
LIKELY BE NEEDED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...

HIGHLIGHTS...

* COLD PATTERN CONTINUES THRU NEXT WEEKEND
* CLIPPER LOW APPEARING MORE LIKELY THAN COASTAL LOW WED/THU

GOOD AGREEMENT AMONG 12Z DETERMINISTIC...12Z GEFS AND 00Z ECENS
ENSEMBLES THAT THE POLAR JET WILL DOMINATE THE NORTHERN TIER STATES
INCLUDING NEW ENGLAND THIS PERIOD. THIS COMBINED WITH STREAMS
EXPECTED TO REMAIN UNPHASED WILL SUPPORT MAINLY DRY WEATHER THIS
PERIOD. ONE CAVEAT WILL BE CLIPPER LOW ENTERING THE NORTHEAST
WED/WED NIGHT. EARLIER MODEL RUNS SUGGESTED SECONDARY DEVELOPMENT
ALONG THE TRAILING COLD FRONT SOUTHWEST OF NEW ENGLAND...WITH
POSSIBLE COASTAL-OCEAN STORM IMPACTING OUR REGION AROUND THU.
HOWEVER LATEST GUID INCLUDING ENSEMBLES SUGGEST MID LEVEL TROUGH
WILL LACK SUFFICIENT AMPLITUDE TO BACK THE FLOW FOR A SECONDARY LOW
TO IMPACT THE REGION. THEREFORE LEANING TOWARD A MORE OFFSHORE TRACK
AND JUST A PERIOD OF LIGHT SNOW POSSIBLE WED/WED NIGHT. HOWEVER AT
THIS TIME RANGE CAN/T BE TOO DETERMINISTIC. THUS WON`T TOTALLY
DISCOUNT CLOSER SECONDARY DEVELOPMENT.

AS FOR TEMPS...BITTERLY COLD TUE BEHIND DEPARTING MON NGT COASTAL
LOW. THEN COLD EASES WED AHEAD OF APPROACHING CLIPPER LOW FOLLOWED
BUT YET ANOTHER ARCTIC BLAST LATE IN THE WEEK BEHIND THE CLIPPER. AS
FOR INTO NEXT WEEKEND ENSEMBLE TRENDS SUGGEST TEMPS COLDER THAN
NORMAL.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM.../THROUGH SUNDAY/...HIGH CONFIDENCE.

BEFORE 00Z...VFR WITH NW GUSTS TO 30-40 KT DIMINISHING AFTER
SUNSET.

AFTER 00Z...VFR WITH GRADUAL DIMINISHING WIND.

SUNDAY...MAINLY VFR...BUT LOW PROB FOR AREAS OF MVFR CIGS
DEVELOPING IN THE AFTERNOON.

SUNDAY NIGHT INTO MONDAY NIGHT...HIGH CONFIDENCE IN TRENDS BUT LOWER
CONFIDENCE IN TIMING.  VFR SUNDAY EVENING DETERIORATES TO IFR-LIFR
CIGS/VSBYS IN MODERATE TO HEAVY SNOW BY DAYBREAK MON AND CONTINUES
AT TIMES INTO MONDAY EVENING.  PTYPE MAY TRANSITION TO A PERIOD OF
SLEET/FREEZING RAIN/RAIN NEAR AND SOUTHEAST OF A PROVIDENCE TO
TAUNTON LINE.  NORTHEAST WIND GUSTS OF 30 TO 45 KNOTS EXPECTED ALONG
THE COAST.

KBOS TAF...HIGH CONFIDENCE.

KBDL TAF...HIGH CONFIDENCE.

OUTLOOK /TUESDAY THROUGH THURSDAY/...

TUESDAY INTO WEDNESDAY...MODERATE CONFIDENCE. MAINLY VFR ON
TUESDAY. COULD SEE SOME MVFR CIGS IN SCT SNOW SHOWERS ON
WEDNESDAY.

THURSDAY...MODERATE CONFIDENCE. MAINLY VFR. LOW RISK OF MVFR
ALONG SOUTHEAST MASS DEPENDING ON TRACK OF CLIPPER LOW.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH MONDAY NIGHT/...

HIGH CONFIDENCE THROUGH SUNDAY AFTERNOON.

TONIGHT...STRONG LOW PRESSURE PULLS FARTHER AWAY WITH WINDS
DIMINISHING BELOW GALE AFTER 06Z...BUT GUSTS 25-30 KT WILL
CONTINUE OVERNIGHT. MODERATE FREEZING SPRAY LIKELY
CONTINUING...ESPECIALLY E MA COASTAL WATERS.

SUNDAY...WINDS AND SEAS GRADUALLY DIMINISH THROUGH THE DAY. WINDS
AND SEAS WILL SLOWLY DIMINISH THROUGHOUT THE DAY BUT EXPECT SCA
WAVES TO REMAINS THROUGH THE PERIOD. LIGHT FREEZING SPRAY WILL
PERSIST.

SUNDAY NIGHT INTO MONDAY...MODERATE TO HIGH CONFIDENCE.

***STRONG GALE FORCE WIND GUSTS/HIGH SEAS AND THE RISK OF HEAVY
  FREEZING SPRAY MONDAY INTO MONDAY NIGHT***

WINDS/SEAS QUICKLY RAMP UP VERY LATE SUN NIGHT INTO MON AS LOW
PRESSURE INTENSIFIES NEAR THE SOUTH COAST. GALE WATCHES ISSUED FOR
EXPECTED 40+ KNOT NORTHEAST WIND GUSTS BY MON MORNING ALONG WITH
SEAS BUILDING TO 15+ FEET ACROSS OUR EASTERN WATERS BY LATE MON
AFTERNOON/EVENING. IN ADDITION...BITTERLY COLD AIR MOVING OVER THE
WATERS MONDAY NIGHT WILL RESULT IN THE POTENTIAL FOR HEAVY
FREEZING SPRAY. HAVE ALSO ISSUED A FREEZING SPRAY WATCH.

OUTLOOK /TUESDAY THROUGH THURSDAY/...MODERATE TO HIGH FORECAST
CONFIDENCE.

TUESDAY...NW GALES LIKELY ALONG WITH FREEZING SPRAY...POSSIBLY
MODERATE TO HEAVY. MAINLY DRY WITH GOOD VSBY EXCEPT FAR OFFSHORE
WHERE SNOW SHOWERS WILL BE COMMON.

WED...WINDS EASE AND BECOME SOUTHWEST AS CLIPPER LOW ENTERS THE
GREAT LAKES AND NY STATE. NOT AS COLD SO FREEZING SPRAY UNLIKELY.
VSBY MAY BRIEFLY LOWER IN A PERIOD OF LIGHT SNOW.

THU...ARCTIC FRONT WITH NW GALES BEHIND FRONTAL PASSAGE. MODERATE TO
HEAVY FREEZING SPRAY POSSIBLE.

&&

.TIDES/COASTAL FLOODING...

*** MINOR TO PERHAPS ISOLATED AREAS OF MODERATE COASTAL FLOODING
  POSSIBLE MON/MON NIGHT EASTERN MA COASTLINE ***

GOOD MODEL AGREEMENT ON SURFACE LOW TRACKING SOMEWHERE BETWEEN
NANTUCKET AND THE 40N/70W BENCHMARK WITH NAM THE FASTEST AND GFS
FARTHEST NORTHWEST. ECMWF SPLITS THE DIFFERENCE. MODEL CONSENSUS
BRINGS STRONGEST ONSHORE WINDS BETWEEN 18Z AND 00Z...CLOSE TO LOW
TIDE. IF THIS TIMING HOLDS UP WORST CASE SCENARIO WOULD BE MINOR
COASTAL FLOODING.

THE FIRST TIDE CYCLE OF CONCERN IS THE MONDAY MID MORNING. HOWEVER
ALL WAVE GUID SUGGEST SEAS LESS THAN 10 FT AT HIGH TIDE GIVEN
ARRIVAL OF STRONGEST WINDS LATER DURING THE AFTERNOON. THIS ALSO
YIELDS SURGE VALUES OF A FOOT OR LESS.

AS FOR THE MONDAY EVENING HIGH TIDE CYCLE...ASTRO TIDES ARE ABOUT A
1 FT LOWER. HOWEVER A STORM SURGE OF 1.5 TO 2.5 FT IS POSSIBLE.
ESTOFS AND ETSS ARE LOWER...SO I BLENDED THE TWO GUID SOURCES AND
ADDED 50 PERCENT TO COME UP WITH SURGE VALUES OF 1.5 TO 2.5 FT. IN
ADDITION...SEAS WILL LIKELY BUILD TO 15 TO 20 FT DURING THE EVENING
HIGH TIDE. ALL OF THESE FACTORS YIELD A MODERATE RISK OF MINOR
COASTAL FLOODING WITH A LOW RISK OF ISOLATED MODERATE FLOODING.

WHILE WINDS...SEAS AND STORM SURGE WILL BE LESS THAN THE PREVIOUS
COASTAL STORM THERE COULD STILL BE SOME MODEST IMPACT ESPECIALLY FOR
THOSE COMMUNITIES SUCH AS MARSHFIELD MA THAT WERE HIT HARD EARLIER
THIS WEEK WHERE COASTAL STRUCTURES SUCH AS SEAWALLS WERE DAMAGED.
GIVEN THE LOW TRACK IS CLOSE TO NANTUCKET THE GREATEST RISK OF
COASTAL FLOODING WILL BE FARTHER NORTHWARD FROM CAPE COD TO CAPE ANN
WITH PERHAPS THE HIGHEST RISK FROM HULL/COHASSET/SCITUATE/
MARSHFIELD/PLYMOUTH TO SANDWICH HARBOR.
/DUXBURY

GIVEN IT APPEARS MARGINAL FOR SIGNIFICANT COASTAL FLOODING AND STILL
48-60 HRS OUT IN TIME WILL HOLD OFF ON A COASTAL FLOOD WATCH.

&&

.CLIMATE...
WITH EXTREMELY COLD AIR MOVING IN BEHIND THE DEPARTING LOW MONDAY
NIGHT...TEMPERATURES MAY FALL BACK CLOSE TO OR SURPASSING RECORD
LEVELS EARLY TUESDAY MORNING. AND THAT IS NOT TAKING INTO ACCOUNT
THE STRONG WINDS.

HERE ARE THE RECORD LOWS FOR TUESDAY 2/3...

BOSTON         -5 SET IN 1881
PROVIDENCE     -6 SET IN 1961
WORCESTER      -7 SET IN 1931, 1955 AND 1971
WINDSOR LOCKS  -3 SET IN 1955
BLUE HILL OBS  -7 SET IN 1955

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER STORM WARNING FROM 9 PM SUNDAY TO 1 AM EST TUESDAY FOR
     CTZ002>004.
MA...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE MONDAY
     NIGHT FOR MAZ020>024.
     WINTER STORM WARNING FROM 9 PM SUNDAY TO 1 AM EST TUESDAY FOR
     MAZ002>019-026.
     WIND ADVISORY UNTIL 9 PM EST THIS EVENING FOR MAZ022>024.
RI...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE MONDAY
     NIGHT FOR RIZ005>008.
     WINTER STORM WARNING FROM 9 PM SUNDAY TO 1 AM EST TUESDAY FOR
     RIZ001>004.
MARINE...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR
     ANZ231>235-237.
     HEAVY FREEZING SPRAY WATCH FROM MONDAY EVENING THROUGH TUESDAY
     MORNING FOR ANZ231>235-237-250-251-254>256.
     FREEZING SPRAY ADVISORY UNTIL 8 AM EST SUNDAY FOR ANZ231-232-
     250-251-254-255.
     GALE WARNING UNTIL 1 AM EST SUNDAY FOR ANZ231-232-250-251-
     254>256.
     FREEZING SPRAY ADVISORY UNTIL 1 AM EST SUNDAY FOR ANZ233>235-
     237.
     GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ233>235-237.
     GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR
     ANZ230-236.
     GALE WARNING UNTIL 9 PM EST THIS EVENING FOR ANZ230.
     GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ236.
     GALE WATCH FROM LATE SUNDAY NIGHT THROUGH TUESDAY MORNING FOR
     ANZ250-251-254>256.
     FREEZING SPRAY ADVISORY UNTIL 8 PM EST THIS EVENING FOR ANZ256.

&&

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




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