Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 291642
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1142 AM EST THU JAN 29 2015

.SYNOPSIS...
HIGH PRESSURE OVER NEW ENGLAND WILL MOVE EAST THIS AFTERNOON AND
EVENING. A CLIPPER LOW PRESSURE WILL MOVE INTO THE GREAT LAKES
TONIGHT WITH A SECONDARY LOW DEVELOPING ALONG THE SOUTHERN NEW
ENGLAND COAST AND INTENSIFYING OVER THE GULF OF MAINE FRI BY FRI
EVENING. THIS WILL BRING A PERIOD OF SNOW LATER TONIGHT AND
FRI...WHICH WILL CONTINUE INTO FRI NIGHT FOR PARTS OF THE REGION.
BLUSTERY AND VERY COLD CONDITIONS ARE EXPECTED THIS WEEKEND.
ANOTHER STORM MAY BRING SNOW TO THE REGION SUNDAY NIGHT AND
MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1135 AM UPDATE... WITH HIGH PRES RIDGE ACROSS THE REGION...
LIGHT/VRBL OR CALM WINDS IN PLACE EXCEPT ACROSS THE OUTER CAPE AND
NANTUCKET WHERE NW WINDS AT AROUND 10 MPH. HIGH CLOUDS ALREADY
APPROACHING THE REGION FROM THE WEST AND THIS INCREASE IN CLOUD
COVER WILL BE THE TREND FOR THE AFTERNOON.

HAVE LOWERED TEMPERATURES INITIALLY PER CURRENT OBSERVATIONS BUT
THE AFTERNOON HIGHS STILL LOOK GOOD...SO LITTLE CHANGE TO THEM.
MAXES WILL REACH THE UPPER 20S TO THE LOWER AND MID 30S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
UPDATE AS OF 1135 AM...

HAVE EXPANDED THE WINTER WEATHER ADVISORY SOUTHWARD TO INCLUDE
NORFOLK...SUFFOLK...AND MUCH OF PLYMOUTH COUNTIES FOR FRI AND FRI
NIGHT. NEW MODEL INFORMATION SHOWS THAT THE STORM WILL BE
REDEVELOPING SOUTH OF CAPE COD AND INTENSIFYING OVER THE GULF OF
MAINE. FORECAST PRECIPITATION AMOUNTS...IN THE FORM OF
SNOW...SHOULD REACH 3 TO 4 OR AN OUTSIDE CHANCE OF 5 INCHES IN
THESE AREAS BY THE TIME THE SNOW ENDS EARLY SAT MORNING.
TRICKY BECAUSE THE AMOUNTS ARE SPREAD OUT OVER A RELATIVELY LONG
DURATION... BUT GIVEN THE BIG SNOWFALL WE JUST HAD...THE IMPACTS
OF ADDITIONAL SNOW COULD BE IMPORTANT...THUS WENT WITH THE
ADVISORY. WE ARE ALSO WATCHING THE POTENTIAL FOR AS MUCH AS 8
INCHES IN FAR NORTHEAST MA...MAINLY ESSEX COUNTY... WHICH COULD
REQUIRE A WARNING. WILL ASSESS THIS DURING THE AFTERNOON.

PREVIOUS DISCUSSION...

TONIGHT AND FRIDAY...
DIGGING SHORTWAVE FROM THE UPPER LAKES WILL MOVE SE AND PHASE
WITH ANOTHER IMPULSE MOVING OUT OF THE OHIO VALLEY TO FORM A NEG
TILT TROF ALONG THE NEW ENG COAST ON FRI. PRIMARY LOW LIFTS NE
INTO NORTHERN NY TONIGHT WHILE SECONDARY LOW DEVELOPS NEAR THE SNE
COAST FRI ASSOCD WITH THE MID LEVEL SHORTWAVE AND HEIGHT FALLS
MOVING TO THE COAST. ECMWF IS FURTHEST SOUTH WITH THE SECONDARY
LOW AND AS A RESULT HAS MORE QPF THAN THE OTHER MODELS. THE TRACK
OF THE 700 MB LOW WILL BE CRITICAL TO WHERE HEAVIER SNOWFALL SETS
UP.

DEEPENING MOISTURE AND INCREASING MID LEVEL LIFT WILL RESULT IN A
PERIOD OF SNOW DEVELOPING ACROSS SNE LATER TONIGHT INTO FRI.
HOWEVER...SOUTHERLY FLOW AHEAD OF THE PRIMARY LOW WILL LIKELY WARM
THE BOUNDARY LAYER ENOUGH FOR A MIX OR CHANGEOVER TO RAIN LATE
TONIGHT INTO FRIDAY ALONG THE IMMEDIATE S COAST AND ESPECIALLY
CAPE/ISLANDS.

THE 700 MB LOW TRACKS ACROSS SNE WHICH SUGGESTS HEAVIER SNOW WILL
SET UP ACROSS NORTHERN AREAS...MAINLY N OF THE MASS PIKE WITH
LIGHTER SNOW TO THE SOUTH. THROUGH FRIDAY...GENERALLY LOOKING AT
2-3 INCHES NORTH OF THE PIKE WITH 1-2 INCHES TO THE
SOUTH...EXCEPT LESS THAN AN INCH NEAR THE SOUTH COAST.

EXPECT GRADUAL IMPROVING CONDITIONS IN THE CT VALLEY DURING THE
AFTERNOON...WITH GUSTY NW WINDS DEVELOPING BY LATE IN THE DAY.

FRIDAY NIGHT...
MID LEVEL TROF CLOSES OFF JUST SOUTH OF THE SNE COAST AS COASTAL
LOW INTENSIFIES IN THE GULF OF MAINE. AS MENTIONED ABOVE...ECMWF
IS FURTHEST S WITH THE SFC LOW AND THUS IS MOST BULLISH ON BRINING
A PERIOD OF HEAVIER SNOW...MAINLY TO N/NE MA. WE USED A MULTI
MODEL BLEND OF QPF AS A BASIS FOR SNOW ACCUM. MODELS ARE IN
AGREEMENT THE MID LEVEL LOW MOVES INTO THE GULF OF MAINE WITH A
BAND OF SNOW IN THE COMMA HEAD ROTATING INTO THE EASTERN HALF OF
SNE. EXPECT AN ADDITIONAL INCH OR 2 FOR CENTRAL AND E MA...WITH
LOCALLY HIGHER AMOUNTS POSSIBLE ACROSS NE MA. WILL HAVE TO WATCH
THIS AREA FOR THE POTENTIAL OF HIGHER ACCUM PER ECMWF.

WE DECIDED ON A WINTER WEATHER ADVISORY FOR AREAS NORTH OF THE
MASS PIKE IN N/NE MA WHERE HEAVIEST SNOW EXPECTED...FOR THE PERIOD
FROM MIDNIGHT TONIGHT TO FRI NIGHT. CURRENT THINKING IS TOTAL
ACCUM THROUGH FRI NIGHT WILL BE 4-6 INCHES N/NE MA WITH LOCALLY
HIGHER AMOUNTS POSSIBLE. LOW PROB THAT WARNING WILL BE NEEDED FOR
NE MA PER ECMWF...BUT CONFIDENCE NOT HIGH ENOUGH SO WE OPTED FOR
AN ADVISORY.

TURNING MUCH COLDER FRI NIGHT AS GUSTY NW WINDS DEVELOP WITH
DEEPENING LOW PRES IN THE GULF OF MAINE. DANGEROUSLY COLD WIND
CHILLS OF 10 TO 20 BELOW ZERO IN HIGHER TERRAIN OF CENTRAL AND W
MA...WITH 5 TO 10 BELOW IN THE COASTAL PLAIN. WIND CHILL
ADVISORIES WILL LIKELY BE NEEDED FOR HIGHER TERRAIN IN CENTRAL
AND W MA.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
HEADLINES...

* ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BLUSTERY NW
  WINDS
* COASTAL STORM POSSIBLE SUNDAY NIGHT AND MONDAY...BUT LOW
  CONFIDENCE CONTINUES

OVERVIEW...
H5 CUTOFF LOW PRES WILL SPIN OFF THE MAINE COAST SATURDAY...WITH
DEEPENING SURFACE LOW SLOWLY SHIFTING INTO NOVA SCOTIA. UPPER
LEVEL WIND FLOW WILL FLATTEN OUT...ALLOWING WEATHER SYSTEMS TO
MOVE ACROSS THE NORTHERN TIER STATES FOR A GOOD PORTION OF THE
LONG TERM. NOTING ANOTHER SHORT WAVE IN THIS FAST FLOW DIGGING
INTO THE MID ATLC STATES...WHICH WILL TRIGGER ANOTHER LOW
DEVELOPING S OF THE REGION. MANY QUESTIONS REMAIN ON THE TRACK
AND STRENGTH OF THIS LOW AS IT PASSES NEAR OR S OF THE
REGION...WHICH WILL DETERMINE ITS EFFECTS. MODEL SOLUTION SPREAD
IS HIGH...SO LOW CONFIDENCE AT THIS POINT. ONE CERTAINTY IS THE
FRIGID TEMPERATURES WINDS AND BLUSTERY WINDS AT TIMES INTO
PORTIONS OF NEXT WEEK.

DETAILS...

SATURDAY-SUNDAY...STRONG LOW PRESSURE WILL SHIFT NE INTO NOVA
SCOTIA SATURDAY. THIS WILL USHER IN THE COLDEST AIR OF THE SEASON.
NW WINDS WILL REMAIN GUSTY INTO SATURDAY NIGHT...THEN WILL
DIMINISH AS HIGH PRES MOVES ACROSS. ANOTHER DRY FRONT WILL SHIFT
SE SUNDAY...JUST REINFORCING THE ARCTIC AIR ACROSS THE REGION.
HIGH TEMPS BOTH DAYS WILL RUN 15 TO 20 DEGREES BELOW SEASONAL
NORMALS. THE HIGH ON SAT AT KBDL MAY BE CLOSE TO THE RECORD LOW
MAX TEMP /RECORD IS 15 DEGREES SET IN 1951/.

SUNDAY NIGHT-MONDAY...ANOTHER H5 SHORT WAVE WILL DIG TO THE MID
ATLC COAST IN THE FAST FLOW ALOFT. BIG QUESTIONS REMAIN...WHERE
WILL THE SURFACE SYSTEM DEVELOP...HOW STRONG WILL IT BE AND HOW
FAR N WILL IT TRACK. LOW CONFIDENCE DUE TO WIDE MODEL SOLUTION
SPREAD. ONE THING NOT IN QUESTION...PRECIP WILL MOST LIKELY BE IN
THE FORM OF SNOW...BUT HOW MUCH. WILL HAVE TO WATCH THE NEXT FEW
MODEL RUNS TO DETERMINE THAT.

AT THIS POINT...HAVE MENTIONED CHANCE POPS FOR MOST AREAS WITH
THE BEST CHANCE ALONG THE S COAST...CAPE AND ISLANDS. UPPER
PATTERN REMAINS PROGRESSIVE...THOUGH...SO THE LOW SHOULD DEPART
LATE MON OR MON NIGHT.

TUESDAY-WEDNESDAY...
MORE ARCTIC COLD ARRIVES ON TUESDAY AS ANOTHER LARGE AREA OF HIGH
PRES BUILDS E. LOOKS LIKE THE LOW WILL SHIFT E ON WED...WHICH
MEANS TEMPS MAY START TO REBOUND BUT WILL REMAIN BELOW SEASONAL
NORMALS. YET ANOTHER LOW MAY APPROACH WED NIGHT BRINGING ANOTHER
CHANCE OF PRECIP...THOUGH TIMING AND TRACK FOR THIS LOW IS ALSO
UNCERTAIN.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM...THROUGH TONIGHT...HIGH CONFIDENCE.

THIS AFTERNOON...VFR. MID AND HIGH LEVEL CLOUDS INCREASE FROM W-E.THIS
LIGHT WINDS.

TONIGHT AND FRIDAY...CIGS LOWER OVERNIGHT TO MVFR-IFR IN
OCCASIONAL SNOW. THE SNOW MAY MIX OR CHANGE TO RAIN ALONG THE
IMMEDIATE S COAST AND ESPECIALLY THE CAPE/ISLANDS LATE TONIGHT AND
FRI. SNOW DIMINISHES FRI AFTERNOON IN THE CT VALLEY BUT CONTINUES
ACROSS E NEW ENG. WINDS SHIFT TO NORTHWEST DURING THE AFTERNOON.
GUSTS TO 25-30 KT AND VFR CIGS DEVELOPING IN THE CT VALLEY BY
MID/LATE AFTERNOON.

KBOS TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING
OF SNOW AND LOWER CIGS/VSBYS.

KBDL TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING
OF SNOW AND LOWER CIGS/VSBYS.

OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...

FRIDAY NIGHT...LOW CONFIDENCE. VFR WEST. POSSIBLE IFR TO START
FOR EASTERN LOCALES...BUT WITH IMPROVEMENT EXPECTED OVERNIGHT.

SATURDAY-SUNDAY...HIGH CONFIDENCE. VFR. NW WINDS GUSTING TO 25-35
KNOTS SATURDAY...HIGHEST ALONG THE COAST. LIGHTER WINDS SUNDAY.

SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. LOW PRES DEVELOPS S OF THE
REGION...BUT TRACK REMAINS UNCERTAIN. TOO EARLY TO HAVE ANY
CONFIDENCE ON VFR OR IFR THIS PERIOD.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH FRIDAY/...HIGH CONFIDENCE.

1135 AM UPDATE...HAVE UPGRADED THE GALE WATCH TO GALE WARNINGS FOR
LATE FRI INTO SAT AND HAVE INCLUDED BOSTON HARBOR.

THIS AFTERNOON...HIGH PRES BUILDS OVER THE WATERS WITH
DIMINISHING WINDS BECOMING LIGHT AND SEAS BELOW SCA.

TONIGHT...INCREASING SOUTHERLY WINDS EXPECTED AHEAD OF LOW PRES
MOVING THROUGH THE GREAT LAKES...BUT WIND GUSTS SHOULD REMAIN
BELOW SCA.

FRIDAY...SOUTHERLY WINDS WILL SHIFT TO W THEN NW DURING FRI
AFTERNOON...WITH GUSTS TO 25-30 KT DEVELOPING ACROSS RI COASTAL
WATERS BY LATE AFTERNOON.

OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE FRI-
SAT...LOW CONFIDENCE SUN-MON.

FRIDAY NIGHT...LOW PRES WILL CROSS THE WATERS. REDUCED VSBYS IN
SNOW MAINLY IN THE EASTERN WATERS EARLY. WINDS WILL SHIFT TO NW
AND INCREASE. GUSTS UP TO GALE FORCE EXPECTED. GALE WATCHES HAVE
BEEN UPGRADED TO GALE WARNINGS FOR ALL WATERS AND NOW INCLUDES
BOSTON HARBOR. FREEZING SPRAY LIKELY.

SATURDAY...NW GALES EXPECTED. FREEZING SPRAY DEVELOPING. HIGH
SEAS FORECAST...10-12 FT OFFSHORE WATERS. WINDS WILL BEGIN TO
DIMINISH SAT NIGHT WITH A CORRESPONDING LOWERING OF SEAS.

SUNDAY...EXPECT WINDS TO DIMINISH BUT REMAIN AT SMALL CRAFT
LEVELS...THOUGH SOME GALE GUSTS MAY LINGER ON THE EASTERN OUTER
WATERS EARLY. SEAS WILL SLOWLY SUBSIDE...BUT WILL REMAIN AOA 5 FT
ON THE OUTER WATERS.

SUNDAY NIGHT-MONDAY...DEPENDING UPON STRENGTH AND TRACK OF
DEVELOPING LOW PRES S OF THE REGION...COULD SEE WIND GUSTS UP TO
SMALL CRAFT CRITERIA. SEAS WILL REMAIN AOA 5 FT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST
     SATURDAY FOR MAZ004>007-013>016-018-019-026.
RI...NONE.
MARINE...GALE WARNING FROM MIDNIGHT FRIDAY NIGHT TO 6 PM EST SATURDAY
     FOR ANZ230>234-251.
     GALE WARNING FROM 2 AM TO 1 PM EST SATURDAY FOR ANZ236.
     GALE WARNING FROM 9 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ235-
     237.
     GALE WARNING FROM 11 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ250-
     254-255.
     GALE WARNING FROM 7 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ256.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...GAF
SHORT TERM...KJC/GAF
LONG TERM...EVT
AVIATION...KJC/EVT/GAF
MARINE...KJC/EVT/GAF


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