Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 290929
AFDBOX

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

.SYNOPSIS...
HIGH PRESSURE OVER NEW ENGLAND WILL MOVE EAST THIS AFTERNOON AND
EVENING. A CLIPPER WILL MOVE INTO THE GT LAKES TONIGHT WITH A
SECONDARY LOW DEVELOPING ALONG THE SOUTHERN NEW ENGLAND COAST AND
MOVING INTO THE GULF OF MAINE FRI INTO 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/...
OCEAN EFFECT CLOUDS OVER THE CAPE AND ISLANDS ARE GRADUALLY
ERODING AND WILL CLEAR OUT BY DAYBREAK. OTHERWISE...A FRIGID
MORNING ACROSS SNE WITH TEMPS SEVERAL DEGREES BELOW ZERO IN SOME
OF COLDER SPOTS.

HIGH PRES BUILDS OVER NEW ENG TODAY...THEN MOVES TO THE EAST
DURING THE AFTERNOON. SUNSHINE WILL GIVE WAY TO INCREASING HIGH
CLOUDS THIS AFTERNOON...ESPECIALLY W NEW ENG AS HIGH LEVEL
MOISTURE MOVES IN AHEAD OF A MID LEVEL SHORTWAVE. WITH LIGHT
WINDS...EXPECT A NICE RECOVERY IN TEMPS AFTER VERY COLD START.
MAXES WILL REACH THE UPPER 20S TO LOW/MID 30S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
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/...
* SNOW EASTERN AREAS FRI NIGHT DIMINISHES AS LOW EXITS THE AREA
* ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BRISK NW WINDS
* COASTAL STORM POSSIBLE SUN NIGHT-MON, BUT LOW CONFIDENCE

OVERVIEW...LOW PRESSURE CENTER IS EXPECTED TO BE OFF THE MAINE COAST
FRI NIGHT. SNOW IS MOST LIKELY EASTERN AREAS...ESPECIALLY COASTAL
AREAS CLOSER TO THIS LOW SUCH AS BOSTON AND POINTS NORTH. THE
SNOW IS FORECAST TO GRADUALLY WIND DOWN DURING THE NIGHT FRI NIGHT
AS THE LOW PULLS AWAY.

ARCTIC AIR WILL USHER INTO NEW ENGLAND BEHIND THIS DEPARTING LOW FOR
THE WEEKEND WITH BLUSTERY NW WINDS AND FRIGID WIND CHILLS. WINDS
CHILL ADVISORIES MAY BE NEEDED FRI NIGHT.

A MORE VIGOROUS SHORTWAVE DIVES INTO THE EASTERN STATES SUN NIGHT
AND MONDAY. MODELS CONTINUE TO STRUGGLE WITH REGARDS TO THE
AMPLITUDE OF THE TROUGH AND THE CORRESPONDING SURFACE LOW AND TRACK.
THE LATEST 28.12Z OPERATIONAL RUNS OF THE GFS AND ECMWF NOW ARE MORE
PROGRESSIVE AND SHOW A WEAKER SURFACE LOW AND WELL EAST OF THE
BENCHMARK. HOWEVER BOTH MODELS DID JUST THE SAME SEVERAL DAYS
BEFORE OUR RECENT BLIZZARD...SO WE CANNOT HAVE ANY DEGREE OF
CONFIDENCE WITH EITHER A HIT OR A MISS THIS FAR OUT IN TIME. WE
WILL CONTINUE TO USE A MODEL BLEND INCLUDING THEIR ENSEMBLES AS
THERE IS A HIGH DEGREE OF SPREAD AMONGST THEM.

HIGH PRESSURE WILL BUILD INTO THE REGION TUE-WED AS THE
SHORTWAVE/LOW MOVES EAST WITH HIGH PRESSURE TAKING OVER...BRINGING
QUIET WEATHER MID WEEK. YET ANOTHER CHANCE OF SNOW OR A WINTRY
MIX ENTERS THE PICTURE BY THU. AN ACTIVE WINTERTIME PATTERN
INDEED!

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
FORECASTER CONFIDENCE LEVELS...

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

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

TODAY...VFR. INCREASING CLOUDS ABOVE 10 K FT IN THE AFTERNOON.
LIGHT WIND

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. GUSTY NORTHWEST WINDS
25-35 KNOTS SATURDAY...LIGHTER WINDS SUNDAY.

SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. COASTAL LOW TRACK HIGHLY
UNCERTAIN. JUST WAY 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.

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

TONIGHT...INCREASING SOUTHERLY WINDS EXPECTED AHEAD OF LOW PRES
MOVING THROUGH  THE GT 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...LOW PRES WILL CROSS THE WATERS. EXPECT REDUCED VSBYS IN
SNOW. EXPECT WINDS TO SHIFT TO NW AND INCREASE FRI NIGHT...WITH
GALES POSSIBLE OVER THE WATERS. FREEZING SPRAY WILL LIKELY DEVELOP
FRI NIGHT.

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

SUNDAY...WINDS AND SEAS AT SMALL CRAFT ADVISORY LEVELS EARLY
SUNDAY...BUT WILL DIMINISH THROUGH THE DAY.

SUNDAY NIGHT-MONDAY...MUCH WILL DEPEND ON STRENGTH AND TRACK OF A
POSSIBLE COASTAL LOW SO TAKE THE OFFICIAL FORECAST OF WINDS/SEAS
DURING THIS PERIOD WITH A GRAIN OF SALT. A LOW CLOSER TO THE COAST
WOULD SPELL A SIGNIFICANT IMPACT TO MARINERS...WHILE AN
OFFSHORE/WEAKER TRACK WOULD HAVE MUCH LESS IMPACT. TOO EARLY TO
SAY EITHER WAY...SO WENT WITH A MODEL BLEND.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST
     SATURDAY FOR MAZ004>007-014-026.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR ANZ250-254.
     SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR ANZ255.

&&

$$
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...99
AVIATION...KJC/99
MARINE...KJC/99



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