Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 311415
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1015 AM EDT TUE MAR 31 2015

.SYNOPSIS...

QUIET WEATHER TODAY IS FOLLOWED BY LIKELY RAIN/SNOW ACROSS THE
SOUTH COAST OVERNIGHT. WARMER THURSDAY INTO FRIDAY AHEAD A COLD
FRONT. LOW PRESSURE DEVELOPS ALONG THE COLD FRONT FRIDAY NIGHT AND
MOVES ACROSS THE REGION BY EARLY SATURDAY BRINGING LOCALLY HEAVY
RAIN SHOWERS. MAINLY DRY AND MUCH COLDER SUNDAY. STILL COOL WITH A
CHANCE OF A RAIN OR SNOW SHOWER ON MONDAY.

&&

.NEAR TERM /THROUGH MIDNIGHT WEDNESDAY/...

10 AM UPDATE...

*/ THROUGH THIS AFTERNOON ...

INCREASING CLOUDS AHEAD OF THE CLIPPER-LOW. WESTERLY FLOW OVER-
NIGHT ALLOWED FOR BOUNDARY-LAYER MIXING AND REDUCED THE POTENTIAL
FOR WIDESPREAD LOWS IN AND AROUND THE UPPER-20S. WITH THE HIGH-
ANGLE MARCH SUN...TEMPERATURES LIKELY TO MODERATE AROUND THE MID-
TO UPPER-50S PRIOR TO THICKER CLOUD COVER WHICH PER LATEST
SATELLITE IS QUICKLY ENCROACHING FROM THE NW. BY MIDDAY MUCH OF
THE REGION WILL BE BENEATH A THICK BLANKET OF BROKEN CLOUDS.

*/ BY LATE AFTERNOON AND TOWARDS MIDNIGHT WEDNESDAY ...

CONSENSUS OF FORECAST GUIDANCE HAS THE CLIPPER-LOW SWEEPING S OF
NEW ENGLAND OFF THE DELMARVA COASTLINE ACROSS REGIONS OF BETTER
BAROCLINICITY N OF WHICH ALONG THE PARENT H7-8 WARM FRONT W-E
ZONAL FLOW AVAILABLE MOISTURE IS SQUEEZED UP AGAINST HIGH PRESSURE
BUILDING OUT OF THE NW YIELDING PRECIP S OF THE CT-RI-MA BORDER.
DECENT MOISTURE AND LIFT APPARENT ON UP TO H5 WITH SIGNIFICANT QG-
FORCING AND OMEGA ALLOWS FOR INCREASED CONFIDENCE OF EXPECTED
OUTCOMES.

SOME APPREHENSION AS TO WHETHER OUTCOMES COULD WOBBLE EVER SO
SLIGHTLY N OR S. ALSO WILL SEE AN ISALLOBARIC RESPONSE RESULTING
IN THE ADVECTION OF COLDER AND DRYER AIR WITHIN THE LOW-LEVELS S
ACROSS NEW ENGLAND. TRICKY TO DETERMINE WHERE THE BATTLE-LINE WILL
EXACTLY BE BETWEEN THE MASSES S OF WHICH OUTCOMES WOULD BE
EXPECTED. NEVERTHELESS WITH THIS UPDATE THE FORECAST HAS BEEN
AMENDED WITH HIGH CATEGORICAL POPS AND EXPECTATION OF IMPACTS.

TOWARDS EVENING:

WITH ONSET EXPECT LIGHT PRECIP. WITHIN THE LOW-LEVELS WET-BULBING /
DYNAMIC COOLING OF THE BOUNDARY LAYER WILL SUBSEQUENTLY BE SLOW.
NOTING THE MODERATE TEMPERATURE PATTERN AT PRESENT WITH ABUNDANT
SUNSHINE...ANTICIPATING THE BOUNDARY-LAYER TO BE ABOVE FREEZING
AND LIGHT PRECIP OUTCOMES TO BE IN THE FORM OF RAIN. CAN NOT RULE
OUT THE POSSIBILITY OF A FEW WET SNOWFLAKES MIXING IN.

EVENING AND TOWARDS MIDNIGHT:

BOTH NOCTURNAL COOLING AND AN INCREASING INTENSITY OF PRECIP IS
LIKELY TO RESULT IN RAIN MIXING WITH AND / OR CHANGING OVER TO
SNOW. ICE SHOULD BE PRESENT WITHIN THE COLUMN WITH LIFT AND
MOISTURE APPARENT WITHIN DENDRITIC GROWTH ZONE. WITH TEMPERATURES
AROUND THE FREEZING MARK DURING THIS PERIOD...SNOW ACCUMULATION
WILL LIKELY BE HARD TO COME BY. WET ROADWAYS LIKELY FOR THE MOST
PART. THE BIGGEST IMPACT WITH BE WITH RESPECT TO VISIBILITIES AND
ESPECIALLY MORE SO ALONG THE S-COASTLINE OF NEW ENGLAND.


&&

.SHORT TERM /12 AM WEDNESDAY TO 6 PM WEDNESDAY/...

COLD ADVECTION AND HIGH PRES FOLLOWS THE DEVELOPING CLIPPER
OFFSHORE. SKIES CLEAR...BUT WITH H85 TEMPS FALLING BACK TO -8C TO
-10C SUSPECT ANOTHER DAY WHERE HIGH TEMPS REMAIN BELOW SEASONAL
NORMALS. MAINLY LOW-MID 40S EXPECTED...BREEZY WITH WIND GUSTS
AROUND 20 MPH AT TIMES.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...

HIGHLIGHTS...

* TEMPERATURES RISING TO NEAR NORMAL THU AND ABOVE NORMAL FRI
* STORM SYSTEM BRINGS SHOWERS THU NIGHT INTO EARLY SAT...

WEDNESDAY NIGHT...HIGH PRESSURE CENTERED OFF THE MID ATLANTIC
COAST WILL RIDGE NORTHWARD ACROSS SOUTHERN NEW ENGLAND PROVIDING
CLEAR SKIES AND COLD TEMPERATURES. LOWS IN THE 20S.

THURSDAY...TEMPERATURES BEGIN TO MODERATE AS HIGH PRESSURE MOVES
OFFSHORE AND LOW PRESSURE MOVES ACROSS ONTARIO. SOUTHWEST FLOW
WILL BOOST TEMPERATURES TO NEAR NORMAL LEVELS...IN THE LOWER 50S
EXCEPT COOLER ON THE CAPE AND ISLANDS. LOW LEVEL JET WILL INCREASE
LATE IN THE AFTERNOON...REACHING 50 KNOTS AT 925 MB. AT THE
SURFACE...EXPECT WINDS TO GUST TO 20-25 MPH TOWARD EVENING.

THURSDAY NIGHT AND FRIDAY...A COLD FRONT MOVES EASTWARD INTO
SOUTHERN NEW ENGLAND AND STALLS SOMEWHERE ACROSS THE INTERIOR.
THERE ARE TIMING DIFFERENCES IN THE MODELS...WITH THE GFS FASTEST
AND ECMWF SLOWEST. NEVERTHELESS...IT WILL BE A CLOUDY PERIOD WITH
A GOOD CHANCE OF SHOWERS. THE SHOWALTER INDEX DROPS TO BELOW ZERO
THU NIGHT BUT OTHER PARAMETERS ARE NOT FAVORABLE FOR CONVECTION...
SO WILL NOT MENTION ANY ELEVATED THUNDER AT THIS TIME.
TEMPERATURES WILL HOLD IN THE 40S THU NIGHT...AND DESPITE
CLOUDINESS..SHOULD RISE TO ACTUAL SPRINGLIKE READINGS...IN THE
LOWER 60S FRI (UPPER 40S TO MID 50S CAPE AND ISLANDS) AS 850 MB
TEMPS RISE TO NEAR +10C. GFS MEX GUIDANCE ACTUALLY GIVES 66 FOR
BDL FRI BUT WITH CLOUDY SKIES AND SCATTERED SHOWERS...HAVE HELD
CLOSE TO PREVIOUS FORECAST OF LOWER 60S.

FRIDAY NIGHT INTO SATURDAY...A LOW PRESSURE STORM SYSTEM IS
FORECAST TO MOVE EASTWARD FROM THE OHIO VALLEY AND INTENSIFY ALONG
THE STALLED FRONT AS IT REACHES SOUTHERN NEW ENGLAND. THE MAIN
IMPACT WILL BE A WIDESPREAD RAINFALL OF ABOUT 0.5 INCHES...BUT
THERE IS THE POTENTIAL FOR POCKETS OF 1 INCH OF RAIN. THE GFS
STRENGTHENS THE LOW TO 995 MB AND HAS IT MOVING INTO THE GULF OF
MAINE WITH ENOUGH PRECIPITATION WRAPPING AROUND TO CAUSE A
CHANGEOVER TO SNOW IN NORTHWEST PORTIONS OF MA. THE ECMWF HAS
TRENDED COLDER...BUT NOT THAT COLD. YESTERDAY IT HAD AN INTENSE
STORM OVER NORTHERN VERMONT AND THIS MORNING/S RUN HAS IT OVER
SOUTHEAST NEW HAMPSHIRE...CLOSER TO THE GFS SOLUTION. HOWEVER...
ANY LEFTOVER SNOW WOULD BE CONFINED TO AREAS NORTH AND WEST OF OUR
FORECAST AREA. THAT IS HOW WE CURRENTLY PLAYED THIS.  THE
PRECIPITATION CLEARS OUT BY ABOUT NOON ON SATURDAY. HIGHS MAINLY
IN THE 40S.

SUNDAY...MAINLY SUNNY AND DRY BUT MUCH COLDER WITH HIGHS ONLY IN
THE LOWER TO MID 40S...BELOW NORMAL AGAIN. CANNOT RULE OUT A BRIEF
PASSING FLURRY IN THE MORNING AS A WEAK UPPER DISTURBANCE PASSES
THROUGH.

MONDAY...A WARM FRONT APPROACHES THE REGION IN ASSOCIATION WITH
LOW PRESSURE MOVING THROUGH THE UPPER MIDWEST AND LOWER GREAT
LAKES REGION. THIS COULD BRING ANOTHER CHANCE OF RAIN...OR
POSSIBLY MIXED PRECIPITATION IN NORTHERN MA...BY LATE MONDAY.
THE ECMWF IMPLIES THAT THIS COULD BE A LONG DURATION EVENT INTO
THE MIDDLE OF NEXT WEEK BECAUSE STRONG HIGH PRESSURE BUILDS INTO
NORTHERN NEW ENGLAND FROM CANADA. A LOT WILL DEPEND ON THE
ORIENTATION OF THAT HIGH. ANYWAY...THAT IS A WHOLE WEEK AWAY.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...

FORECASTER CONFIDENCE LEVELS...

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

.SHORT TERM /THROUGH WEDNESDAY/...

*/ THROUGH AFTERNOON ... HIGH CONFIDENCE.

LOW-END VFR. INCREASING CLOUDS BY MIDDAY. W-WINDS WITH GUSTS UP TO
25 KTS AT TIMES.

*/ LATE AFTERNOON INTO WEDNESDAY MORNING...HIGH CONFIDENCE.

MIX LOW-END VFR / MVFR ESPECIALLY S OF CT-RI-MA BORDER. INITIALLY
-RA MIXING WITH AND / OR OVER TO -SN. IMPACTS MAINLY IN THE FORM
OF VSBYS. LITTLE TO NO SNOW ACCUM. BELIEVE RUNWAYS WILL REMAIN
WET. CONDITIONS IMPROVING AFTER MIDNIGHT WEDNESDAY INTO MORNING
BACK TO VFR WITH W/NW-FLOW.

WEDNESDAY...HIGH CONFIDENCE. VFR.

KBOS TAF...HIGH CONFIDENCE. DRY. BELIEVE OUTCOMES WILL BE S OF
TERMINAL.

KBDL TAF...MODERATE CONFIDENCE. RAIN / SNOW MIX POSSIBLE YET EVER
BRIEF DURING WHICH TIME MVFR IMPACTS IN THE FORM OF CIGS / VSBYS
WILL BE POSSIBLE. TIMING OF GREATEST IMPACT AROUND 8 PM / 0Z.

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...

WEDNESDAY AND THURSDAY...HIGH CONFIDENCE. VFR. GUSTY SOUTHWESTERLY
WINDS ARE POSSIBLE THURSDAY.

THURSDAY NIGHT AND FRIDAY...MODERATE CONFIDENCE. VFR BECOMING
MVFR CEILINGS AND VSBYS IN SHOWERS. LOW LEVEL WIND SHEAR EXPECTED
THROUGHOUT THE REGION WITH SOUTHERLY SURFACE WINDS 10-20 KT
INCREASING TO SOUTHWESTERLY AT 55-65 KT AT 5000 FT.

FRIDAY NIGHT INTO SAT MORNING...HIGH CONFIDENCE. MVFR AND IFR
CONDITIONS IN WIDESPREAD SHOWERS. AREAS OF FOG.

SATURDAY AFTERNOON...HIGH CONFIDENCE. VFR.

&&

.MARINE...

FORECASTER CONFIDENCE LEVELS...

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

.SHORT TERM /TODAY THROUGH TUESDAY/...HIGH CONFIDENCE.

10 AM UPDATE...

NO MAJOR CHANGES.

TONIGHT INTO TOMORROW...

LOW PRES WILL SLIDE S OF THE WATERS. WINDS WILL SHIFT FROM THE W
TO N EARLY WED MORNING WITH GUSTS INCREASING AS THEY SHIFT WITH
GUSTS AROUND 25 KT POSSIBLE. SEAS ALSO INCREASE SUCH THAT 5-7 FT
SEAS ARE POSSIBLE DURING THE DAY ON WED. THEREFORE...AFTER A
BRIEF LULL TODAY...SMALL CRAFT ADVISORIES ARE LIKELY NEEDED LATE
TONIGHT...BUT WITH ONGOING HEADLINE WILL HOLD OFF FOR NOW

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...

WEDNESDAY NIGHT AND THURSDAY...SEAS DIMINISH AS HIGH PRESSURE
BUILDS OVER THE WATERS. NORTHWESTERLY WINDS SHIFT TO THE SOUTHWEST
DIMINISHING THROUGH THE PERIOD. OCCASIONAL 25 KT GUSTS ARE
POSSIBLE ON THE OUTER WATERS AT TIMES.

THURSDAY NIGHT THROUGH SATURDAY...SEAS INCREASE AHEAD OF A COLD
FRONT WHICH STALLS OVER SOUTHERN NEW ENGLAND...AND THEN AS A
STORM SYSTEM DEVELOPS ALONG THE FRONT AND MOVES INTO THE GULF OF
MAINE. SOUTHWESTERLY WINDS 15 TO 25 KTS WITH GUSTS TO 30 KTS
THROUGHOUT THE PERIOD...SHIFTING TO THE TO THE NORTHWEST SATURDAY
MORNING. SMALL CRAFT ADVISORIES ARE LIKELY FOR BOTH WINDS AND
SEAS AT LEAST ON THE OUTER WATERS...IF NOT ON THE INTERIOR BAYS
AND SOUNDS AT TIMES. LOW PROBABILITY OF A GALE FORCE GUST OR TWO
OVER THE OUTER WATERS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ235-
     237.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ250-
     254-255.
     SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ256.

&&

$$
SYNOPSIS...DOODY/GAF
NEAR TERM...DOODY/SIPPRELL/GAF
SHORT TERM...DOODY
LONG TERM...GAF
AVIATION...DOODY/GAF/SIPPRELL
MARINE...DOODY/GAF


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