Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 010008
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
808 PM EDT SUN MAY 31 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE SOUTH OFF THE COAST THIS EVENING...THEN
STALL SOUTH OF NEW ENGLAND THROUGH TUESDAY AS LOW PRES TRACKS
ALONG THE FRONT MONDAY NIGHT INTO TUESDAY. THIS WILL BRING PERIODS
OF HEAVY RAIN TO THE REGION THROUGH TUESDAY. HIGH PRESSURE
RETURNS FOR WEDNESDAY AND THURSDAY. CHANCE OF SHOWERS RETURNS FOR
FRIDAY AND SATURDAY AS ANOTHER COLD FRONT MOVES THROUGH ON SATURDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
8 PM UPDATE...
FRONT THROUGH OUR ENTIRE AREA EXCEPT NANTUCKET...WHICH SHOULD BE
IN THE NEXT HOUR OR SO. TEMPERATURES EVERYWHERE WERE IN THE 50S
WITH CHILLY NORTHEAST WINDS.

AXIS OF HEAVY RAIN AND THUNDERSTORMS STRETCHED FROM WINDHAM COUNTY
CT EASTWARD ACROSS THE NORTHERN HALF OF RI AND EASTWARD TO
PLYMOUTH. 3 TO 5 INCHES OF RAIN HAS FALLEN IN THE HEAVIEST AREAS.
IT APPEARS THAT THERE WILL BE A LULL IN THE PRECIPITATION ACROSS
MUCH OF THE AREA FOR THE NEXT FEW HOURS AS THIS MAIN AREA SLIDES
EASTWARD. HOWEVER...THERE IS A RAPIDLY DEVELOPING AND EXPANDING
AREA OF THUNDERSTORMS IN NORTHERN NJ AND INTO SOUTHEAST NY WHICH
MESOSCALE MODELS SHOW MOVING INTO CT ONCE AGAIN OVERNIGHT. THIS
COULD CAUSE RENEWED FLOODING. A FLASH FLOOD WATCH REMAINS IN
EFFECT FOR THAT AREA UNTIL 11 PM. WILL MONITOR CLOSELY TO SEE IF
THE WATCH NEEDS TO BE EXTENDED FOR TONIGHT.

PREVIOUS DISCUSSION...
TONIGHT...EXPECT CONVECTION TO WEAKEN THIS EVENING WITH JUST
OCCASIONAL LIGHT SHOWERS ACROSS THE REGION...FOCUSED MORE IN THE
INTERIOR. LATER TONIGHT...ANOTHER ROUND OF HEAVY RAINFALL WILL
LIKELY SET UP ACROSS UPSTATE NY AND VT ASSOCD WITH STRONG LOW
LEVEL CONVERGENCE AND FRONTOGENESIS WITH THE 850 MB FRONT TO THE
NORTH. HOWEVER...MODELS ARE SHOWING AN AREA OF ENHANCED MID LEVEL
OMEGA MOVING INTO SNE LATE TONIGHT WHICH WILL LIKELY BRING ANOTHER
PERIOD OF RAIN.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
MONDAY...
A BAND OF RAIN WILL LIKELY BE MOVING ACROSS SNE IN THE MORNING
ASSOCD WITH AREA OF MID LEVEL LIFT. OTHERWISE...850 MB FRONT
WILL REMAIN TO THE NORTH WHILE SFC FRONT IS TO THE S. WITH
DECENT E/NE INFLOW AT 950 MB AND SOUTHERLY FLOW AT 850 MB ALONG
WITH DEEP MOISTURE IN PLACE WITH PWATS NEAR 1.5" WILL SEE PERIODS
OF COOL OVERRUNNING RAIN THROUGH MUCH OF THE DAY WHICH MAY BE
LOCALLY HEAVY AT TIMES. ELEVATED INSTABILITY PARAMETERS ARE
MARGINAL SO ONLY A LOW PROB FOR AN ISOLD TSTM. A VERY COOL DAY
WITH TEMPS AVERAGING 15-20 DEGREES BELOW NORMAL...RANGING FROM
NEAR 50 IN THE HIGHER TERRAIN TO MID/UPPER 50S NEAR THE S COAST.
IN ADDITION...NE WINDS WILL GUST TO 25-30 MPH ACROSS NE MA.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MONDAY NIGHT-TUESDAY...

IMPRESSIVE OVERRUNNING SITUATION SETTING UP WITH THE POTENTIAL
FOR RATHER WIDESPREAD HEAVY RAINFALL. THE SURFACE COLD FRONT
REMAINS STALLED JUST SOUTH OF NEW ENGLAND WHILE THE FRONT AT 850
MB IS PARKED IN SOUTHERN NEW ENGLAND ROUGHLY NEAR THE MASS PIKE.
LOW PRESSURE WILL TRAVEL ALONG THE FRONT FROM NEW JERSEY MON NIGHT
TO THE GULF OF MAINE TUE AFTERNOON. BETWEEN 06Z AND 12Z TUE THE
NAM SHOWS ENE WINDS AT 20-30 KT AT 925 MB ACROSS NORTHERN MA WHILE
S-SW WINDS INCREASE TO 30-40 KT AT 850 MB ACROSS THE ENTIRE
FORECAST AREA BRINGING IN +13-14C 850 MB AIR INTO CT/RI/SE MA
ABOVE THE COOL MOIST SURFACE ENVIRONMENT. GFS WINDS ARE LESSER BUT
STILL SHOW OVERRUNNING. PRECIPITABLE WATER VALUES ARE 1.6 TO 1.7
WHICH IS QUITE HIGH.

EXPECT WIDESPREAD 1-2 INCHES OF RAIN WITH LOCALIZED AREAS OF 2-3
INCHES. MAINLY RAIN BUT COULD SEE SOME EMBEDDED ISOLATED
THUNDERSTORMS ESPECIALLY IN RI AND SOUTHEAST MA WHERE THE SHOWALTER
INDICES ARE DOWN TO 0.5...STILL POSITIVE BUT A MINIMUM AREA.
IT IS TOO EARLY TO PIN DOWN AREAS MOST AT RISK FOR ANY FLOODING. IT
MAY BE DEPENDENT ON WHERE THE HEAVIEST CONVECTION ENDS UP LATE THIS
AFTERNOON AND EVENING. THUS LATER SHIFTS WILL NEED TO MONITOR THE
POTENTIAL FOR A FLOOD OR FLASH FLOOD WATCH FOR A PORTION OF THE
AREA. RAINFALL TAPERS OFF FROM WEST TO EAST TUE AFTERNOON. ECMWF
MUCH SLOWER AT MOVING OUT THE CLOUDINESS SO WILL ERR ON THE
CAUTIOUS SIDE AND KEEP IT MAINLY CLOUDY FOR THE AFTERNOON.
UNSEASONABLY COOL TUE WITH HIGHS MAINLY 55 TO 60.

WEDNESDAY AND THURSDAY...HIGH PRESSURE BUILDS OVER THE NORTHEAST
STATES BOTH AT THE SURFACE AND ALOFT. BY THU EVENING THE HIGH
BECOMES CENTERED EAST AND SOUTH OF NANTUCKET. SKIES WILL BE MOSTLY
SUNNY AND THERE WILL BE A WARMING TREND. FORECASTING HIGHS IN THE
60S TO NEAR 70 WED AND IN THE MID AND UPPER 70S THU...COOLER ON
CAPE ANN...CAPE COD...AND THE ISLANDS. FRIDAY...RETURN FLOW AROUND
THE HIGH PRESSURE LEADS TO AN INCREASE IN MOISTURE AND SOME
CLOUDINESS. THERE IS A CHANCE OF SHOWERS... ESPECIALLY IN WESTERN
AND CENTRAL AREAS IN THE AFTERNOON AND EVENING. HIGHS MAINLY 75 TO
80...COOLER AT THE IMMEDIATE COAST AND 60S ON NANTUCKET.

SATURDAY...MODELS ALL INDICATE A COLD FRONT MOVING THROUGH NEW
ENGLAND. THE ECMWF IS MOST EMPHATIC. IN ADDITION TO THE
FRONT...IT IS FARTHER NORTH THAN THE GFS WITH AN UPPER LEVEL LOW
PRESSURE SYSTEM OVER THE MID ATLANTIC/SOUTHEAST STATES. RIGHT NOW
HAVE INDICATED A LOW CHANCE OF SHOWERS...25 TO 30 PERCENT.
HOWEVER...IF THE ECMWF IS RIGHT THE PROBABILITY WOULD BE GREATER.
COULD ALSO BE THUNDER...BUT TOO FAR OUT NOW TO INCLUDE WITH ANY
CONFIDENCE. HIGHS AGAIN MAINLY 75 TO 80.

SUNDAY...ASSUMING FRONT HAS PASSED THROUGH...EXPECTING PARTLY SUNNY
SKIES AND TEMPS IN THE 70S.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

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

TONIGHT...MODERATE CONFIDENCE. MVFR/IFR CONDITIONS. HEAVY SHOWERS
AND THUNDERSTORMS WILL CONTINUE ACROSS PORTIONS OF RI AND SE MA
THROUGH 02Z. A NEW AREA OF THUNDERSTORMS WILL BE MOVING INTO CT
FROM SOUTHEAST NY BETWEEN 01Z AND 03Z. LOCAL LIFR CONDITIONS IN
FOG/HEAVY RAIN.

MONDAY...MODERATE CONFIDENCE. WIDESPREAD MVFR/IFR CONDITIONS.
OCCASIONAL SHOWERS AND PERHAPS AN EMBEDDED TSTM WILL PERSIST...
WITH GREATEST COVERAGE ACROSS INTERIOR. A PULSE OF GUSTS TO 25 KT
POSSIBLE.

KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. MVFR CIGS WITH LOCAL
IFR POSSIBLE. SCATTERED HEAVY SHOWERS. GUSTY NE WINDS.

KBDL TERMINAL...MODERATE CONFIDENCE IN TAF.

OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE MONDAY
NIGHT AND TUE. HIGH CONFIDENCE WED THROUGH FRI.

MONDAY NIGHT AND TUESDAY...GUSTY EAST TO NORTHEAST FLOW AT THE
SURFACE INCREASING TO 30 KT AT 2000 FT...THEN SHIFTING TO SOUTH-
SOUTHWEST AND INCREASING TO 40 KT BY 5000 FT. A SMALL DEGREE OF
LOW LEVEL WIND SHEAR WITH THIS OVERRUNNING SETUP. MVFR/IFR CIGS
AND VSBYS... HEAVY RAIN EXPECTED MON NIGHT INTO TUE MORNING.
ISOLATED TSTMS POSSIBLE MAINLY S RI AND SE MA. RAIN ENDING FROM W
TO E TUE AFTERNOON WITH IMPROVING CONDITIONS.

WEDNESDAY...VFR. LIGHT NORTHERLY WIND.

THURSDAY...VFR. LIGHT SOUTHERLY WIND. LOCAL SEABREEZES POSSIBLE.
PATCHY FOG POSSIBLE ALONG THE SOUTH COAST.

FRIDAY...VFR. LIGHT SOUTHWEST WIND. CHANCE OF SHOWERS WEST LATE.
LOCAL SEA BREEZES STILL POSSIBLE.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

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

NE GUSTS TO 30 KT WILL CONTINUE INTO THIS EVENING ACROSS NE
COASTAL WATERS. EXPECT A BRIEF LULL OVERNIGHT..THEN ANOTHER PULSE
OF NE GUSTS TO 30 KT IS EXPECTED DURING MONDAY...AGAIN MAINLY
FOCUSED OVER NE COASTAL WATERS. ELSEWHERE...SW WINDS OVER S
COASTAL WATERS WILL SHIFT TO NE THIS EVENING AND PERSIST THOUGH
MONDAY WITH GUSTS TO 20 KT AT TIMES. SEAS WILL BUILD TO 5-8 FT
OVER NE MA COASTAL WATERS. OCCASIONAL SHOWERS AND PATCHY FOG WILL
REDUCE VSBYS.

OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE.

MONDAY NIGHT-TUESDAY NIGHT...SMALL CRAFT ADVISORIES HAVE BEEN
EXTENDED THROUGH MONDAY NIGHT AS ROUGH SEAS FROM 5 TO 7 FT WILL
CONTINUE OVER THE COASTAL WATERS EAST OF MASSACHUSETTS. SMALL
CRAFT ADVISORIES MAY BE NEEDED ACROSS THE SOUTHERN OUTER COASTAL
WATERS AS WELL ON TUE. NORTHEAST WINDS MAY BE GUSTING TO NEAR 25
KT MON EVENING BUT WILL GRADUALLY DIMINISH BY TUE. EXPECTING SEAS
TO SUBSIDE TO BELOW SMALL CRAFT ADVISORY THRESHOLDS TUE NIGHT.

WEDNESDAY AND THURSDAY...QUIET BOATING WEATHER WITH HIGH PRESSURE
OVERHEAD WED AND THEN SLIDING OFF THE COAST LATE THU.

FRIDAY...SOUTHERLY WINDS INCREASE TO 10 TO 15 KT BEHIND DEPARTING
HIGH PRESSURE. STILL NO HEADLINES EXPECTED.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...FLASH FLOOD WATCH UNTIL 11 PM EDT THIS EVENING FOR CTZ002>004.
MA...FLASH FLOOD WATCH UNTIL 11 PM EDT THIS EVENING FOR MAZ009-011-
     012.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ232>236.
     SMALL CRAFT ADVISORY UNTIL 2 PM EDT MONDAY FOR ANZ230-255-256.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ231.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ250-251-254.

&&

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


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