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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 132323
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
723 PM EDT MON MAY 13 2013

.SYNOPSIS...
MAINLY CLEAR SKIES AND LIGHT WINDS WILL BRING COLD CONDITIONS TO
INTERIOR AREAS OVERNIGHT AS HIGH PRESSURE RIDGE MOVES IN. LOW
PRESSURE WILL BRING SHOWERS WEDNESDAY INTO THURSDAY AS TEMPERATURES
RECOVER TO NEAR OR EVEN ABOVE NORMAL LEVELS AT TIMES THROUGH LATE
WEEK. HIGH PRESSURE LATE THIS WEEK INTO THE WEEKEND WILL BRING DRY
SEASONABLE CONDITIONS.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
7 PM UPDATE...
MAJOR POINTS OF THE FORECAST ARE ON TRACK. HOWEVER WE ARE ALREADY
SEEING THE WRN EXTENT OF CI SHIELD FROM OFFSHORE LOW PRES
DIMINISHING AS IT MEETS DECENT SUBSIDENCE FROM HIGH PRES MOVING
OVER FROM THE SW. THEREFORE...ADJUSTED SKIES TO KEEP BKN-OVC
CEILINGS MAINLY IN EXTREME SE MASS. THIS WAS DONE USING A BLEND OF
REGIONAL CMC AND THE NAM-DNG. EXPECT THAT INLAND CU WILL ALSO
CONTINUE TO DIMINISH AS WE HAVE SEEN IN THE LAST HOUR OR SO OF
SATELLITE IMAGERY...THEREFORE...DECOUPLING STILL LOOKS GOOD.

PREVIOUS DISCUSSION...

AREA OF SHOWERS ASSOCIATED WITH AMPLIFYING UPPER LEVEL SHORT WAVE
WILL PUSH INTO THE CT VALLEY THIS EVENING. SOME SHOWERS MAY
SURVIVE CROSSING THE GREEN MOUNTAINS AND BERKSHIRES...BUT WITH DRY
AIRMASS IN PLACE...WILL LIKELY SEE MOST SHOWERS EVAPORATE BEFORE
REACHING THE GROUND. HOWEVER...DID PUT MENTION OF SLIGHT CHANCE
POPS FOR THE EVENING...BUT SHOULD DISSIPATE BY AROUND 02Z-03Z.

LOW PRES WILL PASS WELL SE OF NANTUCKET OVERNIGHT...BUT EXPECT
THIS TO THROW SOME CLOUDS INTO EASTERN AREAS. ALREADY NOTING THE
CLOUD DECK APPROACHING FROM THE S ON VISIBLE SATELLITE LOOP. THIS
MAY CUT BACK ON TEMP DROP AND POSSIBLE PATCHY FROST...SOMETHING TO
KEEP AN EYE ON. ALSO...AFTER MIDNIGHT...AS THE SHORT WAVE MOVES
OFFSHORE AND THE LOW PASSES...W-NW WINDS WILL PICK UP ALONG THE
IMMEDIATE E COAST AS WELL AS CAPE COD AND THE ISLANDS.

AS FOR THE FROST/FREEZE POTENTIAL...LOOKS LIKE BEST SHOT WILL BE
ACROSS CENTRAL AND EASTERN AREAS. MAY MAKE IT INTO EASTERN ESSEX
AND SE MIDDLESEX COUNTIES BEFORE THE CLOUDS MOVE IN...SO ADDED
THEM TO THE FROST ADVISORY. KEPT REMAINING AREAS GOING...BUT DO
QUESTION THE SE INTERIOR MA SECTIONS. CENTER OF H5 COLD POOL /ON
ORDER OF -30C/ WILL PASS S OF THE REGION OVERNIGHT...BUT STILL BE
IN SOLID -26C TO -28C REGION SO WILL SEE COLD TEMPS MOVE IN
ESPECIALLY ACROSS THE INTERIOR. SO...HAVE KEPT FROST/FREEZE
HEADLINES GOING IN THOSE AREAS WHERE GROWING SEASON HAS BEGUN.
SOME LOCATIONS WELL INLAND COULD SEE TEMPS DROP TO THE UPPER
20S...WITH MOST AREAS FALLING TO THE 30S EXCEPT ALONG THE
IMMEDIATE COAST.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
TUESDAY...
AS THE H5 TROUGH MOVES OFFSHORE...EXPECT DRY NW FLOW TO KICK IN.
ANY LEFTOVER CLOUDS ACROSS EASTERN AREAS WILL SHIFT OFFSHORE. WILL
BE SOMEWHAT MILDER THAN TODAY...BUT NOTING ANOTHER WEAK H85 SHORT
WAVE IN THE N-NW UPPER FLOW WITH TEMPS FALLING TO -2C TO -4C. THIS
COULD MEAN SOME DIURNAL CLOUDS DEVELOPING BUT AIRMASS APPEARS TOO
DRY TO SUPPORT ANY SHOWERS AT THIS POINT. EXPECT LIGHTER WINDS
WITH AFTERNOON SEA BREEZES DEVELOPING.

TUESDAY NIGHT...
HIGH PRES RIDGE BUILDS ACROSS NEW ENGLAND. WILL SEE MAINLY CLEAR
SKIES WITH LIGHT/VRBL WINDS. MAY SEE POCKETS OF FROST AGAIN...BUT
APPEARS THIS WILL OCCUR ACROSS S NH/N CENTRAL AND NW MA WHERE
GROWING SEASON HAS NOT STARTED YET. WILL MONITOR THIS THOUGH.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
OVERVIEW AND MODEL PREFERENCES...
13/12Z MODEL GUIDANCE SUITE IS IN FAIRLY GOOD AGREEMENT THROUGH
THE LONG TERM PERIOD IN TERMS OF THE SYNOPTIC SCALE PATTERN.
HOWEVER...THERE ARE SOME SUBTLE DIFFERENCES WHICH WILL HAVE SOME
EFFECTS ON THE DAY-TO-DAY SENSIBLE WX DETAILS. THE UPPER LVL
PATTERN IS REASONABLY ZONAL WITH ONLY MINOR WAVE AMPLIFICATION
THROUGH THE PERIOD. MODEST RIDGING WILL GIVE WAY TO DIGGING AND
SLIGHTLY DEEPENING TROF/CUTOFF WHICH WILL PASS THROUGH NRN NEW
ENGLAND LATE IN THE WEEK. THIS WILL LEAD TO AN INITIAL TRANSITION
TO MORE UNSETTLED WX FOR LATE WED INTO THU. HIGH PRES WILL RETURN
FOR THE LATE WEEK-EARLY WEEKEND TIMEFRAME AS THE BASE OF THE TROF
SLIDES TO THE E. THE FINAL NOTE IS A FRONTAL BOUNDARY WHICH MAY
EFFECT THE REGION SUN-MON...BUT THERE ARE SOME TIMING DIFFERENCES
IN THE UPPER LVL RIDGE BUILDING WHICH COULD HAVE AN EFFECT ON HOW
QUICKLY THIS FRONT ARRIVES...BUT NEVERTHELESS...A WILL TRANSITION
ONCE AGAIN TO MORE UNSETTLED WX FOR LATE IN THE WEEKEND. LOOKING
AT THE CURRENT ECMWF/GFS DETERMINISTIC RUNS...TIMING LOOKS TO BE
IN FAIRLY GOOD AGREEMENT FOR THESE SFC FEATURES...AND COINCIDE
QUITE NICELY WITH PREVIOUS SHIFT/S FORECAST. THEREFORE...WILL BE
BLENDING PERSISTENCE WITH THE LATEST GFS/ECMWF AS A BASELINE FOR
THIS FORECAST.

DETAILS...

WED INTO THU...
WED INITIALLY STARTS DRY AS HIGH PRES SLIDES OFFSHORE. RETURN SLY
FLOW ALLOWS FOR DECENT WARM ADVECTION...SO EXPECT SOME CU
DEVELOPMENT...GUSTY WINDS AT TIMES...BUT MODERATING TEMPERATURES.
HIGHS LIKELY REACH INTO THE 70S IN SEVERAL LOCATIONS. BY WED NIGHT
INTO EARLY THU...A COLD FRONT WILL CROSS THE REGION AS LOW PRES
PASSES THROUGH QUEBEC. AM NOTING DECENT WARM ADVECTION AND LIFT
WITH THIS FRONT...COMBINED WITH PWAT VALUES INCREASING TO ABOUT
1.0 INCHES. NOT EXPECTING A FULL WASHOUT DURING THE OVERNIGHT
HOURS...BUT SCT TO WIDESPREAD -SHRA IS LIKELY. MAY NEED TO MONITOR
FOR SOME ISOLATED THUNDER AS THE SOUNDING WILL HAVE A CHANCE TO
WARM A BIT INITIALLY WITH THE RETURN FLOW...AND THERE IS A DECENT
40 KT H84 LLJ TO WORK WITH. EXPECT PRECIP TO GENERALLY COME TO AN
END BY THU MORNING...WITH HIGH PRES NOSING IN FROM THE W.

FRI INTO SAT...
MID LVL RIDGE BEGINS TO SLIDE OVER THE REGION AS UPPER NRN NEW
ENGLAND TROF SLIDES INTO THE MARITIMES. THIS ALLOWS SFC HIGH PRES
TO FULLY INFLUENCE THE WX THROUGH THE PERIOD...WITH DRY CONDITIONS
EXPECTED. H85 TEMPS ACTUALLY COOL A BIT FROM FRI INTO SAT GIVEN A
N COMPONENT TO THE LOW-MID LVL FLOW. SO EXPECT H85 TEMPS AROUND
+10C ON FRI WITH HIGHS IN THE MID TO UPPER 70S FOR MANY PLACES. ON
SAT H85 TEMPS DROP TO ABOUT +4C...SO LOW 70S WILL BE THE WARMEST
TEMPS EXPECTED.

SUN INTO MON...
WITH CONTINUED BUILDING OF A GREAT LAKES RIDGE...A SFC WARM FRONT
WILL MAKE SLOW PROGRESS TOWARD SRN NEW ENGLAND...POTENTIALLY
CROSSING THE AREA SOMETIME DURING THE PERIOD. TYPICAL SLOW MOVING
WARM FRONT SETUP HERE...WITH DECENT MOISTURE FLUX /PWAT VALUES
INCREASING TO 1.0+ INCHES/. ALSO...CONVECTIVE INDICES ALSO SUGGEST
THE THREAT FOR THUNDER AS WELL THROUGH THE PERIOD...EVEN OVERNIGHT
ABOVE THE WARM LAYER. THE CAVEAT WOULD BE ELY FLOW WHICH MAY BE
STRONG ENOUGH SUCH THAT THE MARINE FLOW STABILIZES THE COLUMN. IN
ANY CASE...UNSETTLED AND WET CONDITIONS LOOK POSSIBLE. TIMING AND
SPEED OF THE FRONT WILL BE OF CONCERN...AS IT WILL DICTATE WHEN
THE POTENTIAL THREAT FOR HEAVIER RAIN/THUNDER IS HIGHEST...OR
WHETHER THE FRONT ACTUALLY WASHES OUT BEFORE MAKING ITS
APPROACH/PASSAGE.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

OVERVIEW...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH TUESDAY
NIGHT.

OTHERWISE...W-NW WINDS DIMINISH SOMEWHAT OVERNIGHT TONIGHT AND
REMAIN ABOUT 10 KT INTO THE DAY TOMORROW. SEA BREEZES LIKELY ALONG
THE EAST COAST. LOW PROBABILITY OF A SPOT -SHRA LATE TONIGHT ON
NANTUCKET.

KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA BREEZE LIKELY TUE.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF.

OUTLOOK...WEDNESDAY THROUGH SATURDAY...

WED AND THU...MODERATE CONFIDENCE.
VFR STARTS THE DAY WED...FOLLOWED BY A PERIOD OF MVFR/IFR
CONDITIONS IN SHOWERS AND FOG WED NIGHT INTO EARLY THU...WITH VFR
TO FOLLOW DURING THE MID TO LATE DAY THU. ISOLATED THUNDER ALSO
POSSIBLE LATE WED AFTERNOON AND OVERNIGHT. WINDS SHIFT FROM S/SW
WED TO W/NW BY THU.

FRI AND SAT...HIGH CONFIDENCE.
MAINLY VFR.
-- End Changed Discussion --

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

HIGH FORECAST CONFIDENCE THROUGH TUESDAY NIGHT.

TONIGHT...WINDS WILL BRIEFLY DIMINISH...THEN WILL PICK UP AGAIN
MAINLY ON THE EASTERN WATERS WITH BRIEF GUSTS TO 25 KT. SEAS WILL
ALSO REMAIN AOA 5 FT ON THE OUTER WATERS. NEAR SHORE...WILL SEE
WINDS AND SEAS SUBSIDE IF NOT ALREADY BELOW SMALL CRAFT CRITERIA.

TUESDAY-TUESDAY NIGHT...W-NW WIND GUSTS MAY REMAIN AOA 25 KT ON
THE OUTER WATERS TUE WITH SEAS AOA 5 FT THROUGH TUE NIGHT.

OUTLOOK...WEDNESDAY THROUGH SATURDAY...

WED INTO THU...
BRIEF LULL IN SCA CONDITIONS DURING THE DAY WED GIVE WAY TO SMALL
CRAFT ADVISORY CONDITIONS WED NIGHT INTO THU. THIS WILL BE FOR
INCREASING SEAS 5-7 FT ESPECIALLY SOUTHERN AND EASTERN OUTER
WATERS...AND GUSTY WINDS OF 20-30 KT AS A COLD FRONT CROSSES WED
NIGHT INTO EARLY THU. IF SMALL CRAFT ADVISORIES ARE DROPPED FOR
WED...THEY WILL LIKELY NEED TO BE REISSUED BY WED EVENING.

FRI INTO SAT...
WINDS WILL REMAIN BELOW SCA THRESHOLDS THROUGHOUT THE PERIOD.
REMNANT SWELL OF 5-7 FT WILL GRADUALLY SUBSIDE INTO THE DAY
FRI...SO SMALL CRAFT ADVISORIES WILL LIKELY LINGER INTO FRI.
HOWEVER...CONDITIONS ARE EXPECTED TO REMAIN BELOW SCA THRESHOLDS
FRI NIGHT INTO SAT.

&&

.FIRE WEATHER...
ALTHOUGH SOME AREAS IN SE MA RECEIVED 1+ INCHES OF RAINFALL
SAT INTO SUN MORNING...MOST OF THE REGION HAD LESS THAN A HALF
INCH. SO...RAINFALL DEFICITS CONTINUE FOR THE MONTH OF MAY.

CONDITIONS EARLY THIS WEEK WILL BE CONDUCIVE FOR ELEVATED FIRE
WEATHER THROUGH WEDNESDAY AT LEAST. TUESDAY...MIN RH VALUES ARE
IN THE 20S AGAIN. HOWEVER...WINDS WILL BE LIGHTER AS HIGH PRESSURE
WORKS IN...WITH GUSTS AROUND 15 MPH. BY WEDNESDAY...STRONGER S TO
SW WINDS COULD APPROACH 20-30 MPH AT TIMES AGAIN WITH MIN RH
VALUES NEAR 30 TO 40 PERCENT.

LOOKING AHEAD...SOME SHOWERS...AND POSSIBLY EVEN AN ISOLATED
THREAT FOR LIGHTNING IS POSSIBLE WED NIGHT INTO EARLY THU...WITH
A RETURN TO DRY WEATHER FOR LATE IN THE WEEK.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR CTZ002>004.
MA...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR MAZ005>007-
     012>014-017-018-020-021-026.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR MAZ009>011.
NH...NONE.
RI...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR RIZ001-003-
     006.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR
     ANZ232>234.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ235-237-
     250.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ254>256.
-- End Changed Discussion --

&&

$$
SYNOPSIS...DOODY/EVT
NEAR TERM...DOODY/EVT
SHORT TERM...EVT
LONG TERM...DOODY
AVIATION...DOODY/EVT
MARINE...DOODY/EVT
FIRE WEATHER...