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000
FXUS61 KBOX 210834
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
434 AM EDT TUE MAY 21 2013

.SYNOPSIS...

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A BACKDOOR COLD FRONT WILL DROP SOUTH ACROSS THE REGION LATE
TONIGHT AND TUESDAY RESULTING IN BRIEFLY COOLER WEATHER ACROSS
EASTERN NEW ENGLAND AND CHANCE OF THUNDERSTORMS IN WESTERN NEW
ENGLAND. WARM AND HUMID CONDITIONS CONTINUE INTO THURSDAY AND
FRIDAY WITH SCATTERED SHOWERS AND STRONG THUNDERSTORMS POSSIBLE. A
COOLER AND LESS HUMID AIR MASS IS EXPECTED FOR THE COMING WEEKEND.
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&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
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STILL TRYING TO NAIL DOWN THE LOCATION OF A BACK-DOOR COLD FRONT
ACROSS EASTERN MA THIS MORNING. WINDS ARE VERY LIGHT ACROSS MOST
OF SOUTHERN NEW ENGLAND. LATEST MESONET WIND DATA INDICATED THIS
FRONT HAD MOVED ONSHORE ACROSS THE NORTH SHORE. FARTHER SOUTH...
ESPECIALLY SOUTH OF BOSTON...THIS FRONT HAS APPARENTLY NOT MADE
MUCH PROGRESS.

THE LOCATION OF THIS FRONTAL BOUNDARY WILL PLAY A CRUCIAL ROLE IN
OUR WEATHER TODAY. SIGNIFICANTLY LOWER TEMPERATURES WILL BE FELT
EAST OF THIS FRONT...WITH ANOTHER DAY OF SUMMER-LIKE WARMTH WELL
TO THE WEST. CLOUD COVER WILL ALSO PLAY A MAJOR ROLE AS WELL.
MARINE STRATUS AND PATCHY DENSE FOG WILL TAKE A WHILE TO DISSIPATE
THIS MORNING.

THESE TEMPERATURES IN TURN WILL INFLUENCE HOW MUCH CONVECTIVE
INSTABILITY IS GENERATED TODAY. LATEST SPC MESOANALYSIS HAD
1000-200 J/KG OF MOST UNSTABLE CAPE. MIXED-LAYER CAPE WAS NON-
EXISTENT. MARGINAL MID-LEVEL LAPSE RATES THIS MORNING SHOULD MEAN
THE BROKEN CONVECTIVE LINE MOVING EAST ACROSS NY STATE SHOULD
WEAKEN AS IT MOVES EAST OF THE CT RIVER VALLEY ACROSS SOUTHERN NH.
THAT SAID...STILL MAINTAINED AT LEAST AN ISOLATED THREAT OF
SHOWERS AND THUNDERSTORMS NORTH OF ROUTE 2 IN MA AND SOUTHERN NH
THIS MORNING.

AS FOR LATER THIS AFTERNOON...THINKING AIRMASS WILL DESTABILIZE TO
RESULT IN MIXED LAYER CAPES OF 750-1250 J/KG. MARGINAL MID-LEVEL
LAPSE RATES SHOULD CONTINUE. GREATEST THREAT OF SHOWERS AND
THUNDERSTORMS SHOULD BE ACROSS THE INTERIOR. HOWEVER...CANNOT RULE
OUT THE POSSIBILITY OF ELEVATED CONVECTION MOVING FARTHER EAST
OVER THE SURFACE MARINE LAYER. SHOULD THIS HAPPEN...THINKING
CONVECTION WOULD BE WEAKENING AS IT DOES SO.

TEMPERATURES WERE A BLEND OF THE MOS GUIDANCE.
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&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
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BACK-DOOR COLD FRONT SHOULD MOVE FARTHER NORTH LATE TONIGHT INTO
WEDNESDAY AS A WARM FRONT. THIS SHOULD ALLOW FOR A WARMER DAY
ACROSS EASTERN MA. STILL NOT CONVINCED SYNOPTIC FLOW WILL BE
STRONG ENOUGH TO PREVENT LOCAL SEABREEZES FROM DEVELOPING...SO
TEMPERATURES WILL BE TRICKY ALONG THE IMMEDIATE COASTLINES.

AM CURRENTLY EXPECTING A BRIEF DIMINISHMENT OF ANY CONVECTION
LATE TONIGHT INTO WEDNESDAY MORNING...AS SUGGESTED BY CLIMATOLOGY.
INSTABILITY REGENERATES WEDNESDAY AFTERNOON...SO KEPT AT LEAST A
CHANCE OF SHOWERS AND THUNDERSTORMS IN THE FORECAST. THE LOWEST
RISK FOR SHOWERS AND THUNDERSTORMS WILL BE ACROSS THE CAPE AND
ISLANDS...WHERE ANOTHER ROUND OF LOW CLOUDS AND FOG WILL KEEP
TEMPERATURES LOWER.

USED A BLEND OF MOS GUIDANCE ONCE AGAIN FOR TEMPERATURES.
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&&

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

* SCATTERED SHOWERS AND THUNDERSTORMS THURS INTO FRIDAY
* COOLER AND LESS HUMID FOR THE WEEKEND

CONFIDENCE LEVEL/MODEL GUIDANCE...MODERATE CONFIDENCE IN THE
OVERALL FORECAST...YET LOW CONFIDENCE ON MODEL PERFORMANCE. THE
00Z GFS/NAM SIGNIFICANTLY SLOWED DOWN THE DIGGING TROUGH FOR THE
NORTHEAST. THE REST OF THE MODEL GUIDANCE FOLLOWED SUIT BUT NOT AS
DRASTICALLY. LEANED FORECAST TOWARDS EC/UKMET WHICH WHERE IN
BETWEEN THE 12Z AND 00Z GUIDANCE AS WELL AS PREV FORECAST. OVERALL
HAVE HIGH CONFIDENCE THAT PRECIP WILL OCCUR THURS AND MODERATE
CONFIDENCE FOR FRIDAY. HIGH CONFIDENCE IN A COOL DOWN FOR THE WEEK
WITH MOD CONFIDENCE FOR SEASONAL TEMPS AND DRY FORECAST FOR
BEGINNING OF THE WORK WEEK.

DETAILS...

THURSDAY INTO FRIDAY...

APPROACHING UPPER LEVEL TROUGH WILL BRING A ROUND OF PRECIP AND
THUNDER TO THE REGION. STILL SOME TIMING ISSUES AS MODELS STILL
DIFFER ON EXACT LOCATION AND MESOSCALE PARAMETERS.
REGARDLESS...SOUTHERN NEW ENGLAND WILL BE LOCATED IN THE WARM SECTOR
OF THE SYSTEM ALLOWING HIGHER DEWPOINTS AND THEREFORE MUGGY
CONDITIONS. TEMPS WILL WARM INTO THE 80S. BELIEVE DIURNAL PRECIP
WILL BE THE MAIN TREAT FOR THIS DAY...WITH STRONG STORMS POSSIBLE.
MAIN THREAT OF THESE STORMS WILL BE HAIL...STRONG WINDS AND HEAVY
DOWNPOURS. A COLD FRONT WILL BEGIN TO APPROACH THE REGION THURSDAY
NIGHT AND MOVE THROUGH THE AREA ON FRIDAY. THIS WILL CHANGE THE
CONVECTIVE MODE TO MORE OF A POSSIBLE SQUALL LINE ON FRIDAY.
CONVECTIVE PARAMETERS APPEAR TO BE MORE IN LINE DUE TO THE SLOW DOWN
OF THE OVERALL SYSTEM. ONLY THING TRULY LACKING IS THE AMOUNT OF
INSTABILITY AS CLOUD DEBRIS WILL BE AROUND FROM THE PREV NIGHTS
SHOWERS/THUNDER. IF STORMS DO DEVELOP THEN BELIEVE THE MAIN THREAT
WILL BE STRONG WINDS AND HEAVY DOWNPOURS AS PWATS REACH CLOSE TO 1.5
IN.

THIS WEEKEND...

UPPER LEVEL TROUGH WILL PUSH THROUGH OVER THE WEEK...CAA WILL
BRING A THERMAL TROUGH INTO THE REGION. THIS WILL DROP TEMPS WELL
BELOW SEASONAL AVG. AM NOT ANTICIPATED ANY FROST/FREEZE HEADLINES
AT THIS TIME BUT MAY NEED TO MONITOR IN THE FUTURE AS THE ENTIRE
AREA IS NOW IN THE GROWING SEASON. EXPECT MAINLY DRY WEATHER FOR
THE WEEKEND AND TEMPS IN THE MID TO UPPER 60S.

MONDAY AND BEYOND...SURFACE HIGH PRESSURE WILL BE IN CONTROL FOR
THE FIRST HALF OF NEXT WEEK. THIS WILL HELP TEMPS REACH SEASONAL
CONDITIONS. APPEARS THAT THERE IS LIMITED MOISTURE...HOWEVER
CANNOT RULE OUT A SPOT SHOWER OR TWO...ESP IF SEA BREEZE DEVELOPS.
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&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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FORECASTER CONFIDENCE LEVELS...

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

OVERVIEW...MODERATE CONFIDENCE IN TIMING AND AREAL COVERAGE OF
STRATUS AND FOG BOTH TUESDAY AND WEDNESDAY MORNING.

PATCHY MVFR CONDITIONS HAVE SPREAD NORTH ACROSS SOUTHERN NEW
ENGLAND THIS MORNING...MAINLY DUE TO VISIBILITY. SOME LOWER CLOUDS
ACCOMPANYING THESE LOWER VISIBILITIES...BUT CIGS ARE DIFFICULT TO
FIND. ONLY TERMINALS ON THE CAPE AND ISLANDS...AS WELL AS THE
IMMEDIATE SOUTH COAST...SHOWING ANY IFR CIGS THIS MORNING.

TODAY...CONDITIONS GRADUALLY IMPROVE TO VFR FROM WEST TO EAST.
SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON...ESPECIALLY
ACROSS THE CT RIVER VALLEY.

TONIGHT...WIDESPREAD IFR/LIFR IN STRATUS AND FOG REDEVELOP.

WEDNESDAY...PRETTY MUCH A REPEAT OF TUESDAY. GRADUAL IMPROVEMENT
TO VFR/MVFR FROM WEST TO EAST.

KBOS TERMINAL...MODERATE CONFIDENCE...MAINLY DUE TO TIMING OF VFR
IMPROVEMENT.

KBDL TERMINAL...MODERATE CONFIDENCE...MAINLY DUE TO TIMING OF VFR
IMPROVEMENT.

OUTLOOK...THURSDAY THROUGH SATURDAY...

THURSDAY INTO FRIDAY...LOW TO MODERATE CONFIDENCE. MODERATE
CONFIDENCE ON SEA BREEZE DEVELOPMENTS. VERY UNSETTLED PATTERN WITH
VARIABILITY BETWEEN VFR CONDITIONS AND MVFR/IFR CONDITIONS IN
SHRA/TSRA/FOG. IMPROVING CONDITIONS LATE FRIDAY NIGHT INTO
SATURDAY MORNING.

SATURDAY...HIGH CONFIDENCE. VFR.
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&&

.MARINE...
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FORECASTER CONFIDENCE LEVELS...

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

HIGH CONFIDENCE THROUGH WEDNESDAY.

WINDS AND SEAS EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA MOST OF TODAY. LEANED MORE HEAVILY UPON THE SWAN WAVE
GUIDANCE AS THE WNA WAVE GUIDANCE APPEARS TO BE TOO HIGH. STILL
EXPECTING AREAS OF FOG TO PERSIST THROUGH TODAY BEFORE EXPANDING
ONCE AGAIN TONIGHT.

INCREASING SOUTHWEST WINDS WEDNESDAY MAY LEAD TO DEVELOPMENT OF
MARGINAL 5 FT SEAS ACROSS THE SOUTHERN OUTER COASTAL WATERS OF MA
AND RI. WILL HOLD OFF ON ISSUING ANOTHER SMALL CRAFT ADVISORY
RIGHT NOW TO AVOID CONFUSION WITH EXISTING ADVISORY.

OUTLOOK...THURSDAY THROUGH SATURDAY...

WEDNESDAY...SEAS INCREASE AS HIGH PRESSURE MOVES AWAY FROM THE
WATERS.  SOUTHWESTERLY WINDS GUST TO NEAR 25 KTS.  SCA WILL BE
NECESSARY FOR SEAS IF NOT WINDS AS WELL. VISIBILITY MAY BE
LIMITED AT TIMES IN SCATTERED SHOWERS AND THUNDERSTORMS.

THURSDAY INTO FRIDAY...HIGH CONFIDENCE. APPROACHING STORM SYSTEM
WILL INCREASE SEAS ABOVE 5FT DURING THIS TIME PERIOD...SCA WILL BE
NEEDED. EXPECT LOW VSBYS IN HEAVY SHOWERS AND SOME THUNDER AS WELL.
BELIEVE FRIDAY IS THE BETTER DAY FOR TSTORMS ACROSS THE WATERS AS
COLD FRONT WILL PUSH THROUGH NEW ENGLAND ON FRIDAY.

THIS WEEKEND...MODERATE CONFIDENCE. SEAS WILL REMAIN ABOVE SCA
FOR MOST OF THE WEEKEND ESP FOR THE OUTER WATERS. GUSTY NW BEHIND
THE FRONT WILL BRING GUSTS CLOSE TO GALE FORCE SAT INTO SAT NIGHT.
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&&

.BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE.
MA...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MAZ020>024.
NH...NONE.
RI...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR RIZ006>008.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT THIS
     MORNING FOR ANZ255-256.
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&&

$$
SYNOPSIS...BELK/DUNTEN
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...DUNTEN
AVIATION...BELK/DUNTEN
MARINE...BELK/DUNTEN