-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 211419
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1019 AM EDT TUE MAY 21 2013

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
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10 AM UPDATE...
CLOUDS HAVE CLEARED ACROSS MUCH OF THE REGION...EXCEPT LOW CLOUDS
AND FOG CONTINUED ACROSS PORTIONS OF E COASTAL MA. MODELS SUGGEST
CLOUDS AND FOG WILL BRIEFLY ERODE THROUGH ABOUT 18Z...THEN LOW
CLOUDS FROM THE N AND NE WILL EXPAND SW ACROSS THE REGION 18-00Z
AS THE BACKDOOR FRONT PUSHES SW. THIS FRONT WILL REMAIN ACROSS
FAR NE ZONES INTO THE AFTERNOON WHICH WILL ALLOW TEMPS TO REACH
INTO THE 80S ACROSS A GOOD PORTION OF THE AREA...WITH UPPER 80S
LOWER CT VALLEY. COOLER READINGS WILL BE FOUND ALONG THE S COAST
AND ESPECIALLY NE MA AND SE NH AND THIS COOLER AIR WILL MOVE SW
AFT 18Z WITH TEMPS FALLING SHARPLY THROUGH THE 70S AND INTO THE
60S BY EVENING ACROSS MUCH OF EASTERN HALF OF NEW ENG...WITH 50S
NE MA.

NEXT CONCERN IS POTENTIAL FOR CONVECTION. SPC MESOANALYSIS
ALREADY SHOWING MLCAPES INCREASING TO 1000 J/KG IN THE CT VALLEY
AND EXPECT MLCAPES 1000-2000 J/KG ACROSS CENTRAL AND WESTERN NEW
ENG THIS AFTERNOON WITH HIGHER CAPES BECOMING MORE FOCUSED IN THE
CT VALLEY LATE AFTERNOON AS THE FRONT PUSHES SW. MID LEVEL LAPSE
RATES ARE FAVORABLE AROUND 6.5-7 C/KM. DEEP LAYER SHEAR IS
MARGINAL BUT VALUES 20-30 KT ARE CERTAINLY ENOUGH TO SUPPORT
SOME ORGANIZATION OF ANY STORMS THAT DEVELOP. SO WE ARE EXPECTING
SCT TSTMS TO DEVELOP IN THE INTERIOR WITH POTENTIAL FOR A FEW
STRONG TO SEVERE STORMS. HRRR IS TARGETING MASS PIKE REGION EARLY
THIS AFTERNOON WITH ACTIVITY SHIFTING FURTHER WEST TO THE CT
VALLEY MID/LATE AFTERNOON.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY/...
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.

&&

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

&&

.AVIATION /14Z 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 THIS MORNING AND WEDNESDAY MORNING.

PATCHY IFR CONDITIONS PORTIONS OF E COASTAL MA AND CAPE/ISLANDS
MAY BRIEFLY IMPROVE TO VFR FOR A TIME EARLY THIS
AFTERNOON...EXCEPT IFR FOG PERSISTING AT ACK. SHOWERS AND
THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON...ESPECIALLY ACROSS THE
INTERIOR.

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. CONDITIONS SHOULD
TEMPORARILY IMPROVE TO VFR AROUND MIDDAY BUT FALL BACK TO IFR BY
MID TO LATE AFTERNOON. TIMING UNCERTAIN.

KBDL TERMINAL...MODERATE CONFIDENCE.

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.
-- End Changed Discussion --

&&

.MARINE...
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...

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.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...NONE.
MA...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MAZ006-007-
     015-016-019>024.
NH...NONE.
RI...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR RIZ006>008.
MARINE...NONE.
-- End Changed Discussion --

&&

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