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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 211748
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
148 PM 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/...
-- Changed Discussion --
145 PM UPDATE...
CU FIELD IS INCREASING ACROSS SNE AWAY FROM THE COASTLINE...WHILE
LOW CLOUDS ASSOCD WITH BACKDOOR FRONT LINGERING ACROSS NE MA AND
SE NH. SPC MESOANALYSIS SHOWS A RATHER UNSTABLE ENVIRONMENT WITH
MLCAPES NEARING 2000 J/KG ACROSS LOWER CT VALLEY AND MID LEVEL
LAPSE RATES 6.5 TO 7 C/KM. THIS IS A FAVORABLE ENVIRONMENT FOR
CONVECTION TO DEVELOP AND EXPECT SHOWERS/STORMS TO DEVELOP AROUND
MID AFTERNOON. BACKDOOR FRONT OVER NE MA WILL BEGIN TO PUSH SW
DURING MID TO LATE AFTERNOON AND WILL PROVIDE A FOCUS FOR
CONVECTION. BEST CHC FOR TSTMS WILL BE ACROSS CENTRAL AND WESTERN
MA...N CT AND POSSIBLY N RI...WITH FOCUS FOR ACTIVITY SHIFTING TO
CT VALLEY LATE AFTERNOON AND TOWARD EVENING AS THE BACKDOOR FRONT
MOVES SW. 0-6KM SHEAR IN THE UNSTABLE AIR IS 25-30 KT WHICH IS
MORE THAN ENOUGH FOR STORM ORGANIZATION GIVEN MAGNITUDE OF CAPE.
EXPECT A FEW STRONG TO POSSIBLY SEVERE STORMS.

TEMPS HAVE RISEN INTO THE 80S SOUTH OF THE FRONT...WHILE READINGS
ARE IN THE 60S ACROSS NE MA. THIS COOLER AIR WILL BEGIN TO SPREAD
SW TOWARD 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 /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
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 THROUGH WEDNESDAY MORNING.

CONDITIONS HAVE IMPROVED TO VFR ACROSS MUCH OF THE REGION...WITH
IFR PERSISTING AT ACK AND STRATUS/PATCHY FOG ACROSS NE MA TO BOS
HARBOR. EXPECT THE IFR CONDITIONS TO GRADUALLY EXPAND SW ACROSS
THE REGION LATE AFTERNOON AND EVENING WHILE THE FOG BANK NEAR THE
ISLANDS GRADUALLY LIFTS NORTH. SCT CONVECTION EXPECTED TO DEVELOP
WITH BRIEF MVFR/IFR CONDITIONS IN SHOWERS/TSTMS. WIDESPREAD
IFR/LIFR LIKELY TONIGHT...GRADUALLY IMPROVING TO VFR 14-16Z AS SW
WINDS DEVELOP...BUT IFR MAY PERSIST MOST OF THE DAY AT ACK.

KBOS TERMINAL...HIGH CONFIDENCE IN LOWERING TREND...LOWER
CONFIDENCE IN TIMING. IFR/LIFR CIGS/VSBYS WILL
REDEVELOP...POSSIBLY AS SOON AS LATE AFTERNOON.

KBDL TERMINAL...HIGH CONFIDENCE THAT CONDITIONS LOWER TO IFR
TONIGHT. EXACT TIMING UNCERTAIN.

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...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.
-- End Changed Discussion --

&&

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