-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 200717
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
317 AM EDT MON MAY 20 2013

.SYNOPSIS...
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A WARM FRONT LIFTING THROUGH THE REGION WILL BRING A FEW SHOWERS
OR THUNDERSTORMS TODAY AS IT HEADS INTO CENTRAL NEW ENGLAND. THE
FRONT WILL DROP BACK SOUTH ON TUESDAY RESULTING IN BRIEFLY COOLER
WEATHER...BEFORE WARM AND HUMID CONDITIONS RETURN WEDNESDAY AND
THURSDAY WITH SCATTERED SHOWERS AND THUNDERSTORMS. IT WILL TURN
COOLER AND LESS HUMID NEXT WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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315 AM UPDATE...

LAST OF SHOWERS WERE EXITING CAPE COD AND ISLANDS EARLY THIS
MORNING. CLOUDS REMAIN LOCKED IN WITH PATCHY FOG AND DRIZZLE...
WHICH WILL PERSIST THROUGH MID MORNING. THEREAFTER MODEL CROSS
SECTIONS SHOW SOME DRYING THROUGH COLUMN AS WEAK WARM FRONT LIFTS
TO OUR N. THIS SHOULD ALLOW FOR BREAKS OF SUNSHINE TO DEVELOP
LATER THIS MORNING AND THIS AFTERNOON FOR MUCH OF SOUTHERN NEW
ENGLAND. EXCEPTION WILL BE NEAR S COAST...CAPE COD AND ISLANDS
WHERE MARINE LAYER SHOULD HOLD STRONG GIVEN SW FLOW.

POTENTIAL FOR CONVECTION THIS AFTERNOON IS LIMITED BY LACK OF
INSTABILITY AS SB CAPES ONLY FORECAST TO BE AS HIGH AS 500
J/KG...WEAK MID LEVEL LAPSE RATES OF LESS THAN 5C/KM...AND
MARGINAL 0-6KM SHEAR OF 30KT. THAT SAID WE DO EXPECT TO SEE AT
LEAST WIDELY SCATTERED SHOWERS/STORMS DEVELOP ACROSS INTERIOR.
MAINTAINED CHANCE POPS AWAY FROM S COAST...ALTHOUGH BEST CHANCE
LOOKS TO BE ACROSS SW NH AND NW MA. HRRR SHOWS SCATTERED ACTIVITY
DEVELOPING IN THOSE AREAS AFTER 18Z.

CERTAINLY LOOKS LIKE A WARMER AND SOMEWHAT MORE HUMID DAY WITH
HIGHS RANGING FROM 60S ALONG S COAST TO 70S AND LOWER 80S
ELSEWHERE. USED A BLEND OF NAM/GFS MOS.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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WARM FRONT STALLS ACROSS CENTRAL NEW ENGLAND TONIGHT. THIS WILL
MAINTAIN LIGHT S/SW FLOW ACROSS REGION AND WITH PLENTY OF LOW
LEVEL MOISTURE...CONFIDENCE IS HIGH ON SEEING LOW CLOUDS/FOG AND
POSSIBLY DRIZZLE SPREAD INLAND FROM COAST. POTENTIAL IS THERE FOR
AREAS OF DENSE FOG...ESPECIALLY AROUND CAPE COD AND ISLANDS.
OTHERWISE NO SIGNIFICANT RAINFALL IS EXPECTED AS BEST DYNAMICS
STAY TO OUR N AND W. RELATIVELY MILD NIGHT WITH LOWS HOLDING IN
50S/LOWER 60S...WHICH IS CLOSER TO NAM MOS.

WEAK UPPER RIDGE BUILDING ACROSS NEW YORK STATE WILL FORCE FRONT
BACK SOUTHWARD TUE AS A BACKDOOR COLD FRONT. MODELS IN GOOD
AGREEMENT IN DROPPING FRONT THROUGH TUE AFTERNOON...BUT GFS SEEMS
TO OVERDO CONVECTION RIDING E ALONG BOUNDARY FROM GREAT LAKES. NAM
SEEMS MUCH MORE REASONABLE IN STABILIZING AIRMASS OVER SOUTHERN
NEW ENGLAND AS FLOW TURNS MORE E/SE AND FOCUSES ANY CONVECTION TO
OUR W/N WHERE IT BECOMES MORE UNSTABLE. WE ARE NOT THINKING WE
WILL SEE MUCH IN WAY OF SHOWERS/STORMS DEVELOP...ALTHOUGH IT IS
POSSIBLE A FEW SHOWERS MAKE IT INTO WESTERN NEW ENGLAND BY END OF
DAY.

SHOULD BE WIDE RANGE IN TEMPERATURES TUE DUE TO ONSHORE FLOW...
FROM LOWER 60S ALONG E MA COASTLINE INCLUDING CAPE COD TO UPPER
70S ACROSS CT RIVER VALLEY. LEANED MORE TOWARD NAM MOS WHICH
CAPTURES THIS WELL.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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HIGHLIGHTS...
  * SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE WED-THU
  * COOLER...LESS HUMID FOR THE WEEKEND

MODELS ARE IN DECENT AGREEMENT THROUGH MUCH OF THE LONG TERM.  THERE
ARE SOME TIMING DISCREPANCIES THROUGHOUT THE LONG TERM BETWEEN THE
ECMWF AND THE GFS...AS WELL AS THE NAM TUE. THE NAM IS QUICKER THAN
EITHER THE ECMWF OR GFS WITH A WARM FRONT MOVING NORTH THROUGH THE
REGION TUES.  THE GFS THEN WHISKS ALONG AND BRINGS LOW PRESSURE
THROUGH QUEBEC MORE QUICKLY WED WITH A COLD FRONT MOVING THROUGH
SOUTHERN NEW ENGLAND SOONER ON THU THAN THE ECMWF.  HOWEVER...THE
OVERALL SYNOPTIC PATTERN IS FAIRLY WELL IN LINE THROUGHOUT THE
PERIOD.  GENERALLY EXPECTING A MORE UNSETTLED BUT WARMER PATTERN
THROUGH THE WORK WEEK...WITH QUIETER BUT COOLER WEATHER FRIDAY AND
INTO THE WEEKEND.

WEDNESDAY AND THURSDAY...THERE ARE SOME TIMING QUESTIONS HERE
REGARDING THE LOW PRESSURE SYSTEM MOVING THROUGH SOUTHERN CANADA
AND THE ACCOMPANYING COLD FRONT THAT WILL MOVE THROUGH SOUTHERN
NEW ENGLAND. NEITHER THE GFS NOR THE ECMWF HAVE THE COLD FRONT
MOVING THROUGH SOUTHERN NEW ENGLAND UNTIL AFTER MIDNIGHT THURSDAY
NIGHT. HOWEVER...THE DIFFERENCES IN THE POSITION AND PATH OF THE
LOW PRESSURE COULD IMPACT THE AMOUNT OF CLOUDS AS WELL AS THE BEST
PLACE FOR SHOWERS AND THUNDERSTORMS ACROSS THE REGION. FOR NOW
HAVE OPTED FOR HIGH END CHANCE POPS WITH SLIGHT CHANCE TO CHANCE
THUNDER PRETTY MUCH ACROSS THE BOARD. INSTABILITY PARAMETERS ARE
SUCH THAT EXPECT THUNDER TO BE FAIRLY WIDESPREAD.

FRIDAY...AS MENTIONED ABOVE...THE COLD FRONT WILL MOVE THROUGH
SOUTHERN NEW ENGLAND SOMETIME ON FRIDAY...WITH THE GFS BRINGING IT
THROUGH THE AREA BETWEEN MIDNIGHT AND 6 AM AND THE ECMWF BRINGING IT
THROUGH ABOUT MIDDAY.  THE TIMING OF THIS FRONT WILL HAVE A LARGE
IMPACT ON THE WEATHER AS MOSTLY CLOUDY SKIES AND WARMER...MORE HUMID
AIR CAN BE FOUND AHEAD OF THE FRONT WHILE CLEARING SKIES AND
COOLER...LESS HUMID AIR WILL MOVE IN BEHIND THE FRONT.  IF THIS
OCCURS DURING THE EARLY MORNING...HIGH TEMPERATURES WILL BE LOWER
BUT THE AREA WILL SEE MORE SUN...WHILE IF IT DOESN/T OCCUR UNTIL
MIDDAY COULD SEE WARMER HIGHS BUT LESS SUN.

SATURDAY AND SUNDAY...WITH HIGH PRESSURE DOMINANT OVER SOUTHERN NEW
ENGLAND...EXPECT A PLEASANT WEEKEND WITH HIGH TEMPERATURES A FEW
DEGREES BELOW NORMAL AND SUNNY SKIES.
-- End Changed Discussion --

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

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

MODERATE CONFIDENCE THROUGH TUE.

WIDESPREAD IFR/LIFR THROUGH 12Z IN LOW CLOUDS/FOG/DRIZZLE. GRADUAL
IMPROVEMENT TO MVFR EXPECTED 12Z-15Z AND EVENTUALLY VFR BY 18Z
EXCEPT AROUND CAPE COD AND ISLANDS WHERE IFR LIKELY TO PERSIST ALL
DAY. SCT SHOWERS WILL REFORM ACROSS INTERIOR AFTER 18Z WITH
ISOLATED THUNDER ALSO POSSIBLE.

SHOULD SEE RAPID DETERIORATION THIS EVENING TO IFR/LIFR 23Z-03Z
AS LOW CLOUDS/FOG/DRIZZLE RETURN IN LIGHT ONSHORE FLOW. WILL BE
HARDER FOR IFR TO ERODE TUE WITH PERSISTENT E/SE WIND...BUT EXPECT
ALL BUT CAPE/ISLANDS TO IMPROVE TO MVFR CIGS BY 18Z.

KBOS TERMINAL...MODERATE CONFIDENCE. CONFIDENT ON TIMING OF
IMPROVEMENT THIS MORNING...BUT CIGS MAY ONLY LIFT TO 025 THROUGH
18Z.

KBDL TERMINAL...MODERATE CONFIDENCE. MAY BE 2-3 HOURS TOO FAST ON
IMPROVEMENT TO MVFR CIGS THIS MORNING.

OUTLOOK...WEDNESDAY THROUGH FRIDAY...

WEDNESDAY THROUGH THURSDAY NIGHT...LOW TO MODERATE CONFIDENCE.
VERY UNSETTLED PATTERN WITH VARIABILITY BETWEEN VFR CONDITIONS AND
MVFR/IFR CONDITIONS IN SHRA/TSRA/FOG.

FRIDAY...MODERATE CONFIDENCE.  CONDITIONS SHOULD IMPROVE TO VFR FROM
WEST TO EAST AS COLD FRONT MOVES THROUGH REGION.

&&

.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 TUE.

WARM FRONT LIFTS N OF COASTAL WATERS TODAY AND STALLS OVER CENTRAL
NEW ENGLAND. LIGHT S/SW FLOW DEVELOPS ACROSS WATERS BUT SEAS
SLOWLY BUILD IN SOUTHERLY SWELL...MOST NOTABLY ACROSS S COASTAL
WATERS WHERE SCA REMAINS POSTED. ALTHOUGH SW FLOW IS MODEST AT
BEST IT SHOULD STILL CREATE STEEP WAVES ON BUZZARDS BAY AND
VINEYARD SOUND DURING OUTGOING TIDE THIS AFTERNOON...SO MAINTAINED
SCA FOR THOSE AREAS AS WELL.

EXPECT AREAS OF DENSE FOG TONIGHT INTO TUE WITH PERSISTENT SW
FLOW...ESPECIALLY AROUND CAPE COD AND ISLANDS. FRONT DROPS BACK S
TUE AND SHIFTS WINDS TO E/SE...SO VSBYS SHOULD IMPROVE TUE
AFTERNOON. SEAS SHOULD BEGIN TO SUBSIDE AS WELL DUE TO DECAYING
SOUTHERLY SWELL.

OUTLOOK...WEDNESDAY THROUGH FRIDAY...

WEDNESDAY...SEAS INCREASE AS HIGH PRESSURE MOVES AWAY FROM THE
WATERS. SOUTHERLY 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...SEAS REMAIN ABOVE 5 FEET AS LOW PRESSURE MOVES INTO THE
MARITIMES AND A COLD FRONT APPROACHES THE WATERS.  SOUTHERLY 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.  WINDS INCREASE OVERNIGHT WITH APPROACHING COLD FRONT.

FRIDAY...SEAS BEGIN TO DIMINISH AS HIGH PRESSURE BUILDS OVER THE
WATERS.  WINDS INCREASE TO 25 TO 30KTS WITH COLD FRONTAL PASSAGE.
WINDS SHOULD BE OUT OF THE SOUTH AHEAD OF THE FRONT...SHIFTING TO
THE NORTHWEST BEHIND THE FRONT.
-- End Changed Discussion --

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 6 AM THIS MORNING
     TO 2 AM EDT TUESDAY FOR ANZ233>235-237.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT TUESDAY
     FOR ANZ254-255.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT TUESDAY
     FOR ANZ256.

&&

$$
SYNOPSIS...NOCERA/JWD
NEAR TERM...JWD
SHORT TERM...JWD
LONG TERM...RLG
AVIATION...NOCERA/JWD
MARINE...NOCERA/JWD