-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 191149
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
749 AM EDT SUN MAY 19 2013

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE TODAY. A WARM FRONT WILL BRING A
FEW SHOWERS TO THE REGION TONIGHT AS IT CROSSES THE AREA. THE
FRONT IS EXPECTED TO STALL OVER CENTRAL NEW ENGLAND MONDAY. A BACK
DOOR COLD FRONT WILL BRING A DRY AND LESS HUMID AIR MASS INTO MOST
OF SOUTHERN NEW ENGLAND TUE BEFORE RETREATING BACK AS A WARM FRONT
ON WED. SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS ARE
ANTICIPATED TUE AFTERNOON IN THE CONNECTICUT RIVER VALLEY AND OVER
MOST OF SOUTHERN NEW ENGLAND WEDNESDAY AND THURSDAY. A COOLER AND
LESS HUMID AIR MASS IS EXPECTED FOR THE COMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
730 AM UPDATE...
SCT SHOWERS HAVE WORKED THEIR WAY INTO SW CT AND POCKETS OF
STRATUS/FOG ERN MA BUT THINK ENOUGH S/SW GRADIENT TO HELP THINK
AND PUSH BACK OFFSHORE IN NEXT HOUR OR TWO. THINK PROGRESSION OF
SHOWERS WILL BE FAIRLY SLOW AND SHOULD INITIALLY BE QUITE LIGHT.
THERE IS A RISK OF ISOLD ELEVATED THUNDER WEST LATE AS WARM
ADVECTION AND INCREASING MOISTURE REFLECTED BY INCREASING K INDEX
VALUES.

320 AM UPDATE...

PLENTY OF MID/HIGH CLOUDS ACROSS SOUTHERN NEW ENGLAND THIS MORNING
BUT LOW CLOUD DECK OVER COASTAL ME/NH PUSHED BACK INTO
MANCHESTER...LAWRENCE AND BEVERLY. HIGH RES MODELS INDICATE THAT
IS ABOUT AS FAR S AS IT WILL GET BEFORE IT BEGINS TO PUSH
OFFSHORE BY MID MORNING.

STILL NOT SEEING MUCH IN WAY OF SHOWERS TO OUR SW AS ACTIVITY OVER
NJ IS PIVOTING OFFSHORE. HIGH RES MODELS ARE INSISTENT WE WILL
SEE DEVELOPMENT INTO HUDSON VALLEY AND CT BEFORE DAYBREAK.
RAP/HRRR BRING SHOWERS TO CT VALLEY BY 8 AM AND TO REST OF AREA
BEFORE NOON. NOT SEEING MUCH SUPPORT FOR THAT TO OCCUR BASED UPON
RADAR MOSAIC SO WE CONTINUED WITH SLOWER TREND SHOWN BY 00Z NAM...
NAMELY ANY SHOWERS HOLD OFF UNTIL THIS AFTERNOON. ANY RAINFALL IS
EXPECTED TO BE LIGHT.

TEMPS ARE A CHALLENGE TODAY WITH VARYING AMOUNTS OF CLOUD COVER.
SHOULD BE ABLE TO WARM QUICKLY THIS MORNING BEFORE SKIES CLOUD
OVER AREAWIDE THIS AFTERNOON. WE WILL CONTINUE TO SHOW WARMEST
TEMPS ACROSS RI/EASTERN MA /UPPER 60S/ AND USED A NAM/GFS MOS
BLEND AS CONFIDENCE IS MODERATE AT BEST.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
WARM FRONT LIFTS THROUGH REGION TONIGHT ACCOMPANIED BY FEW SHOWERS.
DYNAMICS ARE NOT OVERLY STRONG AS MAIN FORCING MECHANISM APPEARS
TO BE MID LEVEL WARM ADVECTION...ESPECIALLY ACROSS CT/RI/SE MA
WHERE WE EXPECT GREATEST COVERAGE. MODELS DO SHOW MARGINAL
INSTABILITY AND MEAGER CAPE SO INCLUDED ISOLATED THUNDER...AGAIN
MAINLY FOR LOCATIONS CLOSER TO S COAST. HIGHER DEWPOINT AIR ON
S/SW WINDS SHOULD PROMOTE PATCHY FOG FORMATION.

ALTHOUGH FRONT REMAINS TO OUR N MON...CROSS SECTIONS SHOW PLENTY
OF LOWER LEVEL MOISTURE WHICH MEANS CLOUD COVER WILL BE TOUGH TO
BREAK...ESPECIALLY NEAR S COAST WHERE SW FLOW WILL MAINTAIN DEEPER
MARINE LAYER. MODELS DIFFER IN COVERAGE AND TIMING OF
PRECIPITATION...BUT IT APPEARS WE WILL SEE AT LEAST SCATTERED
SHOWERS/ISOLATED THUNDER ACROSS INTERIOR THROUGHOUT DAY.

EXPECT WARMER/MORE HUMID DAY BUT NOT QUITE SURE WE CAN REACH
LOWER 80S AS INDICATED BY GFS MOS. TONED BACK A BIT BY BLENDING
NAM MOS AND 2M TEMPERATURES WHICH YIELDS HIGHS IN MID-UPPER 70S
EXCEPT 60S AROUND CAPE COD/ISLANDS WITH ONSHORE FLOW.

&&

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

HIGHLIGHTS...
* BACKDOOR COLD FRONT WILL REDUCE HUMIDITY AND CHANCE FOR SHOWERS/TSTMS
  EAST OF THE CT RIVER VALLEY ON TUE
* WARM AND HUMID WITH SCATTERED SHOWERS AND POSSIBLE TSTMS WED AFTERNOON
  THRU AT LEAST THU NIGHT
* COOLER AND DRIER AIR EXPECTED FOR THE COMING WEEKEND

MEDIUM RANGE MODELS PAINT A CONSISTENT SYNOPTIC SCALE PICTURE FOR
TUE THRU THU BUT STILL DIFFICULT TO RESOLVE TIMING AND
DISTRIBUTION OF SHORT WAVE ENERGY. BOTH 00Z GFS AND 00Z ECMWF
MODELS SUGGEST A BACKDOOR INTRUSION OF DRY AIR ON TUE INTO WED
MORNING THRU ALL EXCEPT POSSIBLY THE CT RIVER VALLEY. THE FRONT
LIFTS BACK NE DURING WED AFTERNOON. THUS FOR TUE WILL RELEGATE
CHANCE SHOWERS/TSTMS JUST TO SW ZONES. THEN THE ECMWF AND GFS
OPERATIONAL RUNS AND THE PRIOR RUN ENSEMBLES DIVERGE ON CHARACTER
OF EASTERN TROF THAT WILL FLUSH OUT THE AIR MASS LATE IN THE WEEK.
THE ECMWF HAS BEEN CONSISTENTLY SHOWING A CONSOLIDATED NORTHERN
STREAM TROF DRIVING A COLD FRONT THRU THU NIGHT/EARLY FRI MORNING.
THE GFS OPERATIONAL RUN AND ENSEMBLE MEAN KEEP A NOTABLE CHUNK OF
ENERGY SOUTH OF THE MAIN STREAM NORTHERN FLOW AND RESULTS IN THE
SPIN UP OF A SFC LOW OFF THE MID ATLC COAST AND WET DAY FOR MUCH
OF THE FORECAST AREA ON FRI.

TUE-WED...WILL INDICATE SCT SHOWERS AND WIDELY SCT TSTMS DURING
THIS PERIOD WITH HIGHEST POPS DURING THE DIURNALLY FAVORED
AFTERNOON/EVENING PERIOD AND SW OF A EEN-ORH-EWB LINE GIVEN THE
POTENTIAL FOR A BACKDOOR AIR MASS TO EASE INTO OUR NE ZONES.

THE TREND FOR BOTH THE GFS AND ECMWF MODELS TO BRING A BACKDOOR
INTRUSION OF DRY AIR INTO THE REGION ON TUE LENDS GREATER
CONFIDENCE THAT ANY SHOWER ACTIVITY TUE WILL LIKELY BE RESTRICTED
TO THE CT RIVER VALLEY AREA. HAVE ALSO LOWERED DEWPOINTS. ONSHORE
FLOW WILL KEEP TEMPS COOLER ALONG THE E COAST. THUS FOR EASTERN MA
AND RI TUE NO LONGER LOOKS TO BE A WARM AND HUMID DAY.

WED...THE WARM AND HUMID AIR MASS ADVANCES BACK NE AND SO DOES
THE RISK OF SCT SHOWERS AND WIDELY SCT TSTMS IN THE AFTERNOON AND
EARLY EVENING.

THU...RELATIVELY STRONG SHORT WAVE TROF AND COLD FRONT WILL BE
APPROACHING FROM THE WEST LATE IN THE DAY. ANTICIPATING RELATIVELY
UNSTABLE AIR MASS AND INCREASING VERTICAL SHEAR THU AFTERNOON AND
EVENING. IT IS POSSIBLE THAT WE MAY EXPERIENCE A FEW STRONG/SEVERE
TSTMS LATE THU AFTERNOON AND EVENING...MOST LIKELY WESTERN HALF OF
AREA GIVEN THE TIMING OF THE SHORT WAVE AND FRONT. RAISED POPS TO
HIGH CHANCE LATE THU AND THU NIGHT.

FRI...HAVE RELATIVELY LOW CONFIDENCE FOR THIS DAY DUE TO MODEL
DISPARITY IN HANDLING THE CONFIGURATION OF THE EASTERN TROF
ENERGY. FOR NOW...PLAN TO HAVE SHOWERS INTO AT LEAST FRI MORNING
FOR MOST LOCATIONS AND PERHAPS HAVE A CHANCE OF SHOWERS THAT
PERSIST OVER THE SE ZONES...OR AT LEAST THE CAPE AND ISLANDS...TO
PERSIST TO AT LEAST FRI EVENING. IN ESSENCE AM LEANING TOWARD
ECMWF SOLUTION WHICH HAS REMAINED RELATIVELY CONSISTENT AND SEEMS
TO BE FAVORED BY WPC. THE GFS HAS...HOWEVER...BEEN FAIRLY
CONSISTENT IN ITS SOLUTION AND THE OPERATIONAL RUN IS SUPPORTED BY
ITS ENSEMBLES SO CANNOT COMPLETELY RULE THAT OUT. IF INDEED A
SURFACE LOW WERE TO DEVELOP AS ADVERTISED BY THE GFS...WE COULD
SEE WINDS APPROACHING MARGINAL GALES ON THE WATER AND A RISK FOR
SOME COASTAL FLOODING WITH THE LATE FRI EVENING HIGH TIDE...WHICH
IS QUITE HIGH ASTRONOMICALLY TO BEGIN WITH. THAT DOES NOT SEEM TO
BE THE MOST LIKELY SOLUTION AT THIS TIME BUT WILL NEED TO KEEP AN
EYE ON IT.

SAT...MODERATE TO HIGH CONFIDENCE OF A COOL DRY AIR MASS
DOMINATING THE REGION.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

OVERVIEW...HIGH CONFIDENCE AFTER PATCHES OF MORNING FOG DISAPPEAR.

AREA OF IFR CIGS DUE TO ST AND POCKETS OF IFR VSBYS FROM FOG NE
MA SHOULD BEGIN TO LIFT OUT TO THE NE BY AROUND 14Z. OTHERWISE
VFR CIGS AOA 080 E AND AOA 035 W EXPECTED THIS MORNING...BEFORE
SLOWLY LOWERING TO MVFR THIS AFTERNOON FROM SW TO NE.

S/SW GRADIENT REMAINS WEAK BUT SEA BREEZES SHOULD BE LIMITED TO S
COAST TODAY. DOES NOT APPEAR FAVORABLE ALONG E MA COAST BUT IF IT
WERE TO OCCUR IT WOULD BE EARLY THIS AFTERNOON.

FAIRLY CONFIDENT ON PERIOD OF SHOWERS LATE THIS AFTERNOON BAF/BDL
WHICH SHIFTS TO RI/MA COASTS THIS EVENING. SHOWERS WILL BE MOST
NUMEROUS NEAR S COAST TONIGHT. ISOLD THUNDER POSSIBLE IN W LATE
THIS AFTERNOON/EARLY EVENING AND THIS EVENING IN THE E.

ALTHOUGH SHOWERS EXIT BEFORE DAYBREAK...ADDITIONAL SHOWERS/
THUNDER MAY REDEVELOP DURING DAY MON AS WARM FRONT LIFTS TO OUR
N. APPEARS COVERAGE WILL BE SCATTERED AT BEST...WITH INTERIOR
SOUTHERN NEW ENGLAND HAVING BEST CHANCE.

KBOS TERMINAL...LOW CONFIDENCE IN HANDLING FOG BANK UNTIL MID
MORNING...THEN HIGH CONFIDENCE IN TAF. THINK FOG WILL FLIRT WITH
AIRPORT FOR ONLY AN HOUR OR TWO BEFORE SW GRADIENT...ALBEIT
WEAK...HELPS LIFT IT OFFSHORE. NOT CONFIDENT SEA BREEZE WILL
OCCUR BUT IF IT DOES IT WOULD BE 16Z- 19Z.

KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. MVFR CIGS POSSIBLE
AFT ABOUT 19 OR 20Z AS SCT SHOWERS SATURATE LOWER PORTION OF
ATMOSPHERE.

OUTLOOK...TUESDAY THROUGH THURSDAY...

MODERATE CONFIDENCE THROUGH THE PERIOD.

TUE...SCT MVFR CIGS/VSBYS IN SCT SHOWERS AND ISOLD TSTMS CT
VALLEY...VFR ELSEWHERE.

WED...AREAS OF MVFR CIGS/VSBYS IN SCT SHOWERS AND WIDELY SCT
TSTMS.

THU...MVFR CIGS/VSBYS WITH FOG AND STRATUS IN THE MORNING
AND THEN AGAIN IN THE AFTERNOON WITH SCT SHOWERS AND TSTMS.
POSSIBLY A FEW STRONG TSTMS LATE THU AFTERNOON/EVENING.
-- 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 MON.

HIGH PRESSURE MOVING OFFSHORE WILL MAINTAIN LIGHT WINDS/FLAT SEAS
TODAY. COULD SEE FEW LIGHT SHOWERS LATER THIS AFTERNOON AS WARM
FRONT APPROACHES.

INCREASING S/SW FLOW DEVELOPS TONIGHT AND MON AS WARM FRONT LIFTS
INTO CENTRAL NEW ENGLAND. THIS WILL BRING SLOWLY BUILDING SEAS TO
OUTER WATERS WHERE CURRENT SCA HAS BEEN EXTENDED INTO MON. ADDED
RI/BLOCK IS SOUNDS TO SCA AS WELL...AND BUZZARDS BAY/VINEYARD
SOUND WHERE SW WINDS WILL CREATE STEEP WAVES DURING TIMES OF
DEPARTING TIDE /HIGH TIDE 355 AM AND 437 PM MON AT NEW BEDFORD/.

SHOULD ALSO SEE PERIOD OF SHOWERS/ISOLATED THUNDER TONIGHT AND
MORE WIDELY SCATTERED ACTIVITY MON. PATCHY DENSE FOG PROBABLE
AROUND CAPE COD AND ISLANDS.

OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...

MODERATE CONFIDENCE THROUGH THE PERIOD.

A LEFT OVER SWELL AT OR A LITTLE ABOVE 7 FT LIKELY TUE...SUBSIDING
WED. BUILDING SEAS LIKELY THU AS SW FLOW STRENGTHENS. AREAS OF
FOG LIKELY WED NIGHT THRU THU. WINDS MAY APPROACH SCA LEVELS LATE
THU AND THU NIGHT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 6 AM TO 7 PM EDT
     MONDAY FOR ANZ233>235-237.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 AM TO 7 PM EDT
     MONDAY FOR ANZ254-255.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM MIDNIGHT TONIGHT
     TO 7 PM EDT MONDAY FOR ANZ256.

&&

$$
SYNOPSIS...JWD/THOMPSON
NEAR TERM...JWD/THOMPSON
SHORT TERM...JWD
LONG TERM...THOMPSON
AVIATION...JWD/THOMPSON
MARINE...JWD/THOMPSON