-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 201101
AFDBOX

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

.SYNOPSIS...
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.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...

-- Changed Discussion --
7 AM UPDATE...

WARM FRONT PROGRESSING NORTHWARD AND WILL MOVE THROUGH THE REGION
BY LATE MORNING OR MIDDAY AT THE LATEST. TEMPS ALREADY OFF TO A
MILD START WITH READINGS IN THE U50S AND L60S AT 7 AM. TEMPS WILL
SOAR THROUGHT THE 70S TO AROUND 80 THIS AFTERNOON AWAY FROM THE
SHORE. ONCE BOUNDARY LIFTS NORTH OF THE AREA NOT MUCH OF A FOCUS
FOR CONVECTION. IN ADDITION 0-6KM WIND FIELD DROPS BELOW 30 KT
THIS AFTERNOON. THUS ANY CONVECTION WOULD NOT BE ORGANIZED OR
WIDESPREAD. PREVIOUS FORECAST CAPTURES THIS WELL SO NO MAJOR
CHANGES WITH THIS 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.
-- End Changed Discussion --

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
HIGHLIGHTS...

  * WARM AND MUGGY WED/THU THEN TURNING COOLER AND LESS HUMID FRI
  * SCATTERED SHOWERS AND THUNDERSTORMS WED AND THU
  * DRY BUT COOLER THAN NORMAL FOR MEMORIAL DAY WEEKEND

GOOD OVERALL AGREEMENT ON THE LARGE SCALE FLOW INCLUDING FRONTAL
POSITIONS FROM THE 12Z/19 GEFS AND ECENS. BOTH OF THESE ENSEMBLE
DATA SETS HAVE A BACKDOOR FRONT SAGGING SOUTHWARD THROUGH THE
SOUTHERN NEW ENGLAND TUE NIGHT THEN LIFTING NORTH OF THE REGION WED
AND THU WITH TRUE WARM SECTOR OVERSPREADING THE AREA. BOTH ENSEMBLES
OFFER +16C AIRMASS AT 850 MB AND +20C AT 925 MB OVER THE REGION
WED. THUS POTENTIAL FOR TEMPS TO SOAR INTO THE 80S BOTH DAYS IF
SUNSHINE DEVELOPS. IT WILL BE MUGGY AS WELL WITH DEW PTS IN THE 60S.
THIS WILL RESULT IN WARM NIGHTS /WED AND THU/ ALONG WITH PATCHY FOG.

SCATTERED SHOWERS AND THUNDERSTORMS LIKELY BOTH WED AND THU GIVEN
WARM SECTOR OVER THE AREA BOTH DAYS. ALSO MODELS IN GOOD AGREEMENT
ON CONVECTION ALONG OR NEAR THE WARM FRONT TUE EVENING/NIGHT.
CONVECTION WILL BE MORE WIDESPREAD DURING PEAK HEATING HOURS OF THE
AFTERNOON AND LINGERING INTO THE EARLY EVENING BOTH DAYS. ENSEMBLES
SUGGEST INSTABILITY GREATER WED (MEAN CAPE ABOUT 1000J/KG) THAN THU.
HOWEVER APPROACHING COLD FRONT WILL YIELD GREATER FRONTAL
CONVERGENCE THU ALONG WITH STRONGER JET DYNAMICS /0-6KM DEEP LAYER
SHEAR/...SO CONVECTION MAY BE MORE ORGANIZED/NUMEROUS THU THAN WED.
IN ADDITION GEFS SUGGEST INSTABILITY RIDGE ACROSS NY/PA AND NJ.
THEREFORE WESTERN NEW ENGLAND HAS GREATEST RISK FOR STRONG TO
PERHAPS SEVERE TSTMS WED AND THU. GIVEN INSTABILITY AND PWATS OF +1
TO +2 STD HEAVY DOWNPOURS ARE POSSIBLE WITH ANY CONVECTION.

GOOD MODEL AGREEMENT THAT FRONTAL PASSAGE WILL OCCUR SOMETIME LATE
THU OR FRI. 00Z GFS SLOWER WITH FROPA AS IT DEVELOPS A WAVE ALONG
THE FRONT. AT THIS TIME RANGE PREFER NOT TO CHASE A SINGLE
DETERMINISTIC SOLUTION SO WILL FOLLOW PRES PATTERN FROM GEFS AND
ECENS. THIS SUGGEST FRI WILL BE OUR TRANSITION DAY FROM WARM AND
MUGGY TO A DRY...MUCH COOLER AND LESS HUMID AIRMASS FOR MEMORIAL DAY
WEEKEND. IN FACT BY SAT BOTH GEFS AND ECENS HAVE A 1030MB HIGH
SETTLING OVER THE GREAT LAKES WITH CORE OF THIS ANOMALOUS COOL
AIRMASS /850 TEMPS 0C TO +2C/ ACROSS NORTHERN MA/SOUTHWEST NH...THEN
SLOWLY MODERATING BY MON. HENCE MILD DAYS BUT COOL NIGHTS. IN FACT
THERE COULD BE SOME PATCHY FROST ACROSS NORTHWEST MA INTO SOUTHWEST
NH WITH TEMPS DIPPING INTO THE MU30S SAT AND SUN MORNING!

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

7 AM UPDATE...
NO CHANGE TO PREVIOUS FORECAST. FORECAST REMAINS ON TRACK.

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...TUESDAY NIGHT THROUGH FRIDAY...

TUESDAY THROUGH THURSDAY NIGHT...MODERATE CONFIDENCE.  VERY
UNSETTLED PATTERN WITH VARIABILITY BETWEEN VFR CONDITIONS AND
MVFR/IFR CONDITIONS IN SHRA/TSRA/FOG. A FEW STRONG TO SEVERE TSTMS
POSSIBLE WED AND THU.

FRIDAY...MODERATE CONFIDENCE.  CONDITIONS SHOULD IMPROVE ALONG WITH
A WIND SHIFT FROM WEST TO EAST AS COLD FRONT MOVES THROUGH REGION.
-- 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 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...TUESDAY THROUGH FRIDAY...

TUESDAY NIGHT... BACKDOOR FRONT SLIPS ACROSS THE AREA WITH NE WINDS
LIKELY OVER THE NORTHERN WATERS AND SW WINDS ACROSS SOUTHERN WATERS.
RAIN AND FOG WILL REDUCE VSBY. MODEST WIND AT BEST WITH MARGINAL
SWELL.

WED AND THU... WARM FRONT LIFTS NORTH OF THE AREA WITH MODEST SSW
WINDS DEVELOPING ACROSS THE WATERS. SSW WINDS MAY INCREASE TO 20-25
KT FROM LATE WED INTO THU AHEAD OF APPROACHING COLD FRONT. SHOWERS
AND TSTMS SHOULD BE MOST NUMEROUS THU WITH APPROACHING COLD FRONT.

FRIDAY...COLD FRONT ALONG WITH WIND SHIFT FROM SSW TO WNW SHOULD
COMMENCE. VSBY WILL IMPROVE WITH THE WIND.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 AM EDT TUESDAY
     FOR ANZ233>235-237.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT TUESDAY
     FOR ANZ254>256.
-- End Changed Discussion --

&&

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