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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 200527
AFDBOX

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

.SYNOPSIS...
A WARM FRONT WILL CROSS THE AREA OVERNIGHT WITH SHOWERS...AND THEN
STALL IN THE VICINITY OF SOUTHERN NEW ENGLAND THROUGH MONDAY
NIGHT. THE FRONT WILL MOVE THRU SOUTHERN NEW ENGLAND TUE.
SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS ARE ANTICIPATED TUE
THRU THU. A COOLER AND LESS HUMID AIR MASS IS EXPECTED FOR THE
COMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --
130 AM UPDATE...

BACK EDGE OF SHOWERS HAS JUST ABOUT REACHED COAST. HRRR/RAP
CONTINUE TO HAVE A GOOD HANDLE ON RADAR TRENDS AND BRING SHOWERS
TO AN END BEFORE DAYBREAK /LAST ON CAPE COD AND ISLANDS/.

OTHERWISE CLOUDS REMAIN LOCKED IN ACROSS SOUTHERN NEW ENGLAND WITH
PATCHY FOG AND DRIZZLE. THIS WILL BE RULE THROUGH DAYBREAK.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
TOMORROW...
SFC WARM FRONT REMAINS ENTRENCHED ACROSS NH AND CENTRAL NEW
ENGLAND THROUGH MUCH OF THE DAY...ALLOWING SRN NEW ENGLAND INTO
THE WARM SECTOR. WITH THE ACTUAL BOUNDARY TO THE N...AFTER SOME
EARLY MORNING FOG/STRATUS IS ALLOWED TO BURN OFF...SOME BREAKS OF
SUN ARE POSSIBLE THROUGH ABOUT MID DAY. THIS WILL HAVE TO BE
MONITORED SINCE WITHIN THE WARM SECTOR SFC DWPTS SHOULD REACH
+15-18C AND TEMPS INCREASING TO THE UPPER 70S TO AROUND 80F IN
SPOTS ESPECIALLY IF THE SUN DOES SHINE THROUGH. WHILE FORCING
MECHANISMS ARE MINIMAL AT BEST...GUIDANCE DOES SUGGEST THE FRONT
MAKES A SLOW SLIDE TO THE S DURING THE DAY. WITH WARM-HUMID
AIRMASS IN PLACE...SFC LI VALUES DIP TO 0 TO -3 WITH ABOUT
500-1000 J/KG OF SB CAPE TO WORK WITH. THEREFORE...MAY SEE A
THREAT FOR SOME DAYTIME T-STORMS ESPECIALLY AWAY FROM THE S
COAST...WHERE SLY MARINE FLOW AND EARLY DAY STRATUS WILL KEEP
TEMPS DOWN...INCREASING STABILITY. GIVEN THIS...HAVE SOME CHANCE
POPS FOR THUNDER IN THE INTERIOR DURING THE AFTERNOON HOURS. SHEAR
IS MINIMAL GIVEN THE WEAK RIDGING FLOW ALOFT...AND NORMALIZED CAPE
IS QUITE LOW SUGGESTING SKINNY PROFILE...SO HEAVY RAIN APPEARS TO
BE THE PRIMARY THREAT WITH ANY STORMS AND WILL INCLUDE THAT WITH
WX FOR THIS UPDATE.

MON NIGHT...
WARM FRONT CONTINUES SLOW MIGRATION OVER SRN NEW ENGLAND THROUGH
THE OVERNIGHT HOURS...BUT WILL LIKELY ONLY HANG SOMEWHERE THROUGH
CENTRAL PORTIONS OF THE CWA BY 12Z TUE. THEREFORE...WITH DIURNAL
HEATING EARLY...MAY SEE LINGERING -SHRA/TSTMS INTO THE EVENING
HOURS UNTIL THE COLUMN IS ABLE TO STABILIZE. WITH SOME DRIER AIR
FILTERING BEHIND THE FRONT TO THE N...MAY ACTUALLY SEE PRECIP COME
TO AN END DURING THE OVERNIGHT HOURS. HOWEVER...WITH HIGH DWPT AIR
HANGING IN THE WARM SECTOR NEAR THE S COAST...A RETURN TO
FOG/STRATUS IS LIKELY ONCE AGAIN. EXPECT THAT OVERNIGHT MINS WILL
REMAIN IN THE UPPER 50S TO LOW 60S WITH A FAIR AMOUNT OF CLOUD
COVER EVEN IF THE PRECIPITATION DOES COMPLETELY CEASE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
HIGHLIGHTS...
  * WARM FRONT MOVES THRU SOUTHERN NEW ENGLAND TUE
  * SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE TUE-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.

TUESDAY...HIGH PRESSURE MOVES OFFSHORE AS LOW PRESSURE MOVES INTO
THE GREAT LAKES BRINGING A FRONT NORTHWARD ACROSS SOUTHERN NEW
ENGLAND.  EXPECT MOSTLY CLOUDY TO CLOUDY SKIES AND SCATTERED TO
WIDESPREAD SHOWERS TO OCCUR WITH THE WARM FRONT.  THERE IS ENOUGH
INSTABILITY INDICATED BY THE MODELS THAT THERE WILL LIKELY BE SOME
SCATTERED THUNDERSTORMS AS WELL.  WITH THE WARM FRONT ACROSS THE
AREA...COULD SEE SOME VARIABILITY IN TEMPERATURES WITH LOWER TEMPS
NORTH OF THE FRONT AND WARMER...MORE HUMID AIR SOUTH OF THE FRONT.
LOOKING AT HIGH TEMPS A FEW DEGREES ABOVE NORMAL...USED A BLEND OF
GUIDANCE FOR THE TEMPS.

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.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
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.
-- 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 NIGHT.

A WARM FRONT CROSSES THE WATERS TONIGHT WITH A MIX OF SHOWERS AND
POTENTIALLY DENSE FOG /PARTICULARLY OVER THE SRN WATERS/ WHICH
WILL REDUCE VISIBILITIES AT TIMES. THE FRONT STALLS NORTH OF THE
WATERS DURING THE DAY MONDAY.

WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT THRESHOLDS THROUGH
THE PERIOD. HOWEVER...WITH LONG-FETCH AND PERSISTENT S FLOW...A
S-SW SWELL WILL BUILD DURING THE OVERNIGHT HOURS ON S COASTAL
WATERS...REACHING 5-7 FT AT TIMES. THIS SWELL IS EXPECTED TO
LINGER UNTIL MON NIGHT. THEREFORE...SMALL CRAFT ADVISORY FOR SEAS
REMAINS IN PLACE.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...WINDS AND SEAS REMAIN BELOW 5 FT.  VISIBILITY MAY BE
LIMITED AT TIMES IN ISOLATED SHOWERS AND FOG.

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.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

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