-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 192017
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
417 PM EDT SUN MAY 19 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 MONDAY MORNING/...
BAND OF WARM ADVECTION SHOWERS CONTINUE TO MOVE E THROUGH THE
REGION THIS AFTERNOON. CURRENTLY...THIS BAND IS LINED FROM SW NH
INTO SRN RI...AND MAKING SLOW PROGRESSION TO THE E. THE PRIMARY
REGION FOR THE SLOW MOVEMENT E HAS BEEN THE NEAR 15-20F DEWPOINT
DEPRESSION WHICH HAS BEEN DIFFICULT TO OVERCOME. ALL
SOUNDINGS...INCLUDING THE LAPS IN THE E...SHOW THE COLUMN MOISTURE
LOADING FROM THE TOP DOWN THROUGH THE EVENING...SO SUSPECT THESE
-SHRA WILL BE EVERYWHERE BY THE TIME THE SUN SETS.

THE SFC WARM FRONT ASSOCIATED WITH THESE -SHRA IS CURRENTLY
SLIDING IN FROM THE W...SO EXPECT THAT THE THREAT FOR -SHRA WILL
LINGER WELL INTO THE OVERNIGHT HOURS AS THIS FRONT MAKES ITS SLOW
PASSAGE. NOT EXPECTING MUCH IN THE WAY OF QPF WITH THIS BUT MOST
LOCATIONS HAVE DAMP GROUND BY DAYBREAK. THE ADDED MOISTURE IN THE
COLUMN /SOUNDINGS SUGGEST 1.0-1.5 INCHES PWAT BY 12Z/ WILL LEAD TO
A FAIR AMOUNT OF CLOUDS AND FOG AFTER THE -SHRA COME TO AN END
DURING THE EARLY MORNING HOURS. LOW CONFIDENCE IN WIDESPREAD DENSE
FOG...BUT A FEW SPOTS MAY DIP TO NEAR 1/4 MILE OR LESS AT TIMES.

THE WARM FRONT WILL STALL SOMEWHERE IN THE VICINITY OF NH BY THE
EARLY MORNING HOURS...SO SUSPECT THAT MUCH OF SRN NEW ENGLAND WILL
BE IN THE WARM SECTOR BY 12Z. ALSO...WITH SOME WEAK MID LVL
RIDGING WITHIN THIS WARM SECTOR...COULD ACTUALLY SEE SOME BREAKS
OF EARLY MORNING SUN ESPECIALLY AWAY FROM THE S AND E COASTS WHERE
STRATUS LINGERS.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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 THROUGH SUNDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

HIGH CONFIDENCE THROUGH THE AFTERNOON...LOWER CONFIDENCE IN TIMING
OF MVFR/IFR DURING THE OVERNIGHT HOURS.

MAINLY VFR SAVE FOR IN AN AREA OF -SHRA IN WRN MA AND CENTRAL CT.
THIS BAND OF -SHRA AND MVFR CIGS WILL GRADUALLY SHIFT TO THE E
INTO THE EVENING. NOT CONFIDENT IN EXACT TIMING...BUT THE TAF
TREND REPRESENTS THE ROUGH TIMING OF BOTH -SHRA ONSET AND MVFR.
MAY SEE SOME MVFR/IFR FOG AS THE -SHRA MOVES OUT AFTER 06Z AT MANY
OF THE TERMINALS. SOME IMPROVEMENT TO VFR IS POSSIBLE EARLY
MON...ESPECIALLY AWAY FROM THE S COASTAL TERMINALS. AN ISOLATED
THUNDERSTORM IS ALSO POSSIBLE OVERNIGHT...AND AGAIN DURING THE
AFTERNOON MON.

KBOS TERMINAL...OVERALL HIGH CONFIDENCE IN THE TAF TRENDS...BUT
LOWER CONFIDENCE IN EXACT TIMING. SEA BREEZE CONTINUES INTO EARLY
EVENING HOURS...WITH THE POSSIBILITY OF SOME BKN LOW STRATUS.
EXPECT MVFR IN -SHRA AND FOG DURING THE OVERNIGHT HOURS WITH SOME
IMPROVEMENT MON MORNING. LOW PROBABILITY OF AN ISOLATED RUMBLE OF
THUNDER TONIGHT AND AGAIN TOMORROW AFTERNOON.

KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. MVFR WILL LIKELY
DOMINATE INTO THE OVERNIGHT HOURS...WITH SOME IMPROVEMENT
FOLLOWING SOME -SHRA/FOG OVERNIGHT. THE BEST CHANCE FOR MVFR WILL
BE DURING THE MORNING MON. LOW PROBABILITY OF AN ISOLATED T-STORM
OVERNIGHT AND AGAIN MON.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY 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...
-- Changed Discussion --
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.
-- 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 MONDAY TO 2
     AM EDT TUESDAY FOR ANZ233>235-237.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 AM MONDAY TO 8
     AM EDT TUESDAY FOR ANZ254-255.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM MIDNIGHT TONIGHT
     TO 8 AM EDT TUESDAY FOR ANZ256.

&&

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