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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 222359
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
759 PM EDT WED MAY 22 2013

.SYNOPSIS...
A STALLED FRONT ACROSS SOUTHERN NH AND NORTHEAST MASS WILL MOVE
NORTH AS A WARM FRONT TONIGHT. EXPECT WARM...HUMID AND SHOWERY
WEATHER TO CONTINUE THURSDAY INTO SATURDAY. SCATTERED STRONG
THUNDERSTORMS ARE POSSIBLE THURSDAY AND FRIDAY. A COLD FRONT WILL
BE SLOW TO CLEAR...SO SHOWERS MAY LINGER INTO SUNDAY...THEN COOLER
AND LESS HUMID CONDITIONS SHOULD MOVE IN FOR THE HOLIDAY INTO NEXT
WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
745 PM UPDATE...
A FEW LEFTOVER THUNDERSTORMS THAT WERE ACROSS S NH/N MA AT 23Z
HAVE MOVED INTO THE COOLER AIR TO THE E AND WEAKENED. BREAKS IN
THE OVERCAST NOTED ACROSS THE BERKSHIRES INTO EASTERN NY STATE.
LOWER CLOUDS REMAIN ALONG THE COAST WITH E WINDS IN PLACE. ALSO
NOTING COASTAL FOG WITH VSBYS BLO 1SM AT KCQX...KACK AND KBID.

AS NOTED BY PREVIOUS FORECASTER...AIRMASS ACROSS CENTRAL AND
WESTERN AREAS REMAINS UNSTABLE...AND NOTING MORE SHOWERS/TSTMS
ACROSS CENTRAL PA/NY STATE. SOME MAY REACH INTO WESTERN AREAS OVER
THE NEXT FEW HOURS. PREVIOUS FORECAST FOR PRECIP LOOKED PRETTY
GOOD SO MADE FEW IF ANY CHANGES.

HAVE UPDATED TEMPS/DEWPTS/WINDS TO BRING CONDITIONS CURRENT.

PREVIOUS DISCUSSION...
UPPER RIDGE SHIFTS EAST OF US OVERNIGHT...SHIFTING UPPER LEVEL
WINDS TO SOUTHWEST. THIS SHOULD MOTIVATE THE SURFACE FRONT TO
MOVE NORTH AS A WARM FRONT. THE EASTERLY MARINE SURFACE FLOW OVER
THE MERRIMACK VALLEY AND METRO BOSTON WOULD THEN BECOME SOUTHERLY
AND BRING IN WARMER MORE HUMID SURFACE AIR.

CONVECTIVE PARAMETERS REMAIN UNSTABLE OVERNIGHT. OVERALL POPS
WILL DIMINISH...BUT WITH A LINGERING CHANCE OF THUNDER. THE
GREATEST RISK WILL BE ACROSS THE CT VALLEY AND CENTRAL HILLS WITH
LESS OF A RISK ALONG THE COAST.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
THURSDAY...
SURFACE LOW PRESSURE MOVES OUT OF THE GREAT LAKES AND UP THE ST
LAWRENCE VALLEY. MEANWHILE THE SUPPORTING UPPER TROUGH DIGS OVER
THE GREAT LAKES AND TURNS THE UPPER FLOW OVER US PAST SOUTHWEST
AND TOWARD SOUTH. THIS WILL SLOW DOWN THE PROGRESS OF THE SURFACE
COLD FRONT AND KEEP NEW ENGLAND IN THE WARM HUMID UNSETTLED
AIRMASS. CONVECTIVE PARAMETERS REMAIN UNSTABLE WITH PREFERENCE FOR
THE CENTRAL HILLS/CT VALLEY/BERKSHIRE EAST SLOPE REGIONS. WILL
NEED TO MONITOR FOR POTENTIAL SEVERE WEATHER. ALSO...PRECIPITABLE
WATER VALUES ARE FORECAST TO INCREASE TO BETWEEN 1.5 AND 1.75
INCHES WHICH INCREASES THE LIKELIHOOD OF HEAVY DOWNPOURS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
HIGHLIGHTS...

* SHOWERS AND THUNDERSTORMS FRIDAY AND SATURDAY
* UNSETTLED WEATHER CONTINUES SUNDAY...THEN SLOWLY IMPROVING
  MONDAY
* DRY BUT COOL CONDITIONS INTO THE MIDDLE OF NEXT WEEK

OVERVIEW AND MODEL PREFERENCES...

NOTING A MAJOR PATTERN CHANGE ACROSS THE LOWER 48 AS SEEN ON THE
LAST FEW OP RUNS OF THE GFS...ECMWF AND...TO A LESSER DEGREE...THE
UKMET. MODELS SIGNALING DIGGING UPPER TROUGH/CUTOFF LOW PRES
MOVING INTO THE WESTERN U.S. WHICH BUILDS A LARGE RIDGE OVER THE
PLAINS STATES...THEN IN TURN DIGS ANOTHER TROUGH MOVING OUT OF THE
GREAT LAKES TO THE EASTERN SEABOARD. LOOKS LIKE H5 CUTOFF LOW
FORMS BY SATURDAY ALONG THE MID ATLC COAST...SLOWING THE
PROGRESSION OF THE COLD FRONT ACROSS NEW ENGLAND INTO THE WEEKEND
AT LEAST. SOME TIMING ISSUES WITH THE EXIT OF THE SYSTEM...MAINLY
DUE TO HOW MUCH THE UPPER SYSTEM DIGS AS WELL AS POSSIBLE NEGATIVE
TILTING OF THE TROUGH.

AT THIS POINT...LEANED TOWARD THE WPC GUIDANCE SOLUTION WHICH USED
MAINLY MODEL ENSEMBLES...THEN BLENDED IN THE 12Z GFS/00Z ECMWF
WHICH WAS MORE AGGRESSIVE IN KEEPING INCLEMENT CONDITIONS GOING
THROUGH A GOOD PORTION OF THE UPCOMING HOLIDAY WEEKEND. DUE TO
TIMING OF THE EXIT OF THE UPPER SYSTEM...CONFIDENCE IS LOWER FOR
TRANSITION TIME /FOR NOW...DURING SUNDAY/. CONDITIONS LOOK TO
IMPROVE AS HIGH PRES BUILDS OUT OF CENTRAL CANADA FOR MON THROUGH
NEXT WED.

DETAILS...

THURSDAY NIGHT...COLD FRONT SLOWS DOWN ACROSS NY STATE AS H5 LONG
WAVE TROUGH STARTS TO DIVE TOWARD THE APPALACHIANS. HAVE KEPT
THREAT OF SHOWERS/CHANCE TSTMS GOING. WILL ALSO SEE SOME HEAVY
DOWNPOURS AS AXIS OF PW VALUES OF 1.5 TO 1.75 INCHES MOVES ACROSS.
WITH S-SW WIND IN PLACE...EXPECT TEMPS TO ONLY FALL BACK TO THE
MID 50S TO AROUND 60.

FRIDAY-SATURDAY...AS THE UPPER TROUGH DIGS ACROSS THE APPALACHIANS
AND EVENTUALLY DEVELOPING H5 CUTOFF LOW OVER THE MID ATLC...THIS
WILL SLOW THE PROGRESSION OF THE COLD FRONT ACROSS THE REGION
DURING THIS TIMEFRAME.

WILL SEE SHOWERS AND TSTMS...WITH BEST CHANCES FOR CONVECTION
DURING THE LATE MORNING INTO THE EVENING HOURS ON FRIDAY AS BEST
INSTABILITY MOVES THROUGH. WOULD NOT BE SURPRISED TO SEE SOME
STRONGER STORMS MAINLY E OF A LINE FROM KMHT-KORH-KIJD WHERE SOME
PEEKS OF SUN MAY BREAK OUT. PW VALUES WILL STILL BE AROUND 1.5
INCHES...SO HEAVY DOWNPOURS STILL POSSIBLE AS WELL AS GUSTY WINDS
AND EVEN SMALL HAIL. CAN NOT RULE OUT SOME THUNDER EVEN DURING THE
NIGHTTIME HOURS. COOLER AIR STARTS TO WORK INTO WESTERN AREAS AS
THE LOW SLOWLY MOVES E TOWARD SE MA AND THE CAPE SAT.

DEPENDING UPON WHETHER CLOUDS BREAK ACROSS W MA/SW NH...TEMPS MAY
FALL BACK TO THE UPPER 30S...OTHERWISE LOWS SAT NIGHT WILL FALL TO
THE 40S.

SUNDAY...FOR NOW...THIS APPEARS TO BE THE TRANSITION DAY AS LOW
PRES SLOWLY MOVES NE TO THE MAINE COAST. WILL STILL SEE SCT
SHOWERS ACROSS S NH/N MA EARLY...THEN SHOULD EXIT. HOWEVER...
RATHER LOW CONFIDENCE AS THIS DEPENDS UPON MOVEMENT OF THE UPPER
TROUGH OFF THE EASTERN SEABOARD AND ITS CUTOFF SYSTEM.

MONDAY THROUGH WEDNESDAY...EXPECT HIGH PRES TO BUILD OUT OF
CENTRAL CANADA DOWN THE EASTERN SEABOARD. TEMPS WILL BE COOL ON
THE HOLIDAY...THEN WILL REBOUND TO SEASONAL LEVELS AS THE HIGH
WORKS OFF THE MID ATLC COAST.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS...

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

OVERVIEW...MODERATE CONFIDENCE IN TIMING OF CEILINGS AND CONVECTION.

OVERNIGHT...LOW TO MODERATE CONFIDENCE.
EXPECT CIGS TO BE MAINLY IFR-LIFR...THOUGH CIGS MAY RISE TO MVFR
AT TIMES ACROSS THE CT VALLEY. VSBYS ALONG THE COAST WILL ALSO
REMAIN AT IFR-LIFR...BUT MAINLY VFR THIS EVENING BUT WILL LIKELY
LOWER TO IFR IN DEVELOPING FOG. MAY ALSO SEE SCT SHOWERS/TSTMS
INTO WESTERN AREAS AROUND OR AFTER MIDNIGHT.

THURSDAY...LOW TO MODERATE CONFIDENCE.
CONTINUED UNSETTLED WEATHER. FOG AND LOW CLOUDS WILL SLOWLY LIFT
DURING THE MORNING. THE TAFS MAY BE TOO FAST IN LIFTING
CIGS/VSBYS. SCATTERED SHOWERS/TSTMS WILL REGENERATE DURING THE DAY
WITH MORE STRONG STORMS IN THE CT VALLEY AND CENTRAL HILLS.

KBOS TERMINAL...LOW TO MODERATE CONFIDENCE IN TRENDS AND CEILINGS.

KBDL TERMINAL...LOW TO MODERATE CONFIDENCE IN TIMING OF CONVECTION
THROUGH THE PERIOD. COULD SEE BRIEF IFR IN AN AREA OF TSRA.
POTENTIAL FOR HAIL OR WIND GUSTS TO 50 KNOTS IN ISOLATED TSTMS.

OUTLOOK...THURSDAY NIGHT THROUGH MONDAY...

THURSDAY NIGHT AND FRIDAY...LOW CONFIDENCE. VERY UNSETTLED
PATTERN WITH VARIABILITY BETWEEN VFR AND MVFR-IFR CONDITIONS IN
SHRA/TSRA/FOG.

SATURDAY...LOW CONFIDENCE. MAINLY MVFR CIGS/VSBYS WITH POCKETS OF
IFR CONDITIONS. ISOLD-SCT TSTMS POSSIBLE THROUGH EARLY AFTERNOON.
POCKETS OF IFR VSBYS IN FOG ALONG THE COAST EARLY.

SUNDAY...LOW TO MODERATE CONFIDENCE. MVFR CIGS/VSBYS POSSIBLE
THROUGH MIDDAY ACROSS S NH/N MA...OTHERWISE SHOULD SEE MAINLY VFR.
LOW CONFIDENCE ON TIMING OF EXIT OF PRECIP.

MONDAY...MODERATE CONFIDENCE. VFR.
-- 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 THURSDAY.
A FRONT IS STALLED ACROSS THE EASTERN WATERS WITH EAST WINDS TO
THE NORTH AND SOUTHWEST WINDS TO THE SOUTH. THIS FRONT WILL SHIFT
NORTH TONIGHT WITH ALL WATERS TURNING TO SOUTHWEST WINDS.
SOUTHWEST WINDS WILL INCREASE OVERNIGHT AND THURSDAY WITH
POTENTIAL FOR 25 KNOTS ON THURSDAY. THIS WIND WILL CAUSE BUILDING
SEAS THROUGH THE PERIOD WITH 5-8 FOOT SEAS ON THE SOUTHERN EXPOSED
WATERS AND POSSIBLY THE EASTERN OUTER WATERS.

EXPECT LOW VSBYS IN FOG AND LOCALLY HEAVY SHOWERS. ISOLATED
THUNDERSTORMS ARE ALSO POSSIBLE.

OUTLOOK...THURSDAY NIGHT THROUGH MONDAY...

THURSDAY NIGHT-FRIDAY...MODERATE CONFIDENCE. COLD FRONT WILL
REMAIN W OF THE WATERS SO EXPECT S WINDS GUSTING TO 25-30 KT. LOW
PROB OF GALE GUSTS. SEAS WELL ABOVE 5 FT...MAINLY OVER THE OUTER
WATERS. WINDS MAY SHIFT TO NW-N OVER THE WESTERN WATERS FRI NIGHT.

SATURDAY...LOW CONFIDENCE DUE TO TIMING OF FRONT. FRONT WILL BE
SLOW TO CLEAR THE EASTERN WATERS...BUT SHOULD DURING THE DAY. N
WINDS WILL GUST TO 25 KT MAINLY ON THE EASTERN WATERS. SEAS REMAIN
AOA 5 FT OVER THE OPEN WATERS.

SUNDAY...LOW TO MODERATE CONFIDENCE. EXPECT W-NW WIND GUSTS UP TO
25 KT AND SEAS AOA 5 FT.

MONDAY...MODERATE CONFIDENCE. WINDS AND SEAS WILL SLOWLY
DIMINISH.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...AIR QUALITY ALERT UNTIL 10 PM EDT THIS EVENING FOR CTZ002>004.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 AM EDT FRIDAY FOR
     ANZ232>234.
     SMALL CRAFT ADVISORY FROM 10 AM THURSDAY TO 6 AM EDT FRIDAY
     FOR ANZ230-231-236-251.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ235-237-
     254>256.
     SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT FRIDAY
     FOR ANZ250.
-- End Changed Discussion --

&&

$$
SYNOPSIS...WTB/EVT
NEAR TERM...WTB/EVT
SHORT TERM...WTB
LONG TERM...EVT
AVIATION...WTB/EVT
MARINE...WTB/EVT