Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 181951
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
351 PM EDT SAT OCT 18 2014

.SYNOPSIS...
COLD FRONT MOVES OFFSHORE EARLY TONIGHT. COLD HIGH PRESSURE BUILDS
IN ON SUNDAY. A LONG DURATION COASTAL STORM IS LIKELY DURING THE
MIDDLE TO END OF NEXT WEEK BUT THE TRACK OF THE STORM AND WHERE
THE HEAVIEST RAIN AND STRONGEST WINDS SET UP REMAINS UNCERTAIN.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

THROUGH 8 PM...A FEW SHOWERS HAVE POPPED OVER SOUTHERN NEW ENGLAND.
MOST CELLS HAVE HAD 40 DBZ VALUES TOPPING OUT BELOW 13K
FEET...LOWER THAN -10C. BUT A FEW HAVE REACHED 18K FEET AND
GENERATED A LITTLE THUNDER. TOTALS IN THE MID 40S IN OUR AREA AND
AROUND 50 IN NORTHERN NEW ENGLAND. SO THE POTENTIAL FOR THUNDER
IS PRESENT THROUGH THIS EVENING BUT EXPECT MOST ACTION TO BE AS
SHOWERS.

TEMPS IN THE MIDDLE TO UPPER 60S IN THE HIGHER TERRAIN...TO THE
LOWER 70S ACROSS PORTIONS OF THE COASTAL PLAIN...SHOULD START
COOLING THIS EVENING. WINDS GUSTS OF 20 MPH ARE POSSIBLE BEFORE
SUNSET.

TONIGHT...
INITIAL SHORTWAVE MOVES OFFSHORE...PUSHING A COLD FRONT THROUGH
OUR AREA. ANOTHER SHORTWAVE MOVES DOWN FROM ONTARIO TONIGHT AND
PUSHES THE TROUGH AXIS OVER NEW ENGLAND BY MORNING. THIS WILL
BRING COLDER TEMPS ALOFT WHICH WILL DESTABILIZE THE AIRMASS. THUS
EXPECT SHOWER COVERAGE TO DIMINISH EARLY TONIGHT...THEN INCREASE
AGAIN OVERNIGHT. EXPECT SCATTERED/CHANCE POPS FOR TONIGHT.

MIN TEMPS UPSTREAM IN ONTARIO WERE IN THE UPPER 30S AND
40S...THIS IS A REASONABLE TARGET FOR TONIGHT.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...

SUNDAY...
SECOND SHORTWAVE AND TROUGH AXIS MOVE OFFSHORE IN THE MORNING.
THIS WILL ALLOW LINGERING SHOWERS IN THE MORNING...THEN A CLEARING
AND DRYING TREND BY AFTERNOON. NORTHWEST WINDS WILL BRING COLDER
AIR AT ALL LEVELS AND SUPPORT DAYTIME MIXING OF THE AIRMASS TO 850
MB. TEMPS AT 850 MB WILL BE -2C TO -5C...WHICH SUPPORTS MAX SFC
TEMPS IN THE UPPER 40S TO MID 50S. WINDS IN THE MIXED LAYER WILL
BE AT LEAST 25 KNOTS. WE WILL USE THESE VALUES.

SUNDAY NIGHT...
AS HIGH PRESSURE BUILDS OVER NEW ENGLAND THE WINDS WILL DIMINISH
DURNING THE EARLY NIGHT. MOSTLY CLEAR SKIES AND LIGHT WINDS WILL
ALLOW FOR RADIATIONAL COOLING. DEWPOINTS IN THE COLDER AIRMASS
WILL BE IN THE 20S...EXCEPT 30-35 ALONG THE COASTLINE AND ISLANDS.
THIS WILL SET UP THE POTENTIAL FOR WIDESPREAD TEMPERATURES AT AND
BELOW FREEZING ACROSS OUR AREA...THE COLDEST NIGHT OF THE SEASON
SO FAR. MOST AREAS ALONG THE COAST WILL COLD ENOUGH FOR A FROST.
WE WILL ISSUE A FREEZE WATCH FOR ALL AREAS AWAY FROM THE COAST
WHERE THE SEASON HAS NOT ALREADY ENDED.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
HIGHLIGHTS...

* DRY BUT MUCH COOLER SUN INTO MON

* A LONG DURATION COASTAL STORM WILL IMPACT NEW ENGLAND FROM TUE
  THROUGH FRI...HOWEVER AXIS OF HEAVIEST RAIN...STRONGEST WIND AND
  MAGNITUDE OF COASTAL FLOODING REMAINS UNCERTAIN

OVERVIEW...
MODELS REMAIN IN EXCELLENT AGREEMENT ON AMPLIFYING NORTHERN STREAM
TROF OVER THE GT LAKES AND NORTHEAST WHICH EVOLVES INTO A SLOW
MOVING CLOSED MID LEVEL LOW WHICH MOVES OFF THE MID ATLC COAST TO
EAST NEW ENG DURING THE MID TO LATE WEEK PERIOD NEXT WEEK.  DESPITE
THE EXTENDED TIME RANGE THERE IS REMARKABLE CLUSTERING OF THE
POSITION AND TRACK OF THE CLOSED MID LEVEL LOW WHICH INCREASES
CONFIDENCE IN THIS STORM IMPACTING SNE.  HOWEVER...THE EXACT DETAILS
OF THE AXIS AND TIMING OF HEAVIEST RAIN AND WIND WILL DEPEND ON THE
TRACK OF THE SFC LOW WHICH REMAINS UNCERTAIN.  GFS/ECMWF HAVE COME
INTO BETTER AGREEMENT ON FOCUSING HEAVIEST RAIN AND WIND ACROSS
MAINE AND NH BUT THERE ARE DIFFERENCES IN THE SFC TRACK AND GIVEN
THE TIME RANGE WE HAVE TO LEAVE OPEN THE POSSIBILITY OF GREATER
IMPACT FURTHER S ACROSS SNE.  FOLLOWED A BLEND OF THE GUIDANCE FOR
THE EXTENDED PERIOD...BUT CONFIDENCE IS FAIRLY HIGH THAT A LONG
DURATION COASTAL STORM WILL IMPACT THE REGION FROM TUE THOUGH FRI.

DAILIES...

MONDAY...
SFC HIGH MOVES EAST OFF THE MID ATLC COAST PASSING S OF NEW ENG.
EXPECT MOSUNNY SKIES AND LESS WIND THAN SUNDAY WITH TEMPS RECOVERING
NICELY INTO THE MID 50S AFTER RATHER COLD START TO THE MORNING. THE
BEST OF THE WEEK.

TUESDAY THROUGH FRIDAY...
HIGH CONFIDENCE ON A SIGNIFICANT COASTAL STORM IMPACTING SOUTHERN
NEW ENGLAND. HOWEVER UNCERTAINTY CONTINUES ON THE EXACT STORM TRACK
WHICH WILL DETERMINE TIMING AND AXIS OF HEAVIEST RAIN AND WIND.
ONSET OF WARM ADVECTION RAIN WILL BEGIN TUE AS PRIMARY LOW GRADUALLY
GIVES WAY TO SECONDARY LOW OFF THE DELMARVA COAST. IT APPEARS
HEAVIEST RAIN AND STRONGEST WIND FROM THIS STORM WILL OCCUR DURING
WED/THU TIMEFRAME.  LATEST GFS AND ECMWF FOCUS THE HEAVIEST RAIN AND
WIND JUST TO THE N ACROSS NH/ME BUT SPILLING INTO NE MA AND S
NH...WITH LESS RAIN AND WIND FURTHER S. HOWEVER...GIVEN THE EXTENDED
TIME RANGE IT IS POSSIBLE AXIS COULD SHIFT FURTHER S. WILL NEED TO
TO MONITOR LATER MODEL RUNS AS A HIGH IMPACT EVENT IS LIKELY FOR A
PORTION OF NEW ENGLAND.

REGARDING COASTAL FLOODING...ASTRONOMICAL TIDES ARE LOW WHICH WILL
LOWER THE THREAT AND LATEST GUIDANCE INDICATES STRONGEST WINDS MAY
END UP JUST N OF THE REGION IN THE GULF OF MAINE. BEST CHANCE OF
COASTAL FLOODING WILL BE ALONG NE MA COASTLINE CLOSEST TO THE
EASTERLY LLJ. HOWEVER ANY SHIFT FURTHER S WOULD RESULT IN A MORE
SIGNIFICANT IMPACT TO THE E MA COAST.  GIVEN THE LONG DURATION OF
THIS COASTAL STORM MULTIPLE TIDE CYCLES WILL BE IMPACTED...THUS
INCREASING THE RISK FOR COASTAL EROSION GIVEN LARGE WAVES POSSIBLY
BATTERING THE COASTLINE FOR SEVERAL DAYS.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH SUNDAY/...

THROUGH 00Z/8 PM...MODERATE CONFIDENCE. MAINLY VFR. BRIEF MVFR
CIGS POSSIBLE IN ANY SHOWERS/TSTMS. SOUTHWEST WIND GUSTS OF 20 TO
25 KNOTS EXPECTED BEFORE SUNSET.

TONIGHT...MODERATE TO HIGH CONFIDENCE. GENERALLY VFR WITH BRIEF
MVFR CIGS IN SCATTERED TO ISOLATED SHOWERS OVERNIGHT.

SUNDAY...HIGH CONFIDENCE. VFR. MORNING CLOUDS BREAK TO MOSTLY
CLEAR IN THE AFTERNOON. NORTHWEST WINDS WILL GUST TO 25 KT FROM
LATE MORNING THROUGH THE EVENING. SCATTERED SHOWERS ARE POSSIBLE
SUNDAY MORNING.

SUNDAY NIGHT...HIGH CONFIDENCE. VFR. MOSTLY CLEAR SKIES AND WINDS
BECOME LIGHT. TEMPERATURES AWAY FROM THE COAST WILL FALL TO NEAR
FREEZING OR A LITTLE BELOW...TURNING ANY WET SPOTS ON THE GROUND
INTO PATCHES OF ICE.

KBOS...HIGH CONFIDENCE IN TAF.

KBDL...HIGH CONFIDENCE IN TAF.

OUTLOOK...MONDAY THROUGH WEDNESDAY...

MON...HIGH CONFIDENCE. VFR.

TUESDAY AND WEDNESDAY...HIGH CONFIDENCE ON OVERALL
THEME...WITH CONDITIONS LOWERING TO MVFR/IFR IN DEVELOPING RAIN BUT
LOW CONFIDENCE ON EXACT TIMING OF DETAILS. GUSTY EASTERLY WINDS
POSSIBLE WED ACROSS NE MA AND S NH.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TONIGHT THROUGH SUNDAY/...HIGH CONFIDENCE.

TONIGHT...SOUTHEAST SWELL FROM GONZALO CONTINUES TO AFFECT THE NEW
ENGLAND WATERS WITH A 14 SECOND PERIOD AND HEIGHTS OF 5 TO 8 FEET.
THIS WILL CONTINUE TONIGHT ON ALL EXPOSED WATERS. SOUTHWEST WINDS
GUSTING TO 20 KNOTS WILL BECOME WEST OVERNIGHT AS A COLD FRONT
MOVES THROUGH. SMALL CRAFT HEADLINES CONTINUE FOR ALL WATERS
EXCEPT BOS HARBOR/NARRAGANSETT BAY/MASSACHUSETTS BAY.

SUNDAY...NORTHWEST WINDS OVER THE WATERS WILL BRING GUSTS OF 25 TO
30 KNOTS TO THE SURFACE. SOUTHEAST SWELL WILL CONTINUE ALTHOUGH
DIMINISHED A LITTLE FROM SATURDAY. SMALL CRAFT ADVISORY IS IN
PLACE FOR ALL WATERS.

SUNDAY NIGHT...HIGH PRESSURE APPROACHES FROM THE WEST. NORTHWEST
WINDS WILL DIMINISH OVERNIGHT AS THE HIGH GETS CLOSER. SOUTHEAST
SWELL FROM GONZALO WILL DIMINISH OVERNIGHT. SMALL CRAFTS WILL END
ON THE NEARSHORE WATERS BUT LINGER ON THE OUTER WATERS.

OUTLOOK...MONDAY THROUGH WEDNESDAY...

MON...HIGH CONFIDENCE. WEST WIND GUSTS TO 15-20 KT MON. HIGH
CONFIDENCE FOR SUBSIDING SEAS MONDAY.

TUE...MODERATE CONFIDENCE. WINDS WILL LIKELY REMAIN BELOW SCA
THRESHOLDS WITH SE WINDS INCREASING TO 15-20 KT. LOWERING VSBY IN
DEVELOPING RAIN AND PATCHY FOG.

WED...LOW CONFIDENCE IN LOCATION OF STRONGEST WINDS ASSOCD WITH THE
COASTAL STORM. IT IS POSSIBLE STRONGEST WINDS AT GALE FORCE STRENGTH
ALONG WITH HIGHEST SEAS WILL REMAIN TO THE N IN THE GULF OF MAINE.
BEST CHANCE FOR E WIND GUSTS TO 30+ KT WILL BE ACROSS NE MA COASTAL
WATERS...WITH LESS WIND ACROSS S COASTAL WATERS. SEAS BUILDING TO 10-
15 FT OVER WATERS EAST OF CAPE ANN WITH MUCH LESS WAVE ACTION OVER
THE SOUTH COASTAL WATERS. VSBYS REDUCED IN RAIN AND FOG...ESPECIALLY
ACROSS NE MA COASTAL WATERS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT SUNDAY FOR ANZ231>234.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ235-237.
     SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR ANZ250-254>256.

&&

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



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