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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