Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 201747 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 147 PM EDT MON OCT 20 2014 .SYNOPSIS... HIGH PRESSURE WILL SLIDE TO THE SOUTH OF THE REGION TODAY KEEPING THE WEATHER QUIET. A LONG DURATION COASTAL STORM WILL BRING PERIODS OF RAIN TUESDAY THROUGH THURSDAY WITH LINGERING SHOWERS FRIDAY AS THE STORM SLOWLY PULLS AWAY FROM NEW ENGLAND. DRY AND MILD WEATHER IS EXPECTED NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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145 PM UPDATE... MOSTLY SUNNY SKIES AT MID AFTERNOON WILL GRADUALLY GIVE WAY TO MORE MID LEVEL CLOUDINESS THAT WILL WORK IN FROM THE WEST THROUGH EARLY EVENING. HIGH TEMPS WILL TOP OUT IN THE MIDDLE TO UPPER 50S IN MOST LOCATIONS...BUT LESS WIND THAN YESTERDAY WILL MAKE IT FEEL MUCH MILDER OVER THE NEXT FEW HOURS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT AND TOMORROW... LOW PRESSURE SYSTEM WILL BEGIN TO DEVELOP ACROSS THE GREAT LAKES OVERNIGHT. THIS PUTS THE REGION IN MORE OF A SOUTHWEST FLOW AND BEGIN TO MOISTEN THE COLUMN. ANTICIPATE CLOUDS TO BE ON THE INCREASE OVERNIGHT LIMITING THE POTENTIAL FOR RADIATIONAL COOLING. THEREFORE KEPT TEMPS IN THE LOW TO MID 40S...WARMER ALONG THE SOUTH COAST THANKS TO THE SW FLOW. SW LLJ WILL BEGIN TO INCREASE CLOSER TO DAYBREAK AND WITHIN THE SW WAA FLOW...SHOWERS WILL DEVELOP IN THE MORNING HOURS. THE BEST SHOT WILL BE ACROSS THE CAPE AND ISLANDS AND PERHAPS THE COASTAL PLAIN...ALIGN WITH THE LOCATION OF THE LLJ. THERE IS A SLIGHT CHANCE FOR SOME THUNDER OVER THE SOUTHEASTERN WATERS AND EVEN THE CAPE AND ISLANDS ON TUESDAY WITH CAPE VALUES NEAR 500 J/KG COMBINED WITH STEEP LAPSE RATES AND LI VALUES BELOW 0. BECAUSE OF THIS AND THE INCREASING LLJ HAVE INSERTED ISO THUNDER INTO THE FORECAST. UPPER LEVEL LOW WILL BECOME CUTOFF OVER THE EASTERN GREAT LAKES DURING THE DAY...AND WILL DOMINATE THE REGION FOR THE REMAINDER OF THE WEEK. ALTHOUGH THE MAIN SHORTWAVE/LIFT WILL BE AWAY FROM THE REGION...THERE IS STILL THE POTENTIAL FOR A FEW SHOWERS TO DEVELOP ACROSS THE WESTERN ZONES. RIGHT NOW HAVE THE HIGHER CONFIDENCE THAT THE CAPE AND THE ISLANDS WILL SEE THE BEST CHANCE FOR RAINFALL ON TUESDAY. BECAUSE OF THE RETURN FLOW AND THAT SOUTHERN NEW ENGLAND IS IN WARM AIR ADVECTION SIDE OF THE SYSTEM...TEMPS WILL WARM INTO THE UPPER 50S TO MID 60S. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGHLIGHTS... * PERIODS OF RAIN OF VARYING INTENSITY EXPECTED THROUGH THU AS A COASTAL STORM STALLS SOUTH OF NEW ENG * LINGERING SHOWERS FRIDAY BUT SLOWLY IMPROVING CONDITIONS * MAINLY DRY AND MILD WEATHER NEXT WEEKEND OVERVIEW... GUIDANCE IN EXCELLENT AGREEMENT ON EVOLUTION OF THE COASTAL STORM THAT DEVELOPS OFF THE MID ATLC COAST TUE NIGHT BEFORE FINALLY PULLING AWAY FROM NEW ENG FRI/FRI NIGHT. TIGHT CLUSTERING AMONG THE MODELS ON THE TRACK OF THE STORM WHICH STALLS S OF NEW ENG FOR A TIME AS IT GETS CAPTURED UNDER THE MID LEVEL CIRCULATION. DESPITE THE GOOD AGREEMENT ON THE MASS FIELDS THERE ARE DIFFERENCES IN THE TIMING AND PLACEMENT OF QPF DURING THE PERIOD. SO WHILE CONFIDENCE IS HIGH THAT PERIODS OF RAIN WILL AFFECT THE REGION THROUGH AT LEAST THU...THERE IS STILL UNCERTAINTY ON WHERE/WHEN HEAVIEST RAIN WILL FALL. STRONG WINDS AND COASTAL FLOODING WILL NOT LIKELY BE SIGNIFICANT FACTOR IN SNE AS CORE OF LOW LEVEL JET EXPECTED TO REMAIN TO THE NORTH. USED A BLEND OF AVAILABLE GUIDANCE FOR POPS/QPF TO ACCOUNT FOR MODEL VARIATION IN THESE FIELDS. DAILIES... TUESDAY NIGHT THROUGH THURSDAY... WHILE WE EXPECT PERIODS OF RAIN TO AFFECT SNE DURING THIS TIME...CONFIDENCE IS BELOW AVERAGE ON EXACT TIMING AND LOCATION OF HEAVIER RAINFALL. MODELS ARE SIGNALING A POSSIBLE DRY SLOT MOVING UP FROM THE SOUTH TUE NIGHT INTO EARLY WED WHICH MAY RESULT IN LIGHTER PRECIP DURING THIS TIME. HEAVIEST RAIN MAY BE DURING WED NIGHT THU AS MID LEVEL LOW LIFTS N INTO REGION WITH INCREASING QG FORCING AND POTENTIAL FOR MORE CONVECTION ASSOCD WITH COOLING TEMPS ALOFT. USING A BLEND OF AVAILABLE GUIDANCE YIELDS RAINFALL OF 1-3 INCHES WITH HIGHEST AMOUNTS ACROSS NE MA INTO S NH. WINDS DO NOT APPEAR TO BE A SIGNIFICANT FACTOR FOR SNE AS CORE OF LOW LEVEL JET WILL REMAIN TO THE NORTH. A PERIOD OF GUSTY NE WINDS COULD AFFECT COASTAL NE MA LATE TUE NIGHT/WED BUT CONFIDENCE IS LOW. WITH STRONGEST WINDS LIKELY N OF THE REGION...THE THREAT FOR COASTAL FLOODING REMAINS LOW AS SEAS AND STORM SURGE WILL NOT LIKELY BE HIGH ENOUGH TO CAUSE PROBLEMS. HOWEVER...THE RISK CONTINUES FOR COASTAL BEACH EROSION WITH WAVE ACTION OVER SEVERAL HIGH TIDE CYCLES. FRIDAY... COASTAL STORM WILL BE EAST OF CAPE COD BY FRI MORNING AND SLOWLY LIFTING N TOWARD NOVA SCOTIA DURING THE DAY. WHILE CONDITIONS SHOULD BE IMPROVING...SCT SHOWERS WILL LIKELY CONTINUE UNDER LINGERING COLD POOL ALOFT WITH MID LEVEL LOW JUST E OF THE REGION. SAT AND SUN... LOOKS MAINLY DRY NEXT WEEKEND. COLD FRONTAL PASSAGE SOMETIME LATE SAT/SAT NIGHT COULD BRING A FEW SHOWERS. SAT WILL LIKELY BE THE MILDEST DAY OF THE WEEKEND WITH MAXES WELL INTO THE 60S...THEN COOLER SUN BEHIND THE COLD FRONT. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY NIGHT/... THIS AFTERNOON...HIGH CONFIDENCE IN VFR. TONIGHT...HIGH CONFIDENCE IN VFR. SCATTERED SHOWERS MAY DEVELOP ACROSS EASTERN NEW ENGLAND TOWARD DAYBREAK. TUESDAY...MODERATE CONFIDENCE. CONDITIONS PROBABLY DETERIORATE TO MAINLY MVFR THRESHOLDS...BUT BRIEF IFR CIGS/VSBYS ARE POSSIBLE. SCATTERED SHOWERS EXPECTED WITH AN ISOLATED THUNDERSTORM OR TWO POSSIBLE. BULK OF THE FOCUS ACROSS EASTERN NEW ENGLAND. TUESDAY NIGHT...MODERATE CONFIDENCE. LOW END MVFR TO PERHAPS IFR CONDITIONS DOMINATE IN LOW CLOUDS...SCATTERED SHOWERS AND FOG PATCHES. THE BULK OF THE ACTIVITY WILL LIKELY BE FOUND ACROSS OUR NORTHERN ZONES. KBOS...HIGH CONFIDENCE IN TAF TONIGHT WITH MODERATE CONFIDENCE ON TUESDAY. LOW PROBABILITY OF AN ISOLATED THUNDERSTORM ON TUESDAY. KBDL...HIGH CONFIDENCE IN TAF TONIGHT WITH MODERATE CONFIDENCE ON TUESDAY. OUTLOOK...WEDNESDAY THROUGH FRIDAY... WEDNESDAY THROUGH THURSDAY...HIGH CONFIDENCE OVERALL WITH AREAS OF MVFR/IFR AND PERIODS OF RAIN OF VARYING INTENSITY...BUT LOW CONFIDENCE ON DETAILS. LOW PROB OF NE WIND GUSTS TO 25 KT ACROSS NE MA COAST LATE TUE NIGHT/WED. FRIDAY...MODERATE CONFIDENCE. A MIX OF MVFR/VFR WITH SCT SHOWERS.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH TUESDAY/...HIGH CONFIDENCE. TODAY... HIGH PRESSURE BUILDS OVER THE WATERS ALLOWING FOR THE WINDS TO SLOWLY DIMINISH. WESTERLY WINDS WILL SWITCH TO THE SOUTHWEST BY THE AFTERNOON. SEAS WILL LINGERING AROUND 5 FEET DURING THE THE AFTERNOON SO HAVE EXPANDED SCA ACCORDINGLY. WOULD NOT BE SURPRISED IF IT IS CANCELLED EARLIER. TONIGHT... HIGH PRESSURE MOVES OFFSHORE. SOUTHWEST WINDS WILL REMAIN BELOW 25 KTS AND SEAS WILL REMAIN BELOW 5 FEET. LIGHT RAIN MOVES UP FROM THE MID ATLANTIC COAST LATE AT NIGHT. TOMORROW...SOUTHWEST FLOW WILL ALLOWING RAIN SHOWERS TO MOVE ACROSS THE SOUTHEASTERN WATERS. CONDITIONS WILL REMAIN BELOW SCA BUT THERE IS A LOW PROB FOR AN ISO THUNDERSTORM DURING THE DAY. OUTLOOK...TUESDAY THROUGH FRIDAY... TUE NIGHT AND WED...WINDS GENERALLY BELOW SCA...BUT A PERIOD OF NE WIND GUSTS TO 25-30 KT POSSIBLE OVER NE MA COASTAL WATERS ALTHOUGH CONFIDENCE IS LOW. LOW PROB WINDS COULD REACH GALE FORCE OVER WATERS EAST OF CAPE ANN. HIGHEST SEAS 6-9 FT LATE TUE NIGHT/WED OVER NE MA COASTAL WATERS. WED NIGHT AND THU...MODERATE CONFIDENCE. EASTERLY WINDS MAINLY BELOW SCA WITH LOW PROB OF SCA NE GUSTS OVER NE MA COASTAL WATERS. HIGHEST SEAS 6-8 FT REMAIN OVER NE MA COASTAL WATERS. FRI...MAINLY NW WIND GUSTS TO 20 KT WITH LOW PROB REACHING 25 KT. SCA SEAS OVER EASTERN MA COASTAL WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ250- 254. && $$ SYNOPSIS...KJC/DUNTEN NEAR TERM...FRANK SHORT TERM...DUNTEN LONG TERM...KJC AVIATION...FRANK/KJC MARINE...KJC/DUNTEN

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