Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250029 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 729 PM EST SAT JAN 24 2015 .SYNOPSIS... A RAPIDLY INTENSIFYING COASTAL STORM WILL QUICKLY MOVE TO THE CANADIAN MARITIMES TONIGHT. DRY AND SEASONABLE WEATHER EXPECTED ON SUNDAY. A SEVERE AND LONG DURATION WINTER STORM MAY IMPACT SOUTHERN NEW ENGLAND MONDAY NIGHT THROUGH TUESDAY INTO EARLY WEDNESDAY MORNING. GREATER CLARITY ON DETAILS SHOULD EMERGE AS WE DRAW CLOSER TO THIS POTENTIAL EVENT. TEMPERATURES WILL LIKELY BE QUITE COLD FOR THE FIRST HALF OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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715 PM UPDATE... HAVE ALLOWED THE WINTER WEATHER ADVISORIES TO EXPIRE AT 7 PM. LAST OF SNOW EXITING CENTRAL MA/NE CT AT 00Z AND WILL CONTINUE TO SLOWLY MOVE E OVER THE NEXT FEW HOURS. WINDS WILL PICK UP OVER THE CAPE AND NANTUCKET THIS EVENING AS PRECIP EXITS SO HAVE KEPT WIND ADVISORY UP FOR NOW. HAVE ALSO MENTIONED ON THE EXPIRING WINTER WEATHER ADVISORY AS WELL AS THE SPECIAL WEATHER STATEMENT FOR CAPE COD ABOUT THE POTENTIAL OF BLACK ICE FORMING OVERNIGHT AS COLDER AIR WORKS IN BEHIND THE EXITING PRECIP. OTHER THAN SOME LIGHT RAIN ACROSS THE OUTER CAPE AND NANTUCKET... NOTING THE LIGHT PRECIP IS MAINLY SNOW NOW AS WINDS HAVE SHIFTED TO N-NW. NOTING GUSTS UP TO 30 KT AT KHYA AND 27 KT AT KACK AT 00Z.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... ANTICIPATE LOTS OF SUNSHINE SUNDAY BUT COLD ADVECTION SHOULD CAP HIGH TEMPERATURES UPPER 20S TO MID 30S ACROSS MOST OF THE AREA. WIND GUSTS OVER LAND GENERALLY BETWEEN 15 AND 20 MPH. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * DRY AND COLD SUNDAY NIGHT * CONFIDENCE INCREASING FOR LONG DURATION WINTER STORM AFFECTING THE REGION LATE MONDAY INTO TUESDAY NIGHT * VERY COLD MON-WED WITH MODERATING TEMPS THU/FRI DETAILS... SUNDAY NIGHT... BLUSTERY NW WIND FLOW IN PLACE BRINGING COLD AIR ACROSS THE REGION. WILL SEE DRY CONDITIONS AS WINDS DIMINISH SOMEWHAT AFTER MIDNIGHT. MAY START TO SEE CLOUDS APPROACH AHEAD OF NEXT SYSTEM. OVERNIGHT LOWS WILL BE COLD...ESPECIALLY INLAND...FALLING TO THE SINGLE DIGITS ACROSS N CENTRAL AND W MA RANGING TO 20-25 ACROSS THE OUTER CAPE AND NANTUCKET. MONDAY... NOTING VIGOROUS H5 SHORT WAVE DIVING SE TO THE SE U.S. STATES FROM SASKATCHEWAN. THIS WILL CAUSE LOW PRES TO FORM OFF THE MID ATLC COAST BY MON EVENING. LIGHT N WINDS ACROSS THE REGION EARLY MON WILL VEER TO NE AND INCREASE DURING THE AFTERNOON... ESPECIALLY ALONG THE S COAST NEAR OR AFTER SUNSET. SOME MOISTURE WELL AHEAD OF THIS LOW MAY BRING SOME LIGHT SNOW TO THE REGION DURING THE AFTERNOON. CARRIED MAINLY SLIGHT CHANCE TO LOW CHANCE POPS FROM MIDDAY ONWARD. EXPECT TEMPS TO REMAIN WELL BELOW SEASONAL NORMALS...RANGING FROM THE UPPER TEENS ACROSS THE HIGHER INLAND TERRAIN TO NEAR FREEZING ALONG THE IMMEDIATE S COAST. MONDAY NIGHT THROUGH TUESDAY NIGHT... MOST OF THE 12Z OPERATIONAL MODELS AND ENSEMBLE MEMBERS HAVE COME MORE IN LINE TO THE 00Z OP ECMWF RUN...SIGNALING VERY STRONG CYCLOGENESIS TAKING PLACE S OF NEW ENGLAND DURING THIS TIMEFRAME. H5 LONG WAVE TROUGH CONTINUES TO AMPLIFY AS IT BECOMES NEGATIVELY TILTED...WHICH MEANS THE SURFACE SYSTEM WILL LIKELY HUG CLOSER TO THE COAST. BIG QUESTION AT THIS POINT IS HOW MUCH THE LOW WILL DEEPEN AND WHERE IT WILL TRACK. THIS IS WHERE THE UNCERTAINTY LIES. IT DOES LOOK LIKE THERE WILL BE A SIGNIFICANT AND LONG DURATION WINTER STORM AFFECTING THE REGION...BUT HOW LONG IS ALSO STILL IN QUESTION. OVERALL...MODELS IN PRETTY GOOD AGREEMENT IN GENERAL BUT DETAILS IN QUESTION. ONE MODEL IN PARTICULAR THAT IS IN QUESTION IS THE 12Z ECMWF...WHICH ACTUALLY HUGS THE LOW CLOSER TO THE COAST AS IT BECOMES CAPTURED BY DEVELOPING H5 CUTOFF LOW. ALL OP MODELS DO THE PRES DOWN TO SUB 980 HPA BY LATE TUE/TUE NIGHT...SO ALSO EXPECT VERY STRONG NE WINDS. HIGH PRES IS ALSO SET UP N OF THE REGION...ACROSS EASTERN QUEBEC INTO THE MARITIMES KEEPING COLD AIR IN PLACE. SO...IT DOES LOOK LIKE THE SEASON/S FIRST MAJOR WINTER STORM WILL BRING HEAVY SNOWFALL AND STRONG...POSSIBLY DAMAGING WINDS ESPECIALLY ACROSS CENTRAL AND EASTERN AREAS. HAVE CARRIED LIKELY TO CATEGORICAL POPS...HIGHEST ACROSS E MA INTO E RI. THE NEXT BIG QUESTION IS...WHETHER THERE WILL BE BLIZZARD CONDITIONS FOR A TIME WITH THIS STORM. NOTE THAT THE DEFINITION OF A BLIZZARD IS SUSTAINED WINDS OR FREQUENT GUSTS OF 35 MPH OR GREATER AND VSBYS LESS THAN 1/4 MILE FOR AT LEAST 3 CONSECUTIVE HOURS. LOOKS LIKE WINDS WILL BE THERE...BUT VSBYS ARE ANOTHER MATTER. WILL ALSO LIKELY SEE HEAVY SNOWFALL...WITH SOME PERIODS OF 1 INCH/HOUR SNOWFALL RATES AND POSSIBLY HIGHER. WITH THE VERY STRONG E-NE FETCH IN PLACE...COULD SEE PROBLEMS WITH THE TUESDAY MORNING HIGH TIDE WITH MINOR SPLASHOVER OR POSSIBLY EVEN SOME MINOR COASTAL FLOODING. WE HAVE HELD OFF ON WATCHES AT THIS TIME SINCE WE ARE STILL IN AN EVENT. ONCE THIS ONE MOVES OFF...AND THE 00Z MODELS COME IN... DECISIONS CAN BE MADE ON HEADLINES FOR THIS UPCOMING EVENT. WEDNESDAY... LOW PRESSURE EXITS TO THE CANADIAN MARITIMES...BUT TIMING OF ITS EXIT STILL IN QUESTION. AT THIS POINT...DO HAVE IMPROVING CONDITIONS FROM W-E...BUT WILL STILL SEE COLD AND BLUSTERY CONDITIONS. THURSDAY THROUGH SATURDAY... HIGH PRES LOOKS TO BUILD ACROSS DURING THURSDAY. MAY SEE ANOTHER LOW MOVE ACROSS EITHER THU NIGHT OR FRI AS THE UPPER PATTERN BECOMES LESS AMPLIFIED. TIMING OF THIS FEATURE IS IN QUESTION SO LOW CONFIDENCE CONTINUES. MODELS AND ENSEMBLES INDICATE THAT WEAK HIGH PRES BUILDS IN FOR NEXT SATURDAY. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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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 SUNDAY/... THIS EVENING...MODERATE CONFIDENCE. WESTERN MA/N CENTRAL CT...MAINLY VFR THOUGH LEFTOVER MVFR VSBYS IN PATCHY FOG. SHOULD IMPROVE TO VFR BY 02Z. CENTRAL-E MA/NE CT/RI...MVFR-IFR CIGS/VSBYS IN BANDS OF LIGHT SNOW. CONDITIONS SHOULD IMPROVE FROM W-E THROUGH 02Z-04Z. MAY SEE ICY SURFACES DEVELOPING AT AIRPORT TARMACS AS TEMPS DROP BELOW FREEZING. NW WINDS GUSTING TO 30-35 KT OVER THE CAPE AND ISLANDS. OVERNIGHT...HIGH CONFIDENCE. CONDITIONS IMPROVE RAPIDLY TO VFR W TO E THROUGH 04Z-05Z. NW WIND GUSTING TO AROUND 30 KT OVER THE CAPE AND ISLANDS. SUNDAY...HIGH CONFIDENCE OF VFR CONDITIONS. NW GUSTS 20 TO 25 KT ALONG THE COASTAL PLAIN. KBOS TAF...HIGH CONFIDENCE IN TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING. RAIN SHOULD MIX WITH AND CHANGE TO SNOW 20Z TO 22Z WITH UP TO AN ADDITIONAL INCH OR SO OF ACCUMULATION POSSIBLE. TEMPERATURES DROPPING BELOW FREEZING WILL CAUSE UNTREATED SURFACES TO BECOME ICY. BECOMING VFR AFTER ABOUT 01Z. KBDL TAF...MODERATE CONFIDENCE. SNOW ENDING BY AROUND 23Z. BECOMING VFR AFTER 00Z OR 01Z. TEMPERATURES WILL DROP BELOW FREEZING AFTER 22Z. OUTLOOK /SUNDAY NIGHT THROUGH THURSDAY/... SUNDAY NIGHT...HIGH CONFIDENCE. VFR. MONDAY...MODERATE CONFIDENCE. VFR TO START...THEN CONDITIONS LOWER TO MVFR-IFR AS LIGHT SNOW DEVELOPS MAINLY DURING THE AFTERNOON. MONDAY NIGHT THROUGH TUESDAY NIGHT...LOW CONFIDENCE. MVFR-IFR CONDITIONS WILL LIKELY DEVELOP AS COASTAL LOW PRESSURE TRACKS SE OF NANTUCKET. MAY SEE PERIODS OF LIFR ACROSS E MA LATE MON NIGHT INTO TUE MORNING. NE WINDS LIKELY GUSTING TO 30-40 KT AT LEAST ACROSS COASTAL AREAS. WEDNESDAY...LOW TO MODERATE CONFIDENCE. CONDITIONS TO IMPROVE TO VFR FROM WEST TO EAST...BUT TIMING IN QUESTION. N-NW WIND GUSTS UP TO 25-30 KT POSSIBLE EARLY ALONG THE COAST. THURSDAY...LOW CONFIDENCE. TIMING OF LOW PRES AND POSSIBLE SNOW SHOWERS IN QUESTION.
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&& .MARINE...
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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 SUNDAY/...HIGH CONFIDENCE. TONIGHT...COASTAL LOW WILL CONTINUE TO RAPIDLY STRENGTHEN AND MOVE TO THE CANADIAN MARITIMES TONIGHT. STRONG GALE FORCE WINDS FROM THE N AND NW LIKELY THIS EVENING AND THEN VERY GRADUALLY DIMINISHING OVERNIGHT. SEAS WILL CONTINUE TO BUILD TO 15 FT ON THE OUTER SE WATERS TONIGHT. NOTING SEAS AT 20 FT AT BUOY 44008 AT 00Z AND 13 FT AT 44097. SUNDAY...NW GUSTS TO 25 TO 30 KT MAY PERSIST ACROSS MOST OF THE WATERS UNTIL MID TO LATE SUNDAY AFTERNOON. OUTLOOK /SUNDAY NIGHT THROUGH THURSDAY/... SUNDAY NIGHT...HIGH CONFIDENCE. SMALL CRAFT WIND GUSTS TO 25 KNOTS EARLY IN THE EVENING ACROSS THE EASTERN OUTER COASTAL WATERS SHOULD DIMINISH DURING THE NIGHT. MONDAY...MODERATE CONFIDENCE. EXPECT WINDS TO SHIFT TO E-NE WITH GUSTS INCREASING TO 30 KT. LOW PROB FOR GALE FORCE GUSTS LATE MON. MONDAY NIGHT THROUGH TUESDAY NIGHT...LOW TO MODERATE CONFIDENCE. RAPIDLY INTENSIFYING LOW PRES WILL LIKELY CROSS THE COASTAL WATERS. LOW PROB OF STORM FORCE NE GUSTS LATE MON NIGHT INTO TUE ACROSS THE OUTER WATERS...MODERATE PROB OF GALE FORCE WINDS ELSEWHERE. VSBYS REDUCED IN PERIODS OF MODERATE TO HEAVY SNOW AT TIMES. SEAS BUILDING TO 20 FEET OR GREATER ESPECIALLY ACROSS THE EASTERN WATERS. WEDNESDAY...LOW CONFIDENCE. SHOULD SEE AT LEAST LEFTOVER N-NW WIND GUSTS UP TO SMALL CRAFT CRITERIA DURING WED...THEN SHOULD DIMINISH WED NIGHT. THURSDAY...LOW CONFIDENCE. WINDS SHOULD REMAIN BELOW SMALL CRAFT CRITERIA. SEAS MAY LINGER AT AROUND 5 FT.
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&& .TIDES/COASTAL FLOODING... OFFSHORE WINDS AND A LOWER ASTRONOMICAL HIGH TIDE SHOULD PRECLUDE ANY NEED FOR COASTAL FLOOD HEADLINES OVERNIGHT. ONLY LOCATIONS THAT MIGHT GET CLOSE TO A FLOOD STAGE WOULD BE THE NORTH SIDE OF CAPE COD AND THE NANTUCKET HARBOR AREA. COASTAL FLOODING MAY BE AN ISSUE DURING THE TUESDAY MORNING TIME FRAME. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MAZ022-024. RI...NONE. MARINE...GALE WARNING UNTIL 7 AM EST SUNDAY FOR ANZ231>235-237-250-251- 254>256. SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR ANZ230-236.
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&& $$ SYNOPSIS...EVT/THOMPSON NEAR TERM...EVT/THOMPSON SHORT TERM...THOMPSON LONG TERM...EVT AVIATION...EVT/THOMPSON MARINE...EVT/THOMPSON TIDES/COASTAL FLOODING...THOMPSON

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