Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251759 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 159 PM EDT MON APR 25 2016 .SYNOPSIS... HIGH PRESSURE FROM CENTRAL CANADA TO NEW ENGLAND WILL REMAIN NEARLY STATIONARY TODAY PROVIDING DRY AND SEASONABLY WARM WEATHER TO THE AREA. A WAVE OF LOW PRESSURE WILL TRACK JUST SOUTH OF NEW ENGLAND TUE PROVIDING A WIDESPREAD APPRECIABLE RAINFALL TO THE REGION ALONG WITH A CHILLY NORTHEAST WIND AND MUCH COOLER THAN NORMAL TEMPS. HIGH PRESSURE BUILDS ACROSS THE REGION WEDNESDAY. ANOTHER LOW PRESSURE CENTER WILL QUICKLY PASS SOUTH OF NEW ENGLAND THURSDAY NIGHT INTO EARLY FRIDAY. HIGH PRESSURE MOVES OUT OF CENTRAL CANADA LATE FRIDAY...BRINGING DRY BUT COOL CONDITIONS THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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200 PM UPDATE... LATEST VISIBLE SATELLITE IMAGERY SHOWS BREAKS IN THE CLOUD DECK WHICH WILL HELP INCREASE SURFACE TEMPS ACROSS SOUTHERN NEW ENGLAND THIS AFTERNOON. HOWEVER ONSHORE FLOW FOR COASTLINES HAVE KEPT TEMPS INTO THE LOW 50S. OTHERWISE MAINLY DRY WEATHER DAY INTO THE AFTERNOON. WATCHING A BATCH OF PRECIP MOVING ACROSS UPDATE NEW YORK. LATEST HRRR GUIDANCE TRIES TO BRING THIS OVER AROUND 21/22Z. IF THAT OCCURS THEN ANTICIPATE EITHER VIRGA OR SPRINKLES AS LOW LEVELS ARE STILL QUITE DRY PER BUFKIT SOUNDINGS. MADE A FEW MINOR TWEAKS TO THE FORECAST BUT OTHERWISE THE BULK OF THE FORECAST REMAINS ON TRACK. PREVIOUS DISCUSSION... MID LEVEL MOISTURE FROM CLOSED LOW OVER SOUTH DAKOTA THIS MORNING CONTINUES TO STREAM EAST-SOUTHEAST IN THE CONFLUENT FLOW OVER THE GREAT LAKES INTO THE NORTHEAST. THIS WILL RESULT IN INCREASING MID AND HIGH CLOUDS ACROSS SOUTHERN NEW ENGLAND AS THE DAY PROGRESSES. ALTHOUGH LATE APRIL SUN ANGLE MAY BE HIGH ENOUGH TO YIELD AT LEAST DIM SUNSHINE THRU THE CLOUD COVER. REGARDING HIGH TEMPS THIS AFTERNOON...GIVEN SURFACE PRESSURES ACROSS THE AREA ARE ONLY ABOUT 1015 MB...THIS PROMOTES A DEEP BLYR WITH MDL SNDGS SUGGESTING MIXING TO 800 MB. THIS COMBINED WITH 850 MB TEMPS AROUND +2C WILL SUPPORT HIGHS IN THE LOW TO MID 60S AWAY FROM COASTAL SEABREEZES. MAY HAVE TO SHAVE A FEW DEGS OFF THESE HIGHS IF MID DECK OF CLOUDS REMAINS PERSISENT. SO OVERALL A PLEASANT DAY BY LATE APRIL STANDARDS WITH DIM SUNSHINE THRU MID/HIGH CLOUDS...LIGHT WINDS AND TEMPS IN THE LOW TO MID 60S AWAY FROM THE IMMEDIATE COASTLINE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... *** MUCH NEEDED WIDESPREAD APPRECIABLE RAINFALL TUE ALONG WITH MUCH COOLER THAN NORMAL TEMPS *** AS CLOSED LOW OVER SOUTH DAKOTA BECOMES AN OPEN WAVE...LOW PRES TRACKS FROM THE GREAT LAKES TONIGHT TO SOUTH OF THE NEW ENGLAND TUE. MODEST PWAT PLUME TO WORK WITH AS ANOMALIES ARE ABOUT +1 STANDARD DEVIATIONS ABOVE CLIMO. FAIRLY BAROCLINIC WAVE BY LATE APRIL STANDARDS ALONG WITH MODEST FGEN. HOWEVER NAM AND GFS DIFFER ON LOCATION AND MAGNITUDE OF FGEN WHICH IS TYPICAL AT THIS TIME RANGE. NONETHELESS DEEP LAYER MOISTURE...SYNOPTIC SCALE LIFT AND FRONTAL SCALE FORCING WILL YIELD A WIDESPREAD RAIN WITH APPRECIABLE QPF. TIMING...DEEP LAYER OF DRY AIR CURRENTLY IN PLACE ACROSS SOUTHERN NEW ENGLAND WILL LIKELY DELAY THE ONSET OF RAIN AROUND OR AFTER MIDNIGHT TONIGHT. GFS AND ITS ENSEMBLES ARE ON THE FAST EDGE OF THE GUID ENVELOPE WITH PRECIP ARRIVING AFTER 21Z TODAY ACROSS HFD-BAF. WHILE THIS IS POSSIBLE ANY RAIN AFTER 21Z WILL BE VERY LIGHT AND SPOTTY. HEAVIEST/STEADIEST RAINFALL OCCURS DURING THE DAY TUE. SOME MODEL SPREAD/UNCERTAINTY ON DEPARTURE OF RAIN. GFS THE FASTEST WITH PRECIP ENDING LATE TUE AFTN WITH REMAINDER OF GUID SUPPORTING TUE EVENING OR OVERNIGHT. PTYPE...DESPITE SUB FREEZING 925 MB AND 850 TEMPS ACROSS NORTHERN MA LATER TUE...WARM LAYER ABOVE 850 MB WILL YIELD A COLD RAIN FOR THE REGION. HOWEVER AS THIS WARM LAYER BEGINS TO ERODE LATER TUE RAIN MAY MIX WITH SLEET AND/OR SNOW BEFORE ENDING ACROSS NORTHERN MA. ANY BRIEF CHANGEOVER TO SLEET AND/OR SNOW WILL HINGE ON PRECIP INTENSITY AND ASSOCIATED DIABATIC COOLING/MELTING. WILL NEED TO WATCH THIS CLOSELY. YES...IT/S STILL APRIL IN NEW ENGLAND. TEMPS...CHILLY AIRMASS ON POLEWARD SIDE OF THIS FRONTAL BOUNDARY. COMBINATION OF PRECIP...LOW WETBULB TEMPS AND NORTHEAST WINDS WILL YIELD TEMPS WELL BELOW NORMAL. THUS BLENDED IN THE COLDER MODEL 2 METER TEMPS AND THIS YIELDS HIGHS ONLY IN THE U30S FOR THE HIGHER TERRAIN INCLUDING WORCESTER. NOT MUCH WARMER ELSEWHERE WITH HIGHS IN THE 40S BUT FEELING COOLER ESPECIALLY EASTERN MA WITH NE WINDS 15-20 MPH OFF THE COOL OCEAN WATERS. QPF...GIVEN EVENT IS STILL 36+ HRS AWAY FOLLOWED A MODEL BLEND WHICH OFFERS 0.25 TO 0.75 INCHES. GEFS HAS 70% AND GREATER PROBS FOR 0.50 INCH OF QPF. IN ADDITION GEFS MEAN CENTERED AROUND 0.50 INCHES. THUS APPRECIABLE RAINFALL EXPECTED HOWEVER DIFFICULT AT THIS TIME RANGE TO PINPOINT EXACT LOCATION OF HEAVIER MESOSCALE RAIN BANDS. IN ADDITION GFS AND NAM SUGGEST SOME UPSLOPE ENHANCEMENT POSSIBLE TUE MORNING ACROSS THE EAST SLOPES OF THE BERKSHIRES INTO NORTHWEST HARTFORD COUNTY. NEVERTHELESS BENEFICIAL RAINS FOR THE ENTIRE REGION. THUNDER POTENTIAL...WITH FRONTAL WAVE TRACKING SOUTH OF NEW ENGLAND WARM SECTOR WILL REMAIN OFFSHORE. HOWEVER MARGINAL ELEVATED INSTABILITY ACROSS THE SOUTH COAST. THUS HAVE KEPT SLIGHT CHANCE OF THUNDER FROM PREVIOUS FORECAST BUT CONFINED TO SOUTH COAST INCLUDING CAPE COD AND THE ISLANDS. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... OVERVIEW... H5 CUTOFF LOW PRESSURE/COLD POOL WILL CONTINUE TO LINGER ACROSS NORTHERN QUEBEC AND LABRADOR THROUGH THE LATTER PORTIONS OF THE WORK WEEK...KEEPING THE REGION IN A W-NW CYCLONIC WIND FLOW. A COUPLE OF SHORT WAVES WILL EJECT OUT OF THE UPPER PLAINS...PUSHING QUICKLY ACROSS THE REGION...FIRST LATE TUE NIGHT INTO WED...THEN A SECOND FRI INTO SAT. LOWERED H5 HEIGHTS WILL KEEP TEMPERATURES GENERALLY NEAR OR JUST BELOW SEASONAL LEVELS. THE CANADIAN CUTOFF UPPER LOW LOOKS TO SLOWLY EXIT TO GREENLAND BY THIS WEEKEND...BUT THE W-NW FLOW WILL LINGER. LARGE HIGH PRES OUT OF CENTRAL CANADA WILL EXPAND INTO THE NORTHEAST...BRINGING DRY AND NEAR SEASONABLE CONDITIONS FOR THE UPCOMING WEEKEND. SOME QUESTIONS ABOUT A SOUTHERN STREAM SYSTEM THAT MAY PUSH FAR ENOUGH N TO BRING SOME PRECIPITATION LATE THIS WEEKEND...BUT TIMING IS VERY MUCH IN QUESTION. DETAILS... TUESDAY NIGHT... LEFTOVER SHOWERS WILL PUSH OFF THE S COAST TUE EVENING AS NOSE OF HIGH PRES RIDGE BUILDS SE OUT OF N NY/CENTRAL CANADA. MOST OF THE SHOWERS SHOULD BE OFFSHORE BY MIDNIGHT...BUT A FEW MAY LINGER ACROSS S COASTAL AREAS A FEW HOURS LONGER. MIGHT SEE A FEW SPOTTY LIGHT SNOW SHOWERS OR EVEN A LITTLE SLEET AS THE PRECIP ENDS ACROSS THE HIGHER TERRAIN OF N CENTRAL AND W MA...BUT THIS WILL NOT LAST LONG. LEFTOVER GUSTS UP TO 20-25 MPH ALONG THE S COAST WILL DIMINISH TUE EVENING. OTHERWISE...EXPECT SKIES TO BECOME PARTLY CLOUDY ACROSS MOST AREAS...WITH MORE CLOUDS LINGERING ALONG THE S COAST INTO THE PRE DAWN HOURS BEFORE MOVING OFFSHORE. AS COLDER AIR FILTERS IN...TEMPS WILL FALL BACK TO THE 30S...AND MIGHT EVEN SEE SOME READINGS IN THE UPPER 20S ACROSS THE HIGHER INLAND TERRAIN. WILL HAVE TO WATCH OUT FOR POSSIBLE FROST IN SOME AREAS WHERE THE GROWING SEASON HAS ALREADY BEGUN...NAMELY PORTIONS OF COASTAL ESSEX COUNTY AS WELL AS INTERIOR SE MA...N RI AND NE CT. WEDNESDAY... HIGH PRESSURE RIDGING BUILDS ACROSS THE REGION SO WILL SEE DRY CONDITIONS AND MAINLY SUNNY SKIES. LOCAL SEA BREEZES WILL LIKELY DEVELOP DURING THE AFTERNOON. TEMPS WILL ONLY RISE TO THE TO THE LOWER 50S ACROSS THE HIGHER INLAND TERRAIN AS WELL AS THE CAPE AND ISLANDS...RANGING TO AROUND 60 ACROSS THE LOWER CT VALLEY. SKIES WILL REMAIN MOSTLY CLEAR THROUGH MOST OF WED NIGHT...THEN SOME CLOUDS WILL START TO WORK INTO N CENTRAL CT TOWARD DAYBREAK. WITH LIGHT/VRBL WINDS...WILL SEE GOOD RADIATIONAL COOLING AGAIN WITH DEWPTS LOWERING TO THE UPPER TEENS AND 20S AWAY FROM THE COAST. MAY SEE TEMPS BOTTOM OUT AROUND 20 DEGREES ALONG THE E SLOPES OF THE BERKSHIRES...RANGING TO THE LOWER-MID 30S ALONG THE S COAST. THURSDAY-FRIDAY... WITH FAST MOVING FLOW ALOFT CONTINUING...WILL SEE ANOTHER H5 SHORT WAVE PUSH TOWARD THE REGION. SOME TIMING ISSUES AMONGST THE 00Z MODEL SUITE...BUT LOOKS LIKE THE NORTHERN EDGE OF PRECIP FROM FAST MOVING LOW PRES PASSING S OF NEW ENGLAND WILL MOVE IN THU AFTERNOON...WITH THE BEST CHANCE FOR SHOWERS ALONG THE S COAST THU NIGHT. WINDS BECOME LIGHT E-NE...SO WILL NOT BE AS COLD THU NIGHT SO EXPECT PRECIP TO BE MAINLY RAIN. KEPT LOW CHANCE GOING AT MOST. THE LOW WILL PUSH OFFSHORE BY MID MORNING FRIDAY...THEN CONDITIONS IMPROVE FROM N-S DURING THE DAY. TEMPS WILL RISE TO NEAR SEASONABLE LEVELS...TOPPING OFF IN THE UPPER 50S TO MID 60S...EXCEPT REMAINING COOLER ALONG THE IMMEDIATE COAST. SATURDAY-SUNDAY... SOUTHERN EXTENT OF LARGE HIGH PRES BUILDS SE OUT OF CENTRAL CANADA. MODELS TENDING TO KEEP DRY AND COOL CONDITIONS ACROSS THE REGION THROUGH THE WEEKEND. DO NOTE THE 00Z ECMWF BRINGS MOISTURE INTO THE REGION SUNDAY NIGHT FROM A SOUTHERN STREAM LOW PRES CENTER ACROSS THE OHIO VALLEY. LOW CONFIDENCE WITH THIS FEATURE THIS FAR OUT SO KEPT DRY AND COOL CONDITIONS GOING FOR NOW. && .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/...HIGH CONFIDENCE. BEFORE 00Z...VFR. A FEW SPRINKLES POSSIBLE. TONIGHT...VFR TO START BUT LOWERING TO MVFR TOWARD MORNING WITH RAIN /MAINLY LIGHT/ BECOMING WIDESPREAD AFTER 06Z. TUESDAY...MVFR BECOMING WIDESPREAD WITH IFR POSSIBLE OVER EASTERN MA. STEADY RAIN WITH EMBEDDED MODERATE TO HEAVY RAIN AT TIMES. NE WINDS INCREASING TO 15 TO 20 KT ACROSS EASTERN MA WITH GUSTS UP TO 25 KT POSSIBLE. LOW POSSIBILITY FOR THUNDER ACROSS THE ISLANDS. TUESDAY NIGHT...MVFR/IFR TO START WITH CONDITIONS IMPROVING THROUGH THE NIGHT TO VFR. KBOS TAF...HIGH CONFIDENCE FOR VFR AND DRY WEATHER. LIGHT S-SW WIND WILL BECOME E-SE EARLY THIS AFTERNOON. KBDL TAF...HIGH CONFIDENCE FOR VFR AND DRY WEATHER. LOW RISK OF SOME VERY LIGHT RAIN/SPRINKLES AFTER 21Z WITH STEADIER RAIN ARRIVING AROUND 06Z TONIGHT. OUTLOOK /WEDNESDAY THROUGH FRIDAY/... WEDNESDAY...HIGH CONFIDENCE. VFR. THURSDAY...MODERATE CONFIDENCE. VFR EARLY THU...THEN AREAS OF MVFR CIGS/VSBYS MAINLY S OF THE MASS PIKE IN SHOWERS AND PATCHY FOG. LOW CHANCE FOR LOCAL IFR CONDITIONS MAINLY THU NIGHT. IMPROVING FROM N-S AFTER MIDNIGHT. FRIDAY...MODERATE TO HIGH CONFIDENCE. LEFTOVER MVFR CIGS/VSBYS ALONG THE S COAST EARLY...THEN IMPROVING. OTHERWISE...VFR.
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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 /THROUGH TUESDAY/...HIGH CONFIDENCE. TODAY ... LIGHT WINDS WITH HIGH PRES OVERHEAD. DRY WEATHER AND GOOD VSBY TOO. TONIGHT ... WINDS BECOMING ENE LATE AS LOW PRES ENTERS PA. RAIN OVERSPREADS RI WATERS LATE. TUE ... LOW PRES TRACKS JUST SOUTH OF NEW ENGLAND. THIS WILL YIELD AN INCREASE IN ENE WINDS OF 15 TO 20 KT WITH LOW RISK OF A FEW 25 KT GUSTS VICINITY OF CAPE COD AND NANTUCKET WATERS EASTWARD TOWARDS WESTERN GEORGES BANK. WIDESPREAD RAIN AND AREAS OF FOG LIMIT VSBY. OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...MODERATE CONFIDENCE. TUESDAY NIGHT... NE WINDS GUSTING TO 20-25 KT ACROSS THE EASTERN WATERS EARLY... THEN WILL DIMINISH AS THEY BACK TO N-NW. SEAS UP TO 5-6 FT FROM EAST OF CAPE COD TO ACROSS THE SOUTHERN WATERS WILL CONTINUE THROUGH THE NIGHT. SMALL CRAFTS LIKELY NEEDED. REDUCED VSBYS IN RAIN AND PATCHY FOG SHOULD IMPROVE BY AROUND MIDNIGHT FROM N-S. WEDNESDAY... N-NW WINDS AT 10-15 KT WILL SHIFT TO SW ACROSS THE SOUTHERN WATERS AND MAY GUST TO 20 KT THERE. SEAS LINGER AT AROUND 5 FT DURING WED...THEN WILL SUBSIDE WED NIGHT. THURSDAY... EXPECT LIGHT E-SE WINDS THU...SHIFTING TO S-SW ON THE EASTERN WATERS THU NIGHT. SEAS 4 FT OR LESS. REDUCED VSBYS IN SCATTERED SHOWERS AND PATCHY FOG ACROSS THE SOUTHERN WATERS AS WELL AS THE WATER E OF CAPE COD. FRIDAY... WINDS SHIFT BACK TO E-NE ACROSS ALL WATERS BY FRI AFTERNOON... THEN BECOME LIGHT AND VARIABLE FRI NIGHT. SEAS 3 FT OR LESS. REDUCED VSBYS EARLY FRI IN SCT SHOWERS AND PATCHY FOG ON THE SOUTHERN WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/EVT NEAR TERM...NOCERA/DUNTEN SHORT TERM...NOCERA LONG TERM...EVT AVIATION...DUNTEN/EVT MARINE...NOCERA/EVT

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