Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250840 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 440 AM EDT MON APR 25 2016 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... CHILLY START TO THE DAY WITH DRY AIRMASS IN PLACE AS DEW PTS REMAIN IN THE 20S AND 30S. THIS COMBINED WITH LIGHT WINDS HAS RESULTED IN AIR TEMPS IN MOST LOCATIONS DOWN IN THE 30S DURING THE PREDAWN HOURS. HOWEVER AS MID DECK OF CLOUDS OVERSPREAD THE AREA EARLY THIS MORNING TEMPS HAVE ACTUALLY RISEN A FEW DEGS WITH 3 AM TEMPS MAINLY IN THE LOW TO MID 40S. GIVEN THIS MID DECK OF CLOUDS WILL REMAIN WITH US THE REMAINDER OF THE MORNING...NOT EXPECTING TEMPS TO DROP AS LOW AS EARLIER THOUGHT. THUS HAVE CANCELLED THE FROST ADVISORY. AS FOR SKY COVER...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 MID AND HIGH CLOUDS ON THE INCREASE 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 PRES OVER 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. && .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/...
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OVERVIEW... H5 CUTOFF LOW PRESSURE/COLD POOL WILL CONTINUE TO LINGER ACROSS NORTHERN QUEBEC AND LABRADOR THE MIDDLE AND 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 THU NIGHT INTO WED...THEN A SECOND FRI INTO SAT. LOWERED H5 HEIGHTS WILL BE 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. THE DAILIES... TUESDAY... SHORTWAVE MOVING AROUND THE LABRADOR UPPER LOW WILL GENERATE AT LEAST ONE WAVE ON THE COLD FRONT SOUTH OF NEW ENGLAND. THIS WILL MAINTAIN RAIN/SHOWERS ACROSS SOUTHERN NEW ENGLAND MUCH OF THE DAY...TAPERING LATE. PRECIPITABLE WATER VALUES WILL BE OVER AN INCH...ENOUGH TO PROVIDE A GOOD WETTING WITH AREAL VALUES FORECAST AT 0.50 TO 0.75 INCHES. WIND WILL ALSO BECOME A FACTOR. THE APPROACHING SURFACE LOW WILL GENERATE A STRONG LOW LEVEL NORTHEAST WIND JUST BEHIND THE FRONT. THIS WILL MOSTLY AFFECT EAST COASTAL MASS WITH GUSTS 20-25 KNOTS POSSIBLE. SHOWERS TAPER OFF DURING THE FIRST PART OF TUESDAY NIGHT. HIGH PRESSURE BUILDS IN FROM THE NORTHWEST WITH CLEARING SKIES WITH A COLDER DRIER AIRMASS. WEDNESDAY... HIGH PRESSURE AND DRY WEATHER. MIXING SHOULD REACH TO 850 MB WHERE TEMPS OF -1C TO -3C WILL SUPPORT MAX TEMPS IN THE 50S...NEAR 60 IN SPOTS. RADIATIONAL COOLING WEDNESDAY NIGHT AND DEW POINTS IN THE 20S WILL ALLOW MIN TEMPS IN THE UPPER 20S TO MID 30S AND POSSIBLY A LITTLE LOWER. THURSDAY-FRIDAY... ANOTHER SHORTWAVE APPROACHES FROM THE MIDWEST AND GENERATES SURFACE LOW PRESSURE WHICH PASSES SOUTH OF NEW ENGLAND. GFS AND ECMWF BRING MEASURABLE PCPN INTO THE REGION LATE THURSDAY AFTERNOON CONTINUE THROUGH FRIDAY MORNING. THE BULK OF FORCING AND QPF REMAIN SOUTH OF NEW ENGLAND SO AMOUNTS SHOULD REMAIN LIGHT. WE HAVE STAYED WITH LOW- END CHANCE POPS. SATURDAY-SUNDAY... HIGH PRESSURE BUILDS SOUTH FROM CANADA WITH DRY WEATHER. ANOTHER SHORTWAVE EJECTS FROM THE SOUTHWEST USA DURING THIS PERIOD. HERE THE MODELS DIVERGE WITH THE ECMWF BRINGING RAIN INTO SOUTHERN NEW ENGLAND SUNDAY MORNING WHILE THE GFS REMAINS DRY. WE HAVE USED A COMPROMISE IN TIMING...BUT ONE THAT KEEPS RAIN OUT OF OUR AREA UNTIL AFTER THE FORECAST PERIOD.
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&& .AVIATION /09Z MONDAY THROUGH FRIDAY/...
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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/ ... HIGH CONFIDENCE. TODAY ... VFR/DRY WEATHER AND LIGHT WINDS. LOW RISK OF VERY LIGHT RAIN OR SPRINKLES AFTER 21Z HFD TO BAF. HIGH FORECAST CONFIDENCE. 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. KBOS TAF...HIGH CONFIDENCE FOR VFR AND DRY WEATHER. LIGHT SSW WIND WILL BECOME ESE 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 03Z- 06Z TONIGHT. OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/... TUESDAY NIGHT...MODERATE CONFIDENCE. MVFR-IFR CIGS/MVFR VSBYS EARLY TUE NIGHT IN LIGHT RAIN AND PATCHY FOG...IMPROVING TO VFR FROM N-S LATE. NE WINDS GUSTING TO AROUND 20 KT ALONG THE CAPE COD AND SOUTH COASTS. 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...
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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/...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.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/EVT NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...WTB/EVT AVIATION...NOCERA/EVT MARINE...NOCERA/EVT

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