Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170652 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 252 AM EDT WED SEP 17 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE REGION BRINGING COOLER AND DRIER WEATHER THROUGH THE REMAINDER OF THE WEEK. SOME FROST IS POSSIBLE EARLY FRIDAY MORNING IN SOME AREAS. THE HIGH WILL THEN SLIP OFFSHORE AND SOUTHWEST FLOW BEHIND IT WILL ALLOW TEMPERATURES TO WARM TO NEAR OR ABOVE NORMAL SUNDAY AND MONDAY. A COLD FRONT MOVES THROUGH ON MONDAY...FOLLOWED BY COOLER WEATHER BY TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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CALM WINDS...CLEAR SKIES...AND A BIT OF LEFTOVER MOISTURE FROM THE SCATTERED RAIN SHOWERS YESTERDAY HAS ALLOWED PATCHY FOG TO DEVELOP ACROSS THE REGION. THIS FOG IS LOCALLY DENSE...REDUCING VISIBILITIES BELOW A MILE IN MANY LOCATIONS AND BELOW A QUARTER OF A MILE IN SOME AREAS. HIGH PRESSURE BUILDS INTO THE REGION TODAY AS LOW PRESSURE MOVES INTO SOUTHERN ONTARIO. EXPECT MOSTLY SUNNY SKIES AND TEMPERATURES CLIMBING INTO THE UPPER 60S TO LOWER 70S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
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TONIGHT...LIGHT WINDS TURN TO THE SOUTHWEST AHEAD OF A COLD FRONT STEMMING FROM A WEAK LOW PRESSURE SYSTEM IN SOUTHEASTERN CANADA. THIS WILL KEEP TEMPERATURES ON THE COOL SIDE BUT STILL IN THE MID 40S TO MID 50S. THURSDAY...THE COLD FRONT WILL MOVE THROUGH SOUTHERN NEW ENGLAND DURING THE DAY...SHIFTING WINDS TO THE NORTHWEST. THE FRONT APPEARS TO BE MOISTURE STARVED BY THE TIME IT MOVES INTO THE AREA SO EXPECT NOTHING MORE THAN A FEW CLOUDS. MAIN CONCERN WITH THE FRONT WILL BE IT USHERING IN COOLER TEMPERATURES.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... BIG PICTURE... UPPER TROUGH OVER THE NORTHEAST USA MOVES OFF BY FRIDAY WITH THE FLOW CONVERTING TO ZONAL FOR FRIDAY AND SATURDAY. SHORTWAVE FROM THE GULF OF ALASKA MERGES WITH ENERGY FROM THE CANADIAN ARCTIC LATE WEEK WHILE AN UPPER RIDGE BUILDS OVER THE PACIFIC COAST. BOTH OF THESE ACTIONS WILL DIG AN UPPER TROUGH OVER THE GREAT LAKES...WHICH MOVES INTO THE NORTHEAST USA EARLY NEXT WEEK. UPPER HEIGHTS ARE BELOW NORMAL THURSDAY-FRIDAY BUT MODERATE TO 60 METERS ABOVE NORMAL BY SUNDAY. THIS SUGGESTS A COOL FINISH TO THE WEEK FOLLOWED BY A SMALL WARMING TREND OVER THE WEEKEND...THEN COOLING AGAIN BY TUESDAY AS THE UPPER TROUGH AND COLDER TEMPS ALOFT MOVE BACK IN. THE DAILIES... THURSDAY... UPPER SHORTWAVE MOVES ACROSS SOUTHERN NEW ENGLAND AND PUSHES A WEAK SECONDARY FRONT THROUGH. SUFFICIENT MOISTURE FOR SOME CLOUDS ESPECIALLY NORTH OF THE MASS PIKE. BUT COLD ADVECTION ALOFT IS WEAK AS IS INSTABILITY...TOTALS IN THE MID 40S AND MID LEVEL LAPSE RATES A LITTLE OVER 5.5C/KM...SO WE/RE NOT BIG ON CONVECTION. MOST LIKELY A FEW SHOWERS. TEMPS AT 850 MB 5-7C SUPPORT MAX TEMPS MID 60S TO LOWER 70S. HIGH PRESSURE BUILDS OVERHEAD THURSDAY NIGHT. MOSTLY CLEAR SKIES AND LIGHT WINDS WILL ALLOW RADIATIONAL COOLING. DEW POINTS WILL BE IN THE 30S AWAY FROM THE COAST AND LOW 40S COAST AND ISLANDS. EXPECT MIN TEMPS 35-40 AWAY FROM THE COAST AND 40S ALONG THE COAST. IF MVY AIRPORT DECOUPLES...IT WILL BE NEAR 40 OR LOW 40S. THESE TEMPS WILL MEAN A POTENTIAL FOR PATCHY FROST. MOSTLY LIKELY AREAS WOULD BE SOUTHWEST NH AND NORTHWEST MASS. FRIDAY-SATURDAY...HIGH PRESSURE OVER THE REGION FRIDAY SHIFTS EAST SATURDAY...BUT PROVIDES DRY WEATHER BOTH DAYS. LIGHT WINDS FRIDAY...DEVELOPING SOUTH WIND SATURDAY. MODEL WIND GUSTS FOR SATURDAY DO NOT REFLECT WINDS ALOFT IN THE MIXED LAYER. SO WE BUMPED VALUES UP TO NEAR 20 KTS. FRIDAY TEMPS ALOFT 0-2C SUPPORTS MAX SFC TEMPS UPPER 50S TO MID 60S...SATURDAY TEMPS ALOFT 4-6C SUPPORTS MAX SFC TEMPS MID 60S TO LOWER 70S. RADIATIONAL COOLING AGAIN FRIDAY NIGHT BUT DEW POINTS WILL BE A LITTLE HIGHER...35-45...SO MIN SFC TEMPS UPPER 30S AND 40S. SOUTH WINDS WILL BRING HIGHER DEW POINTS SATURDAY NIGHT WITH MIN TEMPS UPPER 40S AND 50S. SUNDAY... INCREASING SOUTH WIND SUNDAY WITH SOME INCREASE IN CLOUDS AS A COLD FRONT APPROACHES. BUT THE DAY SHOULD REMAIN DRY WITH PLENTY OF SUN. MODEL GUST FORECASTS ARE AGAIN LOWER THAN THE MIXED LAYER WOULD SUGGEST. SOUTHWEST WINDS SHOW A GUST POTENTIAL TO 25 KNOTS AND POSSIBLY AS HIGH AS 30 KNOTS. WE BUMPED THE SUNDAY WIND GUSTS UP INTO THE LOW 20S. TEMPS ALOFT AROUND 10C AND POSSIBLY TO 12C. THIS MEANS MID TO UPPER 70S...AND WITH SUFFICIENT MIXING THERE MAY BE SOME SPOTS WITH LOW 80S. SOUTHWEST WIND MAY BUFFER THESE VALUES WHERE IT COMES OFF THE OCEAN. SUNDAY NIGHT-MONDAY...COLD FRONT MOVES THROUGH OUR AREA EARLY MONDAY MORNING THROUGH MIDDAY. BEST DYNAMICS MOVE FROM NEW YORK UP THROUGH VERMONT. BUT SUFFICIENT LOW LEVEL CONVERGENCE AND MOISTURE TO FORECAST SHOWERS WITH COLD FROPA. MONDAY NIGHT-TUESDAY...COLDER AIR ADVECTS IN BEHIND THE COLD FRONT. MEANWHILE THE UPPER TROUGH MOVES EAST FROM THE GREAT LAKES WITH COOLING TEMPS ALOFT. TEMPS ALOFT 0-2C SUPPORTING UPPER 50S TO MID 60S. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
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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 WEDNESDAY/...HIGH CONFIDENCE. THROUGH 12Z...MODERATE CONFIDENCE. MAINLY VFR. LOCALLY DENSE FOG HAS DEVELOPED ACROSS PORTIONS OF THE REGION REDUCING VISIBILITIES TO MVFR/IFR. TODAY THROUGH THURSDAY...HIGH CONFIDENCE. VISIBILITIES SHOULD IMPROVE QUICKLY AS FOG DISSIPATES. VFR CONDITIONS EXPECTED. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...THURSDAY THROUGH SUNDAY...HIGH CONFIDENCE. VFR THROUGH THE PERIOD. SOUTHWEST WINDS SATURDAY MAY GUST TO 20 KNOTS. SOUTHWEST WINDS SUNDAY MAY GUST 25 KNOTS...POSSIBLY A LITTLE HIGHER.
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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 WEDNESDAY NIGHT/...MODERATE CONFIDENCE. MODERATE TO HIGH CONFIDENCE. SWELL FROM HURRICANE EDOUARD WILL SLOWLY BUILD INTO THE COASTAL WATERS WITH INCREASING SEAS. REGULAR FORECAST GUIDANCE HAS BEEN UNRELIABLE BUT HURRICANE WAVE WATCH GUIDANCE LOOKS MUCH MORE REASONABLE SO HAVE USED THAT. EXPECT SEAS TO REMAIN BELOW 5 FEET EXCEPT PERHAPS A FEW HOURS THURSDAY MORNING. WINDS REMAIN BELOW 15 KTS THROUGH THE PERIOD. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. THURSDAY... HIGH PRESSURE BUILDS JUST NORTH OF THE WATERS. NORTH WINDS 15 KNOTS OR LESS. LINGERING 5 FEET ON THE EASTERN OUTER WATERS FROM SWELL...BUT THIS WILL BE SUBSIDING. FRIDAY...HIGH PRESSURE NORTH OF THE WATERS WILL BRING A STRONGER NORTHEAST WIND WITH POTENTIAL FOR 20 KNOTS ESPECIALLY AROUND NANTUCKET AND ON THE SOUTHERN OUTER WATERS. SEAS WILL INCREASE TO 5- 7 FEET IN THIS NORTHEAST FLOW...DIMINISHING AS THE WINDS DIMINISH FRIDAY EVENING. SATURDAY-SUNDAY...HIGH PRESSURE MOVES OFF THROUGH THE MARITIMES. THE WINDS WILL SHIFT TO SOUTH SATURDAY AND SOUTHWEST SUNDAY. GUSTS TO 20 KNOTS BOTH DAYS WITH POTENTIAL FOR 25 KNOT GUSTS ON SUNDAY. MOST SEAS WILL REMAIN BELOW 5 FEET...BUT THE WATERS EAST OF MASS BAY AND IPSWICH BAY MAY SEE SEAS RISE AGAIN TO AROUND 5 FEET.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/RLG NEAR TERM...RLG SHORT TERM...RLG LONG TERM...WTB AVIATION...WTB/RLG MARINE...WTB/RLG

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