Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 210810 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 310 AM EST FRI NOV 21 2014 .SYNOPSIS...
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BLUSTERY AND UNSEASONABLY COLD CONDITIONS TODAY. TEMPERATURES MODERATE SATURDAY WITH GUSTY SOUTHWEST WINDS...THEN A SIGNIFICANT WARM-UP IS IN STORE SUNDAY AND MONDAY...BUT IT WILL LIKELY BE ACCOMPANIED BY A PERIOD OF RAIN. A COASTAL STORM MAY AFFECT THE REGION SOMETIME DURING THE MIDDLE OF NEXT WEEK BUT IT IS UNCERTAIN HOW CLOSE IT WILL TRACK TO NEW ENGLAND.
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&& .NEAR TERM /THROUGH TODAY/...
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MID LEVEL TROF AND CORE OF COLD AIR ALOFT MOVES INTO NEW ENG TODAY BUT COLUMN IS VERY DRY SO EXPECT MOSUNNY SKIES. UNSEASONABLY COLD CONDITIONS AS 850 MB TEMPS -13/14C WHICH TRANSLATES TO MAXES UPPER 20S NW HIGHER TERRAIN TO MID 30S COASTAL PLAIN. WIND WILL BE A FACTOR AS PRESSURE GRADIENT AND GOOD MIXING SUPPORTS NW WIND GUSTS TO 25-30 MPH WHICH WILL MAKE IT FEEL CONSIDERABLY COLDER IN THE TEENS AND 20S.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/...
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TONIGHT... CENTER OF HIGH PRES MOVES TO THE MID ATLC COAST BUT RIDGE AXIS BUILDS INTO NEW ENG WHICH WILL RESULT IN CLEAR SKIES AND DIMINISHING WIND AS PRESSURE GRADIENT RELAXES. GIVEN VERY DRY AIRMASS IT WILL BE A COLD NIGHT AS DECENT RADIATIONAL COOLING DEVELOPS. MINS WILL BE MOSTLY IN THE TEENS...EXCEPT LOWER 20S ALONG THE IMMEDIATE COAST. LOW PROB FOR SOME SINGLE NUMBER MIN TEMPS W MA AND SW NH. SATURDAY... HIGH PRES BUILDS S OF NEW ENG WITH SUNSHINE GIVING WAY TO INCREASING AFTERNOON CLOUDS AS LOW AND MID LEVEL MOISTURE INCREASES FROM THE WEST. INCREASING SW FLOW BRINGS MILDER AIR INTO SNE AS PRONOUNCED LOW AND MID LEVEL WARMING OCCURS. AFTER A RATHER COLD START...TEMPS WILL RECOVER INTO THE MID 30S TO LOWER 40S. 40 KT LOW LEVEL JET DEVELOPS BY LATE DAY WHICH WILL LEAD TO GUSTY SW WINDS IN THE AFTERNOON/EVENING...ESPECIALLY NEAR THE COAST WHERE BETTER LOW LEVEL LAPSE RATES.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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BIG PICTURE... BUILDING UPPER RIDGE ALONG THE EAST COAST BRINGS HEIGHTS OVER NEW ENGLAND BACK TO NORMAL DURING THE WEEKEND AND ABOVE NORMAL EARLY WEEK. SOUTHERN STREAM SHORTWAVE JUST OFF THE PACIFIC COAST WILL DIG AS IT MOVES TO TEXAS OVER THE WEEKEND. THE BUILDING RIDGE WILL THEN DEFLECT THE SOUTHERN SHORTWAVE NORTH WHERE IT MERGES WITH A NORTHERN STREAM SHORTWAVE MOVING EAST FROM THE GULF OF ALASKA. THIS MEANS A BROAD TROUGH FORMING OVER THE CENTER OF THE NATION EARLY WEEK WITH BELOW NORMAL HEIGHTS. THIS BROAD TROUGH SLOWLY MOVES EAST TO NEW ENGLAND MID TO LATE WEEK. FOR NEW ENGLAND THIS WOULD MEAN A WARMING TREND OVER THE WEEKEND AND MILD TEMPS EARLY NEXT WEEK...THEN COOLING TO BELOW NORMAL BY THANKSGIVING. THE GFS AND ECMWF ARE IN GOOD AGREEMENT THROUGH TUESDAY. THE ECWMF IS THEN FASTER IN MIGRATING THE PLAINS TROUGH THROUGH NEW ENGLAND AND OFF TO THE EAST WHILE THE GFS MAINTAINS THE TROUGH AXIS TO OUR WEST THROUGH THURSDAY. MODERATE TO HIGH FORECAST CONFIDENCE THROUGH TUESDAY...LOW CONFIDENCE WEDNESDAY AND THURSDAY. THE DAILIES... SATURDAY NIGHT...INCREASING AND THICKENING CLOUDS AS A NORTHERN STREAM COLD FRONT MOVES SOUTH INTO NORTHERN NEW ENGLAND. VERTICAL DISTRIBUTION IS SOMEWHAT FAVORABLE FOR PCPN AHEAD OF THE FRONT...BUT WARM ADVECTION LIFT IS NEGLIGIBLE. JET DYNAMICS IS QUESTIONABLE. CAN/T RULE OUT A FEW LIGHT SPRINKLES. THE QUESTION OF PTYPE THEN COMES UP. TEMPS WILL BE STARTING OUT IN THE 30S AND MAY COOL A LITTLE BELOW FREEZING BEFORE THE CLOUDS THICKEN. THIS WOULD CAUSE SOME LIGHT FREEZING DRIZZLE OR FREEZING SPRINKLES. THE BEST CHANCE WOULD BE IN AREAS NORTH AND WEST OF I-495. BUT IF THE CLOUDS MOVE IN AND THICKEN A LITTLE FASTER...TEMPS WILL STAY ABOVE FREEZING AND PCPN...IF ANY...WOULD BE LIGHT RAIN. WE HAVE SLIGHT CHANCE POPS ACROSS THE REGION OVERNIGHT WITH A MENTION OF FREEZING RAIN AS NOTED ABOVE. SUNDAY...UPPER FLOW REMAINS WEST-EAST SO THAT THE NORTHERN COLD FRONT IS DOUBTFUL TO MAKE IT THROUGH SOUTHERN NEW ENGLAND. EXPECT ANY PRECIP TO MOVE OUT EARLY WITH CLOUDS BREAKING TO ALLOW SOME SUNSHINE. TEMPS AT THE TOP OF THE MIXED LAYER WARM A FEW DEGREES AND SHOULD SUPPORT MAX TEMPS IN THE UPPER 40S AND 50S. SUNDAY NIGHT-MONDAY... THE SOUTHERN STREAM SYSTEM LIFTS NORTH TO THE GREAT LAKES AND PULLS A WARM FRONT NORTH TOWARD NEW ENGLAND. A STRONG LOW LEVEL SOUTH JET WILL GENERATE FAVORABLE ISENTROPIC LIFT AS IT MOVES INTO THE REGION. TIMING OF THIS JET WOULD INDICATE THE LIFT ARRIVES AROUND MIDNIGHT OR SHORTLY AFTER. WE EXPECT RAIN TO DEVELOP IN SOUTHERN NEW ENGLAND AROUND THIS TIME. MODELS INDICATE THE JET WILL BE 60-65 KNOTS AND COULD GENERATE SOME GUSTY WINDS ESPECIALLY ALONG THE SOUTH COAST. PRECIP WATER VALUES ARE EXPECTED TO TOP OUT BETWEEN 0.75 AND 1.0 INCHES WHICH WOULD BE A LITTLE OVER 1 STD DEVIATION ABOVE NORMAL...SO TORRENTIAL RAIN IS NOT EXPECTED. THE WARM FRONT SHOULD LIFT NORTH OF OUR AREA DURING THE AFTERNOON. THIS SHOULD DIMINISH THE COVERAGE OF THE RAIN TO SHOWERS. THE CHANCE OF SHOWERS WILL CONTINUE THROUGH THE EVENING...ENDING AS THE ASSOCIATED COLD FRONT SWINGS OVER THE REGION OVERNIGHT. TUESDAY...THERE REMAINS SOME QUESTION AS TO HOW FAST THE COLD FRONT MOVES OFF TO THE EAST. THE GFS SOLUTION KEEPS A SOUTH-SOUTHWEST FLOW ALOFT AND A STRONG JET OVERHEAD. THE COLD FRONT WOULD HAVE DIFFICULTY MOVING EAST IN SUCH AN ENVIRONMENT. THE ECMWF SOLUTION SHOWS A MORE WESTERLY COMPONENT THAT WOULD BE SUFFICIENT TO MOVE THE FRONT THROUGH NEW ENGLAND AND OFF TO THE EAST. WE HAVE KEPT A LOW CHANCE OF SHOWERS TUESDAY IN EASTERN MASS BUT TRENDED TOWARD PARTIAL CLEARING AND COOLER WEATHER. WEDNESDAY-THANKSGIVING DAY...THE DIFFERENCES BETWEEN MODELS AMPLIFIES MIDWEEK...AND SO CONFIDENCE IS LOW. LOW PRESSURE WAVES MOVING UP THE OFFSHORE COLD FRONT MAY KEEP A CHANCE OF SHOWERS IN EASTERN MASS/RI ON WEDNESDAY BUT OTHERWISE WE HAVE CONTINUED THE TREND TO COOLER AND DRIER WEATHER AS WE MOVE INTO THE HOLIDAY
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...HIGH CONFIDENCE. TODAY...VFR. GUSTY NW WINDS TO 25 KT. TONIGHT...VFR WITH DIMINISHING WIND. SATURDAY...VFR. INCREASING SW WINDS IN THE AFTERNOON WITH GUSTS TO 25-30 KT DEVELOPING IN THE COASTAL PLAIN. KBOS TERMINAL...HIGH CONFIDENCE. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SATURDAY NIGHT... CLOUDS MOVE IN AT NIGHT...BRIEF MVFR POSSIBLE OVERNIGHT IN LIGHT SPRINKLES ESPECIALLY NORTH OF THE MASS PIKE. COULD BE LIGHT FREEZING DRIZZLE/FREEZING SPRINKLES NORTH AND WEST OF I-495. SUNDAY... VFR. DIMINISHING WIND. SUNDAY NIGHT-MONDAY...CIGS/VSBYS LOWER TO MVFR/IFR IN RAIN/FOG. SOUTH WIND AT 2000 FEET INCREASES TO 60-65 KNOTS ALONG THE COASTAL PLAIN LATE NIGHT AND MONDAY MORNING AND MAY GENERATE ANOTHER ROUND OF LOW LEVEL WIND SHEAR IN THAT AREA. CONDITIONS THEN IMPROVE TO VFR IN THE AFTERNOON WITH GUSTY SOUTHWEST WINDS. A COLD FRONT MOVES INTO SOUTHERN NEW ENGLAND AT NIGHT AND SHOULD GENERATE BRIEF MVFR IN SHOWERS. WIND WILL SHIFT FROM SSW TO WSW WITH THE WIND SHIFT. TUESDAY...VFR. A FEW BRIEF SHOWERS POSSIBLE IN EASTERN MASS/RI
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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. HIGH FORECAST CONFIDENCE THRU SATURDAY. TODAY...WE CONVERTED GALE WARNINGS TO SMALL CRAFT ADVISORIES FOR ALL WATERS. EXPECT WIND GUSTS TODAY WILL FALL JUST SHY OF GALES WITH NW GUSTS TO 30 KT. TONIGHT...WINDS GRADUALLY DIMINISH WITH SPEEDS DROPPING BELOW 20 KT LATE TONIGHT. SATURDAY...EXPECT INCREASING SW WINDS IN THE AFTERNOON AS DECENT LOW LEVEL JET DEVELOPS ACROSS THE REGION. GIVEN STILL WARM SST... GOOD MIXING OVER WATER SUPPORTS WIND GUSTS TO 30 KT WITH MARGINAL GALES POSSIBLE BY EVENING. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SUNDAY...SOUTHWEST WINDS CONTINUE TO GUST TO 30 KNOTS DURING THE DAY AND THEN DIMINISH IN THE EVENING. SEAS 5-8 FEET WILL DIMINISH IN THE EVENING. SUNDAY NIGHT-MONDAY...A WARM FRONT MOVES UP ACROSS THE WATERS. VSBYS WILL LOWER TO 1-3 MILES IN RAIN AND FOG STARTING AROUND MIDNIGHT AND CONTINUING INTO THE MORNING. STRONG SOUTH WINDS...ROUGHLY 60-65 KNOTS...AT 2000 FEET ALTITUDE WILL MOVE OVER THE WATERS AFTER MIDNIGHT AND THROUGH MONDAY MORNING. SOME OF THIS WIND MAY BE DRAWN TO THE SURFACE IN HEAVIER BURSTS OF RAIN. AT THE LEAST...SOUTH WINDS WILL BE NEAR GALE FORCE FOR A TIME AND THEN LINGER ABOVE 25 KNOTS THROUGH MONDAY NIGHT. THIS WILL DRIVE SEAS TO 5-10 FEET ON THE EXPOSED WATERS. TUESDAY...SOUTHWEST WINDS WILL GUST NEAR SMALL CRAFT THRESHOLDS. SEAS WILL SLOWLY DIMINISH BUT REMAIN ABOVE 5 FEET ON THE EXPOSED WATERS. SMALL CRAFT ADVISORY WILL BE NEEDED.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST SATURDAY FOR ANZ230- 232>237. SMALL CRAFT ADVISORY UNTIL 3 AM EST SATURDAY FOR ANZ231-251- 255-256. SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ250-254.
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&& $$ SYNOPSIS...KJC/DOODY NEAR TERM...KJC SHORT TERM...KJC LONG TERM...DOODY AVIATION...KJC/DOODY MARINE...KJC/DOODY

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