Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 202113 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 413 PM EST THU NOV 20 2014 .SYNOPSIS...
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A COLD FRONT DELIVERS A REINFORCING SURGE OF BLUSTERY AND UNSEASONABLY COLD CONDITIONS LATER TONIGHT INTO FRIDAY NIGHT. A SIGNIFICANT WARM-UP IS IN STORE SUNDAY AND MONDAY...BUT IT WILL LIKELY BE ACCOMPANIED BY A PERIOD OF RAIN SUNDAY NIGHT INTO MONDAY. COOLER WEATHER RETURNS BY THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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TONIGHT... SECONDARY COLD FRONT/TRAILING SHORT WAVE MOVES ACROSS THE REGION LATE TONIGHT TOWARD SUNRISE FRI. TRUE COLD AIR IS ASSOCIATED WITH THIS FEATURE THUS STRONGER CAA ARRIVES AFTER MIDNIGHT. ONLY CONCERN TONIGHT IS AS LOW LEVEL FLOW BECOMES MORE WESTERLY PER STREAMLINE ANALYSIS...LAKE EFFECT MOISTURE MAY SPILL OVER THE BERKSHIRES INTO SOUTHERN NEW ENGLAND. GIVEN THESE POTENTIAL LAKE EFFECT STREAMERS ARE ON THE MESOSCALE NONE OF THE HIGH RES GUIDANCE /INCLUDING RAP13 AND HRRR/ ARE SIMULATING THESE BANDS VERY WELL ESPECIALLY AWAY FROM THE SOURCE REGION OF THE GRTLKS. THUS WILL PLAY THE FORECAST CONSERVATIVE FOR NOW AND JUST SAY CHANCE OF FLURRIES ESPECIALLY NEAR THE UPSLOPE REGIONS OF WESTERN MA /WEST OF I-91/ INTO SOUTHWEST NH. LATER SHIFTS WILL HAVE TO MONITOR FOR POTENTIAL BRIEF SNOW SHOWERS/SQUALLS SPILLING OVER THE BERKS. OTHERWISE QUIET WEATHER TONIGHT WITH GUSTY SW WINDS BECOMING WEST OVERNIGHT AND SLACKENING A BIT AS WELL.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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FRIDAY... COLD DAY BY LATE NOV STANDARDS WITH HIGHS ONLY IN THE 30S /NORMAL HIGH AROUND 50/ AND A BRISK WNW WIND WILL YIELD WIND CHILLS IN THE 20S /TEENS HIGHER TERRAIN/! GEFS TEMP ANOMALIES INDICATE 850 TEMPS OVER SOUTHERN NEW ENGLAND 18Z FRI ARE ABOUT -2 STD WITH VALUES AROUND -14C. SO DESPITE A WELL MIXED BLYR AND AT LEAST PARTIAL SUNSHINE AND DOWNSLOPE WIND COMPONENT MU30S WILL BE OUR MAX AFTN TEMPS FRI AFTN. AS MENTIONED ABOVE THE BRISK WNW WINDS WILL MAKE IT FEEL MUCH COLDER. FRIDAY NIGHT... DRY WEATHER PREVAILS BUT ANOTHER COLD NIGHT WITH LOWS IN THE TEENS EXCEPT 20S IN THE URBAN AREAS INCLUDING CAPE COD AND THE ISLANDS. NOT AS MUCH OF A WIND CHILL GIVEN THE WEAKENING PGRAD WITH RIDGE OF HIGH PRES APPROACHING FROM THE WEST.
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&& .LONG TERM /SATURDAY 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 FORECEST CONFIDENCE THROUGH TUESDAY...LOW CONFIDENCE WEDNESDAY AND THURSDAY. THE DAILIES... SATURDAY... HIGH PRESSURE WILL BE IN PLACE DURING THE DAY WITH THE AXIS CROSSING DURING THE AFTERNOON. THIS SHOULD TURN THE WIND SOUTHWEST BY AFTERNOON. INCREASING MOISTURE ALOFT BUT EXPECT MOST CLOUDS TO BE MID AND HIGH LEVEL. WITH THE DEVELOPING WARM ADVECTION ALOFT THE MIXING REACHES ONLY TO 950 MB WHICH WOULD SUPPORT MAX SFC TEMPS IN THE MID 30S TO LOW 40S. 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 AMPLIFYS 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 /21Z THURSDAY 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. THRU 00Z/7PM... VFR WITH GUSTY SW WINDS UP TO 30-35 KT. DRY WEATHER PREVAILS. AFTER 00Z/7PM... GUSTY SW WINDS BECOME WEST 20-25 KT. VFR BUT LOW RISK OF BRIEF MVFR CONDITIONS IN AN ISOLATED SNOW SHOWER. FRI... VFR BUT GUSTY WNW WINDS 20-25 KT. LOW RISK OF BRIEF MVFR CONDITIONS IN AN ISOLATED SNOW SHOWER. FRI NIGHT... VFR WITH DIMINISHING WNW WINDS. KBOS TERMINAL...HIGH CONFIDENCE. VERY LOW RISK OF BRIEF MVFR IN ISOLATED SNOW SHOWER TONIGHT INTO FRI. KBDL TERMINAL...HIGH CONFIDENCE. VERY LOW RISK OF BRIEF MVFR IN ISOLATED SNOW SHOWER TONIGHT INTO FRI. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY... VFR. SW WIND 40 KNOTS AT 2000 FEET...POTENTIAL LOW LEVEL WIND SHEAR. 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. MODERATE FORECAST CONFIDENCE THRU FRI NIGHT. TONIGHT...GUSTY SW WINDS BECOME WESTERLY WITH PASSAGE OF SECONDARY COLD FRONT LATE TONIGHT. WIND SPEEDS MAINLY 20-30 KT WITH LOW RISK OF ISOLATED GUSTS TO 35 KT. LONG SW FETCH HAS RESULTED IN LARGE SEAS ON THE SOUTHERN WATERS WITH HEIGHTS UP TO 8 FT. OTHER THAN ISOLATED RAIN SHOWER THIS EVENING/SNOW SHOWER AFTER MIDNIGHT...MAINLY DRY WEATHER PREVAILS. FRI...WNW WINDS UP TO 35 KT. OCEAN EFFECT SNOW SHOWERS WELL OFFSHORE. FRI NIGHT...WNW WINDS SLOWLY EASE. DESPITE SUBFREEZING TEMPS AND MODEST WNW WINDS OCEAN TEMPS STILL TOO WARM FOR ANY FREEZING SPRAY CONCERNS WITH NEAR SHORE WATER TEMPS IN THE MU40S. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... SATURDAY... SOUTHWEST WINDS INCREASE WITH FREQUENT GUSTS TO 30 KNOTS. SEAS BUILD TO 5-6 FEET DURING THE DAY AND 5-8 FEET SATURDAY NIGHT. A SMALL CRAFT ADVISORY WILL BE NEEDED. 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...GALE WARNING UNTIL 10 PM EST FRIDAY FOR ANZ230>237-250-251- 254>256.
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&& $$ SYNOPSIS...WTB/NOCERA NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...WTB AVIATION...WTB/NOCERA MARINE...WTB/NOCERA

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