Area Forecast Discussion
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000 FXUS61 KBOX 261644 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1144 AM EST WED NOV 26 2014 .SYNOPSIS...
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A DEVELOPING COASTAL STORM WILL TRACK NEAR NANTUCKET THIS EVENING... THEN QUICKLY MOVE OUT TO SEA OVERNIGHT. THIS STORM WILL BRING A VARIETY OF WEATHER IMPACTS TO THE REGION TODAY AND TONIGHT WITH HEAVY SNOW WELL INLAND...HEAVY RAIN AND STRONG WINDS ALONG THE COAST. WEATHER CONDITIONS IMPROVE FOR THANKSGIVING DAY. HIGH PRESSURE BUILDS OVER NEW ENGLAND FRIDAY AND SHIFTS OFFSHORE OVER THE WEEKEND. A COLD FRONT SWINGS THROUGH NEW ENGLAND LATE SUNDAY NIGHT OR MONDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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*** WINTER STORM TRENDING CLOSER TO THE COAST RESULTING IN A RAIN/SNOW LINE FARTHER INLAND *** 1130 AM UPDATE...MADE ONLY MINOR UPDATES TO THE FORECAST TO ACCOUNT FOR TRENDS. OTHERWISE THE FORECAST IS ON TRACK. MOST LOCATIONS ACROSS SOUTHERN NEW HAMPSHIRE AND NORTHWESTERN MASSACHUSETTS HAVE CHANGED TO SNOW...AND A FEW LOCATIONS HAVE HAD HEAVY SNOW. THE SNOW HAS BEEN SLOW TO ACCUMULATE ON SURFACES WITH THE GROUND BEING FAIRLY WARM THANKS TO THE LAST FEW DAYS OF ABOVE NORMAL TEMPERATURES. ACROSS THE REST OF SOUTHERN NEW ENGLAND... SEEING MOSTLY RAIN WITH SLEET MIXING IN ROUGHLY FROM PROVIDENCE ALMOST TO BOSTON. EARLIER DISCUSSION BELOW. -------------------------------------------------------------------- IMPACTS... * HEAVY SNOW WESTERN AND CENTRAL MA INTO SOUTHERN NH * STRONG WINDS SOUTHEAST MA AND SOUTHERN RI * HEAVY RAIN AND MINOR POOR DRAINAGE/URBAN FLOODING MUCH OF RI AND SOUTHEAST MA SYNOPTIC OVERVIEW AND MODEL PREFERENCES... 00Z MODEL GUIDANCE HAS TRENDED CLOSER TO THE COAST WITH THE SURFACE LOW PASSING OVER OR NEAR NANTUCKET. THIS SHIFT TO THE NORTHWEST MAY BE THE RESULT OF WIDESPREAD AND PERSISTENT UPSTREAM CONVECTION FROM OFFSHORE OF THE CAROLINAS EXTENDING SOUTHWEST ACROSS FL TO WEST OF CUBA. THIS CONVECTION MAY HAVE YIELDED A STRONGER DOWNSTREAM RIDGE OVER THE WESTERN ATLC RESULTING IN A STORM TRACK CLOSER TO THE COAST. REGARDING MODEL SOLUTIONS ECMWF AND GFS ARE FARTHEST NORTHWEST AND WARMEST. NAM CONSIDERABLY COOLER. FOR EXAMPLE THE NAM BUFKIT AT ORH OFFERS AN ALL SNOW EVENT WITH 9-12 INCHES. MEANWHILE THE GFS BUFKIT HAS MID LEVEL WARM INTRUSION WITH SNOW MIXING WITH OR CHANGING TO SLEET THEN BACK TO SNOW...BUT RESULTING IN ONLY 5 OR 6 INCHES. MORE OF THE SAME AT BDL. PATTERN RECOGNITION SUGGEST AXIS OF HEAVIEST SNOW SHOULD BE ALONG AND JUST NORTHWEST OF H7 LOW TRACK...WHICH MODELS AGREE WILL BE ACROSS NORTHWEST MA INTO SOUTHWEST NH. PTYPE AND SNOWFALL... GIVEN GOOD MODEL AGREEMENT ON TRACK OF H7 LOW FAIRLY CONFIDENT ON AXIS OF HEAVIEST SNOW ALONG AND NORTHWEST OF A LINE FROM BAF-CEF-FIT- ASH-MHT. A SWATH OF 6-12 INCHES IS EXPECTED ACROSS THIS AREA. SNOW WILL LIKELY BE HEAVY AT TIMES ACROSS THIS REGION FROM 18Z-02Z-ISH AS STRONG MID LEVEL FGEN COMBINES WITH SYNOPTIC SCALE LIFT TO PRODUCE SNOWFALL RATES OF 1-2 INCHES PER HOUR. EVEN A LOW PROB OF THUNDERSNOW AS DRY SLOT APPROACHES. GIVEN THERMAL PROFILES ARE ISOTHERMAL HEAVY WET SNOW MAY RESULT IN A RISK OF DOWN BRANCHES/SMALL LIMBS...INCREASING THE RISK FOR POWER OUTAGES ACROSS NORTHWEST MA INTO SOUTHWEST NH. SNOW GROWTH DOES NOT LOOK IDEAL SO EXPECTING SLR TO RANGE FROM 8-1 TO 12-1. FARTHER SOUTHEAST INTO NORTHERN CT-WORCESTER COUNTY OF MA AND INTO NORTHEAST MA...SNOW MAY MIX WITH SLEET FOR A TIME LATE THIS AFTERNOON AND EVENING BEFORE CHANGING BACK TO ALL SNOW LATER IN THE EVENING. THIS MIX OF SLEET WILL REDUCE SNOW TOTALS SOMEWHAT HOWEVER WILL ADD TO THE HAZARDOUS TRAVEL CONDITIONS. FARTHER SOUTH AND EAST INTO THE BOSTON TO PROVIDENCE CORRIDOR EXPECTING A COLD RAIN TO MIX WITH SLEET AND SNOW LATER IN THE DAY AND EVENING...YIELDING A SLUSHY MINOR ACCUMULATION POSSIBLE. NEVERTHELESS THIS WILL YIELD SLIPPERY TRAVEL ESPECIALLY 21Z-03Z WHEN PRECIP INTENSITY IS AT ITS GREATEST. FINALLY FOR SOUTHERN RI AND SOUTHEAST MA...MAINLY A WIND SWEPT RAIN STORM WITH MINOR POOR DRAINAGE/URBAN FLOODING AS RAINFALL TOTALS OF UP TO 2 INCHES POSSIBLE. OVERALL...NOT PLANNING ON CHANGING ANY HEADLINES DESPITE LOWERING SNOWFALL TOTALS. THE COMBINATION OF SNOW AND SLEET ON THIS BUSY TRAVEL DAY WITH PRECIP INTENSITY HEAVY AT TIMES IN THE AFTERNOON AND EVENING JUSTIFIES THE WARNINGS AND ADVISORIES DESPITE SNOW TOTALS POSSIBLY FALLING SHORT OF CRITERIA. THUS HEADLINES WILL BE MAINLY BASED ON IMPACTS. AS FOR SNOWFALL TOTALS...BASICALLY BLENDED THE WARMER 00Z MODEL SOLUTION WITH PREVIOUS SNOWFALL FORECAST WHICH RESULTED IN LOWER SNOW TOTALS AND AXIS OF HEAVIEST SNOWFALL FARTHER INLAND. HOWEVER IF 12Z GUIDANCE TRENDS CLOSER TO THE COAST DAY SHIFT WILL LIKELY HAVE TO LOWER AMOUNTS AND SHIFT AXIS OF HEAVIEST SNOW FARTHER INLAND. ONSET...GOOD MODEL AGREEMENT ON PRECIP COMING ONSHORE TO THE SOUTH COAST 6 AM TO 8 AM AND THEN RAPIDLY OVERSPREADING THE REMAINDER OF CT/RI AND MA RAPIDLY SOUTHWEST TO NORTHEAST 8 AM TO NOON. PRECIP INTENSITY...HEAVIEST 1 PM TO 8 PM FROM SOUTHWEST TO NORTHEAST. WINDS... A STRONG LOW LEVEL NORTHEAST JET WILL MOVE ACROSS RI AND SOUTHEAST MA INCLUDING CAPE COD AND THE ISLANDS AROUND 00Z. MODELS PROJECTING 50 TO 65 KT JET AT 925 MB. GFS IS THE MOST ROBUST. THIS COUPLED WITH STRONG PRES FALLS AND RELATIVELY WARM OCEAN WATERS PROVIDING A WELL MIXED BLYR WILL YIELD A MODERATE RISK OF 50 MPH WIND GUSTS FROM SOUTH COASTAL PLYMOUTH COUNTY/CAPE COD AND THE ISLANDS. GIVEN TRACK OF LOW IS FARTHER NW STRONG WIND FIELD NOW MOVES ACROSS COASTAL RI AND SOUTHEAST MA. THUS WILL EXPAND WIND ADVISORY TO THIS AREA. WINDS MAY DECREASE OVER THE ISLANDS FOR A TIME THIS EVENING AS LOW MAKES IT CLOSEST APPROACH...SOMEWHERE NEAR NANTUCKET. TIMING OF STRONGEST WINDS APPEAR 4 PM WED TIL 1 AM THU.
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&& .SHORT TERM /THURSDAY/... THANKSGIVING DAY...H5 LONG WAVE TROUGH WILL MOVE OFF THE COAST DURING THIS TIMEFRAME WITH A CUTOFF LOW IN THIS FLOW. AMPLE LOW AND MID LEVEL MOISTURE WITH THIS SYSTEM...SO WILL SEE LINGERING CLOUDS AND THE CHANCE FOR RAIN AND/OR SNOW SHOWERS. GOOD SHOT OF COLD AIR ADVECTION WORKING IN. DAYTIME HIGHS ONLY EXPECTED TO BE IN THE MID 30S TO LOWER 40S. H85 TEMPS FALL BACK TO -5C TO -10C THU NIGHT SO TEMPS WILL TUMBLE...BOTTOMING OUT IN THE UPPER TEENS AND 20S FOR MOST LOCATIONS...THOUGH WILL HOLD IN THE 30 TO 35 DEGREE RANGE ACROSS CAPE COD AND THE ISLANDS. WET ROADWAYS AND SIDEWALKS WILL FREEZE UP AS TEMPS FALL THU NIGHT...ESPECIALLY ON UNTREATED SURFACES. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... OVERVIEW AND MODEL PREFERENCES... MEDIUM RANGE MODELS WERE IN PRETTY GOOD AGREEMENT IN FLATTENING OUT THE OVERALL UPPER LEVEL FLOW ACROSS NORTH AMERICA...WITH SURFACE WEATHER SYSTEMS TENDING TO MOVE QUICKLY ESPECIALLY ACROSS THE NORTHERN TIER STATES THROUGH A GOOD PORTION OF THIS TIMEFRAME. HAVE NOTED TIMING DIFFERENCES WORKING IN ESPECIALLY ON THE 00Z OP RUN OF THE ECMWF EARLY NEXT WEEK AS IT TRIES TO DIG AN H5 SHORT WAVE/CLIPPER SYSTEM MOVING ACROSS THE GREAT LAKES WHILE THE GFS KEEPS THIS SYSTEM WEAK AND FLAT. OVERALL...WITH THE GENERAL W-NW WIND FLOW...A COUPLE OF FRONTS WILL PASS WITH LITTLE FANFARE THOUGH WILL BRING SHOTS OF COLDER AIR. MODELS AND ENSEMBLES HAVE MAINTAINED PRETTY GOOD CONTINUITY EARLY IN THIS FORECAST PERIOD...THEN LOWERS AS TIMING ISSUES COME INTO PLAY EARLY NEXT WEEK. USED A BLEND OF AVAILABLE GUIDANCE THROUGH THIS WEEKEND THEN LEANED TOWARD THE MODEL ENSEMBLE MEANS FOR THIS FORECAST. DETAILS... FRIDAY...SHORT WAVE CLEARS THE COAST DURING THE MORNING WITH ANY CLOUDS TENDING TO DISSIPATE AND PUSH OFFSHORE. CORE OF COLDER AIR WORKS IN ON GENERALLY LIGHT NW WINDS. HIGHS ONLY EXPECTED IN THE 30S...RUNNING AROUND 10 DEGREES BELOW SEASONAL NORMALS. HIGH PRES APPROACHES FROM THE W FRI NIGHT. MAINLY CLEAR SKIES AND LIGHT WINDS WILL CAUSE TEMPS TO DROP AGAIN TO THE TEENS TO MID 20S...EXCEPT LOWER 30S ON THE OUTER CAPE AND NANTUCKET. SATURDAY-SUNDAY...HIGH PRES CRESTS ACROSS THE EASTERN SEABOARD DURING SAT THEN SETTLES E OF THE REGION ON SUNDAY. RESIDUAL COLD AIR IN PLACE ON SAT WITH HIGHS MAINLY IN THE 30S...THOUGH WILL RISE TO THE MID 40S ALONG THE S COAST. A WEAK WARM FRONT MAY BRING ISOLD SHOWERS TO THE REGION SAT NIGHT...THEN SW WINDS TAKE OVER FOR SUNDAY. EXPECT HIGHS FROM 45-50 ACROSS THE INTERIOR...RANGING TO THE MID 50S ALONG THE S COAST WITH GUSTY SW WINDS. SOME CLOUDS AND A SLIGHT CHANCE FOR PRECIP WITH APPROACHING FRONT POSSIBLE SUN NIGHT...THOUGH TIMING IN QUESTION. MONDAY-TUESDAY...SOME QUESTION ON TIMING OF NEXT H5 SHORT WAVE APPROACHING THE REGION...THOUGH WILL TEND TO BE A RATHER DRY SYSTEM WITH NEARLY ZONAL UPPER FLOW IN PLACE. CONTINUED TO CARRY SLIGHT CHANCE POPS MON...AND SOME QUESTION ON PTYPE DEPENDING UPON TEMP PROFILE AS SYSTEM APPROACHES. FOR NOW...SHOULD SEE IMPROVING CONDITIONS MON NIGHT/TUE THOUGH LOOKS LIKE ANOTHER SHOT OF COLD AIR MOVES IN. LOW CONFIDENCE ON THIS PORTION OF THE FORECAST. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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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 TONIGHT/...MODERATE CONFIDENCE. 11 AM UPDATE... NO MAJOR CHANGES FROM 12Z TAFS. MODIFIED EARLIER DISCUSSION BELOW. ------------------------------------------------------------------- TODAY...PRECIP MAINLY RAIN ACROSS MOST OF RI /EXCEPT NORTH- NORTHWEST AREAS/ AND SOUTHEAST MA. HEAVY SNOW AND IFR THROUGH 00Z ALONG AND NORTHWEST OF A LINE FROM HFD-ORH-MHT WITH SNOWFALL RATES OF 1-2 INCHES PER HOUR POSSIBLE 18Z-00Z. SNOW MIXES WITH SLEET SOUTHEAST OF THIS AREA TO AROUND THE I-95 CORRIDOR. STRONG NE WINDS UP TO 45 KT LIKELY AFTER 21Z OVER CAPE COD/ISLANDS AND COASTAL PLYMOUTH COUNTY. TONIGHT...HEAVY PRECIP LINGERS UNTIL 02Z/03Z ESPECIALLY EASTERN AREAS INCLUDING MHT. PRECIP TAPERS OFF AFTER 03Z AND ESPECIALLY AFTER 06Z FROM SOUTHWEST TO NORTHEAST. STRONG NNE WINDS TIL 06Z THEN BACKING TO NNW. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS BUT LOWER CONFIDENCE IN EXACT TIMING ESPECIALLY PTYPE. HEAVIEST PRECIP 20Z-03Z KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS BUT LOWER CONFIDENCE IN EXACT TIMING ESPECIALLY PTYPE. HEAVIEST PRECIP 18Z-00Z. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. THURSDAY...MVFR WITH SCATTERED RAIN/SNOW SHOWERS DURING THE DAY THEN SHOULD IMPROVE THU NIGHT. DIMINISHING NORTHWEST WINDS. FRIDAY...VFR. NW WINDS GUSTING 15-20 KNOTS. SATURDAY-SUNDAY...MAINLY VFR...THOUGH CLOUDS INCREASE LATE SAT/SAT NIGHT. LOW PROB FOR MVFR CIGS MOVING NORTH OFF THE OCEAN INTO CAPE COD AND ISLANDS. SW WINDS INCREASE TO 30-40 KT AT 2-3KFT BY SUNDAY...THOUGH WILL REMAIN LIGHTER AT GROUND LEVEL.
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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 TONIGHT/...MODERATE CONFIDENCE. TODAY AND TONIGHT...GALE CENTER TRACKS OVER OR NEAR NANTUCKET EARLY THIS EVENING. THIS WILL RESULT IN A PERIOD OF NE GALES WITH A LOW RISK OF A FEW STORM FORCE GUSTS NEAR SHORE EARLY THIS EVENING. WINDS LIKELY EASE AROUND MIDNIGHT OVER CAPE AND ISLANDS AS LOW CENTER TRACKS ACROSS THIS AREA. SEAS BUILD RAPIDLY TODAY AND THIS EVENING. POOR VSBY IN HEAVY RAIN. WINDS BECOME NNW LATER TONIGHT AS THE GALE CENTER RACES NE TOWARD NOVA SCOTIA. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. THURSDAY...WILL SEE NW WIND GUSTS TO 25-30 KT EARLY...THEN SHOULD DIMINISH DURING THE AFTERNOON. SEAS UP TO 6-11 FEET OVER OPEN WATERS...HIGHEST WELL OFFSHORE...BUT WILL SUBSIDE TO 4-7 FT LATE IN THE DAY AND CONTINUE TO LOWER THU NIGHT. SMALL CRAFT ADVISORY WILL BE NEEDED ON MOST WATERS. FRIDAY...NW WINDS GUSTING TO 20 KT. SEAS LINGER AT AROUND 5 FT ON THE OUTER WATERS. SMALL CRAFT MAY NEED TO BE CONTINUES FOR A TIME. WINDS AND SEAS SHOULD DIMINISH FRI NIGHT. SATURDAY-SUNDAY...WINDS BACK TO SW DURING SAT...WITH GUSTS UP TO 20 KT. WILL SEE GUSTS UP TO 25 KT LATE SAT NIGHT AND SUN. SEAS BUILD TO AROUND 5 FT DURING SUN. SMALL CRAFTS MAY BE NEEDED. && .TIDES/COASTAL FLOODING... HIGH TIDE OF CONCERN IS SHORTLY AFTER MIDNIGHT THURSDAY. STRONGEST WINDS AND PRESSURE FALLS OCCUR DURING LOW TIDE THIS EVENING WITH WINDS AND SURGE EASING TOWARD HIGH TIDE. THUS IMPACTS WILL BE LIMITED WITH VERY MINOR EROSION AND TIDAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR CTZ002>004. MA...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR MAZ002>006- 008>012-026. WIND ADVISORY UNTIL 3 AM EST THURSDAY FOR MAZ019>024. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR MAZ007- 013>016. NH...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NHZ011-012- 015. RI...WIND ADVISORY UNTIL 3 AM EST THURSDAY FOR RIZ005>008. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR RIZ001>003. MARINE...GALE WARNING FROM 3 PM THIS AFTERNOON TO 5 AM EST THURSDAY FOR ANZ230>237. GALE WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST THURSDAY FOR ANZ250-251-254>256.
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&& $$ SYNOPSIS...NOCERA/EVT NEAR TERM...NOCERA/RLG SHORT TERM...EVT LONG TERM...EVT AVIATION...NOCERA/EVT MARINE...NOCERA/EVT TIDES/COASTAL FLOODING...

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