Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 262026 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 326 PM 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 WARM FRONT MOVES ACROSS THE REGION SATURDAY NIGHT. A COLD FRONT THEN SWINGS THROUGH NEW ENGLAND LATE SUNDAY NIGHT OR MONDAY. ANOTHER WARM FRONT APPROACHES NEXT WEDNESDAY.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... *** WINTER STORM TRENDING CLOSER TO THE COAST RESULTING IN A RAIN/SNOW LINE FARTHER INLAND *** 145 PM UPDATE...HAVE ISSUED A FREEZING RAIN ADVISORY FOR NORTHERN BRISTOL COUNTY. WE HAVE RECEIVED SEVERAL REPORTS OF FREEZING RAIN IN NORTHERN RHODE ISLAND AND NORTHERN BRISTOL COUNTY. BECAUSE OF THIS...WE HAVE ISSUED A FREEZING RAIN ADVISORY FOR NORTHERN BRISTOL COUNTY AND ADDED WORDING TO INCLUDE FREEZING RAIN FOR THE WINTER WEATHER ADVISORY. TRAVEL WILL CERTAINLY BE HAZARDOUS ACROSS THE AREA TODAY...REGARDLESS OF WHAT TYPE OF PRECIPITATION IS FALLING. 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. && .SHORT TERM /6 AM THURSDAY THROUGH 6 PM THURSDAY/...
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SEE LONG TERM SECTION.
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&& .LONG TERM /THURSDAY THROUGH WEDNESDAY/...
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BIG PICTURE... THANKSGIVING STARTS WITH A TWO-STREAM TROUGH OVER THE EASTERN USA AND A RIDGE OVER THE WEST. SHORTWAVE IN THE SOUTHERN STREAM MOVES OVER NEW ENGLAND THURSDAY...QUICKLY FOLLOWED BY A NORTHERN STREAM SHORTWAVE ON FRIDAY. THE FLOW GOES ZONAL OVER THE WEEKEND. A SHORTWAVE IN THE NORTHERN STREAM DROPS SOUTH FROM NORTHERN CANADA AND MOVES ALONG THE BORDER EARLY NEXT WEEK. A SECOND NORTHERN SHORTWAVE WILL DEEPEN OVER THE GREAT LAKES MIDWEEK DRAWING MILDER AIR NORTH OVER NEW ENGLAND. MODEL UPPER CONTOURS ARE SIMILAR THROUGH THE WEEKEND. THE GGEM EDGES FASTER EARLY NEXT WEEK. THE ECMWF BECOMES SHARPER WITH THE GREAT LAKES SHORTWAVE NEXT MIDWEEK BUT HAS A SIMILAR AXIS LOCATION AS THE GFS. WE FAVORED A BLEND OF THE MODEL DATA. THE DAILIES... THURSDAY-FRIDAY.... SOUTHERN AND NORTHERN STREAM SHORTWAVES MOVE ACROSS NEW ENGLAND. THIS MAINTAINS SOME WEAK LIFT IN AN AIRMASS THAT MAINTAINS DEEP MOISTURE THROUGH FRIDAY MORNING BEFORE DRYING. WITH THIS COMBINATION WE HELD ON TO CHANCE POPS THURSDAY ACROSS MUCH OF MASS AND NH. THE AIRMASS DRIES FRIDAY SO LAND AREAS SHOULD SEE A CLEARING TREND. OVER WATER THERE WILL BE AN 18C AIR-WATER TEMP DIFFERENCE...AN EQUILIBRIUM LEVEL OF 6400 FEET...AND A 12-14 KNOT NORTHWEST WIND. THIS SHOULD SUPPORT OCEAN EFFECT RAIN/SNOW SHOWERS. THE NORTHWEST FETCH WILL FAVOR MAINLY OFFSHORE SHOWERS ALTHOUGH PROVINCETOWN AND TRURO MIGHT GET CLIPPED. SATURDAY-SUNDAY... HIGH PRESSURE AXIS SHIFTS OFFSHORE. CLOUDS INCREASE IN THE WARM ADVECTION...BUT LIFT IS RATHER WEAK. WE INDICATED SLIGHT CHANCE POPS SATURDAY AS A WARM FRONT LIFTS NORTHEAST THROUGH THE REGION. DECREASING CLOUDS AND POPS SUNDAY AS THE WARM FRONT SHIFTS NORTH OF US. MONDAY...GREAT LAKES SHORTWAVE/SURFACE LOW SWINGS A COLD FRONT THROUGH NEW ENGLAND. THERE IS UNCERTAINTY AS TO TIMING OF THE FRONT...BUT LIMITED SUPPORT FOR LIFT AND SHOWERS FROM THE RIGHT ENTRANCE REGION OF A TRAILING UPPER JET. WE INDICATED CHANCE POPS AND STRETCHED THE TIME FROM EARLY MORNING THROUGH THE EVENING. TUESDAY-WEDNESDAY... HIGH PRESSURE MOVES ACROSS THE REGION TUESDAY AND BRINGS COOLER TEMPS. THE NEXT SHORTWAVE APPROACHES WEDNESDAY WITH WARM ADVECTION RUNNING OVER THE TOP OF THOSE COOLER TEMPS. WE USED CHANCE POPS FROM EARLY MORNING THROUGH THE DAY. TEMPERATURE PROFILES SUGGEST A MIX OF PCPN AT THE START ESPECIALLY NORTH/WEST OF BOSTON...BUT TEMPS WARM ENOUGH ON WEDNESDAY FOR RAIN.
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&& .AVIATION /21Z 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 MONDAY...MODERATE CONFIDENCE THURSDAY...MIXED VFR AND MVFR WITH SCATTERED RAIN/SNOW SHOWERS. DIMINISHING NORTHWEST WINDS. FRIDAY...VFR WITH NORTHWEST WINDS GUSTING 15-20 KNOTS. SATURDAY-SUNDAY...INCREASING SKY COVER BUT MAINLY VFR. LOW POTENTIAL FOR MVFR CIGS MOVING NORTH OFF THE OCEAN INTO CAPE COD AND ISLANDS. INCREASING SOUTHWEST WINDS AT 2000 FEET AGL...REACHING 35-40 KNOTS...WITH LIGHTER SOUTHWEST WINDS AT SURFACE. THIS WOULD MEAN POTENTIAL FOR LOW LEVEL WIND SHEAR SUNDAY. MONDAY...COLD FRONT MOVES ACROSS NEW ENGLAND WITH SCATTERED SHOWERS. BRIEF MVFR CIGS/VSBYS IN ANY SHOWERS. CONTINUED SOUTHWEST WINDS AHEAD OF THE FRONT WITH 35-40 KNOTS AT 2000 FEET AGL AND POTENTIAL LOW LEVEL WIND SHEAR.
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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 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 MONDAY...MODERATE CONFIDENCE. THURSDAY...NORTHWEST WINDS GUST NEAR 25 KNOTS EARLY BUT DIMINISH THROUGH THE DAY. SEAS START THE DAY ROUGH...WITH HEIGHTS 8 TO 12 FEET ON THE EXPOSED WATERS...THEN DIMINISH THROUGH THE DAY. SMALL CRAFT ADVISORY WILL BE NEEDED ON MOST WATERS. FRIDAY... LINGERING 5 TO 6 FOOT SEAS ON THE OUTER WATERS. NORTHWEST WINDS WILL GUST NEAR 20 KNOTS. A SMALL CRAFT ADVISORY MAY BE NEEDED ON SOME OF THE WATERS. SATURDAY-SUNDAY... SOUTHWEST WINDS GUSTING TO 20 TO 25 KNOTS SATURDAY AND AROUND 25 KNOTS SUNDAY. SEAS WILL BE LESS THAN 5 FEET SATURDAY AND THEN BUILD TO 5 TO 6 FEET ON THE EXPOSED WATERS SUNDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED SUNDAY. MONDAY...SOUTHWEST WINDS GUSTING 20 TO 25 KNOTS UNTIL THE COLD FRONT MOVES THROUGH. WINDS THEN SHIFT TO WEST-NORTHWEST BEHIND THE FRONT WITH SIMILAR GUSTS. SEAS ON THE EXPOSED WATERS WILL BE 5 TO 8 FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED.
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&& .TIDES/COASTAL FLOODING...
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HIGH TIDE OF CONCERN IS SHORTLY AFTER MIDNIGHT TONIGHT. 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.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... 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. FREEZING RAIN ADVISORY UNTIL 7 AM EST THURSDAY FOR MAZ017. 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 UNTIL 5 AM EST THURSDAY FOR ANZ230>237. GALE WARNING UNTIL 7 AM EST THURSDAY FOR ANZ250-251-254>256. && $$ SYNOPSIS...WTB/NOCERA NEAR TERM...NOCERA/RLG SHORT TERM...EVT LONG TERM...WTB AVIATION...WTB/NOCERA MARINE...WTB/NOCERA TIDES/COASTAL FLOODING...

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