Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 090011 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 711 PM EST MON FEB 8 2016 .SYNOPSIS... A POWERFUL OCEAN STORM ABOUT 300 MILES EAST OF CAPE COD AT LATE AFTERNOON WILL CONTINUE MOVING SEAWARD. HOWEVER PERIODS OF LIGHT TO MODERATE SNOW WILL CONTINUE TONIGHT ALONG WITH GUSTY NORTHEAST WINDS OVER SOUTHEAST MASSACHUSETTS. THEN A BROAD AREA OF LOW PRESSURE WILL SETUP OVER SOUTHERN NEW ENGLAND TUE AND WED MAINTAINING CLOUDS AND SCATTERED SNOW SHOWERS. AN ARCTIC COLD FRONT WILL CROSS THE REGION THURSDAY...FOLLOWED BY BITTERLY COLD AIR INTO THE WEEKEND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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710 PM UPDATE...SNOW INTENSITY CONTINUES TO DECREASE THIS EVENING WITH THE STRONGEST SNOW JUST OFF THE EAST COAST OF MASSACHUSETTS. GIVEN THIS TREND AND THE OCEAN STORM CONTINUING TO PULL AWAY FROM SOUTHERN NEW ENGLAND...WE ARE REPLACING ALL ADVISORIES AND WARNINGS WITH A WINTER WEATHER ADVISORY THAT WILL CONTINUE THROUGH MIDNIGHT. EXPECT NO MORE THAN AN ADDITIONAL INCH TO POSSIBLY AS MUCH AS THREE ALONG THE EAST COAST IN THE BEST AREAS OF OCEAN ENHANCEMENT. EXPECT SNOW TO START COMING TO AN END ACROSS WESTERN MASSACHUSETTS AND CONNECTICUT FIRST...LIKELY BY 9-10 PM...THEN SLOWLY DIMINISH EASTWARD THROUGH MIDNIGHT. OVERALL...THE FORECAST IS ON TRACK. MADE A FEW MINOR ADJUSTMENTS TO THE TEMPERATURES AND WINDS TO BRING THEM MORE IN LINE WITH THE CURRENT TRENDS. 430 PM UPDATE... KEY SYNOPTIC AND MESOSCALE FEATURES/DETAILS ... IMPRESSIVE VERTICALLY STACKED CYCLONE ABOUT 300 MILES EAST OF CAPE COD OVER EASTERN GEORGES BANK CONTINUES TO MOVE RAPIDLY SEAWARD. THIS HAS RESULTED IN THE SYSTEMS WARM CONVEYOR BELT/TROWAL/ FIREHOSE LIFTING INTO ME AND THE MARITIMES PER LATEST RADAR AND SATELLITE. HOWEVER WV AND IR IMAGERY SHOWS NICE CLOUD ENHANCEMENT/ COOLING CLOUD TOPS OVER SOUTHERN NEW ENGLAND IN RESPONSE TO DUAL UPPER JET COUPLETS OVER THE NORTHEAST. THIS COMBINED WITH MOIST MID LEVEL CYCLONIC FLOW WILL KEEP PERIODS OF LIGHT TO PERHAPS MODERATE SNOW THROUGH THIS EVENING AND POSSIBLY TO AROUND MIDNIGHT OR SHORTLY THEREAFTER. THUS EXPECTING ADDITIONAL SNOW AMOUNTS FROM A COATING UPWARDS TO 2 INCHES. THIS WILL BRING MOST LOCATIONS ACROSS RI AND EASTERN MA INTO THE 4-8" FOR STORM TOTALS BY LATE THIS EVENING. FARTHER WEST INTO NORTHERN CT AND WESTERN-CENTRAL MASSACHUSETTS STORM TOTAL OF 2-5 INCHES SHOULD DO IT. HOWEVER ALONG THE EASTERN MA COASTLINE INCLUDING CAPE ANN/PLYMOUTH COUNTY TO THE UPPER CAPE...OES WILL CONTINUE UNTIL ABOUT 03Z-06Z AS BLYR WINDS REMAIN NNE THRU THAT TIME. THIS MOIST TRAJECTORY COMBINED WITH STEEP LOW LEVEL LAPSE RATES AND OCEAN INDUCED CAPES UP TO 250 J/KG WILL LIKELY YIELD AN ADDITIONAL 2-4" ACROSS THIS REGION. THUS STORM TOTALS OF 8-12" ACROSS PLYMOUTH COUNTY AND CAPE COD ARE LIKELY WITH LOCALIZED AMOUNTS UP TO 16" POSSIBLE. AFTER 06Z BLYR WINDS BACK TO THE NNW AND THIS WILL END THE MOIST LOW LEVEL FETCH INTO PLYMOUTH AND CAPE COD. SNOWFALL MAP HAS BEEN UPDATED TO REFLECT THIS CURRENT THINKING. STRONG WINDS ... LOW LEVEL JET CONTINUES TO PULL AWAY AS PGRADIENT SLACKENS WITH DEPARTING OCEAN STORM. THUS STRONG WINDS OVER EASTERN COASTAL MA WILL SLOWLY DIMINISH THIS EVENING AND ESPECIALLY OVERNIGHT. MISC ... ONE POSSIBLE CONTRIBUTING FACTOR TO VARYING QPF SOLUTIONS FROM THE MODELS LEADING UP TO THIS EVENT WAS THE LACK OF SPECIAL 06Z/18Z SOUNDINGS/BALLOON LAUNCHES LEADING UP TO THE DEVELOPING OCEAN STORM ALONG WITH THE LACK OF ANY DROPSONDES FROM AIRCRAFT.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... BUNDLE OF JET ENERGY OVER THE OH VLY THIS AFTERNOON MOVES EAST TOMORROW AND SPAWNS SOUTH OF NEW ENGLAND IN THE MORNING WITH SURFACE LOW TRACKING AGAIN SE OF THE BENCHMARK. HOWEVER THIS SYSTEM IS MUCH WEAKER THAN TODAY/S SYSTEM. SO MUCH OF ITS AFFECTS WILL REMAIN OUT OVER THE OCEAN. HOWEVER THERE IS ENOUGH MOIST CYCLONIC FLOW ALOFT TO YIELD SCATTERED SNOW SHOWERS WITH ACTIVITY MOST NUMEROUS ACROSS CT/RI AND SOUTHEAST MA. COULD BE SOME OES ENHANCEMENT OVER PLYMOUTH COUNTY AND CAPE COD GIVEN MOIST NE FLOW BUT LAPSE RATES ARE MORE MARGINAL TOMORROW. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * SHORTWAVES BRING SNOW SHOWERS AND CLOUDS TUE NIGHT THRU THU * COLD FRONT THU * SNOW SHOWERS CONTINUE FRI AND SAT * MUCH COLDER AIR MOVES INTO SOUTHERN NEW ENGLAND FOR THE WEEKEND A COMPLEX FORECAST FOR THE LONG TERM. THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE SYNOPTIC SCALE PATTERN WITH CONTINUED TROUGHING OVER THE EAST COAST AND RIDGING OVER THE WESTERN CONUS. DIFFERENCES AND CHALLENGES COME IN THE EXACT PATH OF THE SYNOPTIC FEATURES... INCLUDING SHORTWAVES...AS WELL AS THE MORE MESOSCALE FEATURES. TUESDAY NIGHT AND WEDNESDAY...HIGH CONFIDENCE. MULTIPLE SHORTWAVES WILL MOVE THROUGH OR NEAR SOUTHERN NEW ENGLAND AS THEY ROTATE AROUND AN UPPER LEVEL LOW IN QUEBEC. THIS WILL KEEP OVERCAST SKIES IN PLACE WITH OCCASIONAL SNOW SHOWERS EXPECTED THROUGHOUT SOUTHERN NEW ENGLAND. SEASONABLE TEMPERATURES EXPECTED. THURSDAY AND FRIDAY...MODERATE CONFIDENCE. AN UPPER LEVEL TROUGH MOVES THROUGH SOUTHERN NEW ENGLAND. COUPLED WITH THIS IS A LOW PRESSURE SYSTEM THAT WILL MOVE NORTH OF THE REGION...EXACT TRACK UNKNOWN AT THIS TIME... BRINGING AN ARCTIC FRONT THROUGH THE REGION. AGAIN...THIS WILL BRING A CHANCE OF SNOW SHOWERS AHEAD OF THE FRONT. JUST LIGHT AMOUNTS EXPECTED AT THIS TIME...A DUSTING TO MAYBE AN INCH OR TWO. THE BIG STORY WITH THIS FRONT WILL BE THE STRONG PUSH OF ARCTIC AIR MOVING INTO THE REGION. TEMPERATURES DURING THIS TIME WILL ALREADY BE 5 TO 10 DEGREES BELOW NORMAL FOR MID FEBRUARY AND THE COLDER AIR IS YET TO COME. THIS WEEKEND...MODERATE CONFIDENCE. NOT MUCH...IF ANY...PRECIPITATION EXPECTED. INSTEAD THE COLD WILL TAKE CENTER STAGE...ALONG WITH SOME BITTERLY COLD WIND CHILLS. ARCTIC AIR CONTINUES TO SEEP INTO SOUTHERN NEW ENGLAND WITH HIGHS EXPECTED TO BE 15-20 DEGREES BELOW NORMAL. WHILE THIS IS STILL NEARLY A WEEK OUT AND THERE IS SOME UNCERTAINTY TO BE HAD...08/12Z EPS PROBABILITIES HAVE AN OVER 80 PERCENT CHANCE OF LOW TEMPERATURES DROPPING BELOW ZERO AND OVER 50 PERCENT CHANCE OF LOW TEMPERATURES BELOW NEGATIVE 10 DEGREES! IN ADDITION...ON SATURDAY...STRONG LOW PRESSURE IN THE MARITIMES COUPLED WITH AN EQUALLY STRONG HIGH PRESSURE IN THE GREAT LAKES/OHIO VALLEY REGION WILL RESULT IN A TIGHT PRESSURE GRADIENT ACROSS SOUTHERN NEW ENGLAND. THIS WILL RESULT IN BREEZY CONDITIONS IF NOT DOWNRIGHT STRONG WINDS ACROSS THE AREA. BUT WITH TEMPERATURES AS COLD AS THEY ARE CURRENTLY FORECAST TO BE...EVEN JUST SLIGHTLY BREEZY CONDITIONS WILL RESULT IN VERY COLD WIND CHILLS. POSSIBLY EVEN INTO WIND CHILL ADVISORY CRITERIA AT POINTS DURING THE WEEKEND. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TONIGHT... MAINLY MVFR IN PERIODS OF LIGHT SNOW WITH AREAS OF IFR IN MODERATE SNOW AT TIMES CONFINED TO COASTAL PLYMOUTH/CAPE COD AND THE ISLANDS. NORTH WINDS WILL DIMINISH AS THE NIGHT PROGRESSES. TUESDAY... MAINLY MVFR AND DRY BUT CAN/T RULE OUT A FEW SNOW SHOWERS. WINDS GENERALLY LIGHT AND VARIABLE. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT TIMING OF SNOW ENDING. KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS...SNOW COULD END AN HOUR OR TWO SOONER THAN CURRENTLY FORECAST. OUTLOOK /TUESDAY NIGHT THROUGH SATURDAY/...MODERATE CONFIDENCE. TUESDAY NIGHT THROUGH WEDNESDAY...HIGH CONFIDENCE. MVFR/VFR CONDITIONS EXPECTED IN LOW CLOUDS AND OCCASIONAL -SHSN. EXPECTED ACCUMULATION LESS THAN ONE INCH. THURSDAY THROUGH FRIDAY...MODERATE CONFIDENCE. MAINLY VFR CONDITIONS. ARCTIC FRONT MOVES THROUGH THE REGION WITH GUSTY NW WINDS. CHANCE OF -SHSN. EXPECTED ACCUMULATION LESS THAN ONE INCH. SATURDAY...MODERATE CONFIDENCE. MAINLY VFR CONDITIONS. GUSTY NW WINDS CONTINUE.
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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 TUESDAY/...HIGH CONFIDENCE. TONIGHT... NNE GALES BECOME SUBGALE AROUND 02Z/9PM AS PRES GRADIENT RELAXES. HOWEVER SEAS WILL REMAIN VERY DANGEROUS ACROSS THE OCEAN WATERS OF MA AND RI WITH SEAS 15 TO 20 FT EARLY THIS EVENING AND ONLY SLOWLY SUBSIDING. VSBY LESS THAN 1 MILE AT TIMES BUT IMPROVING AFTER MIDNIGHT. TUESDAY... NE WINDS 15-20 KT AS WEAK LOW PRES TRACKS SOUTHEAST OF THE BENCHMARK. VSBY 1-3 MILES AT TIMES IN SNOW SHOWERS ACROSS SOUTHERN OCEAN WATERS AND EASTERN MA WATERS SOUTH OF BOSTON. OUTLOOK /TUESDAY NIGHT THROUGH SATURDAY/...MODERATE CONFIDENCE. TUESDAY NIGHT THROUGH WEDNESDAY...HIGH CONFIDENCE. WINDS REMAIN MAINLY BELOW SMALL CRAFT CRITERIA. SEAS REMAIN ELEVATED AS SEVERAL WEAK LOW PRESSURE SYSTEMS MOVE THROUGH THE WATERS. EXPECT SMALL CRAFT ADVISORIES FOR SEAS TO BE NECESSARY FOR THIS PERIOD. THURSDAY THROUGH FRIDAY...MODERATE CONFIDENCE. NORTHWESTERLY WINDS AND SEAS INCREASE THURSDAY AS A STRONG ARCTIC FRONT APPROACHES AND THEN CROSSES THE WATERS. SEAS SUBSIDE FRIDAY AS HIGH PRESSURE BUILDS IN BEHIND THE FRONT. SMALL CRAFT ADVISORIES LIKELY. SATURDAY...MODERATE CONFIDENCE. NORTHWESTERLY WINDS CONTINUE BETWEEN LOW PRESSURE IN THE MARITIMES AND HIGH PRESSURE IN THE GREAT LAKES. SMALL CRAFT ADVISORIES LIKELY.
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&& .TIDES/COASTAL FLOODING...
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***AREAS OF MINOR COASTAL FLOODING LIKELY ALONG SOME EAST AND NORTH FACING SHORELINES SOUTH OF BOSTON TONIGHT*** PRELIMINARY REPORTS SUGGEST FAIRLY WIDESPREAD MODERATE COASTAL FLOOD IMPACT FROM THE MONDAY LATE MORNING HIGH TIDE SOUTH OF BOSTON INCLUDING HULL...SCITUATE...MARSHFIELD AND NANTUCKET. LOOKING AHEAD...HAVE ISSUED A COASTAL FLOOD ADVISORY FOR EAST AND NORTH FACING SHORELINES SOUTH OF BOSTON...INCLUDING HULL TO PLYMOUTH...SANDWICH TO DENNIS...ORLEANS TO CHATHAM AND NANTUCKET. THERE APPEARS TO BE ENOUGH RESIDUAL SURGE AND WAVE ACTION FOR AREAS OF MINOR COASTAL FLOODING IN THE ADVISORY AREA AROUND THE TIME OF HIGH TIDE TONIGHT...AT OR A LITTLE AFTER MIDNIGHT IN MOST LOCATIONS ALONG THE MA EAST COAST. WE ANTICIPATE A SWELL OF 12 TO 16 FEET PROPAGATING INTO MASS BAY AND EXPOSED PORTIONS OF CAPE COD BAY AND 14 TO 18 FEET JUST OFF THE OUTER CAPE AND JUST EAST OF NANTUCKET AROUND MIDNIGHT. THE LONGER PERIODS OF PERHAPS 11 TO 13 SECONDS IMPLIES GREATER ENERGY WAVES MOVING ONTO THE SHORELINE...AND THIS IS REFLECTED IN THE EXPERIMENTAL WAVE RUNUP OUTPUT DEPICTING SPLASH OVER AT OUR SCITUATE EXPERIMENTAL LOCATION. WENT NEAR OR A LITTLE BELOW THE ETSS SURGE GUIDANCE BUT ABOVE THE ESTOFS GUIDANCE...WHICH CONTINUES TO HAVE A VERY SIGNIFICANT LOW BIAS. SURFACE WIND DIRECTION IS EXPECTED TO BE FROM THE NORTH AND CONSIDERABLY DIMINISHED IN SPEED FROM EARLIER TODAY. THE ASTRONOMICAL HIGH TIDE TONIGHT RUNS ABOUT A HALF FOOT TO A FOOT LOWER THAN THE MON LATE MORNING TIDE...DEPENDING UPON LOCATION. TOTAL WATER LEVELS LOOK TO BE HIGH ENOUGH FOR SOME MINOR COASTAL FLOODING IN EAST FACING PROTECTIVE BAYS/HARBORS AND SPLASHOVER FROM THE LONG PERIOD SWELLS ALONG THE OPEN SHORELINE. SOME EROSION IS LIKELY AROUND THE TIME OF HIGH TIDE...MOST NOTABLY ALONG THE OUTER CAPE AND EAST SIDE OF NANTUCKET. A FEW ESPECIALLY VULNERABLE SPOTS MAY EXPERIENCE MINOR COASTAL FLOODING AROUND THE TIME OF THE PARTICULARLY HIGH ASTRONOMICAL TIDE AROUND MIDDAY/EARLY AFTERNOON TUE DUE TO A RESIDUAL LONG PERIOD SWELL AND POSSIBLE SURGE NEAR ONE FOOT. CONFIDENCE IS TOO LOW...HOWEVER...TO EXTEND THE ADVISORY HEADLINE AT THIS TIME.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR CTZ002>004. MA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MAZ002>024-026. COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 2 AM EST TUESDAY FOR MAZ019-022-024. RI...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR RIZ001>008. MARINE...GALE WARNING UNTIL 9 PM EST THIS EVENING FOR ANZ231>234-250- 254>256. SMALL CRAFT ADVISORY UNTIL 9 PM EST THIS EVENING FOR ANZ230- 235>237. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ251.
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&& $$ SYNOPSIS...NOCERA/RLG NEAR TERM...NOCERA/RLG SHORT TERM...NOCERA LONG TERM...RLG AVIATION...NOCERA/RLG MARINE...NOCERA/RLG TIDES/COASTAL FLOODING...THOMPSON

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