Area Forecast Discussion
Issued by NWS Boston, MA

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117 FXUS61 KBOX 081924 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 224 PM EST MON FEB 8 2016 .SYNOPSIS... A POWERFUL OCEAN STORM WELL EAST OF CAPE COD EARLY THIS AFTERNOON WILL CONTINUE MOVING OUT TO SEAS WITH SNOW INTENSITY OVER SOUTHERN NEW ENGLAND EASING FOR THE REMAINDER OF THIS AFTERNOON AND EVENING. HOWEVER LIGHTER ACCUMULATING SNOW WILL CONTINUE ALONG WITH STRONG NORTHEAST WINDS. ADDITIONAL SHORTWAVES MOVE PAST NEW ENGLAND TUESDAY THROUGH THURSDAY MAINTAINING CLOUDS AND A CHANCE OF SNOW SHOWERS. AN ARCTIC COLD FRONT WILL CROSS THE REGION THURSDAY...FOLLOWED BY DRY AIR AND COLDER THAN NORMAL TEMPERATURES FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 225 PM UPDATE... HEADLINE CHANGES ... HAVE DOWNGRADED ALL OF NORTHERN CT INTO CENTRAL MA FROM WINTER STORM WARNINGS TO WINTER WEATHER ADVISORIES. THIS IS IN RESPONSE TO HEAVY SNOWFALL RATES UP TO 1" PER HOUR COMING TO AN END AND GIVING WAY TO LIGHTER ACCUMULATING SNOW. SO ESSENTIALLY WINTER STORM WARNINGS CONTINUE FOR ALL OF RI AND EASTERN MA FROM CITY OF WORCESTER EASTWARD. BLIZZARD WARNINGS CONTINUE. KEY SYNOPTIC AND MESOSCALE FEATURES/DETAILS ... WARM CONVEYOR BELT/TROWAL/FIREHOSE IS BEGINNING TO EXIT EASTERN NEW ENGLAND AS IMPRESSIVE VERTICALLY STACKED LOW OVER GEORGES BANK CONTINUES TO MOVE RAPIDLY NORTHEAST AWAY FROM THE REGION. SO WHILE SNOW WILL CONTINUE TO FALL UNTIL ABOUT MIDNIGHT OR GIVEN THE MOIST CYCLONIC FLOW ALOFT...SNOWFALL RATES/INTENSITY ARE TRENDING DOWNWARD AT 2 PM AND WILL CONTINUE THIS AFTERNOON AND EVENING. CAN REALLY SEE THIS IN LATEST RADAR TRENDS WITH MESOSCALE SNOW BANDS DIMINISHING. SNOWFALL MAP HAS BEEN UPDATED TO REFLECT THIS CURRENT THINKING. SO THE FOCUS FOR MODERATE TO HEAVY SNOW GOING FORWARD INTO THIS EVENING WILL BE OCEAN EFFECT ENHANCEMENT AND LAND/SEA CONVERGENCE ACROSS COASTAL PLYMOUTH COUNTY/CAPE COD/THIS ISLANDS AND POSSIBLY COASTAL SECTIONS OF CAPE ANN. THUS 8-12" REMAIN LIKELY FOR THIS AREA WITH LOCALIZED 12-18" POSSIBLE. THIS COMBINED WITH STRONG ONSHORE WINDS WILL CONTINUE TO RESULT BLIZZARD CONDITIONS AT TIMES. FARTHER TO THE WEST ACROSS INTERIOR SOUTHEAST MA/RI AND NORTHEAST MA INCLUDING GREATER BOSTON AREA 4-8" IS EXPECTED. OVER NORTHERN CT/WESTERN-CENTRAL MA WE LOWERED TOTALS MAINLY INTO THE 2-5" CATEGORY WITH HIGHEST AMOUNTS EAST SECTIONS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... TONIGHT... HEAVIEST SNOW WILL COME TO AN END BY EARLY EVENING AS STORM PULLS AWAY AND LOW LEVEL JET WEAKENS. HOWEVER...EXPECT AREAS OF LIGHT SNOW TO PERSIST WELL INTO THE OVERNIGHT HOURS WITH MOIST NORTH TO NORTHEAST FLOW JUST OFF THE DECK. WHILE MOST OF THE SNOW WILL BE LIGHT TONIGHT...VERY LOCALIZED BANDS OF MODERATE TO HEAVY SNOW WILL REMAIN POSSIBLE ALONG THE EASTERN MA COAST AS A RESULT OF OCEAN ENHANCEMENT/LAND SEA INTERFACE. && .LONG TERM /TUESDAY THROUGH SUNDAY/... BIG PICTURE... RIDGE WEST/TROUGH EAST CONTINUES THROUGH THE WEEK. LONG RANGE MODELS SHOW A SIMILAR SERIES OF SHORTWAVES MOVING THROUGH NEW ENGLAND MIDWEEK...THE LAST MOVING THROUGH ON THURSDAY. THE FINAL SHORTWAVE ORIGINITATED OVER ARCTIC CANADA AND IT IS NO SURPRISE THAT TEMPS OVER US COOL SIGNIFICANTLY AFTER IT PASSES. CLOSED LOW FROM BAFFIN ISLAND THEN SLIPS SOUTH AND MAINTAINS THE CYCLONIC FLOW OVER EASTERN CANADA AND THE NORTHEAST USA. THE ECMWF FORMS AN OUTLIER SOLUTION THAT DRAWS THIS CLOSED LOW INTO THE NORTHEAST USA SATURDAY WHILE THE GFS AND GGEM HOLD IT OVER QUEBEC. THE CONSEQUENCE IS THAT THE ECMWF FORMS A SIGNIFICANT WEEKEND SNOWSTORM WHILE THE OTHERS FORM A WEAK WAVE WELL OFFSHORE. THE FORECAST FAVORS A MODEL CONSENSUS THROUGH FRIDAY...THEN FAVORS A CONSENSUS WITHOUT THE ECMWF OVER NEXT WEEKEND. THE DAILIES... TUESDAY...POSITION OF UPPER TROUGH CONTINUES TO FAVOR FORMATION OF ANOTHER COASTAL LOW OFF THE MID ATLANTIC COAST. SAID COASTAL LOW THEN MOVES NORTHEAST TOWARD THE 40N/70W BENCHMARK. THIS WOULD MAINTAIN AT LEAST WEAK LIFT OVER SOUTHERN NEW ENGLAND. FGEN FIELDS ARE MARGINAL BUT FAVOR SOUTH COASTAL SECTIONS AND ESPECIALLY CAPE COD AND THE ISLANDS. NOT CONFIDENT ON SNOW SHOWERS VS A STRATIFORM SNOW. WE WILL MAINTAIN CHANCE POPS FOR SNOW SHOWERS WITH HIGHEST POPS IN THE MIDDAY/AFTERNOON. MOISTURE FIELDS SUGGEST POTENTIAL FOR A FEW INCHES...TECHNICALLY A MODERATE SNOW ACCUM...ACROSS RI/SOUTHEAST MASS. WEDNESDAY-THURSDAY... ADDITIONAL SHORTWAVES MOVE THROUGH AND THE UPPER COLD POOL APPROACHES. THE FINAL SHORTWAVE IN THIS GROUP MOVES THROUGH THURSDAY AND IS ASSOCIATED WITH AN ARCTIC COLD FRONT. THIS SUGGESTS A CONTINUED POTENTIAL FOR SCATTERED SNOW SHOWERS. ONLY LIMITED MIXING WEDNESDAY...TO 950 MB...WITH TEMPS SUPPORTING MAX SFC TEMPS IN THE 30S. DEEPER MIXING THURSDAY AS COLD ADVECTION STARTS. MIXING REACHES ABOVE 900 MB THURSDAY WITH TEMPS SUPPORTING UPPER 20S- LOWER 30S. WINDS IN THE THURSDAY MIXED LAYER ARE FORECAST AT 25-30 MPH...SHOULD BE AVAILABLE AS NORTHWEST GUSTS. FRIDAY-SATURDAY-SUNDAY... ARCTIC AIR POURS INTO NEW ENGLAND AND IS WITH US THROUGH THE WEEKEND. MIXING WILL BRING 25 KNOT WINDS TO THE SURFACE IN GUSTS. TEMPS AT 850 MB WILL FALL INTO THE -20S AND SUGGEST MAX SFC TEMPS IN THE 20S FRIDAY AND 15-25 SAT-SUN. GIVEN THE SOURCE REGION OF THE AIRMASS...MODEL SUGGESTIONS OF MIN TEMPS IN THE SINGLE NUMBERS EITHER SIDE OF ZERO LOOK REASONABLE. SUCH COLD AIR ALOFT AND WINDS OVER 10 KT WILL GENERATE OCEAN EFFECT SNOW SHOWERS...BUT THE WIND DIRECTION SHOULD KEEP THE SHOWERS OFFSHORE. AS NOTED ABOVE...WE WILL NEED TO MONITOR FUTURE MODEL SUITES TO SEE IF THE 00Z ECMWF WEEKEND LOW IS A BLIP OR AN ACTUAL PROBLEM. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 1930Z UPDATE ... THRU 00Z ... MODERATE TO HEAVY SNOW WITH HOURLY RATES OF UP TO AN INCH PER HOUR WERE COMING TO AN ACROSS MUCH OF THE AREA. THE EXCEPTION WILL BE ACROSS CAPE ANN/COASTAL PLYMOUTH COUNTY/CAPE COD AND THE ISLANDS WHERE HEAVIER SNOW BANDS WITH VSBY 1/2SM WILL EXIST AT TIMES. NNE WINDS WILL CONTINUE TO GUSTS 40-50 KT THRU 00Z. AFTER 00Z ... 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...IFR CONDITIONS IN SNOW LATE THIS AFTERNOON WILL TREND UP TO MVFR SOMETIME 21Z-24Z. HEAVIEST SNOWFALL RATES THRU ABOUT 21Z THEN EASING. KBDL TERMINAL...MARGINAL IFR/MVFR IN SNOW CONTINUE UNTIL ABOUT 20Z/21Z THEN TRENDING UPWARD TO MVFR. STEADIEST SNOW THRU 20/21Z THEN DIMINISHING. OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...MODERATE CONFIDENCE. WEDNESDAY...LOW-MODERATE CONFIDENCE. MVFR CIGS/VSBYS IN SCATTERED SNOW SHOWERS. FRIDAY...MODERATE CONFIDENCE. MOSTLY VFR. NORTHWEST WINDS GUSTING 25-30 KNOTS. OCEAN EFFECT SNOW SHOWERS JUST OFF THE COAST WITH LOWER CIGS/VSBYS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TONIGHT/...HIGH CONFIDENCE. ***STRONG GALE TO STORM FORCE WIND GUSTS OF 45 TO 60 KNOTS AND SEAS EXCEEDING 20 FEET EXPECTED ACROSS OUR EASTERN OUTER-WATERS LATER THIS MORNING AND AFTERNOON*** POWERFUL 975 MB LOW PRESSURE SYSTEM PASSING SOUTHEAST OF THE BENCHMARK WILL COMBINED WITH A 1030 MB HIGH PRESSURE SYSTEM OVER EASTERN CANADA. THE RESULT WILL BE STRONG NORTHEAST WIND GUSTS OF 45 TO 60 KNOTS...THE STRONGEST OF THOSE WINDS ACROSS OUR WATERS SOUTHEAST OF NANTUCKET. GALE AND STORM WARNINGS POSTED FOR ALL WATERS WITH SEAS EXPECTED TO BUILD TO OVER 20 FEET ACROSS OUR EASTERN WATERS BY AFTERNOON. HEAVY SNOW WILL ALSO RESULT IN VISIBILITIES ONE QUARTER MILE OR LESS AT TIMES THIS AFTERNOON. THIS IS A VERY DANGEROUS STORM FOR THE MARINE COMMUNITY. WINDS AND SEAS WILL SLOWLY DIMINISH TONIGHT AS POWERFUL LOW PRESSURE MOVES NORTHEAST AND AWAY FROM THE WATERS. NONETHELESS...SEAS WILL BE SLOW TO DIMINISH THOUGH WITH LEFT OVER SWELL AND PERSISTENT NORTHEAST FETCH. OUTLOOK /TUESDAY THROUGH FRIDAY/...MODERATE CONFIDENCE. TUESDAY...NORTH TO NORTHEAST WINDS WILL BE 20 KNOTS OR LESS. SEAS WILL SLOWLY SUBSIDE THROUGH THE DAY BUT REMAIN 5 FEET OR HIGHER ON THE EXPOSED WATERS. SMALL CRAFT ADVISORY WILL BE NEEDED. WEDNESDAY...WINDS BECOME WEST LESS THAN 20 KNOTS. SEAS LINGER 5 FEET OR HIGHER ON THE SOUTHERN WATERS AS WELL AS EAST OF CAPE COD. A SMALL CRAFT ADVISORY WILL BE NEEDED. THURSDAY-FRIDAY...AN ARCTIC COLD FRONT SWEEPS ACROSS THE WATERS THURSDAY...FOLLOWED BY MUCH COLDER AIR. WINDS WILL SHIFT NORTHWEST WITH GUSTS 25 TO 30 KNOTS. SEAS OF 5-7 FEET MAINLY ON THE OUTER WATERS...SUBSIDING FRIDAY. && .TIDES/COASTAL FLOODING... ***POCKETS OF MODERATE COASTAL FLOODING EXPECTED DURING THE LATE MORNING AND EARLY AFTERNOON HIGH TIDE CYCLE SOUTH OF BOSTON ALONG THE EASTERN MA COAST*** 915 AM UPDATE... PRIOR FORECAST LOOKS TO BE RIGHT ON TARGET WITH MODERATE COASTAL FLOODING LIKELY FOR THE LATE MORNING HIGH TIDE FROM HULL TO PLYMOUTH...NORTH AND EAST FACING SHORELINES OF CAPE COD...AND NANTUCKET NORTH AND EAST FACING SHORELINES. AT THE TIME OF HIGH TIDE...PROJECTING SEAS APPROACHING 20 FEET MASS BAY AND 20 TO 25 FEET EAST OF THE OUTER CAPE AND EAST OF NANTUCKET. PRIOR SURGE FORECAST LOOKS REASONABLE. ANTICIPATE SURGE TO BE 1.7 TO 2.2 FEET FROM BOSTON NORTH AND GENERALLY 2.1 TO 2.6 FEET ALONG EAST AND NORTH FACING SHORELINES SOUTH OF BOSTON INCLUDING SCITUATE...SANDWICH/DENNIS...PROVINCETOWN...CHATHAM AND NANTUCKET. AT LEAST SOME EROSION IS EXPECTED ALL ALONG THE MA COASTLINE FROM SALISBURY TO NANTUCKET...MOST SEVERE ALONG THE OUTER CAPE AND THE EAST SIDE OF NANTUCKET INCLUDING SIASCONSET. AS OF 915 PM...REPORTS OF COASTAL FLOODING HAVE STARTED TO COME IN WITH PORTIONS OF OCEANSIDE ROAD AND CENTRAL AVENUE IN SCITUATE AND THE BRANT ROCK AREA OF MARSHFIELD ALREADY IMPACTED. FLOODING SHOULD ALREADY BE STARTING TO OCCUR ALONG PORTIONS OF NANTUCKET HARBOR INCLUDING BUT NOT LIMITED TO EASY STREET. MINOR COASTAL FLOODING LOOKS LIKELY FOR AT LEAST SOME OF THE MA COASTLINE FOR THE LATE EVENING HIGH TIDE DUE TO RESIDUAL SURGE AND WAVE ACTION. THE WIND WILL HAVE BACKED TO A MORE N DIRECTION AND SPEEDS CONSIDERABLY LESS BY THE LATE EVENING HIGH TIDE...WHICH IS A HALF TO A LITTLE LESS THAN A FOOT LOWER ASTRONOMICALLY ALONG MOST OF THE EASTERN MA COASTLINE. SEAS WILL PROBABLY STILL BE RUNNING 14 TO 18 FEET A LITTLE OFFSHORE...PERHAPS AROUND 20 FEET STILL EAST OF NANTUCKET. THUS...AT LEAST SOME EROSION WILL LIKELY BE WITNESSED AGAIN TONIGHT AROUND THE HIGH TIDE. A COASTAL FLOOD ADVISORY MAY NEED TO BE ISSUED FOR PORTIONS OF THE EASTERN COASTLINE FOR THE LATE EVENING HIGH TIDE. EARLY AM DISCUSSION IS STILL RELEVANT AND FOLLOWS... COASTAL FLOOD WARNING CONTINUES SOUTH OF BOSTON THRU COASTAL PLYMOUTH COUNTY TO CAPE COD AND NANTUCKET GIVEN HIGHER CONFIDENCE OF STRONG WIND FIELD ACROSS THIS REGION. EXPECTING AREAS OF MODERATE COASTAL FLOODING IN THIS AREA DURING THE LATE MORNING INTO MIDDAY HIGH TIDE. LOW LEVEL WINDS NOT QUITE AS STRONG FROM BOSTON NORTHWARD. THUS LESS STORM SURGE AND COASTAL FLOODING WILL LIKELY BE MAINLY IN THE MINOR CATEGORY...BUT CAN NOT RULE OUT POCKETS OF LOW- END MODERATE COASTAL FLOODING. HIGH TIDE CYCLE OF GREATEST CONCERN IS THE LATE THIS MORNING INTO MIDDAY...BASICALLY 9 AM TO 1 PM IS THE TIMELINE. EXPECTING A STORM SURGE OF BETWEEN 2.5 AND 3 FT ACROSS THE WARNING AREA AND NEAR 2 FT FROM BOSTON NORTHWARD TO THE MA/NH BORDER. ETSS WAS HIGHER THAN THE ESTOFS AND SEEMS REASONABLE GIVEN NE WINDS WILL GUSTS 45 TO 65 MPH. IN ADDITION LARGE WAVES IN EXCESS OF 20 FT JUST OFFSHORE...WILL PROMOTE WAVE RUNUP PUSHING WAVES AND OVER SEAWALLS AND OTHER STRUCTURES. THIS WILL ALSO RESULT IN POTENTIAL MODERATE BEACH EROSION. AGAIN GREATEST IMPACTS FROM 9 AM TO 1 PM ALONG PLYMOUTH COAST TO CAPE COD BAY TO NANTUCKET...WITH LESS IMPACTS BOSTON NORTHWARD TO MA/NH BORDER. WE MAY HAVE SOME MINOR COASTAL FLOODING DURING THE LATE EVENING HIGH TIDE CYCLE ALONG THE EASTERN MA COAST. HOWEVER ASTRO TIDE IS LOWER...LESS WINDS AND PRES RISES OVERSPREADING THE AREA...BUT A COASTAL FLOOD ADVISORY MAY BE NEEDED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR CTZ002>004. MA...BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR MAZ018-019- 021>024. WINTER STORM WARNING UNTIL 7 AM EST TUESDAY FOR MAZ005>007- 012>017-020. WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR MAZ002>004- 008>011-026. RI...BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR RIZ008. WINTER STORM WARNING UNTIL 7 AM EST TUESDAY FOR RIZ001>007. MARINE...STORM WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ231>234-250- 254>256. GALE WARNING UNTIL 9 PM EST THIS EVENING FOR ANZ230-235-237. GALE WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ236. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ251. && $$ SYNOPSIS...WTB/FRANK NEAR TERM...NOCERA SHORT TERM...FRANK LONG TERM...WTB AVIATION...WTB/NOCERA MARINE...WTB/FRANK TIDES/COASTAL FLOODING...THOMPSON

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