Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 071021 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 521 AM EST SUN FEB 7 2016 .SYNOPSIS... HIGH PRESSURE WILL BRING DRY WEATHER WITH MILD TEMPERATURES TODAY. ALTHOUGH WE WILL BE ON THE WESTERN FRINGE OF A STRONG OCEAN STORM PASSING FAR TO THE SOUTHEAST OF THE REGION...OCEAN-EFFECT ENHANCEMENT MAY BRING A PLOWABLE SNOWFALL TO MUCH OF THE EASTERN HALF OF SOUTHERN NEW ENGLAND MONDAY AND MONDAY NIGHT. PERIODS OF LIGHT SNOW ARE LIKELY THROUGH WEDNESDAY...AND POSSIBLY LINGERING INTO THURSDAY. AN ARCTIC COLD FRONT BRINGS BITTERLY COLD CONDITIONS THE END OF THE WEEK INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 515 AM UPDATE... A MOSTLY SUNNY DAY IS IN STORE TODAY WITH HIGH PRESSURE AT THE SURFACE. LIGHT SOUTHWEST WINDS WILL SHIFT TO A NORTHEASTERLY DIRECTION LATE IN THE DAY. HIGHS WILL BE IN THE LOWER TO MID 40S. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT... 1035 QUEBEC SURFACE HIGH ADVECTS SHALLOW ARCTIC AIR SOUTHWARD INTO SOUTHERN NEW ENGLAND. MEANWHILE MID LEVEL SOUTHERN STREAM TROUGH OVER THE GULF STATES INDUCES CYCLOGENESIS OFF THE EAST COAST OF SC THIS EVENING AND THEN RAPIDLY INTENSIFIES INTO A SUB 980 MB LOW/GALE CENTER WELL EAST OF THE NC COAST TONIGHT. TYPICALLY THIS TRACK IS TOO FAR OFFSHORE TO YIELD ACCUMULATING SNOW TO SOUTHEAST MA. HOWEVER THIS CYCLONE HAS A VERY LARGE CIRCULATION/WCB/FIREHOSE IN ADDITION TO 1035 MB SURFACE HIGH OVER QUEBEC...AND AS INDICATED BELOW...WE ARE EXPECTING OCEAN-EFFECT ENHANCEMENT. LIGHT SNOW SHOULD MOVE ONSHORE FROM THE SOUTH BEFORE DAYBREAK MONDAY. MONDAY... HAVE EXPANDED THE WINTER STORM WATCH TO INCLUDE MUCH OF EASTERN MA INCLUDING WORCESTER AND BOSTON METROPOLITAN AREAS...AND TO THE NORTHEAST HALF OF RI. CONTINUED THE WINTER STORM WATCH FOR SOUTHEASTERN MA...ALTHOUGH CONFIDENCE HAS INCREASED ALMOST TO THE POINT OF WARNINGS THERE BUT WILL LET THE DAY SHIFT GIVE A FINAL ASSESSMENT. ALTHOUGH WE WILL BE ON THE WESTERN FRINGE OF A STRONG OCEAN STORM PASSING FAR TO THE SOUTHEAST OF THE REGION...OCEAN-EFFECT ENHANCEMENT IS EXPECTED TO BE THE KEY TO THE FORECAST. WITH WATER TEMPERATURES RUNNING ABOUT +5C TO +6C...WE WOULD TYPICALLY BEGIN TO SEE OCEAN EFFECT WITH A DIFFERENTIAL OF ABOUT 13 DEGREES C BETWEEN THE OCEAN SURFACE AND 850 MB...OR ABOUT -7C. ALL MODELS INDICATE THAT THIS WILL HAPPEN...AND THE GFS AND ECMWF HAVE -10C AIR AT 850 MB EXTENDING ALONG THE EASTERN MA COAST MON AFTERNOON INTO MON NIGHT. WITH STRONG NE WINDS...GUSTING TO 40+ MPH AT THE COAST...THE SNOW SHOULD EXTEND WELL INLAND. THERE IS INCREASING CONSENSUS IN MODEL QPF BUT STILL SOME BIG DIFFERENCES. THE UKMET HAS BETWEEN 0.5 AND 1.2 INCHES OF LIQUID EQUIVALENT ACROSS EASTERN MA WITH THE HIGHEST ON CAPE COD AND NANTUCKET. THE GFS HAS INCREASED SINCE THE PREVIOUS RUN. THE 00Z NAM IS IN LINE WITH THE GFS AND THE ECMWF. IN GENERAL...4 TO 6 INCHES IS A REAL POSSIBILITY IN THE I-95 CORRIDOR PERHAPS EVEN BACK TO WORCESTER AND NORTHEAST TO THE MERRIMACK VALLEY AND CAPE ANN. ONLY 2 OR 3 INCHES OUT IN HARTFORD/SPRINGFIELD AREAS AND THE CT RIVER VALLEY. HOWEVER...THE JACKPOT COULD BE SOUTHERN PLYMOUTH COUNTY AND PORTIONS OF CAPE COD WHERE 6 TO 10 INCHES ARE POSSIBLE. THE FORECAST IS VERY TRICKY FOR NANTUCKET WHERE WET BULB COOLING SHOULD MEAN ALMOST ALL SNOW. WE MAY NEED TO UP POTENTIAL SNOW AMOUNTS CONSIDERABLY. ONE CONCERN IS THE HIGHER RESOLUTION NAM AND THE LOWER RESOLUTION CANADIAN MODEL WHICH BOTH FORECAST MUCH HIGHER AMOUNTS IN SOUTHEAST MA. WITH THE WINDS NEAR 40 MPH AT TIMES...IT IS POSSIBLE THAT NEAR BLIZZARD CONDITIONS COULD OCCUR ALONG THE COAST...ESPECIALLY IN PLYMOUTH...BARNSTABLE...DUKES...AND NANTUCKET COUNTIES. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... DISCUSSION... AMPLIFIED LONG WAVE UPPER LEVEL PATTERN REMAINS IN PLACE FOR MUCH IF NOT ALL OF THE LONG TERM PERIOD...THOUGH SIGNS CONTINUE TO SHOW SOME DEAMPLIFICATION OF THE LONG WAVE TROUGH LATER THIS WEEK ACROSS THE EAST. MODELS AND ENSEMBLES CONTINUE TO SIGNAL UNSETTLED CONDITIONS THROUGH WED AND POSSIBLY INTO THU...THEN WILL START TO SETTLE DOWN. HOWEVER...LOOKS LIKE WINTER TEMPERATURES WILL PUSH IN WITH THE DRIER CONDITIONS LATE NEXT WEEK INTO THE WEEKEND. STILL PROBLEMS WITH SEPARATION BETWEEN SHORT WAVES IN THE OVERALL CUTOFF LOW PRES/LONG WAVE TROUGH MON-WED...THOUGH DOES LOOK LIKE SOME SETTLING IN WITH SOME OF THE DETAILS. HOWEVER...WITH UPPER LEVEL CYCLONIC FLOW IN PLACE...WILL STILL SEE PERIODS OF PRECIP CONTINUE THROUGH AT LEAST MID WEEK. USED A BLEND OF MOST OF THE AVAILABLE GUIDANCE ALONG WITH ENSEMBLES WHICH GAVE REASONABLE CONTINUITY WITH PREVIOUS FORECAST. DETAILS... MONDAY-TUESDAY...MODELS SETTLING IN WITH CONTINUE NE FLOW IN PLACE. FIRST LOW PRES PASSES WELL SE OF NANTUCKET...BUT COMBINATION OF THIS STRONG STORM /CENTRAL PRES FROM 970-978 HPA AS IT PASSES MON AFTERNOON/ AND HIGH PRES RIDGING EXTENDING S OUT OF QUEBEC ACROSS W NEW ENGLAND...VERY TIGHT PRES GRADIENT IN PLACE. THIS WILL PRODUCE STRONG NE WINDS ACROSS E COASTAL AREAS...GENERALLY S OF BOSTON. GUSTS MAY REACH UP TO 35-45 MPH ALONG E COASTAL AREAS THROUGH MONDAY AFTERNOON...THEN WILL SLOWLY DIMINISH. MODELS DO KEEP PUSHING NW FRINGE OF PRECIP INTO EASTERN AND POSSIBLY CENTRAL AREAS...PLUS WILL LIKELY SEE COMBINATION OF OCEAN EFFECT SNOW. NOTING AT LEAST CONDITIONAL CONDITIONS FOR LAKE EFFECT ON BOTH GFS AND 4 KM BUFKIT SOUNDINGS LATE MON/MON NIGHT. DID HAVE ISSUES WITH QPF FORECAST...THOUGH WITH STRONG ONSHORE WINDS SHOULD SEE SOME ENHANCEMENT THERE. USED A BLEND OF WPC GUIDANCE... 12Z GFS AND A TOUCH OF THE 15Z SREF...WITH HIGHEST AMOUNTS ON THE CAPE AND ISLANDS BETWEEN 12Z AND 18Z MONDAY WITH INITIAL SURGE OF LOW LEVEL MOISTURE AS LOW PASSES. WITH THE COMBINATION OF INITIAL LOW LEVEL MOISTURE AND STRONG ONSHORE WINDS ENHANCING THE PRECIPITATION...EXPECT TO SEE BEST CHANCE FOR SNOW ACROSS CAPE COD AND THE ISLANDS INTO PLYMOUTH COUNTY. PARTIAL THICKNESSES SUPPORT MAINLY SNOW...THOUGH COULD SEE SOME MIX WITH RAIN DURING TUESDAY WITH LIGHTER PRECIP. BASED ON THIS...HAVE ISSUED WINTER STORM WATCH FOR THOSE AREAS MONDAY THROUGH TUESDAY MORNING. PRECIP SHOULD TAPER OFF BUT NOT TOTALLY END DURING TUESDAY AS UPPER LEVEL COLD POOL SITS CLOSE TO THE REGION. THIS WILL KEEP CYCLONIC FLOW IN PLACE AND KEEPING LIGHT SNOWFALL IN PLACE. WILL LIKELY ALSO SEE A MIX WITH RAIN ALONG THE S COAST. BEST SHOT FOR PRECIP WILL REMAIN ACROSS S COASTAL AREAS...THOUGH LOOKS TO BECOME A BIT MORE SPOTTY TUE NIGHT. WEDNESDAY-THURSDAY...WILL REMAIN UNSETTLED FOR MOST OF THIS PERIOD. WILL SEE CLOUDINESS AND SCATTERED SNOW SHOWERS. NOT A LOT OF QPF TO DEAL WITH...MORE NUISANCE SNOW BUT COULD STILL SEE LIGHT SNOW ACCUMULATIONS THROUGH MIDDAY WED. AS UPPER LEVEL LONG WAVE TROUGHING STARTS TO FLATTEN...NOTING AN ARCTIC FRONT IN THE NW FLOW. EXPECT TO CROSS THE REGION LATE WED NIGHT OR EARLY THU...WHICH WILL BE A DRY PASSAGE. EXPECT NW WINDS TO PICK UP ON THU ALONG AS ARCTIC AIRMASS SHIFTS SE. HIGHS THU WILL ONLY BE IN THE 20S TO LOWER 30S. FRIDAY-SATURDAY...EXPECT DRY TO VERY COLD CONDITIONS IN PLACE. ANOTHER REINFORCING ARCTIC FRONT CROSSES FRI NIGHT...WITH EVEN COLDER AIR MOVING IN. CURRENT FORECAST SUGGESTS HIGHS ON SATURDAY RUNNING AROUND 15 DEGREES BELOW SEASONAL NORMALS FOR MID FEBRUARY. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/... TONIGHT...HIGH CONFIDENCE. VFR. SW WINDS MAY GUST TO 20 KT IN THE HIGHER ELEVATIONS OF BERKSHIRE COUNTY AND THE WORCESTER HILLS. SUNDAY...HIGH CONFIDENCE FOR VFR. LIGHT AND VARIABLE WINDS BECOMING NE TOWARD SUNSET. SUNDAY NIGHT...VFR AND DRY THRU ABOUT MIDNIGHT. THEN LOWERING TO MVFR WITH INCREASING CHANCES OF SNOW OR MIX RAIN/SNOW TOWARD DAYBREAK MON. NE WINDS GUSTING UP TO 35 KT CAPE COD AND ISLANDS TOWARD 12Z MON. KBOS TERMINAL...HIGH CONFIDENCE THRU SUN EVENING THEN LOWERING LATE SUN NIGHT REGARDING ARRIVAL OF LOWER CIGS/VSBYS IN SNOW/RAIN. KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS. OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/... MONDAY-TUESDAY...LOW TO MODERATE CONFIDENCE. AREAS OF MVFR CIGS/IFR VSBYS IN -SN ACROSS MOST OF THE REGION. LOWEST CONDITIONS EXPECTED ACROSS E MA/RI...WHERE THEY MAY SEE PERIODS OF MODERATE SNOW IN OCEAN EFFECT ESPECIALLY SE COASTAL MA /PLYMOUTH COUNTY/...CAPE COD AND THE ISLANDS LATE MON AND MON NIGHT. MAY SEE MIXED -RN-SN ALONG E COAST TUE AFTERNOON. NE WIND GUSTS UP TO 35 KT MON INTO MON NIGHT ALONG IMMEDIATE E COASTAL MA...DIMINISHING TO AROUND 25 KT TUE. WEDNESDAY-THURSDAY...LOW CONFIDENCE. EXPECT -SHSN TO LINGER ACROSS THE REGION AS UPPER LEVEL SYSTEM REMAINS ACROSS THE NORTHEAST. MAY SEE MIX WITH -RA ALONG S COAST WED AFTERNOON. COULD SEE PERIODS OF MVFR TO LOCALLY IFR CIGS/VSBYS... MAINLY WED-WED NIGHT. CONDITIONS SHOULD SLOWLY IMPROVE TO VFR FROM WEST TO EAST DURING THU. N-NE WIND GUSTS AROUND 25 KT EARLY WED WILL DIMINISH BY AROUND MIDDAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/...HIGH CONFIDENCE. OVERNIGHT...W TO SW WINDS GUSTING TO 20-25 KT OVER THE EASTERN MA WATERS...GRADUALLY DIMINISHING TOWARD DAYBREAK. SUNDAY...TRANQUIL WIND AND SEAS ALONG WITH DRY WEATHER AND GOOD VSBY. SUNDAY NIGHT ... NE WINDS LIKELY INCREASE TO GALE FORCE ACROSS THE RI AND SOUTHERN MA WATERS. THUS GALE WARNINGS POSTED. LOW PROBABILITY NORTH OF CAPE COD SO GALE WATCHES POSTED THERE. VSBY LOWERING IN SNOW LATE. SEAS WILL BUILD RAPIDLY WITH POWERFUL LOW PRES OFF THE NC COAST COMBINING WITH 1035 MB SURFACE HIGH OVER QUEBEC. OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...MODERATE CONFIDENCE... MONDAY...GALE CENTER WILL PASS WELL SE OF NANTUCKET...BUT GALE FORCE GUSTS WILL CONTINUE TO EXTEND WELL NW OF THE CENTER. NE WINDS GUSTING TO 35-45 KT...HIGHEST E AND S OF CAPE COD AND NANTUCKET... WILL CONTINUE THROUGH LATE MORNING THEN WILL SLOWLY DIMINISH DURING THE AFTERNOON AND MON NIGHT. SEAS UP TO 14-18 FT ON THE EASTERN OUTER WATERS WILL SLOWLY SUBSIDE MON AFTERNOON. VSBY RESTRICTIONS FOR AREAS OF LIGHT RAIN AND/OR SNOW MON-MON NIGHT. TUESDAY-WEDNESDAY...SMALL CRAFT CONDITIONS WILL CONTINUE DURING THIS TIMEFRAME. NE WINDS IN PLACE TUE AND TUE NIGHT...GUSTING UP TO 25-30 KT...WITH SEAS UP TO 8-11 FT. EXPECT WINDS TO BACK TO N-NW WITH GUSTS CONTINUING AT AROUND 25 KT. SEAS WILL BUILD AGAIN ON TUESDAY...HIGHEST E AND S OF NANTUCKET...UP TO 9-14 KT AS ANOTHER LOW PASSES SE OF NANTUCKET. VSBY RESTRICTIONS CONTINUE FOR LIGHT RAIN AND/OR SNOW. THURSDAY...NW WINDS CONTINUE TO GUST UP TO 25-30 KT. LOW RISK OF GUSTS UP TO 35 KT THU NIGHT E AND S OF CAPE COD AND NANTUCKET. SEAS UP TO 7-11 FT ON THE SE OUTER WATERS. LOCAL VSBY RESTRICTIONS IN SCT RAIN AND/OR SNOW SHOWERS...BUT SHOULD IMPROVE THU AFTERNOON/EVENING. && .TIDES/COASTAL FLOODING... ASTRO TIDES LATE MON MORNING ARE HIGH WITH 11.2 FT AT BOSTON. STRONG NE WINDS UP TO 40 KT WILL YIELD A STORM SURGE OF 1.5 FT TO 2.0 FT AT THE TIME OF HIGH TIDE. THIS COMBINED WITH STRONG WAVE ACTION OF 12-18 FT JUST OFFSHORE WILL YIELD A RISK OF MODERATE COASTAL FLOODING. ETSS WAS A BIT HIGHER THAN ESTOFS AND SEEMS REASONABLE. WIND FIELD DECREASES SUBSTANTIALLY NORTH OF PLYMOUTH COUNTY. THUS THREAT OF COASTAL FLOODING IS LOWER FROM BOSTON NORTHWARD. THEREFORE HAVE CONFINED THE COASTAL FLOOD WATCH SOUTH OF BOSTON THRU PLYMOUTH TO CAPE COD AND NANTUCKET. OTHER CONCERN IS BEACH EROSION GIVEN THE HIGH WATER LEVELS...STRONG WAVE ACTION OVER MULTIPLE TIDE CYCLES. AGAIN APPEARS HIGHEST RISK WILL BE SOUTH OF BOSTON. HOWEVER WILL HAVE TO MONITOR LATER MODEL RUNS FOR POSSIBLE EXPANSION OF THE WATCH NORTHWARD. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...COASTAL FLOOD WATCH FROM MONDAY MORNING THROUGH MONDAY AFTERNOON FOR MAZ019-022-024. WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR MAZ005>007-012>024. RI...WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR RIZ001-002-004-005-007. MARINE...GALE WARNING FROM MIDNIGHT TONIGHT TO 6 PM EST MONDAY FOR ANZ231>235-237-254>256. GALE WARNING FROM 4 AM TO 6 PM EST MONDAY FOR ANZ230. SMALL CRAFT ADVISORY FROM 5 AM TO 7 PM EST MONDAY FOR ANZ236. GALE WARNING FROM 4 AM TO 10 PM EST MONDAY FOR ANZ250-251. && $$ SYNOPSIS...EVT/GAF NEAR TERM...EVT/GAF SHORT TERM...GAF LONG TERM...EVT AVIATION...EVT/GAF MARINE...EVT/GAF TIDES/COASTAL FLOODING...

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