Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271334 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 834 AM EST TUE JAN 27 2015 .SYNOPSIS... A CRIPPLING AND HISTORIC WINTER STORM / BLIZZARD WILL IMPACT THE REGION INTO TONIGHT. DRIER WEATHER FOLLOWS WEDNESDAY AFTERNOON INTO EARLY THURSDAY. LOW PRESSURE WILL BRING ANOTHER CHANCE FOR SNOW THURSDAY NIGHT AND FRIDAY. DRY BUT VERY COLD AIR LOOKS TO FOLLOW FOR NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... HIGHLIGHTS... * CRIPPLING AND POTENTIALLY HISTORIC BLIZZARD WITH 1 TO 2 FT OF SNOW...LOCALLY HIGHER AMOUNTS * STRONG TO DAMAGING WINDS / HURRICANE FORCE ACROSS SE NEW ENGLAND * MODERATE TO MAJOR COASTAL FLOODING / SEVERE BEACH EROSION 7 AM UPDATE... WV LOOP SHOWS DEEPENING MID LEVEL LOW NEAR THE BENCHMARK WITH CONVECTION AND LIGHTNING STRIKES NOTED AT THE ED GE OF THE DRY SLOT EAST OF NEW ENGLAND. DRY SLOT WILL REMAIN EAST OF NEW ENG. SFC LOW DOWN TO NEAR 980 MB ALSO NEAR THE BENCHMARK AS SYSTEM IS BECOMING VERTICALLY STACKED. ONLY SLOW MOVEMENT NORTH EXPECTED DURING TODAY AS THE LOW GETS CAPTURED BY THE UPPER LEVEL SYSTEM WHICH WILL PROLONG OCCASIONAL HEAVY SNOW THROUGH TODAY. SNOWFALL / BANDING / BLIZZARD... CLASSIC DEFORMATION/FRONTOGENESIS BAND ACROSS CENTRAL/NE MA EXTENDING INTO NE CT AND N RI. VERY HEAVY SNOW UNDER THIS BAND WITH SNOWFALL RATES LIKELY 2-3"/HOUR. NAM MID LEVEL FGEN FIELDS DOING A VERY GOOD JOB SIGNALING THIS BAND AND SHOW A SLOW WEAKENING DURING THE DAY AS IT GRADUALLY MOVES EAST. SO WHILE THE INTENSITY IS EXPECTED TO DIMINISH A BIT...STILL EXPECT OCCASIONAL HEAVY SNOW TODAY ACROSS E HALF NEW ENG. MEANWHILE...PULSES OF HEAVIER SNOW BANDS WHICH ARE CONVECTIVE IN NATURE CONTINUE TO MOVE FROM THE OCEAN ACROSS SE MA. IN FACT...RECEIVING REPORTS OF THUNDER SNOW ACROSS THE CAPE AS MID LEVEL LAPSE RATES OVER 6 C/KM ACROSS SE NEW ENG SUGGESTING POTENTIAL FOR UPRIGHT CONVECTION. HEAVIEST SNOW WILL REMAIN EAST OF WESTERN NEW ENGLAND BUT STILL EXPECT WIDESPREAD LIGHT TO MODERATE NOW. ADDITIONAL SNOWFALL TODAY INTO THIS EVENING WILL LIKELY RANGE FROM 6-10 INCHES WITH LESSER AMOUNTS IN WESTERN NEW ENGLAND. MADE SOME MODIFICATIONS TO THE SNOW ACCUM MAP...WITH MAX ACCUM AROUND 2 FT AND LOCALLY SLIGHTLY HIGHER AMOUNTS FROM NE CT THROUGH CENTRAL/NE MA AND EXTENDING S ALONG E COASTAL MA TO THE UPPER CAPE. LOWERED AMOUNTS ACROSS FAR WESTERN NEW ENG AND ACROSS RI AND ADJACENT INTERIOR SE MA WHICH WILL LARGELY REMAIN OUTSIDE OF THE HEAVIEST BANDING. COMBINATION OF HEAVY SNOW AND STRONG WIND WILL RESULT IN BLIZZARD CONDITIONS...ESPECIALLY ACROSS EASTERN HALF NEW ENG WITH CONSIDERABLE BLOWING AND DRIFTING. IN ADDITION...WIND CHILLS WILL BE DOWN INTO THE SINGLE NUMBERS ABOVE AND BELOW ZERO ADDING TO THE SEVERITY AND LIFE THREATENING ASPECT OF THE STORM. TRAVEL WILL BE NEARLY IMPOSSIBLE. WIND... CORE OF STRONGEST WINDS WILL BE OCCURRING THROUGH ABOUT 18Z FOR THE CAPE/ISLANDS TO COASTAL SE MA AS LOW PRES DEEPENS NEAR THE BENCHMARK. LOW LEVEL JET AROUND 75 KTS PERSISTS IN THIS REGION. SOUNDINGS SHOW POTENTIAL FOR NEAR HURRICANE FORCE GUSTS TO 75 MPH IN THIS REGION...WITH GUSTS TO 50-60 BACK TO THE I-95 CORRIDOR AND 30-40 FURTHER IN THE INTERIOR. EXPECT WIND DAMAGE AND WIDESPREAD POWER OUTAGES ACROSS PORTIONS OF SE MA AND ESPECIALLY THE CAPE/ISLANDS WHERE HEAVY WET SNOW WILL ADD TO LOAD. TEMPS... COASTAL FRONT CURRENTLY ACROSS SE MA WITH TEMPS IN THE TEENS WEST OF THE FRONT AND 20S TO LOWER 30S TO THE EAST. EXPECT TEMPS TO REMAIN IN THE TEENS TO NEAR 20 TODAY FOR MOST OF THE REGION...AND EVENTUALLY FALLING INTO THE TEENS AND LOWER 20S SE COASTAL MA THIS AFTERNOON AS THE COASTAL FRONT MOVES THROUGH. TONIGHT... AS MID LEVEL LOW LIFTS NORTH FROM EAST OF CAPE COD...EXPECT SNOW TO GRADUALLY WIND DOWN AND END FROM WEST TO EAST. SOME MINOR ADDITIONAL ACCUM POSSIBLE. OTHERWISE VERY COLD WITH LOWS DOWN INTO THE SINGLE NUMBERS...EXCEPT TEENS IMMEDIATE COAST. EXPECT SUBZERO WIND CHILLS DEVELOPING AND APPROACHING WIND CHILL THRESHOLD OF -15 OVER THE HIGHER TERRAIN IN WESTERN AND NORTHERN MA. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... WEDNESDAY... EXPECT COASTAL STORM TO DRIFT NE THROUGH THE GULF OF MAINE ACROSS NOVA SCOTIA DURING THE DAY. LAST OF LIGHT SNOW WILL PUSH OFF THE COAST WED MORNING...WITH IMPROVING CONDITIONS. HOWEVER...WILL STILL SEE BLUSTERY NW WINDS BEHIND THE DEPARTING LOW ALONG THE COAST AS TIGHT PRES GRADIENT LINGERS THROUGH MIDDAY BEFORE DIMINISHING. BRIEF SHOT OF COLD AIR MOVES ACROSS WITH H85 TEMPS DOWN TO -10C TO -12C. THIS WILL TRANSLATE TO HIGH TEMPS ONLY IN THE 20S ACROSS THE REGION...POSSIBLY ONLY IN THE UPPER TEENS ACROSS THE INTERIOR HIGHER TERRAIN. WEDNESDAY NIGHT... WEAK H5 RIDGE BUILDS ACROSS ALONG WITH ASSOCIATED N-S ELONGATED HIGH PRES. AS RIDGE AXIS MOVES ACROSS AFTER MIDNIGHT...WINDS WILL DROP OFF TO LIGHT/VRBL OR CALM. THIS...ALONG WITH MOSTLY CLEAR SKIES AWAY FROM THE COAST AND THE NEW SNOW PACK...EXPECT OVERNIGHT LOWS INLAND TO DROP TO BETWEEN ZERO AND -5 ACROSS THE COLDER INLAND VALLEYS...RANGING TO 5 TO 10 DEGREES FOR MOST OTHER AREAS EXCEPT HOLDING AROUND 20 ACROSS THE OUTER CAPE AND NANTUCKET. THURSDAY... PROGRESSIVE UPPER PATTERN BRINGS ANOTHER H5 SHORT WAVE/CLIPPER SURFACE LOW IN THIS W-NW FLOW. RIDGE EARLY THU MORNING WILL PUSH E AS LOW SHIFTS OUT OF THE GREAT LAKES AND OHIO VALLEY. WILL SEE INCREASING CLOUDS DURING THE AFTERNOON. SOME LIGHT SNOW MAY SNEAK INTO THE E SLOPES OF THE BERKSHIRES LATE IN THE DAY. WINDS BACK TO SW...SO WILL BRING SOMEWHAT MILDER AIR TO THE REGION. EXPECT HIGHS TO RECOVER TO THE UPPER 20S TO MID 30S...MILDEST ALONG THE S COAST. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * CLIPPER LOW MAY BRING MORE MEASURABLE SNOW THU NIGHT AND FRI * MUCH COLDER EARLY NEXT WEEK OVERVIEW... NOTING RATHER GOOD AGREEMENT ON SYNOPTIC FEATURES ON THE 00Z MODEL SUITE INTO THE UPCOMING WEEKEND...THOUGH SOME QUESTIONS LIE IN THE DETAILS. CONTINUE TO SEE SIGNAL FOR POSSIBLE LOW PRES MOVING OUT OF THE LOWER MISSISSIPPI VALLEY TOWARD THE REGION LATE NEXT WEEKEND OR EARLY NEXT WEEK...BUT TIMING IS IN QUESTION. USED A BLEND OF AVAILABLE GUIDANCE ALONG WITH ENSEMBLES FOR A CONSENSUS FORECAST. DETAILS... THURSDAY NIGHT AND FRIDAY... EXPECT CLIPPER LOW TO CROSS THE REGION DURING THIS TIMEFRAME. NOTING A COUPLE OF WEAK H5 SHORT WAVES WHICH ARE NOT WELL ORGANIZED AND SURFACE SYSTEM REMAINS ON THE WEAK SIDE. HOWEVER... FAIRLY GOOD QPF ASSOCIATED WITH THE SYSTEM SO COULD SEE A PLOWABLE SNOWFALL. FRIDAY NIGHT THROUGH MONDAY... LOW PRES AND SHORT WAVE EXIT THE REGION DURING FRI NIGHT...THOUGH TIMING THE EXIT OF THE PRECIP ACROSS EASTERN AREAS IS STILL SOMEWHAT IN QUESTION. HOWEVER...NOTING ANOTHER SHOT OF VERY COLD AIR WORKING IN AS H85 TEMPS DIVE TO -18C TO -22C BY 12Z SAT. SHOULD BE DRY BY MIDDAY SAT BUT VERY COLD. HIGH PRES LOOKS TO CROSS DURING SUNDAY...THEN TIMING ISSUES COME INTO PLAY WITH ANOTHER POSSIBLE SYSTEM OUT OF THE LOWER MISSISSIPPI VALLEY FOR SUN NIGHT AND/OR MON. LOW CONFIDENCE AS UNCERTAINTY ON TIMING AND TRACK CONTINUE. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH TUESDAY NIGHT... TODAY AND TONIGHT... SIGNIFICANT SNOWSTORM CONTINUES THROUGH THE PERIOD WITH SNOWFALL RATES OF 1-3 INCHES PER HOUR. ISOLATED THUNDER POSSIBLE. MOST AIRPORTS ARE EXPECTED TO BE AT OR BELOW MINIMUMS DURING THIS PERIOD WITH CONDITIONS RANGING FROM IFR TO VLIFR. VERY STRONG WIND CONTINUE WITH GUSTS 70-80 KNOTS CAPE AND ISLANDS AND PARTS OF SOUTHEAST MASS. LOW LEVEL WIND SHEAR CONTINUES TODAY AND DIMINISHES TONIGHT. KBOS TAF...HIGH CONFIDENCE IN TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING. KBDL TAF...HIGH CONFIDENCE IN TAF TRENDS...LOWER CONFIDENCE IN EXACT TIMING. OUTLOOK /WEDNESDAY THROUGH SATURDAY/... WEDNESDAY...HIGH CONFIDENCE IN TRENDS...MODERATE CONFIDENCE IN TIMING. CONDITIONS IMPROVE TO VFR FROM WEST TO EAST...ALTHOUGH MVFR CIGS MAY LINGER ACROSS CAPE COD AND THE ISLANDS THROUGH MIDDAY OR EARLY AFTERNOON. NORTHWEST WIND GUSTS TO 20-25 KNOTS THROUGH MIDDAY ALONG THE COAST. THURSDAY THROUGH FRIDAY NIGHT...MODERATE CONFIDENCE. VFR THROUGH MOST OF THU. ANOTHER ROUND OF MVFR-IFR CONDITIONS IN -SN AND PATCHY FOG THU NIGHT INTO FRI NIGHT...THEN IMPROVING FROM W-E AFTER MIDNIGHT. NW WINDS BECOMING GUSTY AFTER MIDNIGHT FRIDAY. SATURDAY...MODERATE CONFIDENCE. VFR. LEFTOVER MVFR CIGS/VSBYS ACROSS E MA EARLY. NW WINDS WITH GUSTS UP TO 25-35 KT POSSIBLE. && .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. *** POWERFUL STORM PRODUCE LIFE THREATENING CONDITIONS *** EXPECT NE WIND GUSTS OF 55-65 KT WITH SEAS 30-35 FT OVER THE E WATERS AS WELL. HURRICANE FORCE WIND WARNINGS CONTINUE FOR THE OPEN WATERS...WITH STORM WARNINGS CLOSER TO THE SHORE. CONDITIONS IMPROVE SOMEWHAT LATER TODAY INTO TONIGHT...ALTHOUGH A PERIOD OF GALES ARE POSSIBLE UNTIL CONDITIONS DROP DOWN TO SMALL CRAFT ADVISORY THRESHOLDS. OUTLOOK /WEDNESDAY THROUGH SATURDAY/... WEDNESDAY...HIGH CONFIDENCE. ANY LEFTOVER GALE FORCE NORTHWEST WIND GUSTS EARLY IN THE MORNING WILL QUICKLY DIMINISH TO SMALL CRAFT ADVISORY LEVELS...THEN SHOULD SUBSIDE BELOW SMALL CRAFT WED NIGHT. SEAS WILL CONTINUE TO SUBSIDE...BUT WILL REMAIN WELL ABOVE SMALL CRAFT THRESHOLDS ACROSS THE OUTER WATERS. THURSDAY AND FRIDAY...MODERATE CONFIDENCE. EXPECT WINDS AND SEAS BELOW SMALL CRAFT THU INTO THU NIGHT. W-NW WINDS INCREASE DURING FRIDAY. LOW END GALE GUSTS POSSIBLE FRI NIGHT. SEAS BUILDING. LIGHT FREEZING SPRAY LIKELY. SATURDAY...NW GALE GUSTS REMAIN POSSIBLE ON THE OUTER WATERS ALONG WITH LIGHT FREEZING SPRAY. SEAS REMAIN HIGH...POSSIBLY UP TO 7-9 FT ON THE OUTER WATERS. && .TIDES/COASTAL FLOODING... *** MODERATE TO MAJOR COASTAL FLOODING TODAY ALONG THE EASTERN MA COAST FOR BOTH THIS MORNING AND LATE AFTERNOON HIGH TIDE CYCLES *** POWERFUL WINTER STORM DEVELOPING NEAR THE 40N/70W BENCHMARK AND COMBINING WITH ARCTIC HIGH PRESSURE OVER SOUTHEAST QUEBEC TO YIELD HURRICANE FORCE WIND GUSTS THIS MORNING AND INTO MIDDAY ACROSS NANTUCKET...CAPE COD AND COASTAL PLYMOUTH COUNTY. TIDE GAUGES ALONG THE EASTERN MA COASTLINE AT 3 AM INDICATING STORM SURGE VALUES ALREADY 2.5 TO 3.0 FT! THIS WILL YIELD MODERATE TO MAJOR COASTAL FLOODING WITH THIS MORNING/S HIGH TIDE CYCLE. THE HIGHEST IMPACT AREAS WILL LIKELY BE NANTUCKET/CAPE COD BAY COMMUNITIES AND NORTHWARD ALONG THE COAST INTO PLYMOUTH COUNTY INCLUDING THE COMMUNITIES OF HULL/MARSHFIELD AND SCITUATE. COASTAL FLOODING WILL OCCUR FARTHER NORTHWARD INTO CAPE ANN HOWEVER THE MAGNITUDE OF THE FLOODING SHOULD BE SLIGHTLY LESS THAN THE SOUTH SHORE. THESE HIGH WATER LEVELS WILL RESULT IN SIGNIFICANT INUNDATION OF SEA WATER. STRUCTURAL DAMAGE IS LIKELY AS WELL GIVEN SEAS OFFSHORE HAVE ALREADY CLIMBED TO 18 TO 22 FT AND WILL ONLY CONTINUE TO INCREASE. COULD SEE OFFSHORE SEAS 25 TO 35 FT THIS AFTERNOON! THIS WILL RESULT LARGE WAVES BATTERING SEAWALLS AND OTHER SHORELINE STRUCTURES. IN ADDITION THE HIGH WATER LEVELS WILL COMBINE WITH THE LARGE WAVE ACTION TO YIELD SEVERE BEACH EROSION. AS FOR THE LATE AFTERNOON HIGH TIDE...WATER LEVELS MAY BE ABOUT A HALF A FOOT LOWER HOWEVER SEAS WILL BE AT LEAST AS LARGE AS THIS MORNING OR POSSIBLE A FEW FEET HIGHER. THUS IMPACTS WILL BE SIMILAR HOWEVER THE FOCUS WILL SHIFT TO COASTAL PLYMOUTH COUNTY SOUTHWARD TO CAPE COD BAY COMMUNITIES SUCH AS SANDWICH HARBOR. THUS LESS IMPACT FOR NANTUCKET THAN THIS MORNING. NEVERTHELESS AT LEAST MODERATE COASTAL FLOODING EXPECTED FOR NANTUCKET. SO IN A NUTSHELL...NO CHANGES TO ANY HEADLINES WITH COASTAL FLOOD WARNINGS REMAINING IN PLACE FOR THE NEXT TWO TIDE CYCLES. AS FOR RI...THE RISK FOR MINOR COASTAL FLOODING HAS COMMENCED WITH HIGH TIDE ALREADY OCCURRING. THEREFORE THE RISK HAS DIMINISHED AND THE ADVISORY WILL BE ALLOWED TO EXPIRE. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...BLIZZARD WARNING UNTIL 1 AM EST WEDNESDAY FOR CTZ002>004. MA...BLIZZARD WARNING UNTIL 1 AM EST WEDNESDAY FOR MAZ005>007- 012>021. COASTAL FLOOD WARNING FROM 3 PM THIS AFTERNOON TO 7 PM EST THIS EVENING FOR MAZ007-015-016-019-022-024. WINTER STORM WARNING UNTIL 1 AM EST WEDNESDAY FOR MAZ002>004- 008>011-024-026. HIGH WIND WARNING UNTIL 1 AM EST WEDNESDAY FOR MAZ024. BLIZZARD WARNING UNTIL NOON EST TODAY FOR MAZ022-023. RI...BLIZZARD WARNING UNTIL 1 AM EST WEDNESDAY FOR RIZ001>008. MARINE...HURRICANE FORCE WIND WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ231>235. FREEZING SPRAY ADVISORY UNTIL 8 AM EST WEDNESDAY FOR ANZ231>235-237-251. STORM WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ230-236-237- 251. HURRICANE FORCE WIND WARNING UNTIL NOON EST TODAY FOR ANZ250- 254>256. && $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...EVT LONG TERM...EVT AVIATION...WTB/EVT MARINE...KJC/EVT TIDES/COASTAL FLOODING...

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