Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290929 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 429 AM EST THU JAN 29 2015 .SYNOPSIS...
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HIGH PRESSURE OVER NEW ENGLAND WILL MOVE EAST THIS AFTERNOON AND EVENING. A CLIPPER WILL MOVE INTO THE GT LAKES TONIGHT WITH A SECONDARY LOW DEVELOPING ALONG THE SOUTHERN NEW ENGLAND COAST AND MOVING INTO THE GULF OF MAINE FRI INTO FRI EVENING. THIS WILL BRING A PERIOD OF SNOW LATER TONIGHT AND FRI...WHICH WILL CONTINUE INTO FRI NIGHT FOR PARTS OF THE REGION. BLUSTERY AND VERY COLD CONDITIONS ARE EXPECTED THIS WEEKEND. ANOTHER STORM MAY BRING SNOW TO THE REGION SUNDAY NIGHT AND MONDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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OCEAN EFFECT CLOUDS OVER THE CAPE AND ISLANDS ARE GRADUALLY ERODING AND WILL CLEAR OUT BY DAYBREAK. OTHERWISE...A FRIGID MORNING ACROSS SNE WITH TEMPS SEVERAL DEGREES BELOW ZERO IN SOME OF COLDER SPOTS. HIGH PRES BUILDS OVER NEW ENG TODAY...THEN MOVES TO THE EAST DURING THE AFTERNOON. SUNSHINE WILL GIVE WAY TO INCREASING HIGH CLOUDS THIS AFTERNOON...ESPECIALLY W NEW ENG AS HIGH LEVEL MOISTURE MOVES IN AHEAD OF A MID LEVEL SHORTWAVE. WITH LIGHT WINDS...EXPECT A NICE RECOVERY IN TEMPS AFTER VERY COLD START. MAXES WILL REACH THE UPPER 20S TO LOW/MID 30S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
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TONIGHT AND FRIDAY... DIGGING SHORTWAVE FROM THE UPPER LAKES WILL MOVE SE AND PHASE WITH ANOTHER IMPULSE MOVING OUT OF THE OHIO VALLEY TO FORM A NEG TILT TROF ALONG THE NEW ENG COAST ON FRI. PRIMARY LOW LIFTS NE INTO NORTHERN NY TONIGHT WHILE SECONDARY LOW DEVELOPS NEAR THE SNE COAST FRI ASSOCD WITH THE MID LEVEL SHORTWAVE AND HEIGHT FALLS MOVING TO THE COAST. ECMWF IS FURTHEST SOUTH WITH THE SECONDARY LOW AND AS A RESULT HAS MORE QPF THAN THE OTHER MODELS. THE TRACK OF THE 700 MB LOW WILL BE CRITICAL TO WHERE HEAVIER SNOWFALL SETS UP. DEEPENING MOISTURE AND INCREASING MID LEVEL LIFT WILL RESULT IN A PERIOD OF SNOW DEVELOPING ACROSS SNE LATER TONIGHT INTO FRI. HOWEVER...SOUTHERLY FLOW AHEAD OF THE PRIMARY LOW WILL LIKELY WARM THE BOUNDARY LAYER ENOUGH FOR A MIX OR CHANGEOVER TO RAIN LATE TONIGHT INTO FRIDAY ALONG THE IMMEDIATE S COAST AND ESPECIALLY CAPE/ISLANDS. THE 700 MB LOW TRACKS ACROSS SNE WHICH SUGGESTS HEAVIER SNOW WILL SET UP ACROSS NORTHERN AREAS...MAINLY N OF THE MASS PIKE WITH LIGHTER SNOW TO THE SOUTH. THROUGH FRIDAY...GENERALLY LOOKING AT 2-3 INCHES NORTH OF THE PIKE WITH 1-2 INCHES TO THE SOUTH...EXCEPT LESS THAN AN INCH NEAR THE SOUTH COAST. EXPECT GRADUAL IMPROVING CONDITIONS IN THE CT VALLEY DURING THE AFTERNOON...WITH GUSTY NW WINDS DEVELOPING BY LATE IN THE DAY. FRIDAY NIGHT... MID LEVEL TROF CLOSES OFF JUST SOUTH OF THE SNE COAST AS COASTAL LOW INTENSIFIES IN THE GULF OF MAINE. AS MENTIONED ABOVE...ECMWF IS FURTHEST S WITH THE SFC LOW AND THUS IS MOST BULLISH ON BRINING A PERIOD OF HEAVIER SNOW...MAINLY TO N/NE MA. WE USED A MULTI MODEL BLEND OF QPF AS A BASIS FOR SNOW ACCUM. MODELS ARE IN AGREEMENT THE MID LEVEL LOW MOVES INTO THE GULF OF MAINE WITH A BAND OF SNOW IN THE COMMA HEAD ROTATING INTO THE EASTERN HALF OF SNE. EXPECT AN ADDITIONAL INCH OR 2 FOR CENTRAL AND E MA...WITH LOCALLY HIGHER AMOUNTS POSSIBLE ACROSS NE MA. WILL HAVE TO WATCH THIS AREA FOR THE POTENTIAL OF HIGHER ACCUM PER ECMWF. WE DECIDED ON A WINTER WEATHER ADVISORY FOR AREAS NORTH OF THE MASS PIKE IN N/NE MA WHERE HEAVIEST SNOW EXPECTED...FOR THE PERIOD FROM MIDNIGHT TONIGHT TO FRI NIGHT. CURRENT THINKING IS TOTAL ACCUM THROUGH FRI NIGHT WILL BE 4-6 INCHES N/NE MA WITH LOCALLY HIGHER AMOUNTS POSSIBLE. LOW PROB THAT WARNING WILL BE NEEDED FOR NE MA PER ECMWF...BUT CONFIDENCE NOT HIGH ENOUGH SO WE OPTED FOR AN ADVISORY. TURNING MUCH COLDER FRI NIGHT AS GUSTY NW WINDS DEVELOP WITH DEEPENING LOW PRES IN THE GULF OF MAINE. DANGEROUSLY COLD WIND CHILLS OF 10 TO 20 BELOW ZERO IN HIGHER TERRAIN OF CENTRAL AND W MA...WITH 5 TO 10 BELOW IN THE COASTAL PLAIN. WIND CHILL ADVISORIES WILL LIKELY BE NEEDED FOR HIGHER TERRAIN IN CENTRAL AND W MA.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/... * SNOW EASTERN AREAS FRI NIGHT DIMINISHES AS LOW EXITS THE AREA * ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BRISK NW WINDS * COASTAL STORM POSSIBLE SUN NIGHT-MON, BUT LOW CONFIDENCE OVERVIEW...LOW PRESSURE CENTER IS EXPECTED TO BE OFF THE MAINE COAST FRI NIGHT. SNOW IS MOST LIKELY EASTERN AREAS...ESPECIALLY COASTAL AREAS CLOSER TO THIS LOW SUCH AS BOSTON AND POINTS NORTH. THE SNOW IS FORECAST TO GRADUALLY WIND DOWN DURING THE NIGHT FRI NIGHT AS THE LOW PULLS AWAY. ARCTIC AIR WILL USHER INTO NEW ENGLAND BEHIND THIS DEPARTING LOW FOR THE WEEKEND WITH BLUSTERY NW WINDS AND FRIGID WIND CHILLS. WINDS CHILL ADVISORIES MAY BE NEEDED FRI NIGHT. A MORE VIGOROUS SHORTWAVE DIVES INTO THE EASTERN STATES SUN NIGHT AND MONDAY. MODELS CONTINUE TO STRUGGLE WITH REGARDS TO THE AMPLITUDE OF THE TROUGH AND THE CORRESPONDING SURFACE LOW AND TRACK. THE LATEST 28.12Z OPERATIONAL RUNS OF THE GFS AND ECMWF NOW ARE MORE PROGRESSIVE AND SHOW A WEAKER SURFACE LOW AND WELL EAST OF THE BENCHMARK. HOWEVER BOTH MODELS DID JUST THE SAME SEVERAL DAYS BEFORE OUR RECENT BLIZZARD...SO WE CANNOT HAVE ANY DEGREE OF CONFIDENCE WITH EITHER A HIT OR A MISS THIS FAR OUT IN TIME. WE WILL CONTINUE TO USE A MODEL BLEND INCLUDING THEIR ENSEMBLES AS THERE IS A HIGH DEGREE OF SPREAD AMONGST THEM. HIGH PRESSURE WILL BUILD INTO THE REGION TUE-WED AS THE SHORTWAVE/LOW MOVES EAST WITH HIGH PRESSURE TAKING OVER...BRINGING QUIET WEATHER MID WEEK. YET ANOTHER CHANCE OF SNOW OR A WINTRY MIX ENTERS THE PICTURE BY THU. AN ACTIVE WINTERTIME PATTERN INDEED! && .AVIATION /08Z THURSDAY 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...HIGH CONFIDENCE. TODAY...VFR. INCREASING CLOUDS ABOVE 10 K FT IN THE AFTERNOON. LIGHT WIND TONIGHT AND FRIDAY...CIGS LOWER OVERNIGHT TO MVFR/IFR IN OCCASIONAL SNOW. THE SNOW MAY MIX OR CHANGE TO RAIN ALONG THE IMMEDIATE S COAST AND ESPECIALLY THE CAPE/ISLANDS LATE TONIGHT AND FRI. SNOW DIMINISHES FRI AFTERNOON IN THE CT VALLEY BUT CONTINUES ACROSS E NEW ENG. WINDS SHIFT TO NORTHWEST DURING THE AFTERNOON. GUSTS TO 25-30 KT AND VFR CIGS DEVELOPING IN THE CT VALLEY BY MID/LATE AFTERNOON. KBOS TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. KBDL TAF...HIGH CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/... FRIDAY NIGHT...LOW CONFIDENCE. VFR WEST. POSSIBLE IFR TO START FOR EASTERN LOCALES...BUT WITH IMPROVEMENT EXPECTED OVERNIGHT. SATURDAY-SUNDAY...HIGH CONFIDENCE. VFR. GUSTY NORTHWEST WINDS 25-35 KNOTS SATURDAY...LIGHTER WINDS SUNDAY. SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. COASTAL LOW TRACK HIGHLY UNCERTAIN. JUST WAY TOO EARLY TO HAVE ANY CONFIDENCE ON VFR OR IFR THIS PERIOD.
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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 FRIDAY/...HIGH CONFIDENCE. TODAY...HIGH PRES BUILDS OVER THE WATERS WITH DIMINISHING WINDS BECOMING LIGHT AND SUBSIDING SEAS BELOW SCA. TONIGHT...INCREASING SOUTHERLY WINDS EXPECTED AHEAD OF LOW PRES MOVING THROUGH THE GT LAKES...BUT WIND GUSTS SHOULD REMAIN BELOW SCA. FRIDAY...SOUTHERLY WINDS WILL SHIFT TO W THEN NW DURING FRI AFTERNOON...WITH GUSTS TO 25-30 KT DEVELOPING ACROSS RI COASTAL WATERS BY LATE AFTERNOON. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE FRI- SAT...LOW CONFIDENCE SUN-MON. FRIDAY...LOW PRES WILL CROSS THE WATERS. EXPECT REDUCED VSBYS IN SNOW. EXPECT WINDS TO SHIFT TO NW AND INCREASE FRI NIGHT...WITH GALES POSSIBLE OVER THE WATERS. FREEZING SPRAY WILL LIKELY DEVELOP FRI NIGHT. SATURDAY...NW GALES EXPECTED WITH POTENTIAL FOR FREEZING SPRAY. HIGH SEAS FORECAST...10-12 FT OFFSHORE WATERS. WINDS WILL BEGIN TO DIMINISH SAT NIGHT WITH A CORRESPONDING LOWERING OF SEAS. SUNDAY...WINDS AND SEAS AT SMALL CRAFT ADVISORY LEVELS EARLY SUNDAY...BUT WILL DIMINISH THROUGH THE DAY. SUNDAY NIGHT-MONDAY...MUCH WILL DEPEND ON STRENGTH AND TRACK OF A POSSIBLE COASTAL LOW SO TAKE THE OFFICIAL FORECAST OF WINDS/SEAS DURING THIS PERIOD WITH A GRAIN OF SALT. A LOW CLOSER TO THE COAST WOULD SPELL A SIGNIFICANT IMPACT TO MARINERS...WHILE AN OFFSHORE/WEAKER TRACK WOULD HAVE MUCH LESS IMPACT. TOO EARLY TO SAY EITHER WAY...SO WENT WITH A MODEL BLEND.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST SATURDAY FOR MAZ004>007-014-026. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR ANZ255.
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&& $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...KJC LONG TERM...99 AVIATION...KJC/99 MARINE...KJC/99

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