Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 291642 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1142 AM EST THU JAN 29 2015 .SYNOPSIS... HIGH PRESSURE OVER NEW ENGLAND WILL MOVE EAST THIS AFTERNOON AND EVENING. A CLIPPER LOW PRESSURE WILL MOVE INTO THE GREAT LAKES TONIGHT WITH A SECONDARY LOW DEVELOPING ALONG THE SOUTHERN NEW ENGLAND COAST AND INTENSIFYING OVER THE GULF OF MAINE FRI BY 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1135 AM UPDATE... WITH HIGH PRES RIDGE ACROSS THE REGION... LIGHT/VRBL OR CALM WINDS IN PLACE EXCEPT ACROSS THE OUTER CAPE AND NANTUCKET WHERE NW WINDS AT AROUND 10 MPH. HIGH CLOUDS ALREADY APPROACHING THE REGION FROM THE WEST AND THIS INCREASE IN CLOUD COVER WILL BE THE TREND FOR THE AFTERNOON. HAVE LOWERED TEMPERATURES INITIALLY PER CURRENT OBSERVATIONS BUT THE AFTERNOON HIGHS STILL LOOK GOOD...SO LITTLE CHANGE TO THEM. MAXES WILL REACH THE UPPER 20S TO THE LOWER AND MID 30S. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... UPDATE AS OF 1135 AM... HAVE EXPANDED THE WINTER WEATHER ADVISORY SOUTHWARD TO INCLUDE NORFOLK...SUFFOLK...AND MUCH OF PLYMOUTH COUNTIES FOR FRI AND FRI NIGHT. NEW MODEL INFORMATION SHOWS THAT THE STORM WILL BE REDEVELOPING SOUTH OF CAPE COD AND INTENSIFYING OVER THE GULF OF MAINE. FORECAST PRECIPITATION AMOUNTS...IN THE FORM OF SNOW...SHOULD REACH 3 TO 4 OR AN OUTSIDE CHANCE OF 5 INCHES IN THESE AREAS BY THE TIME THE SNOW ENDS EARLY SAT MORNING. TRICKY BECAUSE THE AMOUNTS ARE SPREAD OUT OVER A RELATIVELY LONG DURATION... BUT GIVEN THE BIG SNOWFALL WE JUST HAD...THE IMPACTS OF ADDITIONAL SNOW COULD BE IMPORTANT...THUS WENT WITH THE ADVISORY. WE ARE ALSO WATCHING THE POTENTIAL FOR AS MUCH AS 8 INCHES IN FAR NORTHEAST MA...MAINLY ESSEX COUNTY... WHICH COULD REQUIRE A WARNING. WILL ASSESS THIS DURING THE AFTERNOON. PREVIOUS DISCUSSION... 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. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... HEADLINES... * ARCTIC AIR INVADES NEW ENGLAND THIS WEEKEND ON BLUSTERY NW WINDS * COASTAL STORM POSSIBLE SUNDAY NIGHT AND MONDAY...BUT LOW CONFIDENCE CONTINUES OVERVIEW... H5 CUTOFF LOW PRES WILL SPIN OFF THE MAINE COAST SATURDAY...WITH DEEPENING SURFACE LOW SLOWLY SHIFTING INTO NOVA SCOTIA. UPPER LEVEL WIND FLOW WILL FLATTEN OUT...ALLOWING WEATHER SYSTEMS TO MOVE ACROSS THE NORTHERN TIER STATES FOR A GOOD PORTION OF THE LONG TERM. NOTING ANOTHER SHORT WAVE IN THIS FAST FLOW DIGGING INTO THE MID ATLC STATES...WHICH WILL TRIGGER ANOTHER LOW DEVELOPING S OF THE REGION. MANY QUESTIONS REMAIN ON THE TRACK AND STRENGTH OF THIS LOW AS IT PASSES NEAR OR S OF THE REGION...WHICH WILL DETERMINE ITS EFFECTS. MODEL SOLUTION SPREAD IS HIGH...SO LOW CONFIDENCE AT THIS POINT. ONE CERTAINTY IS THE FRIGID TEMPERATURES WINDS AND BLUSTERY WINDS AT TIMES INTO PORTIONS OF NEXT WEEK. DETAILS... SATURDAY-SUNDAY...STRONG LOW PRESSURE WILL SHIFT NE INTO NOVA SCOTIA SATURDAY. THIS WILL USHER IN THE COLDEST AIR OF THE SEASON. NW WINDS WILL REMAIN GUSTY INTO SATURDAY NIGHT...THEN WILL DIMINISH AS HIGH PRES MOVES ACROSS. ANOTHER DRY FRONT WILL SHIFT SE SUNDAY...JUST REINFORCING THE ARCTIC AIR ACROSS THE REGION. HIGH TEMPS BOTH DAYS WILL RUN 15 TO 20 DEGREES BELOW SEASONAL NORMALS. THE HIGH ON SAT AT KBDL MAY BE CLOSE TO THE RECORD LOW MAX TEMP /RECORD IS 15 DEGREES SET IN 1951/. SUNDAY NIGHT-MONDAY...ANOTHER H5 SHORT WAVE WILL DIG TO THE MID ATLC COAST IN THE FAST FLOW ALOFT. BIG QUESTIONS REMAIN...WHERE WILL THE SURFACE SYSTEM DEVELOP...HOW STRONG WILL IT BE AND HOW FAR N WILL IT TRACK. LOW CONFIDENCE DUE TO WIDE MODEL SOLUTION SPREAD. ONE THING NOT IN QUESTION...PRECIP WILL MOST LIKELY BE IN THE FORM OF SNOW...BUT HOW MUCH. WILL HAVE TO WATCH THE NEXT FEW MODEL RUNS TO DETERMINE THAT. AT THIS POINT...HAVE MENTIONED CHANCE POPS FOR MOST AREAS WITH THE BEST CHANCE ALONG THE S COAST...CAPE AND ISLANDS. UPPER PATTERN REMAINS PROGRESSIVE...THOUGH...SO THE LOW SHOULD DEPART LATE MON OR MON NIGHT. TUESDAY-WEDNESDAY... MORE ARCTIC COLD ARRIVES ON TUESDAY AS ANOTHER LARGE AREA OF HIGH PRES BUILDS E. LOOKS LIKE THE LOW WILL SHIFT E ON WED...WHICH MEANS TEMPS MAY START TO REBOUND BUT WILL REMAIN BELOW SEASONAL NORMALS. YET ANOTHER LOW MAY APPROACH WED NIGHT BRINGING ANOTHER CHANCE OF PRECIP...THOUGH TIMING AND TRACK FOR THIS LOW IS ALSO UNCERTAIN. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH TONIGHT...HIGH CONFIDENCE. THIS AFTERNOON...VFR. MID AND HIGH LEVEL CLOUDS INCREASE FROM W-E.THIS LIGHT WINDS. 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. NW WINDS GUSTING TO 25-35 KNOTS SATURDAY...HIGHEST ALONG THE COAST. LIGHTER WINDS SUNDAY. SUNDAY NIGHT-MONDAY...LOW CONFIDENCE. LOW PRES DEVELOPS S OF THE REGION...BUT TRACK REMAINS UNCERTAIN. TOO EARLY TO HAVE ANY CONFIDENCE ON VFR OR IFR THIS PERIOD. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH FRIDAY/...HIGH CONFIDENCE. 1135 AM UPDATE...HAVE UPGRADED THE GALE WATCH TO GALE WARNINGS FOR LATE FRI INTO SAT AND HAVE INCLUDED BOSTON HARBOR. THIS AFTERNOON...HIGH PRES BUILDS OVER THE WATERS WITH DIMINISHING WINDS BECOMING LIGHT AND SEAS BELOW SCA. TONIGHT...INCREASING SOUTHERLY WINDS EXPECTED AHEAD OF LOW PRES MOVING THROUGH THE GREAT 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 NIGHT...LOW PRES WILL CROSS THE WATERS. REDUCED VSBYS IN SNOW MAINLY IN THE EASTERN WATERS EARLY. WINDS WILL SHIFT TO NW AND INCREASE. GUSTS UP TO GALE FORCE EXPECTED. GALE WATCHES HAVE BEEN UPGRADED TO GALE WARNINGS FOR ALL WATERS AND NOW INCLUDES BOSTON HARBOR. FREEZING SPRAY LIKELY. SATURDAY...NW GALES EXPECTED. FREEZING SPRAY DEVELOPING. HIGH SEAS FORECAST...10-12 FT OFFSHORE WATERS. WINDS WILL BEGIN TO DIMINISH SAT NIGHT WITH A CORRESPONDING LOWERING OF SEAS. SUNDAY...EXPECT WINDS TO DIMINISH BUT REMAIN AT SMALL CRAFT LEVELS...THOUGH SOME GALE GUSTS MAY LINGER ON THE EASTERN OUTER WATERS EARLY. SEAS WILL SLOWLY SUBSIDE...BUT WILL REMAIN AOA 5 FT ON THE OUTER WATERS. SUNDAY NIGHT-MONDAY...DEPENDING UPON STRENGTH AND TRACK OF DEVELOPING LOW PRES S OF THE REGION...COULD SEE WIND GUSTS UP TO SMALL CRAFT CRITERIA. SEAS WILL REMAIN AOA 5 FT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST SATURDAY FOR MAZ004>007-013>016-018-019-026. RI...NONE. MARINE...GALE WARNING FROM MIDNIGHT FRIDAY NIGHT TO 6 PM EST SATURDAY FOR ANZ230>234-251. GALE WARNING FROM 2 AM TO 1 PM EST SATURDAY FOR ANZ236. GALE WARNING FROM 9 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ235- 237. GALE WARNING FROM 11 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ250- 254-255. GALE WARNING FROM 7 PM FRIDAY TO 6 PM EST SATURDAY FOR ANZ256. && $$ SYNOPSIS...KJC/EVT NEAR TERM...GAF SHORT TERM...KJC/GAF LONG TERM...EVT AVIATION...KJC/EVT/GAF MARINE...KJC/EVT/GAF

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