Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280912 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 412 AM EST SUN DEC 28 2014 .SYNOPSIS...
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A COLD FRONT OVER EASTERN NEW YORK EARLY THIS MORNING WILL RACE EASTWARD ACROSS SOUTHERN NEW ENGLAND BY MID AFTERNOON. LIGHT RAIN SHOWERS WILL ACCOMPANY THE FRONT. FAR REACHING HIGH PRESSURE INITIALLY CENTERED OVER THE HIGH PLAINS AND THEN SHIFTING TO THE EAST COAST BY THE END OF THE WEEK WILL KEEP THE REGION DRY AND COLD THROUGH FRIDAY. AN APPROACHING WARM FRONT WILL BRING A CHANCE OF PRECIPITATION TO THE REGION ON SATURDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 345 AM UPDATE... A COLD FRONT WAS RACING ACROSS NEW YORK STATE EARLY THIS MORNING. WINDS HAD ALREADY SHIFTED TO THE WEST AT ITHACA AND ELMIRA AS OF 345 AM. OUT AHEAD OF THE FRONT THERE WAS A LARGE AREA OF LIGHT RAIN AND RAIN SHOWERS. THE PRECIPITATION WAS ONLY MEASURING A FEW HUNDREDTHS TO A TENTH OF AN INCH AND THIS IS WHAT CAN BE EXPECTED ACROSS MUCH OF SOUTHERN NEW ENGLAND THIS MORNING INTO THE EARLY AFTERNOON. HAVE RAISED POPS TO CATEGORICAL IN WESTERN AND CENTRAL MA...WITH LIKELY POPS ELSEWHERE. AGAIN...THE RAIN WILL BE LIGHT. THE FRONT WILL MOVE SO QUICKLY THAT NORTHWEST AREAS SHOULD BECOME PARTLY SUNNY BY MID AFTERNOON...AND SKIES WILL BEGIN TO CLEAR IN THE SOUTHEASTERN AREAS BY EARLY EVENING. SOUTH TO SOUTHWEST WINDS AHEAD OF THE FRONT CAUSED TEMPERATURES TO JUMP WELL INTO THE 40S OVERNIGHT. WITH THIS MILD HEAD START...HAVE RAISED THE FORECAST MAXIMUMS FOR TODAY TO THE UPPER 40S AND LOWER 50S. WINDS MAY GUST TO 20 TO 25 MPH AT TIMES AHEAD OF THE FRONT AND BRIEFLY BEHIND THE FRONT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT...SKIES WILL BECOME CLEAR AND THIS WILL ALLOW TEMPERATURES TO DROP TO COLDER THAN GUIDANCE VALUES IN NORTHWEST MA AND IN THE NORMALLY COLDER LOCATIONS. FORECASTING LOWS IN THE MID 20S AWAY FROM THE COAST...TO 30 TO 35 FOR THE CAPE AND ISLANDS. MONDAY...HIGH PRESSURE BUILDING IN FROM THE NORTHWEST MEANS MOSTLY SUNNY SKIES AND COLDER WEATHER. FAR NW MA...IN THE SLOPES OF THE BERKSHIRES...COULD HAVE A PERIOD OF PARTLY TO MOSTLY CLOUDY SKIES. HIGHS FROM THE MID 30S TO LOWER 40S...MORE TOWARD SEASONAL NORMALS. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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HIGHLIGHTS... * DRY AND COLD THROUGH FRIDAY * CHANCE OF RAIN OR MIXED PRECIPITATON TO RAIN ON SATURDAY AS WARM FRONT APPROACHES OVERVIEW... MEDIUM RANGE MODELS NOW APPEAR IN GOOD AGREEMENT ON AT LEAST THE LARGE SCALE PATTERN THROUGH NEXT WEEKEND. OVER THE COURSE OF THE COMING WEEK...A HIGH AMPLITUDE RIDGE BUILDS OVER ALASKA WHILE THE NORTH AMERICAN POLAR VORTEX SETS UP OVER HUDSON BAY. THIS OPENS THE DOOR TO ARCTIC INTRUSION INTO NEW ENGLAND BUT WITH WHAT WILL PROBABLY BE A TEMPORARY RELAPSE TO MILD TEMPERATURES NEXT WEEKEND IN ASSOCIATION WITH WHAT LOOKS TO BE STILL ANOTHER INSIDE RUNNER. ENSEMBLE MEMBERS SUGGEST A RETURN TO A POSITIVE NAO INDEX AFTER JAN 1 AND A STRONG RIDGE REMAINS ROOTED ACROSS THE BAHAMAS. THUS...ALTHOUGH THE PATTERN IN GENERAL FAVORS COLD TEMPERATURES ACROSS SOUTHERN NEW ENGLAND FOR THE FORESEEABLE FUTURE...SHORT WAVE ENERGY CAN DISLODGE THE COLD AIR AT LEAST TEMPORARILY WITH NO DOWNSTREAM BLOCKING AVAILABLE TO EITHER HOLD IN THE COLD AIR OR PROMOTE SIGNIFICANT COASTAL CYCLOGENESIS. DAY TO DAY... MON NIGHT THROUGH WED...GENERALLY DRY AND COLDER THAN NORMAL TEMPERATURES SUPPORTED BY BROAD TROF ALOFT CENTERED OVER HUDSON BAY AND MASSIVE 1059 MB HIGH SPREADING S AND SE FROM WESTERN SASKATCHEWAN. TUE NIGHT/WED AM LOOKS TO BE THE COLDEST NIGHT WITH 850 MB TEMPERATURES OF -15C TO -16C...PROBABLY MOSTLY CLEAR SKIES AND LIGHT WINDS. WILL LIKELY EXPERIENCE SURFACE TEMPERATURES IN TEENS ACROSS MOST OF INTERIOR SOUTHERN NEW ENGLAND WITH POSSIBLY POCKETS OF 5 TO 10 ABOVE TEMPERATURES NW MA. LACK OF SNOWCOVER PREVENTS WHAT MIGHT OTHERWISE BE COLDER TEMPERATURES. WED NIGHT THROUGH FRI...SHORT WAVE TROF EMBEDDED IN BROAD CYCLONIC FLOW ALOFT PASSES ACROSS NEW ENGLAND ON THU BUT LACKS MOISTURE. HOWEVER...IT IS NOT OUT OF THE QUESTION THAT LOW LEVEL LAPSE RATES COULD SUPPORT OCEAN EFFECT FLURRIES OR SNOW SHOWERS ACROSS NANTUCKET WITH WESTERLY GRADIENT. THE 00Z GFS THERMAL PROFILE IS MORE FAVORABLE THAN THE 00Z ECMWF THERMAL PROFILE FOR THIS. THE OTHER POTENTIAL ISSUE FOR THU IS WIND. MEDIUM RANGE MODELS HAVE DEPICTED FOR QUITE A FEW RUNS A TIGHTENING OF THE SURFACE PRESSURE GRADIENT ON THU WITH BRISK WESTERLY WINDS THE RESULT...POSSIBLY GALE FORCE GUSTS JUST OFF THE COAST. THIS COULD MAKE THU FEEL COLDER DUE TO LOWER WIND CHILLS. WINDS WILL LIKELY SLACKEN BY FRI MORNING AS MEDIUM RANGE MODELS CONSISTENT WITH SURFACE RIDGE MOVING ACROSS THE REGION. FRI NIGHT THROUGH SAT...THIS IS THE ONLY VIABLE OPPORTUNITY FOR SIGNIFICANT PRECIPITATION DURING THIS FORECAST PERIOD. MEDIUM RANGE OPERATIONAL MODELS AND NEARLY ALL ENSEMBLE MEMBERS POINT TO AN INSIDE RUNNER WITH SOME VARIATIONS IN TIMING AND STRENGTH OF THE SYSTEM. AT THIS TIME IT LOOKS LIKE THIS SHOULD BE MAINLY A RAIN EVENT...BUT ENOUGH LOW LEVEL COLD AIR AT THE OUTSET COULD SET THE STAGE FOR A PERIOD OF MIXED PRECIPITATION AT THE START OF THE EVENT ACROSS SOME OF THE INTERIOR. BOTH THE ECMWF AND GFS OPERATIONAL RUNS DEPICT A STRONG LOW LEVEL JET AT 925 MB OF 70+ KT. DEPENDING UPON MIXING POTENTIAL...THIS COULD RESULT IN STRONG WINDS ACROSS THE SE COASTAL PLAIN SOMETIME ON SAT...PROBABLY AFTERNOON. A STRONG LOW LEVEL JET COULD ALSO SIGNAL SIGNIFICANT QPF...BUT THE EVENT IS TOO FAR OUT TO HAVE MUCH CONFIDENCE IN RAINFALL AMOUNTS.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY...HIGH CONFIDENCE. GENERALLY VFR WITH CEILINGS LOWERING TO 3500-6000 FT. LIGHT RAIN AND RAIN SHOWERS OVERSPREADING THE REGION THIS MORNING AND EXITING THE SOUTHEAST THIS AFTERNOON. VISIBILITIES SHOULD REMAIN ABOVE 3 MILES BUT LOCAL MVFR VISIBILITY POSSIBLE IN AN ISOLATED BRIEF MODERATE RAIN SHOWER. SW WINDS GUSTING TO 15 TO 20 KT...SHIFTING TO THE W AT THE SAME SPEEDS. TONIGHT...HIGH CONFIDENCE. VFR WITH A LIGHT WEST TO NORTHWEST WIND. MONDAY...HIGH CONFIDENCE. VFR. MVFR CEILINGS POSSIBLE IN EXTREME NW MA IN THE SLOPES OF THE BERKSHIRES. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MODERATE TO HIGH CONFIDENCE OF MAINLY VFR THROUGH THE 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 MONDAY/...MODERATE TO HIGH CONFIDENCE. TODAY...A MARGINAL SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL WATERS EXCEPT FOR BOSTON HARBOR AND NARRAGANSETT BAY. WE COULD SEE SW WIND GUSTS TO AROUND 25 KT THIS MORNING AND EARLY AFTERNOON... FOLLOWED BY A SHIFT TO THE W AND WNW LATER THIS AFTERNOON AT THE SAME SPEEDS. SEAS SHOULD BE BUILDING FROM 3 FT THIS MORNING TO UP TO 5 TO 6 FT ON THE OUTERMOST WATERS LATER THIS AFTERNOON. TONIGHT...WINDS DIMINISH AND SEAS SUBSIDE. HOWEVER A SMALL CRAFT ADVISORY WILL REMAIN POSTED FOR THE SOUTHEASTERN WATERS UNTIL ABOUT 1 AM BECAUSE THE 5 FT SEAS WILL BE SLOWEST TO SUBSIDE IN THOSE AREAS. MONDAY...NORTHWEST WINDS 10 TO 15 KT WITH GUSTS TO 20 KT OFF THE NORTHEAST MA COAST. SEAS GENERALLY 3 TO 4 FT OVER THE OUTER WATERS. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MODERATE TO HIGH CONFIDENCE. MON NIGHT THROUGH WED NIGHT...EXPECT WINDS AND SEAS BELOW SMALL CRAFT ADVISORY THRESHOLDS. THU...W WIND WILL LIKELY INCREASE ABOVE SMALL CRAFT ADVISORY THRESHOLDS ALL WATERS WITH A CHANCE OF GALE FORCE GUSTS OVER AT LEAST THE OUTER WATERS. ALTHOUGH THIS OUTLOOK GOES ONLY TO THU...THE HWO IS FOR 7 DAYS. WILL MENTION A RISK OF SOUTHERLY GALES ACROSS THE WATERS ON SAT IN THE HWO. TYPICALLY, AN INVERSION AT THIS TIME OF YEAR LIMITS HOW MUCH MOMENTUM IS MIXED TO THE SEA SURFACE IN A SOUTHERLY GRADIENT. HOWEVER...GIVEN A SIGNAL OF 70+ KT AT 925 MB...THINK THERE IS A CHANCE OF MIXING WINDS STRONG ENOUGH TO RESULT IN POSSIBLE GALE FORCE GUSTS ACROSS THE OUTER WATERS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ231>235-237-250-251. SMALL CRAFT ADVISORY UNTIL 1 AM EST MONDAY FOR ANZ254>256. && $$ SYNOPSIS...GAF/THOMPSON NEAR TERM...GAF SHORT TERM...GAF LONG TERM...THOMPSON AVIATION...GAF/THOMPSON MARINE...GAF/THOMPSON

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