Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271518 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1018 AM EST SAT DEC 27 2014 .SYNOPSIS... LARGE HIGH PRESSURE ACROSS THE MID ATLANTIC STATES WILL DRIFT EASTWARD OFF NORTH CAROLINA COAST THIS AFTERNOON. SOUTHWEST WINDS AROUND THIS HIGH WILL BRING DRY CONDITIONS WITH ABOVE NORMAL TEMPERATURES TO THE REGION. A COLD FRONT WILL BRING SCATTERED RAIN SHOWERS ON SUNDAY. MONDAY THROUGH FRIDAY LOOKS TO BE MAINLY DRY WITH BELOW NORMAL TEMPERATURES. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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HIGH PRESSURE IN CONTROL SURFACE AND ALOFT. SKIES SHOW PATCHY CIRRUS OVER MOST OF SOUTHERN NEW ENGLAND. STILL A PATCH OF LOWER STRATOCU OVER NORTHWEST MASS PRIMARILY ADAMS-ROWE-COLRAIN. THIS HAS SHOWN NO SIGNS OF MOVEMENT. WE WILL MAINTAIN THE FORECAST OF SUNNY/MOSTLY SUNNY SKIES EXCEPT FOR THE NOTED CLOUDS IN WESTERN FRANKLIN COUNTY MASS. AMADAR SOUNDINGS SHOW POTENTIAL MIXING TO 925 MB...BOSTON AND MANCHESTER SOUNDINGS SUGGEST 900 MB. TEMPS AT THESE LEVELS WOULD SUPPORT MAX SFC TEMPS AROUND 50 OR THE LOW 50S. COULD BE A FEW DEGREES COOLER IN THE NORTHWEST DUE TO THE EXISTING CLOUDS. THE CURRENT FORECAST LOOKS ON TRACK FOR THESE VALUES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT...LOW PRESSURE MOVES NE FROM THE GREAT LAKES INTO QUEBEC WITH ITS TRAILING COLD FRONT APPROACHING THE BERKSHIRES BY DAYBREAK SUNDAY MORNING. CLOUDS WILL BE ON THE INCREASE TONIGHT ACROSS OUR AREA IN ADVANCE OF THE FRONT. SCATTERED RAIN SHOWERS ARE POSSIBLE AFTER 3 AM IN THE SLOPES OF THE BERKSHIRES. HAVE GONE WITH A NON-DIURNAL TEMPERATURE TREND FOR TONIGHT. AM THINKING THAT IT WILL COOL DOWN EARLY IN THE EVENING BEFORE THE THICK CLOUD COVER COMES IN...THEN TEMPERATURES WILL HOLD NEARLY STEADY OR EVEN RISE A FEW DEGREES DURING THE OVERNIGHT HOURS. SUNDAY...A COLD FRONT WILL MOVE ACROSS SOUTHERN NEW ENGLAND BRINGING SCATTERED SHOWERS. HAVE UPPED PROBABILITIES TO 40-50 PERCENT. AMOUNTS ARE EXPECTED TO BE LIGHT...WITH LESS THAN ONE-QUARTER INCH OF RAINFALL FORECAST. SOUTHWEST WINDS WILL SHIFT TO THE NORTHWEST DURING THE AFTERNOON BEHIND THE FRONT. HIGHS WILL BE IN THE 40S BUT WE COULD SEE SOME 30S WORKING INTO WESTERN ZONES LATE IN THE DAY. THE OPERATIONAL GFS RUN WAS THE SLOWEST OF THE MODELS TO HAVE THE PRECIPITATION EXIT...AND A RESULT...IT WOULD IMPLY THAT THERE COULD EVEN BE A CHANCE OF A FEW SNOWFLAKES ON THE BACK END...OVER NORTHERN CT. HAVE DISCOUNTED THIS FOR NOW...THINKING THAT THE FRONT WILL MOVE STEADILY THROUGH AND THAT SHOWERS WILL HAVE ENDED BY THE TIME THE AIR GETS COLD ENOUGH TO SUPPORT SNOW. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * MAINLY DRY AND COLD THROUGH THE PERIOD OVERVIEW... MEDIUM RANGE MODELS IN FAIRLY GOOD AGREEMENT THROUGH THIS FORECAST PERIOD...AND FORECAST CONFIDENCE IS MODERATE TO HIGH. OVER THE NEXT WEEK...A SPLIT FLOW PREVAILS ACROSS NORTH AMERICA AS ENERGY DIVES TO THE SW USA WHILE EASTERN CANADA AND THENORTHEAST USA ARE DOMINATED BY A BROAD TROF. THIS OPENS THE DOOR TO AN INTRUSION OF ARCTIC AIR INTO NEW ENGLAND FOR MOST OF THE WEEK AND A DRY W TO NW LOW LEVEL FLOW. BEYOND THIS FORECAST PERIOD...THERE IS WIDER DISPARITY IN HOW THE MODELS HANDLE THE EJECTION OF THE ENERGY FROM THE SW AND THE EVENTUAL IMPACT ON SOUTHERN NEW ENGLAND DURING THE FOLLOWING WEEKEND. DAY TO DAY... SUN NGT...COLD FRONT SWEEPS S AND SE OF NEW ENGLAND WITH LINGERING SHOWERS ENDING. THERE IS A SLIGHT CHANCE THAT THE RAIN COULD END AS A LITTLE WET SNOW...BUT WE THINK THE MORE PROBABLE OUTCOME IS THAT THE COLDER AIR WILL ARRIVE AFTER THE PRECIPITATION ENDS. MON-TUE...COLD AIR MOVES INTO REGION BEHIND THE COLD FRONT WHICH STALLS S OF NEW ENGLAND. THE MEDIUM RANGE MODELS HAVE SIGNALED THE LIKELIHOOD OF ONE OR TWO WEAK WAVES MOVING ALONG THE FRONT IN THE MON TO TUE TIME FRAME. MORE THAN LIKELY THESE WAVES WILL BE SUPPRESSED ENOUGH TO KEEP ANY PRECIPITATION OFFSHORE. HOWEVER...THERE REMAINS A SMALL CHANCE OF FLURRIES OR VERY LIGHT SNOW GLANCING THE ISLANDS AND CAPE COD AND SO HAVE KEPT SLIGHT CHANCE POPS THERE. DID NOTE THAT THE SREF DEPICTS A 50 PERCENT CHANCE OF 12 HOUR QPF REACHING .25 INCHES NEARLY AS FAR NORTH AS THE MASS PIKE BUT THIS PRODUCT IS HEAVILY INFLUENCED BY THE NAM RUNS WHICH HAVE A FAIRLY TRACK RECORD BEYOND 36 OR 48 HOURS. TUE NIGHT THROUGH FRI...LOOKS TO BE DRY WITH BELOW NORMAL TEMPERATURES AS ARCTIC AIR SETTLES INTO THE REGION. HAVE DROPPED TEMPERATURES A FEW DEGREES TUE NIGHT AND WED NIGHT FROM THE CONSENSUS GUIDANCE...WHICH HAS A TENDENCY TO BE A LITTLE TOO CONSERVATIVE IN THESE SITUATIONS. WE SHOULD HAVE CLEAR SKIES AND LOW DEWPOINTS TUE AND WED NIGHTS BUT SOME QUESTION ON WHETHER THE LOW LEVEL WIND WILL FULLY DECOUPLE. COULD SEE SOME WED AM AND THU AM LOWS BELOW 10 DEGREES IN NW MA. ANTICIPATE A LITTLE MODERATION IN TEMPERATURES BY FRI. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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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 SUNDAY/... THIS AFTERNOON...MODERATE TO HIGH CONFIDENCE. VFR WITH MOST AREAS HAVING AT WORST SOME SCATTERD CIRRUS AT 25K FEET. AREA OF LOWER CLOUDS OVER NORTHWEST MASS WITH CIGS AROUND 3200 FEET SHOULD LINGER AND THEN SLOWLY MOVE OFF TO THE NORTH. TONIGHT...MODERATE TO HIGH CONFIDENCE. MAINLY VFR. LOW PROBABILITY OF MVFR CIGS/LOCAL MVFR VSBYS IN SCATTERED SHOWERS ACROSS WESTERN MA AND NW CT WELL AFTER MIDNIGHT. SUNDAY...MODERATE CONFIDENCE. MVFR CEILINGS AND VSBYS POSSIBLE IN SCATTERED RAIN SHOWERS. SW WINDS 10 TO 20 KT SHIFTING TO THE NW. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MODERATE TO HIGH CONFIDENCE OF MAINLY VFR CONDITIONS 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 SUNDAY/...MODERATE TO HIGH CONFIDENCE. THIS AFTERNOON...WINDS AND SEAS BELOW SMALL CRAFT ADVISORY CRITERIA. W WINDS BECOME SW AND MAY GUST TO AROUND 15 KT AT TIMES. SEAS AT BUOY 44097 SOUTHEAST OF BLOCK ISLAND DROPPED TO 3 FEET AT 11Z. NOTED THAT MOST BUOYS ARE REPORTING A LONG PERIOD SWELL OF ABOUT 5 SECONDS. USED SWANNAM GUIDANCE WHICH IS HANDLING THE SEAS SOMEWHAT BETTER THAN THE WAVEWATCH HERE IN THE NEAR TERM PART OF THE FORECAST. TONIGHT... SW WINDS WILL INCREASE AHEAD OF AN APPROACHING COLD FRONT. SOUTHWEST WIND GUSTS COULD REACH 20 TO ALMOST 25 KT TOWARD DAYBREAK...ESPECIALLY OVER THE SOUTHERN WATERS. SUNDAY...A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE SOUTHERN AND EASTERN OUTER WATERS...AND FOR RHODE ISLAND SOUND. SEAS ARE EXPECTED TO BUILD TO 5 OR 6 FEET IN THOSE AREAS...AND THERE COULD BE WIND GUSTS TO 25 KT FROM THE SOUTHWEST AHEAD OF THE COLD FRONT. SCATTERED SHOWERS COULD CAUSE SOME VISIBILITY RESTRICTIONS. WINDS SHOULD SHIFT TO THE WEST LATE IN THE AFTERNOON BEHIND THE FRONT. OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...MODERATE TO HIGH CONFIDENCE. IN SPITE OF SURFACE COLD ADVECTION DURING THE PERIOD...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS. HOWEVER...SHOULD A SURFACE WAVE OF LOW PRES PASS ON THE NW ENVELOPE OF POSSIBLE SOLUTIONS ON TUESDAY...THEN THE RESULTANT NE GRADIENT COULD BE ENOUGH TO CAUSE WIND GUSTS TO NEAR 25 KT AND SEAS TO NEAR 5 FEET S AND SE OF NANTUCKET.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST SUNDAY FOR ANZ235- 250-254>256. && $$ SYNOPSIS...GAF/THOMPSON NEAR TERM...WTB/GAF/THOMPSON SHORT TERM...GAF LONG TERM...GAF/THOMPSON AVIATION...GAF/THOMPSON/WTB MARINE...GAF/THOMPSON

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