Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 300246 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 946 PM EST THU JAN 29 2015 .SYNOPSIS... 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 FRIDAY INTO FRIDAY EVENING BRINGING WITH IT A PERIOD OF SNOW FOR THE FORECAST AREA. BLUSTERY AND VERY COLD CONDITIONS ARE EXPECTED THIS WEEKEND. WATCHING FOR THE POTENTIAL OF NOREASTERS NEXT WEEK...ONE POSSIBLE SUNDAY NIGHT INTO MONDAY AND ANOTHER POSSIBLE WEDNESDAY NIGHT INTO THURSDAY. LOW CONFIDENCE ON BOTH. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 945 PM UPDATE... 00Z ALY SOUNDING STILL VERY DRY IN LOW LEVELS SO DESPITE LIGHT REFELECTIVITY MOVING ACROSS SNE...PRECIP IS MOSTLY ALOFT. NAM SHOWS LOW LEVELS MOISTENING 03-06Z. EXPECT LIGHT SNOW DEVELOPING 03-06Z WESTERN HALF NEW ENG AND 06-10Z IN THE EAST. LATEST NAM/RAP ARE SLIGHTLY COOLER IN THE LOW LEVELS AND WITH GENERALLY LIGHT WINDS NOT ALLOWING MUCH ADVECTION OF WARMER SFC TEMPS AWAY FROM THE ISLANDS...EXPECT A MIX OF RAIN/SNOW TO BE CONFINED TO CAPE/ISLANDS TOWARD DAYBREAK...WITH MOSTLY RAIN ON THE ISLANDS WHERE SOUTHERLY WINDS WILL BE A BIT STRONGER. AN INCH OR TWO IS POSSIBLE BY DAYBREAK ACROSS CT/WESTERN-CENTRAL MA TO A DUSTING TO LESS THAN AN INCH OVER RI AND EASTERN MA. CALM WINDS AND RADIATIONAL COOLDING HAS ALLOWED TEMPS TO FALL TO UPPER TEENS TO LOWER 20S ACROSS PORTION OF SE COASTAL MA AND CAPE COD/MVY. TEMPS WILL RISE QUICKLY INTO THE 30S ON THE ISLANDS WHEN S WINDS NICREASE. NOTE BID IS 34 WITH A S WIND 10 KTS. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... *** PLOWABLE SNOWFALL LIKELY FOR MUCH OF NORTH-NORTHEAST MA *** FORECAST WAS BASED ON A MODEL BLEND GIVEN GOOD CLUSTERING AMONGST THE MODELS REGARDING THEIR MASS FIELDS...QPF AND THERMAL. AMPLIFYING NORTHERN STREAM TROUGH TAKES ON A NEGATIVE TILT LATE FRI AND THEN EVOLVES INTO A CLOSED MID LEVEL OVER SOUTHERN NEW ENGLAND. THIS STRONG FORCING ALOFT RESULTS IN PARENT LOW OVER NY STATE FADING/FILLING AND GIVING WAY TO CYCLOGENESIS ALONG OR JUST OFF THE SOUTHERN NEW ENGLAND COAST FRI. THIS ROBUST MID/UPPER TROUGH RESULTS IN SECONDARY LOW PRES DEEPENING TO ABOUT 985 MB OVER THE WESTERN GULF OF MAINE 12Z SAT. IN ADDITION THE MID/UPPER LOW CAPTURES THE SURFACE CYCLONE AND PULLS IT BACK BRIEFLY TOWARD EASTERN MA COASTLINE LATE FRI NIGHT INTO SAT. THIS SLOWS THE SYSTEM DOWN AND RESULTS IN A ROBUST COMMA-HEAD DEVELOPING FRI NIGHT OVER NORTHEAST MA POSSIBLY WESTWARD INTO WORCESTER COUNTY. AS MID LEVEL TROUGH TRANSITIONS FROM AN OPEN WAVE TO A CLOSED CIRCULATION FRI NIGHT OVER EASTERN MA A MODEST SNOW BAND WILL LIKELY DEVELOP. ALSO UNCERTAINTY ON EXACTLY WHERE THESE BANDS SETUP AND INTENSITY. HOWEVER MODEL CONSENSUS QPF YIELDS 0.5-0.6 INCHES OVER NORTHEAST MA...POSSIBLY WESTWARD INTO WORCESTER COUNTY. THEREFORE HAVE UPGRADED TO A WINTER STORM WARNING FOR ESSEX AND MIDDLESEX COUNTIES. LATER SHIFTS MAY HAVE TO EXPAND THE WARNING WESTWARD INTO WORCESTER COUNTY PENDING 00Z MODEL TRENDS. GIVEN THE BANDING SIGNATURE AND MODEL CONSENSUS QPF EXPANDED ADVISORIES INTO SOUTHERN WORCESTER/NORTHEAST CT/NORTHERN RI INTO NORTHERN BRISTOL COUNTY OF MA FOR 2-4 INCHES OF SNOWFALL. THOUGHT PROCESS WAS SNOWFALL MAY FALL JUST SHORT OF WARNING AND/OR ADVISORY CRITERIA BUT REALIZING ANY ADDITIONAL SNOWFALL WILL BE PROBLEMATIC REGARDING SNOW REMOVAL ESPECIALLY IN THE URBAN AREAS THAT RECEIVED 30+ EARLIER THIS WEEK. ALSO ADDITIONAL SNOWFALL MAY RESULT IN SNOW LOAD/STRESS TO ROOFS. THEREFORE OUR WARNINGS AND ADVISORIES ARE SOMEWHAT BASED ON IMPACTS TOO. PTYPE...ALL SNOW MOST OF THE AREA EXPECT SOUTH COAST OF MA AND RI INCLUDING CAPE COD AND THE ISLANDS WHERE RAIN OR A RAIN/SNOW CHANGES BACK TO ALL SNOW FRI EVENING. FOG? MAY NEED TO MONITOR FOR THE POTENTIAL OF WARM/MOIST AIR OVER THE DEEPER SNOWPACK TO RESULT IN DENSE GROUND FOG. AREAS ACROSS E/SE MA WHICH SAW CONSIDERABLE AMOUNTS OF SNOW WOULD /CLIMATOLOGICALLY- SPEAKING/ EXPECT TO BE SOCKED IN CONDITIONS WHEN A WARM/HUMID AIRMASS SPREADS ACROSS THE REGION. WILL HAVE TO MONITOR CLOSELY. IN ADDITION TO THE SNOWFALL FRI NIGHT NORTH AND EVENTUALLY NORTHWEST WINDS WILL INCREASE TO 35 TO 45 MPH AS LOW INTENSIFIES EAST OF MA. 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 MAY BE NEEDED FOR HIGHER TERRAIN IN CENTRAL AND W MA. LOOKS BORDERLINE SO DID NOT HOIST ANY HEADLINES THERE. LATER SHIFTS WILL NEED TO REEVALUATE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... HEADLINES... * SNOW ENDS ACROSS EASTERN AREAS EARLY SATURDAY FOLLOWED BY ARCTIC HIGH PRESSURE FOR THE REST OF THE WEEKEND * WATCHING FOR POTENTIAL NOREASTERS NEXT WEEK AN ACTIVE WEATHER PATTERN WILL CONTINUE ACROSS SOUTHERN NEW ENGLAND. OCEAN STORM OFF THE MAINE COAST ON SATURDAY WILL EXIT TO THE EAST... BRINGING AN END TO ANY SNOWFALL ACROSS COASTAL LOCALES SATURDAY MORNING. IMPROVING CONDITIONS WILL OCCUR DURING THE DAY ON A BLUSTERY NW WIND FLOW AS A COLD AIRMASS MOVES INTO NEW ENGLAND FROM CANADA. THIS WILL ENSURE A VERY COLD WEEKEND WITH TEMPS RUNNING WELL BELOW AVERAGE. THE SYNOPTIC PATTERN NEXT WEEK WILL FEATURE SHORTWAVES DIVING INTO THE UPPER MIDWEST AND ACROSS NEW ENGLAND. THIS WILL ALLOW FOR POTENTIAL NOREASTERS TO DEVELOP. HOWEVER, MUCH WILL DEPEND ON HOW SHARP THE TROUGHS BECOME...WHETHER THEY BECOME NEGATIVELY TILTED AND PHASE OR NOT WITH SOUTHERN STREAM ENERGY. THERE HAVE BEEN MODEL DIFFERENCES FROM BOTH GFS/ECMWF IN TERMS OF THE STRENGTH AND TRACK OF THE LOWS SO WILL FOLLOW A BLENDED MODEL APPROACH. THE TIMING OF THESE POTENTIAL SYSTEMS LOOKS TO BE SUNDAY NIGHT AND MONDAY AND AGAIN WEDNESDAY NIGHT THROUGH THURSDAY. THESE ARE THE PERIODS TO MONITOR FOR POTENTIAL HIGH IMPACTS TO THE AREA. WHETHER OR NOT WE RECEIVE SIGNIFICANT ADDITIONAL SNOWFALL OR THESE OCEAN STORMS MISS US TO THE EAST IS JUST TOO TOUGH TO SAY WITH ANY DEGREE OF CONFIDENCE. SO STAY TUNED. FOR THE SUN NIGHT-MONDAY LOW...BOTH THE OPERATIONAL 29.12Z GFS AND ECMWF RUNS HAVE THE LOW CENTER PASSING JUST OUTSIDE THE BENCHMARK WHICH WOULD MEAN A GLANCING BLOW TO SOUTHEASTERN NEW ENGLAND...BUT STILL A PLOWABLE SNOWFALL TO EASTERN AREAS. HOWEVER, A FEW ENSEMBLE MEMBERS ARE FURTHER NORTHWEST WITH THE LOW TRACK...SO A MORE SIGNIFICANT IMPACT IS A POSSIBILITY...AS IS NO IMPACT IF THE LOW WERE TO TRACK EVEN FURTHER OFF SHORE. THE FIRST RUNS OF THE OPERATIONAL ECMWF FOR THE BLIZZARD OF 2015 DIDN`T SHOW MAJOR IMPACTS TO NEW ENGLAND UNTIL 72 HR IN ADVANCE OF THE EVENT. WE ARE STILL OUTSIDE OF THIS WINDOW...SO LOTS CAN CHANGE. TUESDAY WILL BE A LULL DAY IF THE AFOREMENTIONED LOW IMPACTS NEW ENGLAND. THEN WE LOOK TO YET ANOTHER POTENTIAL OCEAN STORM MID WEEK...WITH MODELS CENTERING ON THE WED NIGHT-THU TIMEFRAME. THE 29.12Z OPERATIONAL ECMWF IS AGGRESSIVE WITH THIS LOW...SLAMMING HEAVY SNOWS OVER THE INTERIOR WITH A SNOW TO RAIN SCENARIO FOR THE COAST. HOWEVER, THE GFS DOES NOT PHASE THE NORTHERN AND SOUTHERN STREAMS...SO IS PROGRESSIVE AND SHOWS MINIMAL IMPACTS. SO USED A MODEL BLEND AND...ONCE AGAIN...TOO EARLY TO BANK ON EITHER A HIT OR A MISS. CERTAINLY A LOT TO MONITOR CLOSELY IN THE DAYS AHEAD! && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH FRI NIGHT...MODERATE CONFIDENCE. 0Z UPDATE... TONIGHT INTO FRIDAY NIGHT... CIGS LOWER MVFR / IFR WITH S-DRAW OF AIR ADVECTING MARINE STRATUS ONSHORE AS -SN BEGINS TO ENVELOP THE TERMINALS W TO E MIXING / CHANGING TO RAIN ALONG THE IMMEDIATE S/SE-COAST INCLUDING THE CAPE AND ISLANDS. TAILORED DETERIORATING CONDITIONS TOWARDS THE MIDDAY INTO LATE-AFTERNOON PERIOD. HIGHLIGHTED THE WORST OF ANTICIPATED CONDITIONS WITH IFR VSBYS. GOING TO HAVE TO WATCH CLOSELY THE S-DRAW OF WARM/MOIST AIR OVER DEEP SNOWPACK. COULD SEE CONDITIONS BECOME SOCKED IN WITH AN APPRECIABLE GROUND FOG JUST ABOVE THE SNOW. SHOULD SEE IMPROVEMENT INTO EVENING AS WINDS SHIFT OUT OF THE NW GUSTING 25-30 KTS ALLOW CONDITIONS TO IMPROVE VFR. KBOS TAF...MODERATE CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. KBDL TAF...MODERATE CONFIDENCE...BUT LOWER CONFIDENCE ON EXACT TIMING OF SNOW AND LOWER CIGS/VSBYS. OUTLOOK /SATURDAY THROUGH MONDAY/... 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. TUESDAY...MODERATE CONFIDENCE. IF LOW IMPACTS THE TERMINALS MONDAY, CONDITIONS WOULD BE IMPROVING ON TUE. && .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. 7 PM UPDATE...NO MAJOR CHANGES. 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. FRI NIGHT...LOW PRES INTENSIFIES OVER WESTERN GULF OF MAINE WITH WIDESPREAD NNW GALES. SNOW REDUCES VSBY AS WELL. OUTLOOK /SATURDAY THROUGH MONDAY/...MODERATE CONFIDENCE SATURDAY NIGHT...WINDS AND SEAS WILL DIMINISH AS LOW PRESSURE DEPARTS THE AREA. 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-TUESDAY...HIGHLY DEPENDENT ON STRENGTH AND TRACK OF DEVELOPING LOW PRESSURE SOUTH OF THE REGION AND THUS A LOW CONFIDENCE FORECAST. WORSE CONDITIONS WOULD BE MONDAY WITH SLOW IMPROVEMENT ON TUESDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY UNTIL 6 AM EST SATURDAY FOR CTZ004. MA...WINTER WEATHER ADVISORY UNTIL 6 AM EST SATURDAY FOR MAZ004-012- 013-015>019. WINTER STORM WARNING UNTIL 6 AM EST SATURDAY FOR MAZ005>007- 014-026. RI...WINTER WEATHER ADVISORY UNTIL 6 AM EST SATURDAY FOR RIZ001. 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...NOCERA/GREGORIA NEAR TERM...KJC SHORT TERM...NOCERA LONG TERM...GREGORIA AVIATION...NOCERA/SIPPRELL/GREGORIA MARINE...NOCERA/GREGORIA

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