Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 172029 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 429 PM EDT FRI OCT 17 2014 .SYNOPSIS... ONE MORE MILD DAY ON SATURDAY WITH JUST A FEW BRIEF SPOT SHOWERS POSSIBLE. A STRONG COLD FRONT BRINGS MUCH CHILLIER TEMPS FOR SUNDAY AND MONDAY BUT WITH DRY WEATHER. A SIGNIFICANT LONG DURATION COASTAL STORM IS LIKELY DURING THE MIDDLE TO END OF NEXT WEEK...BUT ITS TRACK AND IMPACTS TO OUR REGION REMAIN HIGHLY UNCERTAIN. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... DIURNAL CUMULUS CLOUDS WILL DISSIPATE THIS EVENING WITH THE LOSS OF DAYTIME HEATING. HOWEVER...SHOULD SEE SOME MORE CLOUDS INCREASE FROM THE WEST OVERNIGHT AHEAD OF AN APPROACHING SHORTWAVE. ALSO...EXPECT TO SEE SOME PATCHY FOG DEVELOP OVERNIGHT IN THE TYPICALLY PRONE LOCATIONS. LOW TEMPS WILL MAINLY BE IN THE 50S. DRY WEATHER EXPECTED TONIGHT WITH BEST FORCING WELL TO OUR WEST. THERE IS A LOW RISK FOR A SPOT SPRINKLE/SHOWER TOWARD DAYBREAK IN THE WARM AIR ADVECTION PATTERN...BUT NOT WORTH MENTIONING IN THE FORECAST. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... ***A RETURN TO FALL TEMPERATURES SATURDAY NIGHT*** SATURDAY... ONE MORE PLEASANT DAY OF WEATHER ACROSS SOUTHERN NEW ENGLAND. AREAS OF LOWER CLOUDS AND FOG PATCHES WILL BURN OFF DURING THE MORNING...ALLOWING FOR A PERIOD OF PARTIAL SUNSHINE ESPECIALLY ON THE COASTAL PLAIN. A STRONG SHORTWAVE/COLD FRONT WILL APPROACH FROM THE WEST BY LATE MORNING/AFTERNOON. A FEW BRIEF SHOWERS ARE POSSIBLE ACROSS THE ENTIRE REGION DURING THE LATE MORNING/AFTERNOON...BUT THE BEST CHANCE WILL BE ACROSS OUR NORTHERN ZONES...CLOSER TO THE COLD POOL ALOFT. IN FACT...CAPES APPROACHING 500 J/KG MAY EVEN RESULT IN THE LOW RISK FOR AN ISOLATED THUNDERSTORM OR TWO ACROSS OUR FAR NORTHERN ZONES. WE ALSO CAN/T RULE OUT A REPORT OR TWO OF PEA SIZE HAIL EITHER GIVEN 500 MB TEMPS NEAR -18C. ALL IN ALL...THE VAST MAJORITY OF THE DAY WILL BE DRY AND PLEASANT IN A GIVEN LOCATION. HIGH TEMPS MAINLY IN THE MIDDLE TO UPPER 60S IN THE HIGHER TERRAIN...TO THE LOWER 70S ACROSS PORTIONS OF THE COASTAL PLAIN. SATURDAY NIGHT... MUCH CHILLIER AIR WILL WORK INTO THE REGION ON WEST TO NORTHWEST WINDS BEHIND THE COLD FRONT. LOW TEMPERATURES WILL BE WELL DOWN INTO THE 40S ACROSS THE ENTIRE REGION BY DAYBREAK SUNDAY. WHILE GENERALLY DRY WEATHER IS EXPECTED SATURDAY NIGHT...A SECOND SHORTWAVE WILL APPROACH FROM THE WEST DURING THE OVERNIGHT HOURS. THIS MAY TRIGGER A FEW SPOT SPRINKLES/SHOWERS AFTER MIDNIGHT...BUT AGAIN THE VAST MAJORITY OF THE NIGHT WILL BE DRY. THE MAIN STORY WILL BE MUCH CHILLIER AIR THAT WILL MOVE INTO THE REGION. && .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... *** DRY BUT MUCH COOLER SUN INTO MON *** *** A SIGNIFICANT LONG DURATION COASTAL STORM IS LIKELY SOMEWHERE ALONG THE NEW ENGLAND COAST NEXT TUE THRU FRI...HOWEVER AXIS OF HEAVIEST RAIN...STRONGEST WIND AND MAGNITUDE OF COASTAL FLOODING REMAINS TO BE DETERMINED *** SYNOPTIC OVERVIEW AND GUIDANCE EVALUATION... GOOD MODEL AGREEMENT ON A LARGE AMPLITUDE TROUGH SWINGING ACROSS THE REGION. IMPRESSIVE COLD AIR ADVECTION ASSOCIATED WITH THIS TROUGH AS ENSEMBLES AND DETERMINISTIC GUIDANCE HAVE 850 TEMPS PLUMMETING TO -4C TO -6C BY DAYS END OVER SOUTHERN NEW ENGLAND. THIS IS ABOUT -2 STANDARD DEVIATIONS FROM CLIMO. THUS MUCH COOLER SUNDAY ESPECIALLY AFTER SEVERAL MILD DAYS. BY MON THE MID LEVEL MEAN TROUGH AXIS IS WELL OFFSHORE AND IS REPLACED BY RISING HEIGHTS AND ANTICYCLONIC FLOW OVER NEW ENGLAND. SO DESPITE A CHILLY START TO THE DAY MONDAY THERE SHOULD BE A NOTICEABLE TEMP RECOVERY ALONG WITH A DIMINISHING WIND. THEN THE FORECAST FOCUS SHIFTS TO AN AMPLIFYING NORTHERN STREAM TROUGH OVER THE OH VLY AND MID ATLC REGION TUE-WED...WHICH THEN ALL GUID AGREES ON THE TROUGH EVOLVING INTO A CLOSED MID LEVEL CIRCULATION SOMEWHERE VICINITY VA/DE COAST. STRONG COLD AIR ADVECTION FROM THE LEAD SHORT WAVE TROUGH SUN/MON SHARPENS THE BAROCLINIC ZONE OFF THE SOUTHERN NEW ENGLAND COAST. THIS SETS THE STAGE FOR THE PARENT LOW OVER OH/PA TUE TO GIVE WAY TO CYCLOGENESIS OFF THE SOUTHERN NEW ENGLAND TUE NIGHT/WED. ENSEMBLES AND DETERMINISTIC GUID ARE VERY TIGHTLY CLUSTERED ESPECIALLY GIVEN THE TIME RANGE HERE. THUS FORECAST CONFIDENCE IS HIGH FOR AT LEAST SOME STORM IMPACT HERE TUE THRU FRI. HOWEVER MODELS DIFFER ON EXACT TRACK AND HOW QUICKLY MID LEVEL CIRCULATION CAPTURES THE SURFACE LOW...WHICH IS QUITE NORMAL AT THIS TIME RANGE. HOWEVER THIS HAS IMPLICATIONS ON EXACT TRACK OF DRY SLOT AND DURATION AND LOCATION OF WARM CONVEYOR BELT RAINS. GFS AND ITS ENSEMBLES HAVE BEEN TRENDING FARTHER NORTH AND CLOSER TO THE ECMWF AND ITS ENSEMBLES. THIS SUGGEST GREATEST IMPACT REGARDING HEAVY RAIN/STRONG WIND AND COASTAL FLOODING WOULD BE NORTHERN NEW ENGLAND. HOWEVER AT THIS TIME RANGE NEED TO LEAVE ALL SOLUTIONS IN PLAY. THUS A MODEL BLEND OFFERS THE MOST SKILLFUL SOLUTION AT THIS TIME RANGE. NEVERTHELESS A PORTION OF NEW ENGLAND /SOUTHERN-CENTRAL OR NORTHERN/ HAS THE POTENTIAL FOR A LONG DURATION HEAVY RAIN/STRONG WIND AND COASTAL FLOOD EVENT. DAILIES... SUNDAY/SUNDAY NIGHT...STRONG COLD AIR ADVECTION WILL YIELD HIGHS ONLY IN THE L50S WITH MU40S HIGHER TERRAIN! THIS IS ABOUT 10 DEGS COLDER THAN NORMAL. WE SHAVED A FEW DEGS OFF GUID GIVEN TIME SECTIONS INDICATE A LOT OF DIURNAL SC CLOUDS GIVEN CYCLONIC FLOW COUPLED WITH STEEP LOW LEVEL LAPSE RATES. IN ADDITION A GUSTY NW WIND UP TO 30 MPH WILL YIELD WIND CHILL VALUES IN THE 40S. QUITE A DIFFERENCE FROM OUR 70 DEGS TEMPS TODAY AND TOMORROW. SUNDAY NIGHT WILL BE COLD AS WELL WITH LOWS IN THE 30S AND MU20S WELL INLAND. FROST/FREEZE HEADLINES WILL LIKELY BE NEEDED FOR A PORTION OF THE AREA WHERE GROWING SEASON HAS NOT ENDED. MONDAY...COLD ADVECTION ENDS WITH MEAN MID LEVEL TROUGH WELL OFFSHORE. RISING HEIGHTS AND ANTICYCLONIC FLOW WILL YIELD ABUNDANT SUNSHINE AND TEMPS REBOUNDING IN THE MU50S. IT WILL FEEL EVEN WARMER GIVEN DIMINISHING WINDS AND PLENTY OF SUNSHINE. LIKELY PICK OF THE WEEK. TUESDAY THRU FRI... HIGH CONFIDENCE ON A SIGNIFICANT COASTAL STORM IMPACTING SOUTHERN NEW ENGLAND. HOWEVER UNCERTAINTY CONTINUES ON THE EXACT STORM TRACK ESPECIALLY EVOLUTION AND TRAJECTORY OF THE STORMS DRY SLOT AND LOW LEVEL CIRCULATION. THIS WILL DETERMINE MAGNITUDE AND DURATION OF HEAVY RAIN/STRONG WINDS AND COASTAL FLOODING. TOO EARLY TO GIVE SPECIFICS BUT DEFINITELY NEED TO MONITOR LATER MODEL RUNS AS A HIGH IMPACT EVENT IS CERTAINLY POSSIBLE FOR A PORTION OF NEW ENGLAND. REGARDING COASTAL FLOODING...ASTRONOMICAL TIDES ARE LOW AND WOULD TYPICAL LOWER THE THREAT OF COASTAL FLOODING. HOWEVER GIVEN THE LONG DURATION OF THIS COASTAL STORM MULTIPLE TIDE CYCLES MAY BE IMPACTED...THUS INCREASING THE RISK FOR MORE SIGNIFICANT COASTAL FLOODING AND ESPECIALLY EROSION GIVEN LARGE WAVES POSSIBLY BATTERING THE COASTLINE FOR SEVERAL DAYS. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY NIGHT/... TONIGHT...HIGH CONFIDENCE THROUGH THIS EVENING...THEN MODERATE CONFIDENCE FOR THE OVERNIGHT HOURS. VFR THIS EVENING...BUT MAY SEE SOME SCATTERED MVFR-IFR CIGS/VSBYS DEVELOP IN LOW CLOUDS/FOG PATCHES OVERNIGHT. HOWEVER...LOW CONFIDENCE ON AREAL COVERAGE OF SCATTERED LOW CLOUDS/FOG PATCHES. SATURDAY...MODERATE CONFIDENCE. ANY SCATTERED MVFR-IFR CONDITIONS IN PATCHY LOW CLOUDS/FOG PATCHES SHOULD IMPROVE TO VFR BY LATE MORNING. SOUTHWEST WIND GUSTS OF 20 TO 25 KNOTS EXPECTED DURING THE AFTERNOON ALONG THE SOUTHEAST NEW ENGLAND COAST. A FEW BRIEF SHOWERS ARE ALSO POSSIBLE...WITH THE BEST CHANCE IN OUR NORTHERN ZONES DURING THE AFTERNOON. LOW PROBABILITY FOR EVEN AN ISOLATED THUNDERSTORM. SATURDAY NIGHT...MODERATE TO HIGH CONFIDENCE. VFR CONDITIONS IN THE EVENING. MAY SEE SOME MVFR CIGS DEVELOP AS THE NIGHT WEARS ON ESPECIALLY IN THE INTERIOR. KBOS...HIGH CONFIDENCE IN TAF THROUGH THIS EVENING WITH MODERATE CONFIDENCE TOWARDS 12Z. KBDL...HIGH CONFIDENCE IN TAF THROUGH THIS EVENING WITH MODERATE CONFIDENCE TOWARDS 12Z. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY...HIGH CONFIDENCE FOR DRY WEATHER. VFR WITH BKN050 CIGS. NW GUSTS TO 25 KT LIKELY SUNDAY AND SUNDAY EVENING BEFORE DIMINISHING TOWARD MON MORNING. MONDAY...HIGH CONFIDENCE. VFR ALONG WITH LIGHT WINDS AND DRY WEATHER. TUESDAY AND WEDNESDAY...HIGH CONFIDENCE ON OVERALL THEME...INCREASING E-NE WINDS...PERIODS OF RAIN IN IFR AND/OR MVFR CONDITIONS. LOW CONFIDENCE ON EXACT TIMING OF DETAILS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...NEAR SHORE SOUTHWEST WIND GUSTS OF 25 KNOTS WILL DIMINISH ALONG THE SOUTH COAST THIS EVENING...WITH THE LOSS OF DAYTIME HEATING. OTHERWISE...6 TO 9 FOOT SOUTHEAST SWELL WILL CONTINUE ACROSS THE OPEN WATERS FROM DISTANT HURRICANE GONZALO. SATURDAY AND SATURDAY NIGHT...SCA HEADLINES CONTINUE FOR ALL OPEN WATERS SATURDAY AND SATURDAY NIGHT FROM A COMBINATION OF SOUTHEAST SWELL AND WIND WAVE. SEAS GENERALLY 6 TO 10 FEET OVER THE OPEN WATERS. SOUTHWEST WIND GUSTS OF 20 TO 25 KNOTS EXPECTED SATURDAY AHEAD OF A COLD FRONT. THE COLD FRONT MOVES THROUGH SATURDAY EVENING...SHIFTING WINDS TO THE WEST NORTHWEST WITH GUSTS BETWEEN 20 AND 25 KNOTS IN THE COOL AIR ADVECTION PATTERN. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY...IMPROVING VSBY AS NW WINDS INCREASE. HOWEVER ROUGH SEA CONDITIONS ON THE OCEAN WATERS AS LEFTOVER SE SWELLS FROM HURRICANE GONZALO COMBINE WITH INCREASING NW WIND WAVES. MONDAY...HIGH CONFIDENCE FOR SUBSIDING SEAS AND DIMINISHING WINDS. GOOD VSBY AND DRY WEATHER. LIKELY PICK OF THE WEEK. TUESDAY/WED...HIGH CONFIDENCE FOR A COASTAL STORM BUT LOCATION OF STRONGEST WINDS REMAINS LOW. LONG DURATION OF E-NE WINDS THAT WILL LIKELY BE OF GALE FORCE SOMEWHERE ALONG THE NEW ENGLAND COAST. LONG DURATION AND LONG FETCH WILL LIKELY YIELD 15+ SEAS SOMEWHERE ACROSS THE NEW ENGLAND WATERS. HEAVY RAINS WILL REDUCE VISIBILITY AS WELL. POTENTIALLY A VERY DANGEROUS STORM GIVEN STRONG HIGH PRES OVER QUEBEC TO ENHANCE WIND FIELDS. STAY TUNED! && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ231>234. SMALL CRAFT ADVISORY UNTIL 7 PM EDT SUNDAY FOR ANZ235-237-250- 254>256. && $$ SYNOPSIS...FRANK/NOCERA NEAR TERM...FRANK SHORT TERM...FRANK LONG TERM...NOCERA AVIATION...FRANK/NOCERA MARINE...FRANK/NOCERA

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