Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221046 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 646 AM EDT MON SEP 22 2014 .SYNOPSIS... A DRIER AND LESS HUMID AIRMASS OVERSPREADS THE REGION TODAY BEHIND A DEPARTING COLD FRONT THIS MORNING...WITH BREEZY CONDITIONS AND A MIX OF SUN AND CLOUDS. THIS AIRMASS REMAINS OVER THE REGION MUCH OF THE WEEK YIELDING MILD DAYS AND COOL NIGHTS. BY WEEKS END TEMPERATURES BEGIN TO WARM WITH POSSIBLE RECORD WARMTH NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 7 AM UPDATE... QUITE A CHANGE IN AIRMASS AS A COLD FRONT EXITS THE NEAR SHORE WATERS AT SUNRISE. LOW CLOUDS OVER CAPE COD AND NANTUCKET HAVE NOW MOVED OFFSHORE AND IS REPLACED BY WEST WINDS ADVECTING IN MUCH DRIER AIR WITH DEW PTS IN THE 50S ACROSS WESTERN NEW ENGLAND. AS THE BLYR WARMS AND DEEPENS LATER THIS MORNING GUSTS UP TO 30 MPH WILL BE POSSIBLE INTO THIS AFTERNOON. PREVIOUS FORECAST CAPTURES THESE DETAILS NICELY SO NO MAJOR CHANGES WITH THIS UPDATE. EARLIER DISCUSSION BELOW. ===================================================================== USING A BLEND OF SFC OBS AND MSAS...IT APPEARS THAT SFC COLD FRONT IS CURRENTLY LOCATED FROM THE LOW CT VALLEY IN SRN CT THROUGH ABOUT AFN. IT HAS SLOWED SOMEWHAT AS IT BEGINS TO PARALLEL THE UPPER LVL FLOW GIVEN THE UPPER SHORTWAVE IS NOW E OF THE HUDSON VALLEY. THEREFORE...ALTHOUGH IT WILL CONTINUE IT/S PROGRESSION TO THE E...IT MAY TAKE UNTIL AFTER DAYBREAK TO FULLY MOVE OFFSHORE OF THE CAPE/ISLANDS ESPECIALLY. IN SPITE OF THIS...MUCH OF THE EARLY MORNING FOG HAS NOW DISSIPATED THANKS TO WESTERLY ISALLOBARIC COMPONENT TO THE FLOW. THIS W FLOW ALSO CONTINUES TO LEAD TO DOWNSLOPING AND DIMINISHING OF WHAT IS LEFT OF THE -SHRA ASSOCIATED WITH THE FRONT...WHICH IS UNLIKELY TO MAKE IT MUCH FURTHER E OF THE WORCESTER HILLS AND MONADNOCKS. AS THE FRONT SHIFTS OFFSHORE...AND UPPER LVL SHORTWAVE SLIDES INTO NRN NEW ENGLAND...A ROBUST SFC PRES GRADIENT IS LIKELY TO DEVELOP. THEREFORE...AS SKIES CLEAR AND MIXING COMMENCES...EXPECT A BREEZY DAY TODAY WITH WIND GUSTS OF 25-30 MPH NOT UNCOMMON OUT OF THE WNW. COLD ADVECTION CU IS ALSO LIKELY ESPECIALLY ACROSS THE INTERIOR...AND NOT OUT OF THE QUESTION A SPRINKLE IS ABLE TO BE SQUEEZED OUT AS WELL...BUT NOT CONFIDENT ENOUGH THERE WILL BE ENOUGH MOISTURE IN THE COLUMN TO REFLECT THIS IN POPS. REGARDING HIGHS...H85 TEMPS ARE DROPPING RAPIDLY...AND MAY NOT BE MIXED TO FULLY. SO SUSPECT HIGHS NEAR TO SLIGHTLY BELOW NORMAL LOOK GOOD GIVEN AT PEAK MIXING...H85 TEMPS AVERAGE ABOUT +8C. DWPTS DROP INTO THE 40S...SO AT THE VERY LEAST...MUCH LESS HUMID TODAY. A BUILDING OFFSHORE SWELL TODAY...MAY YIELD HIGH SURF PARTICULARLY AT SOUTH COASTAL BEACHES TODAY. THEREFORE...WILL CONTINUE HIGH SURF ADVISORY FOR THE TIME BEING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT... COOL DRY AIRMASS SETTLES IN PLACE AS NOSE OF STRONG 1035 HPA HIGH PRES MOVES IN FROM THE W. IN SPITE OF THIS MORE AUTUMN-LIKE AIRMASS...MINS MAY NOT BE ABLE TO REALIZE THEIR FULL POTENTIAL. THE COMBINATION OF LINGERING DIURNAL CU EARLY...AND SFC PRES GRADIENT TAKING SOME TIME TO FULLY SLACKEN MAY LIMIT RADIATIONAL COOLING. LOWS IN THE UPPER 30S-MID 40S ARE LIKELY...WITH MINS CLOSER TO 50 IN THE URBAN SPOTS. THE COLDEST SPOTS ARE LIKELY IN NW MA AND SW NH. IT/S VERY CLOSE TO FROST THRESHOLDS...BUT WITH THE MITIGATING FACTORS MENTIONED...NOT CONFIDENT ENOUGH TO ISSUE FROST ADVISORY AT THIS TIME. THIS WILL HAVE TO BE WATCHED THROUGH THE DAY. TUE... HIGH PRES BEGINS TO CREST ACROSS THE REGION ON TUE. THEREFORE...MOSTLY SUNNY SKIES ARE EXPECTED. H85 TEMPS HOVER AROUND +6C...BUT MAY NOT BE FULLY REALIZED UNDER STRONG SUBSIDENCE INVERSION. THEREFORE...KEEPING HIGHS GENERALLY A DEGREE OR TWO BELOW NORMAL. MAINLY THE MID 60S TO AROUND 70. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGHLIGHTS... * THE 1ST WEEK OF AUTUMN WILL FEATURE MILD DAYS AND COOL NIGHTS FOLLOWED BY POTENTIAL NEAR RECORD WARMTH NEXT WEEKEND * HIGH PRESSURE PROVIDES DRY WEATHER THROUGH THE PERIOD SYNOPTIC OVERVIEW AND MODEL EVALUATION... FAIRLY STRONG TELECONNECTION FOR RIDGING HERE IN THE EAST THIS COMING WEEK AND NEXT WEEKEND AS +PNA TRENDS TOWARD NEUTRAL ALONG WITH NAO AND AO TRENDING OR REMAINING POSITIVE. DURING THIS TIME THE LARGE SCALE FLOW EVOLVES INTO A WEST COAST TROUGH WITH A DOWNSTREAM RIDGE OVER THE GREAT LAKES NORTHWARD TOWARD JAMES BAY. THIS IS A WARM AND DRY SETUP FOR NEW ENGLAND. HOWEVER GIVEN THE CHAOTIC NATURE OF THE ATMOSPHERE THERE ARE ALWAYS WILDCARDS AT THIS TIME RANGE AND THIS CASE IS NO EXCEPTION. THE FIRST WILDCARD WILL BE THE DOWNSTREAM MEAN TROUGH OVER THE MARITIMES. WILL HAVE TO WATCH IF ANY NORTHERN STREAM IMPULSES CLIMBING OVER THE GREAT LAKES RIDGE AND THEN INTO THE MARITIMES DRAGS ANY BACKDOOR FRONTS INTO EASTERN NEW ENGLAND. THIS WOULD YIELD COOLER TEMPS ESPECIALLY FOR EASTERN MA. THE OTHER WILDCARD WILL BE MOISTURE AND JET ENERGY THAT BREAKS OFF OVER THE SOUTHEAST STATES FROM THE MID LEVEL TROUGH MOVING ACROSS THE EASTERN SEABOARD TODAY. SOME OF THE DETERMINISTIC GUIDANCE HAS THIS MOISTURE/INVERTED TROUGH CREEPING NORTHWARD DURING THIS WEEK AND GETTING CLOSE TO NEW ENGLAND WED NIGHT INTO THU NIGHT BEFORE THEN GETTING SHUNTED OUT TO SEA FRI. OTHERWISE DESPITE AUTUMN ARRIVING LATER TODAY THE SUBTROPICAL RIDGE DELIVERS ONE OR MORE DAYS OF ANOMALOUS WARMTH TO THE REGION NEXT WEEKEND. THE 12Z ECENS AND 00Z GEFS HAVE 850 TEMPS WARMING TO +14C ACROSS SOUTHERN NEW ENGLAND DURING THIS TIME. DAILY SENSIBLE WEATHER DETAILS... TUESDAY NIGHT THRU THU... DRY AIRMASS OVER NEW ENGLAND ALONG WITH LIGHT WINDS AS SURFACE RIDGE AXIS SETTLES ACROSS THE AREA WILL YIELD IDEAL RADIATIONAL COOLING CONDITIONS. THIS WILL RESULT IN CHILLY NIGHTS WITH MOST LOCATIONS DIPPING INTO THE 40S OUTSIDE THE URBAN AREAS AND AWAY FROM THE COASTLINE. HOWEVER AFTERNOON TEMPS WILL RECOVER NICELY TO 65-70. GIVEN PROXIMITY OF THE SURFACE HIGH WINDS WILL BE LIGHT WITH LOCAL SEABREEZES DEVELOPING DURING THE AFTERNOON. GIVEN THE RADIATIONAL COOLING CONDITIONS WILL STRAY AWAY FROM A MODEL BLEND AND FOLLOW THE COOLER MOS GUIDANCE AND EVEN SHAVE OFF A FEW MORE DEGS IN THE TYPICALLY COOLER LOCATIONS /I.E. NORWOOD-TAUNTON-MARTHAS VINEYARD- ETC/. AS MENTIONED ABOVE WILL HAVE TO WATCH MOISTURE AND INVERTED TROUGH CREEPING UP THE COAST WED NIGHT THRU THU NIGHT. 00Z GEFS HAS TRENDED NORTH WITH LOW PROBS OF 0.05 QPF ALONG THE SOUTH COAST. THIS SUPPORTS THE FARTHER NORTH SOLUTION OF THE OPERATIONAL 00Z GFS. IN ADDITION A MODEL BLEND OF ALL DATASETS BRINGS SLIGHT CHANCE POPS TO THE SOUTH COAST WITH A MODEL BLEND OF QPF BRINGING MEASURABLE RAIN INTO NORTHERN CT-RI TO SOUTHERN SUBURBS OF BOSTON. FRI/SAT AND SUN... SURFACE HIGH SHIFTS WESTWARD FROM OVER NEW ENGLAND TO ACROSS THE GREAT LAKES. THIS YIELDS A WARMER WNW LOW LEVEL WIND FLOW INTO NEW ENGLAND. THIS SHOULD YIELD TEMPS WELL INTO THE 70S FRI AND THEN PUSHING 80 OR SO NEXT WEEKEND. THE RECORDS FOR THE DAY INCLUDE 9/27... BOS...86...1998 BDL...88...1998 PVD...86...1998 ORH...85...1933 GIVEN THE TIME RANGE HERE ALONG WITH DEGREE OF UNCERTAINTY WILL FOLLOW A MODEL BLEND. HUMIDITY SHOULD BE IN THE COMFORTABLE RANGE GIVEN WNW LOW LEVEL LAND TRAJECTORY. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/... 7 AM UPDATE... COLD FRONT NOW OFFSHORE WITH WEST WINDS AT ALL TERMINALS AND VFR CONDITIONS. WEST WINDS GUSTS UP TO 25 KT TODAY ALONG WITH VFR CONDITIONS. 06Z TAFS CAPTURE THESE DETAILS SO NO MAJOR CHANGES WITH UPCOMING 12Z TAFS. EARLIER DISCUSSION BELOW. =================================================================== TODAY INTO TUESDAY...HIGH CONFIDENCE. VFR...ALTHOUGH MVFR/IFR CONDITIONS MAY LINGER AT ACK THROUGH MID MORNING. WINDS MAINLY WNW TODAY...GUSTING TO AROUND 25 KT AT TIMES THEN DIMINISHING OVERNIGHT. KBOS TERMINAL...HIGH CONFIDENCE FOR MAINLY VFR FROM NOW ON. KBDL TERMINAL...HIGH CONFIDENCE FOR MAINLY VFR FROM NOW ON. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... HIGH CONFIDENCE FOR VFR EACH DAY. EXCEPTION WILL BE A LOW RISK OF MVFR IN SHOWERS SOUTH COAST INCLUDING THE ISLANDS FROM WED NIGHT THRU THU NIGHT. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/... TODAY AND TONIGHT...MODERATE CONFIDENCE. SLOWLY BUILDING SWELL MAY APPROACH 10 FT WELL OFFSHORE...BUT INCREASE TO 5-8FT CLOSER TO THE THE SRN NEW ENGLAND COAST THROUGH THE DAY...AS W-NW WINDS REACH ABOUT 25 KT. THEREFORE...SMALL CRAFT ADVISORIES HAVE BEEN ISSUED AND WILL CONTINUE INTO TONIGHT...DROPPING CLOSE TO SHORE THIS EVENING AS WINDS DIMINISH. HOWEVER...THE SWELL MAY TAKE UNTIL EARLY TUE MORNING TO COMPLETELY DIMINISH ON THE S AND SE WATERS. TUE...HIGH CONFIDENCE. AFTER THE LEFTOVER SWELL SUBSIDES...A PROLONGED PERIOD OF QUIET BOATING WEATHER IS EXPECTED AS HIGH PRES BEGINS TO CREST OVER THE WATERS. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... HIGH CONFIDENCE... LIGHT WINDS THRU THE PERIOD AS HIGH PRES REMAINS OVER OR NEAR THE REGION. DRY WEATHER AND GOOD VSBY TOO. POSSIBLE EXCEPTION WILL BE RAIN SHOWERS WED NIGHT THRU THU NIGHT AS MOISTURE ADVECTS UP THE EASTERN SEABOARD. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH SURF ADVISORY UNTIL 6 PM EDT THIS EVENING FOR MAZ020>024. NH...NONE. RI...HIGH SURF ADVISORY UNTIL 6 PM EDT THIS EVENING FOR RIZ006>008. MARINE...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 2 AM EDT TUESDAY FOR ANZ231>234. SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR ANZ230-236. SMALL CRAFT ADVISORY UNTIL 8 AM EDT TUESDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 11 AM EDT TUESDAY FOR ANZ250- 254>256. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ251. && $$ SYNOPSIS...NOCERA/DOODY NEAR TERM...NOCERA/DOODY SHORT TERM...DOODY LONG TERM...NOCERA AVIATION...NOCERA/DOODY MARINE...NOCERA/DOODY

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