Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220200 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1000 PM EDT SUN SEP 21 2014 .SYNOPSIS... A PERIOD OF STEADY RAIN WILL AFFECT THE FAR SOUTHEAST NEW ENGLAND COAST THIS EVENING. OTHERWISE...DRIER AND LESS HUMID WEATHER IS ON TAP FOR MONDAY AS A DRY COLD FRONT SWEEPS ACROSS THE REGION. STRONG HIGH PRESSURE WILL BRING SUNNY DAYS AND CLEAR NIGHTS TO THE REGION FROM TUESDAY THROUGH NEXT WEEKEND WITH A WARMING TREND. WE COULD APPROACH RECORD WARMTH ON SATURDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 10 PM UPDATE... A BAND OF STEADY RAIN HAS GENERALLY DIMINISHED ACROSS PORTIONS OF E MA THIS EVENING AS LOW PRES DEVELOPING OFFSHORE BEGINS TO SHIFT NE. A FEW MORE SHOWERS ARE LIKELY TO REMAIN FROM THIS BUT JUST OVER THE NEXT COUPLE OF HOURS. OTHERWISE...HAVE BEEN WATCHING A DOWNWARD TREND IN CONVECTIVE ACTIVITY IN NY ASSOCIATED WITH THE COLD FRONT...STILL A BIT OF -SHRA ACTIVITY LEFT...BUT NOT MUCH CONVECTION. LOOKS LIKE MAINLY WRN MA AND SW NH WILL BE HAVE THIS RAIN IN THE CARDS BUT GENERALLY AFTER 03Z. AFTER THAT...THE RAPID ENTRAINMENT OF DRY AIR...LONG SINCE LOSS OF DIURNAL HEATING AND SHIFT OF BEST DYNAMICS INTO NRN NEW ENGLAND SHOULD ALLOW FOR MOST OF THESE TO DISSIPATE SUCH THAT VERY LITTLE ACTIVITY...ASIDE FROM A BRIEF GUST OF WIND AND WIND SHIFT...IS SEEN ELSEWHERE WITH THIS FROPA. OTHERWISE...A POCKET OF VERY DENSE FOG HAS DEVELOPED FROM THE N SHORE OF MA INTO COASTAL MAINE. THIS WILL LIKELY CONTINUE INTO THE MORNING HOURS. HAVE ISSUED A DENSE FOG ADVISORY FOR THIS AREA. OTHERWISE...ONLY OTHER LOCATIONS REPORTING UNDER HALF A MILE ARE ORH AND TAN...BUT FEEL THESE ARE LIKELY MORE COLOCATED WITH THE AIRPORT. PREVIOUS DISCUSSION... MARGINAL INSTABILITY WITH DEEP LOW LEVEL MOISTURE HAS ALLOWED ISOLATED TO SCATTERED SHOWERS TO CONTINUED TO AFFECT SOUTHERN NEW ENGLAND. WE SHOULD SEE THIS ACTIVITY DIMINISH EARLY THIS EVENING WITH THE LOSS OF DAYTIME HEATING. THE MAIN CONCERN WILL BE THE SURFACE LOW PRESSURE SYSTEM OFF THE MID ATLANTIC COAST WHICH WILL BE TRACKING NORTHEAST AND PASSING NEAR THE BENCHMARK THIS EVENING. THE MAIN QUESTION IS HOW FAR NORTHWEST THE RAIN SHIELD WILL GET. LATEST NEAR TERM GUIDANCE HAS BEEN TRENDING FURTHER NORTHWEST. THEREFORE...EXPECT A PERIOD OF STEADY RAIN ACROSS THE CAPE/ISLANDS AND PROBABLY FURTHER NORTHWEST INTO INTERIOR SOUTHEAST MA/RHODE ISLAND FOR AT LEAST A TIME. IN FACT...LATEST HRRR SHOWING THE POTENTIAL FOR A BRIEF PERIOD OF RAIN ACROSS THE NORTHEAST MA COAST INCLUDING BOSTON. NOT SURE IF IT WILL GET THAT FAR NORTHWEST...BUT ITS CERTAINLY POSSIBLE. REGARDLESS...THE HEAVIEST RAINFALL WILL OCCUR ACROSS NANTUCKET... WHERE BETWEEN 0.50 TO PERHAPS UP TO 1 INCH OF RAIN MAY OCCUR. THE RAIN MAY PERSIST THROUGH MUCH OF THE EVENING ACROSS THE CAPE AND ISLANDS...BUT SHOULD WIND DOWN NEAR OR JUST AFTER MIDNIGHT. MEANWHILE...ONCE THE ISOLATED TO SCATTERED DIURNALLY DRIVEN SCATTERED SHOWERS WIND DOWN EARLY THIS EVENING...THE REST OF THE REGION WILL MAINLY BE DRY TONIGHT. HOWEVER...A COLD FRONT WILL BE APPROACHING OUR WESTERN ZONES TOWARD MIDNIGHT. WHILE SHEAR IS QUITE IMPRESSIVE...VERY LITTLE INSTABILITY WILL BE LEFT. SO WHILE WE MAY SEE A FEW SPOT SHOWERS AFFECT OUR WESTERN ZONES...THEY WILL BE IN THE PROCESS OF WEAKENING AND NOT EXPECTING MUCH MORE THAN THAT. LOW TEMPS WILL ONLY BOTTOM OUT IN THE UPPER 50S AND THE LOWER 60S BY DAYBREAK MONDAY. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... MONDAY... A MUCH DRIER AIRMASS WILL WORK INTO THE REGION BEHIND THE COLD FRONT ON MONDAY. WHILE PARTLY TO MOSTLY SUNNY SKIES ARE EXPECTED EARLY...MAY SEE A SCATTERED TO BROKEN DECK OF STRATO- CUMULUS CLOUDS WORK INTO AT LEAST THE INTERIOR BY AFTERNOON. HIGHS SHOULD MAINLY BE IN THE 60S ACROSS THE INTERIOR...BUT STILL WILL REACH BETWEEN 70 AND 75 ALONG HE COASTAL PLAIN. GUSTY WEST WINDS OF 20 TO 30 MPH ARE EXPECTED AS BUFKIT SOUNDINGS SHOWING VERY GOOD MIXING. HIGH SURF...GIVEN LARGE SOUTH TO SOUTHEAST SWELL FROM DEPARTING COASTAL LOW PRESSURE SYSTEM HAVE ISSUED A HIGH SURF ADVISORY FOR THE SOUTH COAST ON MONDAY. WE ISSUE HIGH SURF PRODUCTS THROUGH THE END OF SEPTEMBER IF CONDITIONS WARRANT. MONDAY NIGHT... HIGH PRESSURE WILL BE BUILDING IN FROM THE WEST. THIS WILL ALLOW FOR DIMINISHING WINDS AND SKIES TO BECOME MOSTLY CLEAR. LOOKS LIKE A PRETTY GOOD NIGHT OF RADIATIONAL COOLING...WITH LOWS BOTTOMING OUT IN THE UPPER 30S TO THE MIDDLE 40S IN MOST LOCALES. THE URBAN HEAT ISLAND OF BOSTON WILL BE THE MILD SPOT WITH THE LOW BOTTOMING OUT NEAR 50. && .LONG TERM /TUESDAY THROUGH SUNDAY/... HIGHLIGHTS... * HIGH PRESSURE AND DRY WEATHER THROUGH THE PERIOD * NEAR RECORD WARMTH POSSIBLE NEXT SATURDAY OVERVIEW... VERY GOOD AGREEMENT AMONGST MODEL GUIDANCE THE ENTIRE FORECAST PERIOD. AN UPPER LEVEL TROUGH DEPARTS THE NORTHEAST STATES ON TUESDAY. THEN...MUCH ADO ABOUT BUILDING HIGH PRESSURE...BOTH AT THE SURFACE AND ALOFT THE REMAINDER OF THE WEEK. THE UPPER RIDGE IS VERY STRONG AS IT IS PARKED FROM THE GREAT LAKES TO SOUTHERN NEW ENGLAND BY NEXT WEEKEND. DETAILS... TUESDAY WILL FEATURE MOSTLY SUNNY SKIES EXCEPT ONLY PARTLY SUNNY NW MA AND SW NH CLOSER TO SOME HIGHER 925 MB HUMIDITY. OTHERWISE...EXPECT SUNNY DAYS AND CLEAR NIGHTS THROUGH NEXT WEEKEND. HAVE GONE A FEW DEGREES LOWER THAN MODEL CONSENSUS TEMPERATURE MINIMUMS THROUGH THU DUE TO EXCELLENT RADIATIONAL COOLING EXPECTED ALONG WITH VERY DRY DEWPOINTS. AS THE CENTER OF THE UPPER HIGH APPROACHES...AM EXPECTING A DRAMATIC WARMUP FRI AND ESPECIALLY SAT. THE 12Z ECMWF RUN IS EVEN WARMER THAN THE PREVIOUS RUN WITH 925 MB TEMPERATURES WARMING FROM +12C TUE...TO +17C FRI... TO +19C OR +20C ON SAT... WITH WARM TEMPERATURES LIKELY CONTINUING INTO EARLY THE FOLLOWING WEEK. HAVE GONE SEVERAL DEGREES ABOVE MODEL CONSENSUS MAXIMUMS FOR NEXT SATURDAY...WITH HIGHS SOARING TO 80 TO 85 ACROSS INTERIOR SOUTHERN NEW ENGLAND. RECORDS FOR THAT DAY INCLUDE 85 AT WORCESTER AND 86 AT BOTH BOSTON AND PROVIDENCE. LIGHT WINDS ARE EXPECTED FOR THE PERIOD...SO ALTHOUGH IT WILL BE DRY WE ARE NOT EXPECTING FIRE WEATHER CONCERNS. LOCAL SEA BREEZES WILL OCCUR...ESPECIALLY FRI THROUGH NEXT SUNDAY. IT SHOULD BE NOTED THAT THE GFS HAS A HINT OF A POTENTIAL BACKDOOR FRONT/TROUGH OVER NORTHEAST MA ON SAT BUT THIS WAS NOT ENOUGH TO DETRACT FROM THE VERY WARM FORECAST...AS YET. AN UPPER LOW OVER VIRGINIA AND AN ASSOCIATED INVERTED TROUGH IS LIKELY TO BE CAUSING PRECIPITATION IN THE MID ATLANTIC REGION MID TO LATE IN THE WORK WEEK THAT TRIES TO WORK ITS WAY NORTHWARD. THERE IS EXCELLENT MODEL AGREEMENT THAT THIS AREA ONLY GETS AS FAR NORTHWARD AS OFF THE NJ COAST BY FRI...BEFORE RETREATING SOUTHWARD AS STRONG HIGH PRESSURE BECOMES ESTABLISHED OVER THE NORTHEAST ON THE WEEKEND. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY NIGHT/... TONIGHT...LOW TO MODERATE CONFIDENCE. IFR CONDITIONS WITH SOME LOW IFR CONDITIONS ACROSS FAR SOUTHEAST MA INCLUDING THE CAPE AND ISLANDS WITH VISIBILITIES BELOW 1/2 MILE AT TIMES IN LOCALLY DENSE FOG. MOST OF THE REST OF THE REGION WILL BE MVFR CEILINGS...WITH MANY AREAS BECOMING IFR CEILINGS BETWEEN 02Z AND 06Z. BEST CONFIDENCE FOR IFR IS FROM ABOUT A JAFFREY-WORCESTER-WILLIMANTIC LINE EASTWARD. STEADY RAIN WITH EMBEDDED SHOWERS WILL AFFECT THE FAR SOUTHEAST NEW ENGLAND COAST THIS EVENING. THE RAIN WILL LIKELY REACH INTO RHODE ISLAND/INTERIOR SOUTHEAST MA FOR A SHORT TIME AND PERHAPS EVEN INTO NORTHEAST MA. MONDAY AND MONDAY NIGHT...HIGH CONFIDENCE IN VFR CONDITIONS. JUST A LOW RISK FOR BRIEF MVFR CIGS ACROSS THE INTERIOR ON MONDAY AS A DECK OF STRATOCUMULUS CLOUDS MOVES INTO THE REGION. OTHERWISE...GUSTY WEST TO NORTHWEST WINDS OF 20 TO 25 KNOTS EXPECTED DURING THE DAY MONDAY. KBOS TERMINAL...MODERATE CONFIDENCE TONIGHT WITH HIGH CONFIDENCE ON MONDAY. KBDL TERMINAL...MODERATE CONFIDENCE TONIGHT WITH HIGH CONFIDENCE ON MONDAY. OUTLOOK...TUESDAY THROUGH FRIDAY... HIGH CONFIDENCE. TUE...VFR. WED...VFR THU...VFR. FRI...VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... TONIGHT...MODERATE TO HIGH CONFIDENCE. LOW PRESSURE PASSING NEAR THE BENCHMARK WILL RESULT IN ENOUGH SOUTH TO SOUTHEAST SWELL FOR SCA SEAS TO DEVELOP ACROSS THE OUTER-WATERS AND WESTERN SOUNDS. SOUTHEAST WINDS SHOULD BECOME SOUTHWEST TONIGHT AT 10 TO 15 KNOTS LATER TONIGHT. AREAS OF FOG...SOME LOCALLY DENSE...WILL OCCUR ACROSS THE WATERS...ESPECIALLY SOUTH OF BOSTON HARBOR. MONDAY AND MONDAY NIGHT...MODERATE TO HIGH CONFIDENCE. SCA SEAS ON THE WESTERN SOUNDS AND OUTER-WATERS WILL CONTINUE THROUGH MONDAY NIGHT. IN ADDITION...A PERIOD OF WEST TO NORTHWEST WIND GUSTS NEAR 25 KNOTS IS POSSIBLE FOR A TIME ON MONDAY. THEREFORE...IT IS POSSIBLE WE MAY NEED TO EXPAND SCA FOR A TIME DURING THE DAY MONDAY INTO SOME OF THE NEARSHORE SOUNDS AND WATERS. CONFIDENCE NOT QUITE HIGH ENOUGH TO DO THIS RIGHT NOW... SO WILL DEFER TO THE NEXT SHIFT. OUTLOOK...TUESDAY THROUGH FRIDAY... HIGH CONFIDENCE... TUE AND WED...SEAS NEAR 5 FT MAY LINGER AT TIMES TUE AND WED OVER THE WATERS S AND E OF NANTUCKET. OTHERWISE WINDS AND SEAS SHOULD BE BELOW SMALL CRAFT ADVISORY CRITERIA. A NORTHEAST WIND GRADIENT WILL INCREASE OVER THE SOUTHERN COASTAL WATERS TUE NIGHT INTO WED AS STRONG HIGH PRESSURE PUSHES INTO NORTHERN NEW ENGLAND. BUT GUSTS ARE EXPECTED TO ONLY REACH 20 KT. WED NIGHT THROUGH FRI...QUIET BOATING WEATHER WITH HIGH PRESSURE DOMINATING THE WEATHER. WINDS AND SEAS BELOW SCA THRESHOLDS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH SURF ADVISORY FROM 8 AM TO 5 PM EDT MONDAY FOR MAZ020>024. DENSE FOG ADVISORY UNTIL 5 AM EDT MONDAY FOR MAZ006-007-014. NH...NONE. RI...HIGH SURF ADVISORY FROM 8 AM TO 5 PM EDT MONDAY FOR RIZ006>008. MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT TUESDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 8 AM EDT TUESDAY FOR ANZ250-254>256. SMALL CRAFT ADVISORY FROM 6 AM TO 4 PM EDT MONDAY FOR ANZ251. && $$ SYNOPSIS...FRANK/GAF NEAR TERM...FRANK/DOODY/GAF SHORT TERM...FRANK LONG TERM...GAF AVIATION...FRANK/GAF MARINE...FRANK/GAF

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