Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 300755 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 355 AM EDT SAT MAY 30 2015 .SYNOPSIS... DRY WEATHER WILL CONTINUE FOR TODAY THANKS TO AN AREA OF HIGH PRESSURE. A COLD FRONT WILL SLOWLY MOVE ACROSS THE REGION SUNDAY...THEN STALL SOUTH OF NEW ENGLAND EARLY NEXT WEEK. THIS WILL BRING A CHANCE OF SHOWERS AND A FEW THUNDERSTORMS SUNDAY...AND A PERIOD OF RAIN EARLY NEXT WEEK. HIGH PRESSURE BRINGS DRY WEATHER FOR THE LATTER PART OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 4 AM UPDATE... SOUTHWEST FLOW WILL CONTINUE TO ADVECT IN MOISTURE INTO THE REGION. STRATUS AND FOG HAVE SPREAD ACROSS THE SOUTH COAST/CAPE AND ISLANDS AND IS BEGINNING TO MOVE NORTHWARD. BIGGEST QUESTION IS HOW FAR NORTH AND HOW DENSE WILL VSBYS DROP. CURRENTLY HAVE THE SOUTH COAST/CAPE AND ISLANDS IN A DENSE FOG ADVISORY AND WILL ADD PLYMOUTH COUNTY AND THE REST OF BRISTOL COUNTY AS WELL. FOG IS ALSO DEVELOPING ACROSS SOME OF THE LOWER VALLEY REGIONS...ANTICIPATE THIS FOG TO REMAIN 1SM AS TEMPS/DEWPOINT SPREAD DECREASES. OTHERWISE TEMPS HAVE DROPPED INTO THE MID 50S TO LOW 60S. EXPECT THEM TO DROP ANOTHER DEGREE OR TWO...BUT THEN RISE ONCE THE SUN RISES. TODAY... HIGH PRESSURE WILL SLOWLY SHIFT OFFSHORE TODAY ALLOWING FOR THE SOUTHERLY FLOW TO DOMINATE THE REGION. DEWPOINTS WILL BE ON THE INCREASE ALLOWING FOR ANOTHER WARM AND MUGGY DAY. ANTICIPATE GOOD MIXING TODAY SO SW WIND MAY GUST BETWEEN 20-30 KTS. IN THE LATTER HALF...COLD FRONT WILL MOVE ACROSS THE GREAT LAKES REGION ALLOWING FOR SHOWERS AND THUNDERSTORMS TO DEVELOP. THE BETTER DYNAMICS AND FORCING WILL BE WELL TO THE WEST OF THE REGION...HOWEVER BECAUSE WE ARE IN A VERY WARM AND MOIST AIRMASS CANNOT RULE OUT A FEW POP-UP SHOWERS AND THUNDERSTORMS OUT AHEAD OF THIS FRONT. THEREFORE KEPT THE SLIGHT CHC POP ACROSS THE WESTERN ZONES...WHICH IS IN CONJUNCTION WITH SPC CONVECTIVE OUTLOOK. OTHERWISE BELIEVE THAT MOST OF THE REGION WILL REMAIN DRY FOR TODAY WITH HIGH TEMPS REACHING INTO THE MID TO UPPER 80S AWAY FROM THE SOUTH COASTLINE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT... NOTICED GUIDANCE CONTINUES TO SLOW DOWN THE FRONTAL PASSAGE...SO HAVE ADJUSTED THE FORECAST TO ACCOUNT FOR THIS TREND. THE COLD FRONT WILL BEGIN TO APPROACH THE REGION TONIGHT...BRINGING SOME MUCH NEED RAINFALL TO THE REGION. AS THE FRONT APPROACHES GUIDANCE INDICATES THAT SHOWALTERS WILL BE BELOW 0 WITH K VALUES ABOVE 30C. THEREFORE CANNOT RULE OUT SOME EMBEDDED THUNDER OVERNIGHT. AREA THAT WILL SEE THE HIGHER RAINFALL AMOUNTS WILL BE NORTH OF THE PIKE...ESP NORTH OF ROUTE 2. SINCE THE FRONT WILL STILL BE NORTHWEST OF THE REGION...ANTICIPATE ANOTHER ROUND OF FOG TO DEVELOP ALONG THE SOUTH COAST/CAPE AND ISLANDS AS MOISTURE POOLS ALONG THE FRONT. LOW CONFIDENCE IF IT WILL BE DENSE OR NOT. TOMORROW... TIMING OF THE COLD FRONT IS STILL IN QUESTION AS LATEST GUIDANCE TREND IS TO SLOW DOWN THE FRONT. REGARDLESS BELIEVE THAT THE FRONT WILL CROSS SOUTHERN NEW ENGLAND ON SUNDAY BRINGING SOME MUCH NEEDED RAIN. GUIDANCE STILL SHOWS ELEVATED THUNDER PARAMETERS...SO WILL CONTINUE TO MENTION THUNDER IN THE FORECAST...BUT STRONG TO SEVERE STORMS ARE NOT EXPECTED. BOTH THE NAM AND GFS INDICATE GOOD BOUNDARY LAYER MOISTURE ALONG THE FRONT AS IS BEGINS TO STALL OVER THE REGION. WITH PWAT VALUES AROUND 1.6 INCHES AND THE FRONT BECOMING ALIGNED WITH THE UPPER FLOW ALOFT...COULD SEE THE POTENTIAL FOR HEAVY RAIN AND FLOODING DUE TO A SLOW STORM MOTION. BECAUSE OF THE UNCERTAINTY ON WHERE THE FRONT WILL STALL...HELD OFF ON ISSUING ANY SORT OF FLOOD WATCH AT THIS TIME. RIGHT NOW BELIEVE THAT LOCATIONS ALONG AND NORTH OF THE MASS PIKE WILL SEE THE HIGHER PRECIP AMOUNTS ON SUNDAY. PERHAPS IT WILL PUSH WORCESTER OUT OF THE TOP 5 DRIEST MAYS ON RECORD. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... BIG PICTURE... CHANGEABLE PATTERN THROUGH THE WEEK. UPPER RIDGE MOVES OFFSHORE SUNDAY. UPPER TROUGH SLOWLY CROSSES THE NORTHEAST USA EARLY WEEK. UPPER RIDGE FROM THE WESTERN USA THEN SHIFTS EAST OVER THE EASTERN USA LATE WEEK. DIFFERENCES AMONG THE MODELS REGARDING TIMING WITH THE UPPER TROUGH EARLY WEEK WITH THE GGEM THE FASTEST AND ECMWF SLOWEST. WE USED A MODEL CONSENSUS IN TIMING. THE DAILIES... SUNDAY THROUGH TUESDAY... COLD FRONT EITHER OVER OR JUST NORTH OF NORTHERN MASS SUNDAY MORNING WILL MOVE SOUTH ACROSS THE REGION DURING THE DAY. PRECIPITABLE WATER VALUES ALONG AND AHEAD OF THE FRONT WILL BE 1.50 TO 1.75 INCHES WHICH IS AROUND 2 STD DEV ABOVE NORMAL. TOTALS OF 47-49 AND SHOWALTERS OF 0 TO -2. ALL OF THIS SUGGESTS SUFFICIENT MOISTURE FOR SHOWERS AND ENOUGH INSTABILITY OVER THE LOW LEVEL CONVERGENCE TO SUPPORT A FEW THUNDERSTORMS. DIFFERENCES AMONG THE MODELS ON TIMING THE FROPA BUT ALL MOVE IT SOUTH OF THE COAST BY SUNDAY EVENING. THE FRONT IS THEN ALIGNED WITH THE UPPER FLOW AND STALLS. SHORTWAVE MOVING THROUGH THE GREAT LAKES IS FORECAST TO GENERATE A WAVE ALONG THE FRONT WHICH CROSSES THE APPALACHIANS MONDAY AND PASSES SOUTH OF NEW ENGLAND TUESDAY. THIS ALONG WITH HIGH PRESSURE IN EASTERN CANADA SHOULD BRING A COOL NORTHEAST FLOW TO THE REGION MONDAY AND TUESDAY. MEANWHILE A SOUTHWEST FLOW CONTINUES ABOVE 5OOO FEET AGL AND SUPPIES LIFT AND MOISTURE OVER THE TOP. WE WILL MAINTAIN LIKELY POPS MONDAY DIMINISHING TO CHANCE POPS DURING THE DAY TUESDAY AS THE LOW MOVES EAST. WEDNESDAY THROUGH FRIDAY... HIGH PRESSURE BUILDS SURFACE AND ALOFT BRINGING DRY WEATHER TO SOUTHERN NEW ENGLAND. WITH THE DEMISE OF THE NORTHEAST MARINE FLOW...MIXING SHOULD RETURN WITH HEIGHTS REACHING AT LEAST 875 MB WEDNESDAY AND AT LEAST 850 MB THURSDAY AND FRIDAY. TEMPERATURES AT THE TOP OF THE MIXED LAYER EACH DAY SUGGEST MAX SFC TEMPS IN THE MID 60S TO LOW 70S WEDNESDAY...70S TO NEAR 80 THURSDAY...AND 75-85 FRIDAY. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TONIGHT...MODERATE CONFIDENCE. IFR STRATUS/FOG MOVING IN FROM THE SOUTH COAST DROPPING VSBYS BELOW 1/4SM. THIS SHOULD DISSIPATE BY MORNING. TODAY...MODERATE CONFIDENCE. ANY LOW CLOUDS/FOG PATCHES SOUTH OF PIKE PROBABLY SCOUR OUT BY LATE MORNING...LINGERING ACROSS THE CAPE/ISLAND BY EARLY AFTERNOON. DRY WEATHER EXPECTED...ALTHOUGH THERE IS A LOW RISK OF A SPOT SHOWER/THUNDERSTORM ACROSS NORTHWEST MA LATE IN THE AFTERNOON/EARLY EVENING. TONIGHT INTO SUNDAY...MODERATE CONFIDENCE. VFR TO START WITH CONDITIONS DETERIORATING BY LATE TONIGHT INTO SUNDAY DUE TO WIDESPREAD -SHRA/-TSRA. FOG AND STRATUS MAY FILL BACK IN ALONG THE SOUTH COAST OVERNIGHT TONIGHT. OTHERWISE COULD SEE SOME LLWS ACROSS THE SOUTHERN SITES ON SUNDAY. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. UNCERTAIN ON IF FOG WILL FILL BACK IN OVERNIGHT. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. MONDAY THROUGH TUESDAY... MVFR/IFR CIGS AND VSBYS WITH BEST CHANCE OVER THE COASTAL PLAIN AND EASTERN SLOPES OF THE WORCESTER HILLS. SHOWERS POSSIBLE THROUGH BOTH DAYS. WEDNESDAY... VFR WITH A NORTH-NORTHWEST WIND. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH SUNDAY/... TODAY...MODERATE TO HIGH CONFIDENCE. EXCELLENT MIXING OVER THE LAND WILL GENERATE NEAR SHORE SMALL CRAFT WIND GUSTS OF 25 TO 30 KNOTS THIS AFTERNOON. IN ADDITION...SOUTHEAST SWELL WILL GENERATE 5 FOOT SEAS ACROSS THE OUTER-WATERS. THEREFORE...SMALL CRAFT HEADLINES POSTED FOR ALL WATERS. AREAS OF FOG SHOULD IMPROVE SOMEWHAT BY AFTERNOON. TONIGHT...MODERATE TO HIGH CONFIDENCE. NEAR SHORE SMALL CRAFT WIND GUSTS SHOULD DIMINISH BY THE EVENING. HOWEVER...5 FOOT SWELL WILL CONTINUE ACROSS THE OUTER-WATERS. AREAS OF DENSE FOG POSSIBLE TONIGHT. SUNDAY...MODERATE CONFIDENCE. MAY NEED TO EXTEND SCA FOR CAA BEHIND A PASSING COLD FRONT FROM THE NORTH. OTHERWISE EXPECT SHOWERS WITH EMBEDDED THUNDER COULD OCCUR AHEAD OF THE FRONT DURING THE AFTERNOON HOURS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. MONDAY-TUESDAY...SMALL CRAFT ADVISORY MAY BE NEEDED ESPECIALLY ON THE EASTERN WATERS. NORTHEAST WINDS GUSTING 20 TO 25 KNOTS EACH DAY. SEAS 5 TO 8 FEET ON THE EASTERN MASS WATERS...AND 3 TO 5 FEET ON THE SOUTHERN WATERS. WEDNESDAY...A SMALL CRAFT ADVISORY MAY BE NEEDED...MAINLY ON THE EASTERN WATERS. DIMINISHING NORTHEAST TO NORTH WINDS. SEAS OF 5 FEET MAY LINGER ON THE EASTERN WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MAZ017>024. RI...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR RIZ002>008. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EDT THIS EVENING FOR ANZ230>237-251. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 3 PM EDT SUNDAY FOR ANZ250-254>256. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...WTB AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN

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