Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 311130 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 730 AM EDT SUN MAY 31 2015 .SYNOPSIS... A COLD FRONT WILL MOVE SLOWLY SOUTH ACROSS THE REGION TODAY...THEN STALL SOUTH OF NEW ENGLAND EARLY THROUGH TUESDAY. HIGH PRESSURE BUILDS OVER THE REGION WITH FAIR WEATHER FOR WEDNESDAY THROUGH FRIDAY. TEMPERATURES DROP BELOW NORMAL MONDAY...THEN SHOULD GRADUALLY RETURN TO SEASONABLE LEVELS BY WEDNESDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 730 AM UPDATE... VISIBLE SATELLITE DATA SHOWING PLENTY OF CLOUDS OVER THE MAJORITY OF SOUTHERN NEW ENGLAND. SOME STRATUS AND FOG DID MANAGE TO DEVELOP ALONG THE SOUTH COAST. EXPECTING THIS STRATUS AND FOG TO DISSIPATE QUICKLY THIS MORNING. PRE-FRONTAL TROUGH CONTINUES TO PUSH OVER THE REGION AND WITH ENOUGH MOISTURE AND ELEVATED INSTABILITY. SCATTERED SHOWERS ALREADY MOVING INTO PORTIONS OF SOUTHERN NEW ENGLAND THIS MORNING. TRIED TO UPDATE TIMING FOR THESE SHOWERS THIS MORNING. LATEST RUNS OF THE HRRR LOOKED REASONABLE...SO USED THAT AS THE BASIS FOR THESE CHANGES. OTHERWISE...TWEAKED NEAR TERM FORECAST TO BRING CONDITIONS BACK IN LINE WITH OBSERVED TRENDS. PREVIOUS DISCUSSION... A COLD FRONT THAT IS CURRENTLY DRAPED ACROSS NORTHERN NEW ENGLAND EARLY THIS MORNING...WILL SLOWLY MOVE TOWARDS SOUTHERN NEW ENGLAND TODAY. AS THE FRONT APPROACHES...EXPECT SHOWER COVERAGE TO INCREASE THROUGHOUT THE DAY AS WELL AS THE POTENTIAL FOR A FEW EMBEDDED THUNDERSTORMS. THE FRONT SHOULD BEGIN TO MOVE ACROSS NORTHERN ZONES BETWEEN 15-18Z AND DOWN TO THE SOUTH COAST BY 21-00Z. APPEARS THAT THE 00Z GUIDANCE HAS FINALLY AGREED ON PLACEMENT AND TIMING OF THE FRONT. MODELS CONTINUE TO INDICATE GOOD BOUNDARY LAYER MOISTURE ALONG THE FRONT AS IS BEGINS TO SLOW DOWN OVER THE REGION. WITH PWAT VALUES AROUND 1.8 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. STILL APPEARS THAT LOCATIONS ALONG THE MASS PIKE AND ACROSS 1-84 IN CT HAVE THE BEST CHANCE TO SEE THE HIGHEST RAINFALL AMOUNTS. CANNOT RULE OUT THUNDER POTENTIAL TODAY. SBCAPES ARE FORECASTED TO BE AROUND 1500 J/KG DURING PEAK HEATING THIS AFTERNOON. 0-6KM SHEAR REMAINS WEAK WITH HIGHER VALUES IN THE MORE STABLE AIRMASS BEHIND THE FROPA. STILL CANNOT RULE OUT A TIME WHERE PERHAPS THE SHEAR AND INSTABILITY LINE UP TO PRODUCE A STRONG STORM...BUT CONFIDENCE IS LOW. BEST CHANCES FOR ANY THUNDERSTORMS WILL BE ACROSS NORTHERN CT/RI TO THE MASS PIKE REGION AS SOUTH COAST WILL REMAIN STABLE DUE TO THE MARITIME FLOW. LASTLY...APPEARS THAT TEMPERATURES WILL FALL THROUGHOUT THE DAY ESP NORTH OF THE PIKE AS WINDS WILL SWITCH TO THE NORTH AND BRING IN DESCENT CAA. IN FACT 850 MB TEMPS WILL DROP FROM 14C DOWN TO 8C THROUGHOUT THE DAY. LOCATIONS SOUTH OF THE PIKE MAY SEE TEMPS WARM INTO THE MID TO UPPER 70S WHILE NORTH OF THE PIKE WILL BE IN THE UPPER 60S TO LOW 70S BEFORE THE FRONTAL PASSAGE. GUSTY SOUTHWESTERLY WINDS OUT AHEAD OF THE FRONT THIS MORNING WILL SLOWLY DIE DOWN DURING FROPA...HOWEVER ON THE BACKSIDE WINDS WILL GUST BETWEEN 20-30 MPH...ESP ALONG THE NORTHEAST MASS COASTLINE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT... SURFACE COLD FRONT WILL PUSH NEAR OR JUST SOUTH OF THE REGION ALLOWING FOR COOL NORTHERLY FLOW TO MOVE INTO THE REGION. TEMPS WILL BE A LOT COOLER THEN WHAT HAS BEEN FELT IN SEVERAL DAYS. NOT EXPECTING MUCH IN THE WAY OF HEAVY PRECIP TONIGHT AS SURFACE FORCING MECHANISM IS SOUTH OF THE REGION AND THE 850 MB FRONT WILL BE WELL NORTH OF THE REGION. BUT COULD SEE STRATUS/DRIZZLE AND FOG OVERNIGHT. APPEARS THAT NORTHERN NEW ENGLAND WILL SEE THE HEAVIEST PRECIP WHERE THE 850 MB FRONT WILL BE COLLOCATED WITH THE UPPER LEVEL JET AND SHORTWAVE APPROACHING THE REGION. TOMORROW... MARITIME AIR WILL CONTINUE TO DOMINATE SOUTHERN NEW ENGLAND KEEPING HIGHS WELL BELOW AVERAGE....IN THE MID 50S TO LOW 60S. SURFACE AND 850MB LOW WILL BEGIN TO DEVELOP AND APPROACH THE REGION TOMORROW. EXPECT THE FIRST HALF OF THE DAY TO BE SCT SHOWERS WITH PERHAPS SOME DRIZZLE. BUT AS THE SYSTEM AND BETTER FORCING APPROACHES FROM THE WEST EXPECT COVERAGE TO INTENSIFY...ESP ACROSS WESTERN ZONES. PWAT VALUES WILL BE NEAR 1.5 INCHES COMBINED WITH AN INCREASING LLJ...BELIEVE HEAVY RAINFALL IS POSSIBLE. LOW PROBABILITY THAT THUNDER WILL DEVELOP AS THE MARITIME AIR WILL KEEP MOST OF THE REGION STABLE. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... BIG PICTURE... CHANGEABLE PATTERN MUCH OF THIS WEEK. AN UPPER TROUGH SLOWLY CROSSES THE NORTHEAST USA EARLY THIS WEEK. AN UPPER RIDGE FROM THE WESTERN USA THEN SHIFTS EAST OVER THE EASTERN USA LATE THIS WEEK. EARLY INDICATIONS FOR THE END OF THE WEEK SHOW POTENTIAL INTERACTION BETWEEN NORTHERN AND SOUTHERN STREAM SHORTWAVES THAT COULD BRING SHOWERS TO NEW ENGLAND TOWARD NEXT WEEKEND. MODELS DIFFER MONDAY-TUESDAY REGARDING PLACEMENT OF FEATURES THAT WOULD FOCUS RAIN/SHOWERS AND BRING HIGHER AMOUNTS. BUT THE LONG RANGE MODELS ARE SIMILAR REGARDING LARGER SCALE FEATURES AND THE GENERAL FLOW OF WEATHER THROUGH THE WEEK. WE USED A BLEND OF THE MODELS TO GENERATE OUR GRID DATA. THE DAILIES... MONDAY NIGHT-TUESDAY... COLD FRONT REMAINS STALLED SOUTH OF NEW ENGLAND. A HIGH PRESSURE BUILDS OVER EASTERN CANADA. THIS WILL BRING AN INCREASING EAST- NORTHEAST WIND ACROSS THE GULF OF MAINE AND INTO SOUTHERN NEW ENGLAND. EXPECTING A COOL MOIST ENVIRONMENT...ESPECIALLY ACROSS EASTERN MA...WITH BELOW NORMAL TEMPERATURES. A LOW PRESSURE MOVES ALONG THE STALLED FRONT TO OUR SOUTH DURING THIS TIME. THIS WILL PROVIDE THE FOCUS FOR WIDESPREAD SHOWERS...AND PERHAPS A THUNDERSTORM OR TWO. THE MAIN CONCERN WILL BE LOCALLY HEAVY RAINFALL. RAINFALL CHANCES BEGIN TO DIMINISH FROM WEST TO EAST TUESDAY AFTERNOON. WEDNESDAY THROUGH FRIDAY...A NORTHERN STREAM SHORTWAVE MOVES EAST OF OUR REGION WEDNESDAY. HIGH PRESSURE BUILDS OVER THE NORTHEAST USA. THIS WILL FAVOR A DRY PERIOD WITH TEMPERATURES TRENDING HIGHER EACH DAY. THE PREVAILING FLOW WEDNESDAY WILL BE NORTHERLY. LIGHTER WINDS WILL FAVOR SEA BREEZES ALONG PORTIONS OF THE COASTLINE THURSDAY AND FRIDAY. SATURDAY...NORTHERN STREAM SHORTWAVE MAY DRIVE A COLD FRONT TOWARD NEW ENGLAND. SHOWERS AHEAD OF THIS FRONT MAY REACH THE WESTERN HALF OF SOUTHERN NEW ENGLAND...BUT LOW CONFIDENCE AT THIS TIME. WE ARE ALSO WATCHING A SOUTHERN STREAM TROUGH...WHICH MAY GENERATE A COASTAL LOW LATE THIS WEEK THAT COULD BRING RAIN UP THE COAST LATE NEXT WEEKEND. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY...MODERATE CONFIDENCE. DEVELOPING WIDESPREAD MVFR/IFR CONDITIONS FROM NUMEROUS SHOWERS AND TSTMS AS A COLD FRONT DROPS SOUTH ACROSS SOUTHERN NEW ENGLAND. LOWER VSBYS/CIGS EXPECTED TO BE NEAR THE MASS PIKE. WINDS SHIFTING FROM SW TO NE BEHIND THE FRONT WITH G25 KT POSSIBLE NE MA IN THE AFTERNOON. TIMING OF FRONT... 15-18Z ALONG AND N OF MASS PIKE REACHING SOUTH COAST 21-00Z. TONIGHT...MODERATE CONFIDENCE. WIDESPREAD MVFR/IFR CONDITIONS. SCT SHOWERS AND DRIZZLE ARE EXPECTED. COULD SEE MARINE STRATUS ESP ALONG MASS EAST COASTLINE. MONDAY...MODERATE CONFIDENCE. MVFR CIGS WITHIN ANY SCT -SHRA MONDAY MORNING. COVERAGE WILL PICK UP AND COULD DROP TO IFR DURING THE AFTERNOON ESP NORTH OF THE PIKE. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. IFR CONDITIONS LIKELY DEVELOP THIS AFTERNOON AS WINDS SHIFT TO NE BEHIND A FRONT. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE CONFIDENCE. MONDAY NIGHT AND TUESDAY...EAST TO NORTHEAST FLOW WITH WINDS ALONG THE MA EAST COAST 10 TO 15 KNOTS WITH GUSTS 15 TO 20 KNOTS POSSIBLE. LIGHTER NORTHEAST WINDS FARTHER INLAND. MVFR/IFR CIGS AND VSBYS... WITH THE GREATEST RISK ACROSS THE COASTAL PLAIN AND EASTERN SLOPES OF THE WORCESTER HILLS. SHOWERS POSSIBLE BOTH DAYS. WEDNESDAY...VFR WITH A NORTH-NORTHWEST WIND. THURSDAY...VFR. LOCAL SEABREEZES POSSIBLE. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH SUNDAY/...HIGH CONFIDENCE. TODAY...SW WINDS WILL SHIFT TO NE ACROSS E MA WATERS THIS AFTERNOON. A PERIOD OF GUSTS TO 30 KT EXPECTED OVER NE MA WATERS...A SCA HAS BEEN ISSUED. ACROSS S COASTAL WATERS...SW WINDS WILL PERSIST. EXPECT SHOWERS WITH EMBEDDED THUNDERSTORMS TO DEVELOP BY THE AFTERNOON. TONIGHT...SCT SHOWERS ALONG WITH PATCHY FOG REDUCING VSBYS. OTHERWISE ANY SOUTHERLY FLOW SHOULD SWITCH TO THE NORTHEAST AND GUST TO NEAR 15 KTS. SCA FOR BUILD SEAS FOR NORTHERN OUTER WATERS HAS BEEN ISSUED. TOMORROW...PERSISTENT NORTHEASTERLY FLOW WILL CONTINUE TO BUILD SEAS AND SWELLS ACROSS THE NORTHEASTERN WATERS. A SCA MAY NEED TO BE EXTENDED. OTHERWISE EXPECT SCT SHOWERS LIMITING VSBYS DURING THE DAY. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE CONFIDENCE. MONDAY NIGHT-WEDNESDAY NIGHT...SMALL CRAFT ADVISORIES FOR ROUGH SEAS WILL LIKELY BE NEEDED ACROSS THE COASTAL WATERS EAST OF MASSACHUSETTS. SMALL CRAFT ADVISORIES MAY BE NEEDED ACROSS THE SOUTHERN OUTER COASTAL WATERS AS WELL. THURSDAY...NO HEADLINES EXPECTED. HIGH PRESSURE MOVES OVERHEAD. WINDS AND SEAS WILL BE LESS THAN SMALL CRAFT ADVISORY THRESHOLDS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 2 AM EDT MONDAY FOR ANZ230-231-251. SMALL CRAFT ADVISORY UNTIL 9 AM EDT MONDAY FOR ANZ250-254. SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ255- 256. && $$ SYNOPSIS...BELK/DUNTEN NEAR TERM...BELK/DUNTEN SHORT TERM...DUNTEN LONG TERM...BELK AVIATION...BELK/DUNTEN MARINE...BELK/DUNTEN

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