Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 031048 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 648 AM EDT TUE MAY 3 2016 .SYNOPSIS... RAIN RE-DEVELOPS EARLY THIS MORNING AS LOW PRESSURE TRACKS SOUTH OF NEW ENGLAND. RAIN TAPERS OFF THIS AFTERNOON FROM WEST TO EAST BUT IT WILL REMAIN RATHER CLOUDY AND COOL. AN UNSETTLED AND COOL PATTERN CONTINUES THROUGH THE REMAINDER OF THE WEEK BENEATH A CLOSED LOW...CLEARING OUT OVER THE WEEKEND AS A COLD FRONT SWEEPS THE REGION. DRY AND MILD WEATHER MAY RETURN INTO NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 7 AM UPDATE... NOT MANY CHANGES TO THE GOING FORECAST ONLY TO REFLECT THE ONGOING TRENDS. AS NOTED IN THE DISCUSSION BELOW...AN OVER-RUNNING SETUP PRESENTLY THAT EVOLVES INTO A POTENTIAL HEAVY RAIN EVENT ALONG THE S COAST AS LOW TO MID LEVEL FORCING EVOLVES AS A MODEST POCKET OF FRONTOGENESIS BENEATH THE RIGHT-REAR QUADRANT OF THE UPPER LEVEL JET. STRONG LIFT WITH POTENTIAL INSTABILITY...CAN NOT DISAGREE WITH THE PRIOR FORECAST OF HEAVY RAIN POTENTIAL ALONG THE S COAST WHICH WOULD LIKELY BRING ABOUT VISIBILITY RESTRICTIONS AND PERHAPS SOME NUISANCE FLOODING ISSUES. FOCUS THIS MORNING INTO MIDDAY WITH RAIN TAPERING OFF THEREAFTER. */ HIGHLIGHTS... * A PERIOD OF STEADY RAIN THIS MORNING POSSIBLY HEAVY AT TIMES ALONG THE SOUTH COAST */ DISCUSSION... FRONTAL WAVE OVER THE MID ATLC REGION THIS MORNING WILL TRACK ENE TODAY IN THE DEEP SW FLOW ALOFT ALONG THE E SEABOARD. WITHIN THIS AIRSTREAM COPIOUS AMOUNTS OF MOISTURE AVAILABLE AS PWATS OF UP TO 1.5 INCHES CURRENTLY STREAMING NE ACROSS DE INTO S NJ. THIS DEEP LAYER MOISTURE WILL BE OVERSPREADING A FAIRLY BAROCLINIC ENVIRONMENT WITH GOOD THERMAL PACKING ACROSS S NEW ENGLAND. THIS WILL RESULT IN A LARGE RAIN SHIELD CONTINUING TO OVERSPREAD THE REGION THIS MORNING. AS FRONTAL WAVE TRACKS S OF NEW ENGLAND LATER THIS MORNING MODELS SUGGEST INCREASING LOW LEVEL FRONTOGENESIS ACROSS THE S COAST OF MA AND RI. NOT VERY MAY-ISH BUT MORE LIKE A LATE WINTER/EARLY SPRING SYSTEM. SOME ELEVATED INSTABILITY TOO SO ISOLATED THUNDER POSSIBLE BUT THE GREATER IMPACT WILL BE THIS INSTABILITY TO ENHANCE THE RISK FOR BANDS OF MODERATE TO HEAVY RAIN ESPECIALLY ALONG THE S COAST OF MA AND RI 09Z TO 15Z FROM W TO E. MAIN IMPACTS HERE WOULD BE CONFINED TO MINOR LOCAL URBAN/POOR DRAINAGE FLOODING. ELSEWHERE EXPECTING LESS RAINFALL NORTH OF THE MASS PIKE TOWARD THE MA/NH BORDER. OTHERWISE SYSTEM IS FAIRLY PROGRESSIVE WITH RAIN TAPERING OFF THIS AFTERNOON FROM W TO E. LOW CLOUDS LIKELY PERSIST GIVEN WEAK RIDGING BUILDS DOWN FROM THE NORTHEAST. THIS SUBSIDENCE INVERSION COMBINED WITH LOW MOISTURE TRAPPED MAY YIELD SPOTTY LIGHT DRIZZLE LATER IN THE DAY. ANOTHER COOL DAY AHEAD GIVEN THE RAIN AND LIGHT ONSHORE WINDS. THIS WILL ONLY YIELD HIGHS IN THE U40S TO L50S...ABOUT 10-15 DEGS COOLER THAN NORMAL. THE COOLER 2 METER TEMPS SEEM MORE REASONABLE COMPARED TO THE MILDER MOS HIGHS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... UPDATED 330 AM ... TONIGHT ... COLUMN BEGINS TO DRY FROM TOP DOWN AS SUBSIDENCE INCREASES BEHIND DEPARTING FRONTAL WAVE. HOWEVER NOT EXPECTING SKIES TO CLEAR MUCH IF ANY GIVEN LOTS OF LOW LEVEL MOISTURE TRAPPED BENEATH SUBSIDENCE INVERSION. IN FACT THIS MAY YIELD PATCHY DRIZZLE/MIST OVERNIGHT. WEDNESDAY ... LONG WAVE TROUGH SHARPENS AS NORTHERN STREAM JET ENERGY DIVING SOUTHWARD FROM ONTARIO THRU THE GREAT LAKES FORMS A CLOSED LOW OVER THE OH VALLEY LATE IN THE DAY. THIS BACKS THE UPPER LEVEL FLOW ALONG THE EASTERN SEABOARD WITH A NEW FRONTAL WAVE AND PLUME OF MOISTURE SURGING NORTHWARD INTO SOUTHERN NEW ENGLAND BY DAYS END. SO THE WEATHER THEME FOR WED WILL BE A MAINLY DRY START /OTHER THAN MORNING MIST-DRIZZLE/ FOLLOWED BY INCREASING THREAT FOR RAIN ESPECIALLY LATE IN THE DAY FROM SOUTH TO NORTH. ANOTHER COOLER THAN NORMAL DAY WITH SURFACE RIDGE WEDGED FROM THE MARITIMES INTO NEW ENGLAND ALONG WITH CLOUDY SKIES AND LIGHT ONSHORE WINDS. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... */ HIGHLIGHTS... - AN UNSETTLED AND COOL PATTERN THROUGH WEEKS END - POTENTIALLY CLEARING OUT OVER THE WEEKEND IN WAKE OF A COLD FRONT - THE POTENTIAL NEXT WEEK FOR A MORE TYPICAL PATTERN FOR MAY */ DISCUSSION... A COOL UNSETTLED WEATHER PATTERN SETTING UP THROUGH EARLY NEXT WEEK GIVEN THE BLOCKY PATTERN. ENSEMBLE FORECAST APPROACH PREFERRED GIVEN ANOMALOUS SETUP OF 3 TO 4 STANDARD DEVIATIONS BELOW-AVERAGE ATYPICAL FOR MAY. THIS PARENT WITH A DEEP TROUGH W EVOLVING INTO A CLOSED CUT- OFF LOW BY WEEKS END PRIOR TO N-STREAM KICKER OVER THE WEEKEND. LOTS OF ENERGY WITHIN THE OVERALL PATTERN DRAWING AND FORCING MOISTURE N AS COOLER AIR IS ISENTROPICALLY DRAWN S. DAMP AND DREARY GIVEN THE LIKELIHOOD A MAJORITY OF THE FORECAST PERIOD WILL BE SOCKED IN BY CLOUDS AND POSSIBLY FOG/DRIZZLE GIVEN DOMINANT N/NE ONSHORE FLOW. MAYBE A BRIEF BREAK PRIOR TO THE N-STREAM KICKER AND ATTENDANT COLD FRONT CENTERED AROUND SUNDAY. CHANCE TO LIKELY POPS THROUGHOUT. FOR NEXT WEEK A MORE AVERAGE AND DRIER WEATHER PATTERN POSSIBLY SETS UP WITH DOMINANT W/SW FLOW MORE TYPICAL FOR THE MONTH OF MAY. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 12Z UPDATE... SHORT TERM /THROUGH WEDNESDAY/...MODERATE CONFIDENCE. TODAY... TOUGH FORECAST. -RA OVERALL...WITH POSSIBLE RA/+RA ALONG THE S COAST THIS MORNING TOWARDS MIDDAY. A WOBBLING OF CONDITIONS RANGING FROM LOW-END VFR DOWN TO LIFR. EVALUATING UPSTREAM AND CONSIDERING FORECAST TRENDS...LOW CONDITIONS OVER ALL S NEW ENGLAND TERMINALS THIS MORNING. GRADUAL IMPROVING TREND NW TO SE BUT IT IS LIKELY THAT THE S TERMINALS ESPECIALLY CLOSE TO THE COAST WILL BE SOCKED IN WITH LOW CLOUDS MUCH OF TODAY. -DZ / BR LINGERING FOR THOSE LOCALES. TONIGHT... IFR AND MVFR WITH IFR LIKELY OVER SOUTHEAST MA AND THE HIGHER TERRAIN. MVFR ELSEWHERE. SPOTTY DRIZZLE/MIST POSSIBLE IN IFR AREAS. OTHERWISE MAINLY DRY. FORECAST CONFIDENCE HIGH ON TRENDS BUT LOWER ON EXACT DETAILS. WEDNESDAY... IFR LIKELY SOUTHEAST MA WITH MVFR ELSEWHERE. MAINLY DRY EARLY WITH JUST SPOTTY MIST/DRIZZLE. RAIN REDEVELOPS LATE IN THE DAY FROM SOUTH TO NORTH. LIGHT ENE WINDS. FORECAST CONFIDENCE HIGH ON TRENDS BUT LOWER ON EXACT DETAILS. KBOS TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF. BULK OF HEAVY RAIN TODAY SHOULD SLIDE SOUTH OF LOGAN. KBDL TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF. HEAVIEST RAIN TODAY IS FROM 09Z TO 15Z THEN TAPERING OFF. OUTLOOK /WEDNESDAY NIGHT - SATURDAY NIGHT/...MODERATE CONFIDENCE. MVFR TO LIFR MIX ESPECIALLY WITH -RA. WORST CONDITIONS POISED E/S ALONG THE COASTS. DOMINANT E/NE FLOW. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE. 7 AM UPDATE...NO MAJOR CHANGES TO THE FORECAST. LIGHT TO MODEST ENE WINDS TODAY THRU WED. PERIOD OF STEADY RAIN THIS MORNING...HEAVY AT TIMES THEN TAPERING OFF THIS AFTERNOON. MIST/DRIZZLE AND FOG TONIGHT INTO WED MORNING. THEN ANOTHER WEAK FRONTAL WAVE SOUTH OF NEW ENGLAND BRINGS ANOTHER ROUND OF RAIN LATE WED. OUTLOOK /WEDNESDAY NIGHT - SATURDAY NIGHT/...MODERATE CONFIDENCE. PERSISTENT E/NE FLOW THOUGH REMAINING BELOW 20 KTS WITH AREAS OF LOW PRESSURE DEVELOPING NE ACROSS THE WATERS AT THE BEGINNING OF THE PERIOD AND AGAIN FRIDAY INTO FRIDAY NIGHT. WAVES BUILDING 5 TO 7 FEET REQUIRING SMALL CRAFTS FOR HAZARDOUS SEAS. CONFIDENCE ON THE OUTER WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL

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