Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 060811 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 411 AM EDT FRI MAY 6 2016 .SYNOPSIS... CLOUDY...DREARY AND COOL WEATHER CONTINUES TODAY WITH RAIN REDEVELOPING ACROSS MUCH OF THE AREA LATER THIS MORNING AND AFTERNOON...AS LOW PRESSURE TRACKS FROM THE MID ATLANTIC TO NJ. DESPITE SCATTERED SHOWERS THIS WEEKEND THERE WILL BE MANY HOURS OF DRY WEATHER ALONG WITH MODERATING TEMPERATURES. ALL OF THIS MOVING OUT SUNDAY AHEAD OF A SWEEPING COLD FRONT BEHIND WHICH COOL TEMPERATURES FOLLOW WITH BREEZY W/NW WINDS. SEE- SAW OF DRY WEATHER FOLLOWED BY QUICK BOUTS OF WET WEATHER NEXT WEEK WITH NEAR OR BELOW SEASONABLE TEMPERATURES. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 4 AM UPDATE ... WATCHING AN AREA OF RAIN AT 4 AM ACROSS LONG ISLAND...NYC/LOWER HUDSON VALLEY OF NY AND SOUTHWARD INTO NJ. THIS AREA OF RAIN IS ASSOCIATED WITH A CLOSED LOW OVER THE MID ATLC STATES AND AN IMPRESSIVE SHORT WAVE/PVA ANOMALY PIVOTING NORTHWARD UP THE COAST. THIS AREA OF MOISTURE AND LIFT WILL OVERSPREAD CT THIS MORNING AND THEN ACROSS RI AND WESTERN-CENTRAL MA THIS AFTERNOON. GIVEN THIS TRAJECTORY DRY WEATHER MAY LINGER ACROSS EASTERN MA MUCH OF THE DAY. COOLING TEMPS ALOFT WITH THIS UPPER LEVEL FEATURE MAY RESULT IN ISOLATED ELEVATED CONVECTION TODAY ACROSS CT AND POSSIBLY INTO RI AND WESTERN-CENTRAL MA. PWATS AOA 1.0 INCH TODAY ACROSS MUCH OF THE AREA...SO GIVEN MODEST FORCING...MARGINAL INSTABILITY AND DEEP LAYER MOISTURE A FEW DOWNPOURS ARE POSSIBLE...HIGHEST RISK ACROSS CT AND POSSIBLY INTO RI AND WESTERN-CENTRAL MA. LIGHTER WINDS TODAY THAN YESTERDAY AND LAST NIGHT...HOWEVER FLOW REMAINS ONSHORE. THIS COMBINED WITH OVERCAST CONDITIONS AND RAIN REDEVELOPING ACROSS MUCH OF THE AREA EXPECT ANOTHER UNSEASONABLY COOL DAY. TEMPS MAINLY IN THE 50S /EXCEPT U40S ALONG IMMEDIATE COAST/ EXCEPT POSSIBLY LOW 60S NORTHWEST MA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... TONIGHT ... GREATEST RISK OF SHOWERS APPEARS TO BE EARLY IN THE EVENING BEFORE SHORT WAVE/PV ANOMALY LIFTS NORTHWEST OF THE REGION. HIGHEST POPS ACROSS CT INTO WESTERN MA WHERE DEEPEST MOISTURE AND LIFT TRACK. COLD TEMPS ALOFT COMBINED WITH STRONG DEEP LAYER SHEAR WILL SUPPORT POTENTIAL FOR A FEW T-STORMS ACROSS CT AND WESTERN-CENTRAL MA. STILL A RISK OF A FEW SHOWERS FARTHER EAST INTO RI AND EASTERN MA. FOR THE REMAINDER OF THE NIGHT SHOWERS EXIST GIVEN DEEP MOIST CYCLONIC FLOW PERSIST ACROSS THE AREA IN RESPONSE TO VERTICALLY STACKED LOW SETTING UP OVER EASTERN PA. AS THE NIGHT PROGRESSES AREAS OF FOG AND DRIZZLE MAY DEVELOP AS WELL. SATURDAY ... VERTICALLY STACKED LOW OVER EASTERN PA BECOMES AN OPEN WAVE AND MOVES ACROSS THE AREA. THUS CYCLONIC FLOW CONTINUING ACROSS THE MAY YIELD ISOLATED TO WIDELY SCATTERED SHOWERS. IN ADDITION MID LEVELS DRY OUT A BIT AND RESULT IN MID LEVEL LAPSE RATES ON THE ORDER OF 7C/KM. DILEMMA HERE IS ARE MID LEVELS TOO DRY TO SUPPORT CONVECTION? IF ANY SHOWERS CAN DEVELOP -21C TEMPS AT H5 COMBINED WITH DEEP LAYER SHEAR WILL SUPPORT THE POTENTIAL FOR A FEW T-STORMS. OTHERWISE MANY HOURS OF DRY WEATHER SAT AND POSSIBLY BREAKS OF SUNSHINE IN THE AFTERNOON ACROSS CT/RI AND SOUTHEAST MA. THIS MAY PUSH TEMPS INTO THE L60S IN THIS REGION...WITH 50S ELSEWHERE. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... */ HIGHLIGHTS... - RAIN LIKELY SUNDAY MORNING AHEAD OF A SWEEPING COLD FRONT - COOLER AND BREEZY SUNDAY AFTERNOON AND AGAIN MONDAY - SEE-SAW PATTERN OF WET AND DRY WEATHER MID TO LATE WEEK */ DISCUSSION... CONTINUING AN ENSEMBLE FORECAST APPROACH WITH A BROAD VIEW TOWARDS MID-UPPER LEVEL FLOW. N-STREAM PACIFIC / POLAR ENERGY KICKS OUT THE DYING REMNANTS OF THE CLOSED LOW OVER THE DELMARVA. THE SUBSEQUENT CONCLUSION OF THE BLOCKY PATTERN ALLOWS WEATHER SYSTEMS TO SHIFT E AS EVIDENT IN THE SHORT-LIVED NEGATIVE PACIFIC NORTH AMERICAN /PNA/ PATTERN. HEREAFTER FORECAST SOLUTIONS IN AGREEMENT OF PNA RETURNING POSITIVE WITH A STRONGLY NEGATIVE EAST PACIFIC OSCILLATION /EPO/ AND NEAR NEUTRAL AO/NAO TRENDS. SO WITH CERTAINTY RIDGING EXTENDS ACROSS THE NW PACIFIC / W COASTAL N AMERICA YIELDING A FAVORABLE TROUGHING ENVIRONMENT OVER THE N-CENTRAL CONUS WITH PREVALENT RIDGING E. BUT NOT ABSOLUTELY CONFIDENT ON DOWNSTREAM OUTCOMES. DOES APPEAR THAT A PROGRESSIVE FLOW PATTERN EVOLVES E OF N-CENTRAL CONUS TROUGHING CONSIDERING THE NEAR NEUTRAL AO/NAO TREND AND AS THE N ATLANTIC RIDGE DEAMPLIFIES. A STRONG -EPO SIGNAL...FAVOR ENSEMBLE MEANS MAINTAINING TROUGHING OVER THE N-CENTRAL CONUS WITH RIDGING E. TAKING THESE TWO POINTS TOGETHER ALONG WITH N-STREAM INFLUENCES AND INHERENT UNCERTAINTIES...BELIEVE EITHER A CONFLUENT MID-UPPER LEVEL FLOW OR RIDGING PATTERN PREVAILS ACROSS THE NE-CONUS THROUGH WHICH ANY ENERGY FROM THE N-CENTRAL CONUS SLIPPING E UNDERGOES STRETCHING AND WEAKENING BUT STILL RESULTS IN POTENTIAL WET WEATHER OUTCOMES. DO NOT FAVOR THE QUICKNESS OF DETERMINISTIC SOLUTIONS IN A PATTERN BREAKDOWN FURTHER OUT IN TIME SHIFTING IT FURTHER E. SO HIGH CONFIDENCE DREARY DRIZZLY CONDITIONS EMERGE SATURDAY NIGHT BENEATH WEAK RIDGING AHEAD OF N-STREAM ENERGY AND TRAILING COLD FRONT SWEEPING NEW ENGLAND SUNDAY MORNING. LIKELY POPS WITH STRONG LOW-MID LEVEL FORCING OF A FAIRLY MOIST COLUMN UP TO H6. DECENT PRESSURE COUPLING. BREEZY S WINDS BUT STRONGER W/NW FLOW IMMEDIATELY BEHIND THE COLD FRONT AS A COLD POOL DROPS S AND DAYTIME CLEARING / HEATING ALLOWS LAPSE RATES TO STEEPEN UP TO H8 ALLOWING THE MIX-DOWN OF FASTER MOMENTUM AND DRIER AIR. QUIET-DRY OVERNIGHT AS SCATTERED TO BROKEN MID LEVEL CLOUD DECKS WRAP ACROSS THE AREA WITHIN THE CYCLONIC FLOW. BELOW AVERAGE TEMPERATURE TREND. INTO THE WEEK LESSER CONFIDENCE WITH CHALLENGES IN FORECAST MODELS IN HANDLING THE MORPHOLOGY OF INDIVIDUAL WAVES FROM THE W AND ANY N- STREAM INFLUENCES. LOOKING AT A SEE-SAW OF WEATHER OUTCOMES. BRIEF PERIODS OF DRY WEATHER ARE FOLLOWED BY WEAK OVER-RUNNING RAINFALL EVENTS THAT YIELD LIGHT TO MODERATE RAIN OUTCOMES AROUND A QUARTER OF AN INCH. ENSEMBLE WEIGHTING THAT LOOKS OVERALL MARGINAL. NOTHING APPEARING ROBUST NOR A SOAKER. TEMPERATURES NEAR OR BELOW SEASONABLE WILL FOLLOW CLOSE TO ENSEMBLE MEANS / PROBABILITY PREDICTIONS. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 2 AM UPDATE... SHORT TERM /THROUGH SATURDAY/... THRU 12Z ... HIGH CONFIDENCE. MVFR ACROSS CT INTO WESTERN MA WILL CONTINUE WITH IFR PERSISTING OVER RI AND EASTERN/CENTRAL MA. MAINLY DRY BUT CAN/T RULE OUT SPOTTY LIGHT RAIN/DRIZZLE AT TIMES. AFTER 12Z ... MODERATE CONFIDENCE. MVFR WITH IFR SOUTH COAST INCLUDING CAPE COD AND ISLANDS MAY LIFT TO MVFR ALL TERMINALS. HOWEVER RAIN ALONG AND OFF THE NJ COAST WILL PIVOT NORTHWARD INTO CT AND POSSIBLY RI AND WESTERN-CENTRAL MA THIS AFTERNOON. ISOLATED ELEVATED T-STORM POSSIBLE. DRY WEATHER MAY LINGER MUCH OF THE DAY ACROSS EASTERN AND NORTHEASTERN MA. TONIGHT ... MODERATE TO LOW CONFIDENCE. MVFR TO START BUT LOWERING TO IFR. UNCERTAIN HOW WIDESPREAD RAIN AND OR DRIZZLE WILL BE SAT NIGHT. ISOLATED ELEVATED T-STORM POSSIBLE TOO. SATURDAY ... MODERATE CONFIDENCE. IFR TO START IN PATCHY DRIZZLE/FOG THEN LIFTING OT MVFR DURING THE AFTERNOON AND POSSIBLY VFR LATE ACROSS CT/RI AND SOUTHEAST MA. HOWEVER ANY SUNSHINE WILL FUEL SCATTERED SHOWERS AND ISOLATED T-STORM TO FORM. KBOS TERMINAL ... MVFR THIS MORNING MAY IMPROVE TO MARGINAL VFR- MVFR THIS AFTERNOON. MAINLY DRY WEATHER BUT RISK OF SHOWERS AND ISOLATED ELEVATED T-STORM THIS AFTERNOON...HIGHER RISK ACROSS CT/RI AND WESTERN-CENTRAL MA. KBDL TERMINAL ... MVFR AND MAINLY DRY EARLY BUT THEN SHOWERS LIKELY FROM LATE MORNING INTO THE AFTERNOON ALONG WITH ISOLATED T-STORM. OUTLOOK /SATURDAY NIGHT - TUESDAY NIGHT/...MODERATE CONFIDENCE. VFR TO BEGIN LOWERING TO IFR TOWARDS SUNDAY MORNING WITH -RA AHEAD OF A SWEEPING COLD FRONT. BEHIND THIS CONDITIONS QUICKLY IMPROVE VFR WHILE W/NW WINDS IMMEDIATELY GUST AROUND 25 TO 35 KTS MIDDAY SUNDAY INTO EVENING. A LULL OVERNIGHT SUNDAY...VFR AND BREEZY W/NW WINDS CONTINUE MONDAY AND TUESDAY. CIGS LOWER AND CONDITIONS DETERIORATE AS -RA MOVES BACK IN TUESDAY NIGHT INTO WEDNESDAY MORNING. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 4 AM UPDATE... TODAY ... SCA FOR NNE WINDS BECOMING EAST THIS AFTERNOON. ROUGH SEAS FOR THE OCEAN WATERS GIVEN THE LONG WIND FETCH. RAIN LIKELY RI WATERS LATE MORNING INTO THE AFTERNOON. TONIGHT ... MODEST EAST WIND BUT NE SWELLS PERSIST ACROSS THE OCEAN WATERS. VSBY LOWERING IN AREAS OF DRIZZLE/FOG AND SCATTERED SHOWERS. SAT ... WINDS BECOMING SSW WHICH WILL RESULT IN IMPROVED VSBYS. LOW RISK OF SCATTERED SHOWERS WITH ISOLATED T-STORM POSSIBLE. OUTLOOK /SATURDAY NIGHT - TUESDAY NIGHT/...MODERATE CONFIDENCE. 5 TO 6 FOOT WAVES AND S FLOW LINGER SATURDAY NIGHT AHEAD OF A COLD FRONT SWEEPING THE WATERS DURING THE EARLY HALF SUNDAY. MAIN CONCERN IS BEHIND THE FRONT WITH W/NW GALES CONTINUING INTO MONDAY. ACTIVITY DIMINISHES MONDAY NIGHT INTO TUESDAY PRIOR TO ANOTHER WET WEATHER SYSTEM AND THE RETURN OF S FLOW TUESDAY NIGHT INTO WEDNESDAY MORN. && .TIDES/COASTAL FLOODING... 4 AM UPDATE... VERY HIGH ASTRO TIDES TONIGHT /AROUND MIDNIGHT/ WITH BOSTON 12.3 FT AT 1146 PM. MODEST ONSHORE WINDS AND SURFACE PRES ONLY AROUND 1010MB SHOULD RESULT IN SURGE AROUND 0.5 FT. THAT/S SUFFICIENT FOR A MODERATE TO HIGH RISK OF MINOR COASTAL FLOODING ENTIRE EASTERN MA COASTLINE. THUS A COASTAL FLOOD ADVISORY HAS BEEN POSTED FOR THE ENTIRE EASTERN MA COASTLINE FROM 10 PM TONIGHT THRU 2 AM SATURDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 2 AM EDT SATURDAY FOR MAZ007-015-016-019-022-024. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ231>235-237-250-251. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ254>256. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL TIDES/COASTAL FLOODING...NOCERA

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