Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 060736 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 336 AM EDT FRI MAY 6 2016 .SYNOPSIS...
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* UPDATES TO LONG TERM FORECAST PORTION ONLY... CLOUDY...DREARY AND COOL WEATHER CONTINUES THROUGH SATURDAY WITH PERIODS OF RAIN AS WAVES OF LOW PRESSURE TRACK SOUTH OF SOUTHERN NEW ENGLAND. 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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 2 AM UPDATE ... LOW PRES OVER GEORGES BANK EARLIER THIS EVENING AND ITS ASSOCIATED RAIN SHIELD IS NOW PULLING AWAY FROM NEW ENGLAND. THUS DRYING TREND HAS DEVELOPED. HOWEVER WATCHING NEW WARM MOIST CONVEYOR BELT FORMING OFF MD/DE AND NJ COAST IN RESPONSE TO CLOSED LOW OVER THE MID ATLC REGION. THIS MOIST AIRSTREAM WILL CIRCULATE NORTHWARD IN THE LARGE CYCLONIC FLOW ALONG THE EASTERN SEABOARD. THIS WILL RESULT IN RAIN OVERSPREADING WESTERN-CENTRAL CT TOWARD SUNRISE. OTHERWISE NNE WINDS CONTINUE TO SLOWLY SLACKEN AS PGRAD WEAKENS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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FRIDAY... A SECOND LOW PRESSURE SYSTEM WILL DEVELOP OFF OF DELMARVA BY DAYBREAK FRI AND WORK ITS WAY WESTWARD INTO NEW JERSEY DURING THE DAY. THIS KEEPS OUR REGION IN MOIST FLOW OFF THE OCEAN...BUT MORE OF AN EAST TO SOUTHEAST DIRECTION INSTEAD OF NORTHEAST. THIS WILL ALLOW TEMPERATURES TO MODERATE WITH HIGHS REACHING 55 TO 60 EXCEPT COOLER ON THE CAPE AND ISLANDS AND IMMEDIATE COAST OF CAPE ANN. IT WILL BECOME BREEZY ONCE AGAIN ACROSS EASTERN AND SOUTHERN PORTIONS OF THE AREA. WHILE IT COULD SHOWER AT ANY TIME...THE GREATEST CHANCE OF SHOWERS WILL BE OVER CT AND WESTERN MA FROM MID AFTERNOON INTO FRI EVENING. PROBABILITIES INCREASE TO LIKELY WEST OF THE CONNECTICUT RIVER IN BOTH MA AND CT BY LATE AFTERNOON. QPF AMOUNTS RANGE FROM LESS THAN A TENTH OF AN INCH ON THE GFS TO 0.3 TO 0.4 INCHES ON THE ECMWF AND NAM. FRIDAY NIGHT... A COLD POOL ALOFT WITH 500 MB TEMPERATURES OF -22C MOVES INTO WESTERN PORTIONS OF CT AND MA FRI EVENING. THIS CAUSES A FAIR AMOUNT OF INSTABILITY WITH TOTAL TOTALS INDICES REACHING 50-55...THE SHOWALTER INDEX BETWEEN 0 AND -2...AND EVEN THE LIFTED INDEX FROM 0 TO -1 IN THOSE AREAS. WILL CONTINUE WITH A CHANCE OF SHOWERS AND CANNOT EVEN RULE OUT AN ISOLATED THUNDERSTORM ANYWHERE ACROSS THE FORECAST AREA FRI NIGHT. LOWS WILL BE IN THE MID AND UPPER 40S. WE CANNOT RULE OUT POCKETS OF MINOR COASTAL FLOODING FRI NIGHT AGAIN...BUT THE THREAT IS LESS THAN TONIGHT. PLEASE SEE COASTAL FLOOD SECTION BELOW.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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*/ 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.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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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.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 430 PM UPDATE... TONIGHT...HAVE CONTINUED THE GALE WARNINGS FOR ALL COASTAL WATERS THIS EVENING BUT HAVE ENDED ALL GALES BY 09Z LATE TONIGHT. AT THAT TIME...THEY WILL NEED TO BE CONVERTED TO SMALL CRAFT ADVISORIES FOR AT LEAST THE OUTER WATERS. BUZZARDS BAY TOWER HAS INCREASED TO 39 KT GUSTS FROM 36 KT GUSTS EARLIER AND BOSTON LIGHT WAS GUSTING TO NEAR GALE AT 31 KT. MESOSCALE MODELS SHOW AN INCREASE IN WINDS THIS EVENING...THEN DIMINISHING AFTER 10 PM OR SO...HENCE THE REASON FOR KEEPING GALE WARNINGS POSTED EARLY TONIGHT. WAVES WILL BUILD TO 9 TO 11 FT OVER THE OUTER WATERS. VISIBILITIES WILL BE REDUCED TO 1 TO 3 MILES IN RAIN...DRIZZLE...AND AREAS OF FOG TONIGHT. FRIDAY...ANOTHER LOW PRESSURE SYSTEM WILL MOVE FROM OFF THE DELMARVA COAST TO NEW JERSEY. THIS WILL RESULT IN EAST WINDS INCREASING AS THE DAY PROGRESSES...PERHAPS TO 20-25 KT. THERE WILL ALSO BE RENEWED CHANCES OF SHOWERS...ESPECIALLY ALONG THE SOUTH COAST IN THE AFTERNOON. SEAS...MAINLY SWELLS...OF 6 TO 9 FT CONTINUING. FRIDAY NIGHT...CONTINUED CHANCES OF SHOWERS AND AN OUTSIDE CHANCE OF AN ISOLATED THUNDERSTORM TOWARD DAYBREAK. VISIBILITIES GREATLY REDUCED IN AREAS OF FOG AND DRIZZLE. WINDS TURNING BACK TO THE NORTHEAST BUT LESS THAN 20 KT. SEAS SLOWLY SUBSIDING TO 5-7 FT OVER THE OUTER WATERS. 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.
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&& .TIDES/COASTAL FLOODING... 1015 PM UPDATE... SURGE FORECAST FROM PREVIOUS SHIFT SPOT ON...RUNNING AROUND A FT OR JUST ABOVE. AT 1006 PM BOSTON WAS AT 12.45 FT WITH A SURGE OF 1.1 FT. EXPECTING BOSTON TO TOP OUT AROUND 13 FT. IN ADDITION WAVE ACTION RUNNING ABOUT 8 TO 11 FT JUST OFFSHORE. THIS COMBINATION OF ELEVATED WATER LEVELS AND WAVE ACTION SHOULD RESULT IN WIDESPREAD MINOR COASTAL FLOODING OF THE TYPICAL SHORELINE ROADS OF EASTERN MA. EARLIER DISCUSSION BELOW. =================================================================== COASTAL FLOOD ADVISORY REMAINS IN EFFECT FOR BOSTON SOUTH TO NANTUCKET INCLUDING PLYMOUTH COUNTY AND BOTH THE BAY AND OCEAN SIDES OF CAPE COD. HAVE EXTENDED THE COASTAL FLOOD ADVISORY TO ALSO INCLUDE THE ESSEX COUNTY COAST...BUT REALLY ONLY FOR SALISBURY TO CAPE ANN. THIS PROVIDES CONTINUITY WITH THE COASTAL FLOOD ADVISORY ISSUED FOR THE NH SEACOAST AND APPEARS WARRANTED GIVEN FETCH ACROSS THE GULF OF MAINE. ASTRO HIGH TIDE AT BOSTON IS 11.95 FT AT 1055 PM. HIGHER RESOLUTION MODELS INDICATE NE WINDS INCREASING A TAD THIS EVENING...NEAR MINIMAL GALE AT LEAST IN GUSTS ALONG THE MA E COAST WITH A REASONABLY SIZABLE FETCH ACROSS THE GULF OF MAINE. ANTICIPATE THE STORM SURGE TO RUN GENERALLY 1 TO 1.5 FT AT THE TIME OF THE EVENING HIGH TIDE. SEAS ACROSS IPSWICH BAY...MASS BAY AND OPEN AREA OF NORTHERN CAPE COD BAY EXPECTED TO BE MOSTLY 8 TO 10 FT. AT 4 PM GULF OF MAINE BUOY REPORTED 10 FOOT SEAS AND THOSE WILL LIKELY PROPAGATE CLOSER TO CAPE ANN AND INTO AT LEAST STELLWAGEN BANK AND PORTIONS OF MASS BAY THIS EVENING. SEAS OF 10 TO 12 FT EXPECTED EAST OF CAPE COD. THIS SETS UP THE LIKELIHOOD FOR MINOR COASTAL FLOODING ALONG THE MA E AND NE FACING SHORELINES FROM SALISBURY TO CAPE ANN...BOSTON TO PLYMOUTH TO DENNIS...ORLEANS AND CHATHAM...AND NANTUCKET HARBOR. INUNDATION WILL BE FROM A COMBINATION OF HIGH TOTAL WATER LEVEL AND WAVE SPLASHOVER. MINOR EROSION IS POSSIBLE BUT WOULD NEED GREATER WAVE ACTION FOR A MORE SERIOUS EROSION CONCERN. AT LEAST POCKETS OF MINOR COASTAL FLOODING ARE POSSIBLE FOR THE MA EAST COAST FOR THE FRIDAY LATE EVENING HIGH TIDE DUE TO AN EVEN HIGHER ASTRO TIDE AND A RESIDUAL SURGE. WEAK ONSHORE WINDS AND A LINGERING SWELL ARE EXPECTED TO KEEP A .5 TO 1.0 FOOT SURGE PERSISTING THROUGH THE FRIDAY EVENING HIGH TIDE. && .BOX WATCHES/WARNINGS/ADVISORIES...
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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.
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&& $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA/DOODY SHORT TERM...NOCERA/DOODY LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL TIDES/COASTAL FLOODING...WFO BOX STAFF

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