Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 231918 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 318 PM EDT THU OCT 23 2014 .SYNOPSIS...
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A POWERFUL EARLY SEASON COASTAL STORM WILL PASS SOUTHEAST OF NANTUCKET THIS EVENING. SHOWERS WILL PERSIST THROUGH TONIGHT BEFORE DIMINISHING FRIDAY...AS THE STORM SLOWLY PULLS AWAY FROM NEW ENGLAND. SHOWERS ARE POSSIBLE AGAIN SATURDAY NIGHT INTO SUNDAY...THEN DRY WEATHER RETURNS SUNDAY INTO EARLY NEXT WEEK. A COLD FRONT MAY BRING MORE RAIN LATE WEDNESDAY INTO THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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* CONDITIONS SLOWLY IMPROVE THROUGH TONIGHT * 315 PM UPDATE... REGIONAL RADAR MOSAIC SHOWS MAIN BAND OF HEAVY RAIN ASSOCIATED WITH MID LEVEL DEFORMATION ZONE HAS SHIFTED INTO EASTERN NY AND CENTRAL NEW ENGLAND...AND HAS BECOME FRAGMENTED AS IT OUTRUNS BETTER SUPPORT. IN ITS WAKE MORE SHOWERS WERE ROTATING WESTWARD ONTO COAST AROUND UPPER LOW WHICH WAS LOCATED S OF NEW ENGLAND. HIGH-RES MODELS HAVE A GOOD HANDLE ON THIS AND SHOW SOME POTENTIAL FOR THUNDER ACROSS EASTERN MA...ESPECIALLY AROUND CAPE COD AND ISLANDS WHERE THERE ARE A FEW HUNDRED J/KG OF ML/MUCAPE. SEEING PLENTY OF BREAKS IN CLOUDS ON SATELLITE SE OF NANTUCKET WITH BUILDING CLOUDS/ CONVECTION FARTHER SE...WHICH SHOULD CLIP SE NEW ENGLAND THIS EVENING. NOT LOOKING FOR ANY SEVERE WEATHER...BUT HIGHER CORES COULD PRODUCE STRONG WIND GUSTS AS WELL AS BRIEF DOWNPOURS. THIS ADDITIONAL RAINFALL MAY BE BRIEFLY HEAVY BUT WILL NOT LAST LONG AT A GIVEN LOCATION...SO THREAT OF RENEWED FLOODING REMAINS LOW. ACTIVITY WILL DIMINISH THIS EVENING AS LOW PASSES SE OF NEW ENGLAND. DECIDED TO TRIM BACK WIND ADVISORY AND ONLY INCLUDE E MA COAST THROUGH EARLY TONIGHT. STILL LOOKING FOR SECONDARY SURGE OF WINDS ON BACKSIDE OF SURFACE LOW...BUT MODELS KEEP AXIS OF STRONGEST WINDS CLOSER TO E MA COASTAL WATERS. DIRECTION IS MORE N/NW AS WELL WHICH TYPICALLY DOES NOT FAVOR INLAND AREAS UNLESS THERE IS STRONG COLD ADVECTION...WHICH WE DO NOT HAVE IN THIS CASE. STRONGEST WINDS ON COAST STILL LOOK TO OCCUR THROUGH 7 OR 8 PM. CYCLONIC FLOW AND LEFTOVER MOISTURE WILL KEEP CLOUDS LOCKED IN TONIGHT ALONG WITH FEW SHOWERS. LOWS WILL DROP BACK INTO 40S/50S.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... GRADUAL IMPROVEMENT FRI AS LOW SLOWLY PULLS TOWARD MARITIMES. MAY SEE FEW LEFTOVER SHOWERS ESPECIALLY THU MORNING AND CLOSER TO COAST. CROSS SECTIONS INDICATE LITTLE HOPE FOR SIGNIFICANT CLEARING UNTIL FRI NIGHT...SO CLOUDS WILL DOMINATE UNTIL THEN... ALTHOUGH SOME BREAKS OF SUN ARE CERTAINLY POSSIBLE IN WESTERN NEW ENGLAND. STAYED CLOSE TO BLEND OF MODEL GUIDANCE FOR TEMPS...WHICH GIVES HIGHS IN 50S THU AND BACK INTO 40S THU NIGHT. && .LONG TERM /SATURDAY THROUGH THURSDAY/...
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* CHANCE OF SHOWERS SATURDAY NIGHT INTO SUNDAY * DRIER WEATHER FOR MONDAY AND TUESDAY WITH HIGH PRESSURE AROUND * RAINY WEDNESDAY NIGHT INTO THURSDAY WITH A COLD FRONTAL PASSAGE OVERVIEW... THE PERIOD STARTS WITH AN UPPER LEVEL SUBTROPICAL HIGH AROUND ARIZONA AND TEXAS WITH TROUGHS FLANKING EITHER SIDE OF THE RIDGE IN THE CENTER OF THE COUNTRY. THE UPPER LEVEL LOW FROM TODAY EXITS THE REGION TO THE EAST ON SATURDAY GIVING WAY TO ANOTHER SHORTWAVE FOR SATURDAY NIGHT THAT MOVES WEST TO EAST...PASSING TO THE NORTH OF THE REGION. THE SUBTROPICAL HIGH MOVES EAST MONDAY AND BRINGS DRIER AIR INTO THE REGION ESPECIALLY ON TUESDAY. ON THE BACK END OF THE HIGH PRESSURE SYSTEM...SOUTHWEST WINDS PRECEDE ANOTHER COLD FRONT. DECENT AGREEMENT AMONGST THE MODELS THAT THE FRONT ARRIVES WEDNESDAY NIGHT INTO THURSDAY. THIS LOOKS TO HAVE GOOD WIND DYNAMICS AND ABOVE NORMAL PWATS FOR GOOD MOISTURE TRANSFER. DURING THIS PERIOD...ENSEMBLES ARE HINTING AT THE AO BECOMING MORE AND MORE POSITIVE WHICH WOULD ALSO IMPLY AT GOOD MOISTURE TRANSPORT TO THE NORTHEAST US. DAILIES... SATURDAY...CLOUDINESS AND MOISTURE FROM THE UPPER LEVEL LOW LEAVES THE REGION AND WEAK RIDGING ARRIVES SO WE CAN EXPECT DRYING ON NORTHWEST WINDS. TOWARDS THE EVENING AND INTO SUNDAY...A SHORTWAVE ARRIVES FROM CENTRAL CANADA THAT SCOOTS WEST TO EAST JUST NORTH OF THE REGION. THE COLD FRONT LOOKS WASHED OUT SO ONLY WEAK SCATTERED SHOWERS ARE POSSIBLE. DECENT SHEAR EXISTS AND WIND GUSTS COULD BE AROUND 30 KTS ESPECIALLY AS SHOWERS MIX THE 30 TO 35 KT 925 MB WINDS TO THE SURFACE. THE MID LEVEL LAPSE RATES ARE AROUND 7C/KM ESPECIALLY UP IN NORTHERN NEW ENGLAND AS THE COLD POOL ALOFT ARRIVES...BUT CAPE IS LOW SO THE THUNDER RISK IS LOW ENOUGH TO NOT BE INCLUDED IN THE FORECAST AT THIS TIME. SUNDAY AFTERNOON DRIES OUT ON THE ENCROACHING NORTHWEST WINDS AND RISING HEIGHTS. WINDS ARE GUSTY STILL AS 30 KT WINDS ARE ABLE TO MIX TO THE SURFACE. MONDAY AND TUESDAY...THE MID LEVEL RIDGE MOVES EAST AND IMPACTS THE REGION. MONDAY LOOKS COLDER...MORE CLOUDY AND BREEZY THAN TUESDAY. MONDAY/S HIGHS SHOULD BE IN THE UPPER 50S AND TUESDAY/S HIGH SHOULD BE IN THE LOW 60S. WEDNESDAY AND THURSDAY...THE WEST COAST TROUGH WILL ARRIVE IN OUR AREA WITH AN ASSOCIATED COLD FRONT. THIS COLD FRONT HAS PWATS FROM 1.25 TO 1.5 INCHES WHICH IS 2 STANDARD DEVIATIONS ABOVE NORMAL WITH A STRONG LOW LEVEL JET FOR GOOD MOISTURE TRANSPORT ALONG WITH UPPER LEVEL DIVERGENCE AROUND SO PRECIPITATION AMOUNTS SHOULD BE WATCHED. SHOWALTER AND LIFTED INDICES ARE POSITIVE AND CAPE IS VERY LOW SO THUNDER REMAINS TO BE SEEN AT THIS POINT. HOWEVER THE K-INDEX AND TOTAL TOTALS INDEX ARE WHERE YOU WANT THEM TO BE FOR THUNDER. IT IS ALSO INTERESTING THAT THE ECMWF HAS A NEGATIVELY TILTED TROUGH EARLY THURSDAY MORNING WHILE THE GFS KEEPS IT POSITIVELY THE WHOLE TIME WITH THE CUTOFF LOW FARTHER SOUTH IN SOUTHEAST CANADA. NEGATIVELY TILTED TROUGHS ARE HELPED ALONG BY STRONGER WINDS ON THE WESTERN SIDE OF THE TROUGH...HOWEVER THE ECMWF HAS STRONGER UPPER LEVEL WINDS ON THE EASTERN SIDE WHICH WOULD MEAN A MORE POSITIVELY TILTED TROUGH. THIS IS ALSO THE FIRST IN THE ECMWF/S MODEL RUNS THAT DOES THIS. THIS TIMEFRAME IS STILL VERY FAR OUT AND WILL NEED FURTHER IRONING BEFORE DETAILS ARE SMOOTHED OUT.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THU NIGHT/...MODERATE CONFIDENCE. NOT MUCH CHANGE IN CONDITIONS THROUGH EARLY TONIGHT WITH MVFR/IFR CIGS...ALTHOUGH VFR CIGS MORE LIKELY AROUND CAPE COD AND ISLANDS AND POINTS OFFSHORE. SHOULD SEE RETURN TO IFR CIGS NEAR COAST TONIGHT WITH MVFR CIGS FARTHER INLAND. SCATTERED SHOWERS/ISOLATED THUNDER MAINLY AROUND CAPE COD AND ISLANDS WITH MVFR CIGS/VSBYS. GUSTY N/NW WINDS TO 35KT ESPECIALLY NEAR COAST THROUGH 00Z. SLOW IMPROVEMENT THU WITH MVFR/IFR CIGS IN MORNING GIVING WAY TO VFR CIGS BY AFTERNOON FROM W TO E. VFR THU NIGHT AS CLEARING WORKS INTO NEW ENGLAND. KBOS...MODERATE CONFIDENCE IN TAF. LOWER-END MVFR CIGS MOST LIKELY THROUGH THIS EVENING BEFORE CIGS DROP TO IFR TONIGHT. KBDL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY THROUGH TUESDAY...MODERATE CONFIDENCE. VFR. LOW PROBABILITY OF SCATTERED SHOWERS LATE SATURDAY.
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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. SHORT TERM /THROUGH FRIDAY NIGHT/... * CONDITIONS GRADUALLY IMPROVE * COASTAL STORM PASSES SE OF NANTUCKET THIS EVENING AND TO MARITIMES THU AND THU NIGHT. THIS WILL BRING GRADUALLY DIMINISHING WINDS AND ESPECIALLY SEAS...WHICH WILL TAKE A COUPLE OF DAYS TO SUBSIDE. MAINTAINED GALE WARNINGS ON MOST WATERS THROUGH TONIGHT AS WE EXPECT ANOTHER SURGE OF N GALES LATER THIS AFTERNOON AND EVENING...BEFORE WINDS DIMINISH TONIGHT AND THU. SCATTERED SHOWERS AND ISOLATED STORMS THROUGH THIS EVENING... ESPECIALLY AROUND CAPE COD AND ISLANDS. OTHERWISE FEW LEFTOVER SHOWERS THU MORNING. OUTLOOK...SATURDAY THROUGH MONDAY... SATURDAY AND SUNDAY...MODERATE CONFIDENCE...AFTER A BRIEF LULL...SEAS AND WINDS WILL INCREASE AHEAD OF A COLD FRONT. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED FOR AT LEAST A PORTION OF THE WATERS AS THE WINDS RISE ABOVE 25 KTS AND THE SEAS HAVE 5-8 FT SWELLS. MONDAY...MODERATE CONFIDENCE...WINDS AND SEAS DIMINISH AS HIGH PRESSURE BUILDS OVER THE WATERS. TUESDAY...MODERATE CONFIDENCE...WINDS AND SEAS BELOW SCA THRESHOLD AS HIGH PRESSURE IS STILL OVER THE REGION.
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&& .HYDROLOGY...
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STILL HAVE A FEW FLOOD WARNINGS POSTED...PRIMARILY FOR RESIDUAL FLOODING NOW THAT MOST SMALLER RIVERS AND STREAMS HAVE CRESTED. LARGER MAINSTEM RIVERS EXPECTED TO REMAIN WITHIN THEIR BANKS. SIGNIFICANT URBAN FLOODING THAT AFFECTED PEABODY MA WILL GRADUALLY EASE THROUGH EARLY TONIGHT...DESPITE ADDITIONAL SHOWERS MOVING THROUGH.
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&& .TIDES/COASTAL FLOODING...
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NEXT HIGH TIDE ALONG E MA COAST IS AROUND MIDNIGHT. DUE TO WINDS BEING MORE NORTHERLY AS OPPOSED TO ONSHORE...IMPACT WILL BE MUCH LESS THAN PREVIOUS HIGH TIDE CYCLES. SURGE BETWEEN 0.5 AND 1.0 FT IS EXPECTED...ESPECIALLY ALONG N SHORE OF CAPE COD ON CAPE COD BAY...BUT WE ARE ONLY ANTICIPATING SOME SPLASHOVER AND MINOR BEACH EROSION AT THIS TIME. DO NOT BELIEVE IT WILL REACH AN ADVISORY LEVEL.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...WIND ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MAZ007-014>016- 019. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT FRIDAY FOR ANZ231>234. GALE WARNING UNTIL 11 PM EDT THIS EVENING FOR ANZ230-250-251- 256. SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ236. GALE WARNING UNTIL 10 PM EDT THIS EVENING FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ254-255.
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&& $$ SYNOPSIS...JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...HR/FIELD AVIATION...JWD/HR/FIELD MARINE...JWD/HR/FIELD HYDROLOGY...JWD/FRANK TIDES/COASTAL FLOODING...JWD

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