Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230609 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 209 AM EDT THU OCT 23 2014 .SYNOPSIS...
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A POWERFUL EARLY SEASON COASTAL STORM WILL BRING STRONG TO DAMAGING WINDS ALONG WITH LOCALLY VERY HEAVY RAINFALL IN SQUALLS AND ISOLATED THUNDERSTORMS INTO THURSDAY MORNING...THEN LESSENING THURSDAY AFTERNOON. SHOWERS WILL LINGER FRIDAY AS THE STORM SLOWLY PULLS AWAY FROM NEW ENGLAND. SHOWERS POSSIBLE AGAIN SATURDAY AS LOW PRES MOVES INTO SOUTHERN QUEBEC. DRY...SEASONABLE WEATHER RETURNS EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH TODAY/...
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*** A POWERFUL EARLY SEASON COASTAL STORM WILL BRING STRONG TO DAMAGING WINDS AND LOCALLY HEAVY RAINFALL AND MINOR FLOODING INTO THU MORNING *** 2 AM UPDATE... IMPRESSIVE EARLY SEASON COASTAL STORM SOUTH OF NEW ENGLAND WITH ITS WARM CONVEYOR BELT/TROWAL RAINS AND EMBEDDED CONVECTION PINWHEELING FROM GEORGES BANK NORTHWESTWARD INTO MASSACHUSETTS AND SLOWLY PIVOTING NORTHWEST. HEAVY RAINFALL AND CONVECTION WITHIN THIS WARM CONVEYOR BELT WILL CONTINUE THE THREAT FOR FLOODING ACROSS EASTERN MA AND EVENTUALLY INTO SOUTHEAST NH. THUS WILL CONTINUE WITH THE FLOOD WATCH. OCCLUDED LOW SOUTH OF NEW ENGLAND AND STRONG HIGH PRES OVER QUEBEC WILL CONTINUE TO FOCUS A STRONG LOW LEVEL NORTHEAST JET ACROSS SOUTHEAST NH/NORTHEAST MA/RI AND NORTHEAST CT. THIS LOW LEVEL JET WILL REMAIN STRONG THRU 12Z AND THEN SLOWLY WEAKENING THIS AFTERNOON. THUS WIND HEADLINES WILL REMAIN IN PLACE. PREVIOUS FORECAST CAPTURES THESE DETAILS NICELY SO NO MAJOR CHANGES WITH THIS UPDATE. EARLIER DISCUSSION BELOW. ============================================================= POTENT CLOSED UPPER LEVEL LOW WILL CONTINUE TO AMPLIFY TONIGHT. THIS WILL ALLOW SURFACE LOW PRESSURE TO INTENSIFY AS IT SLOWLY LIFTS TO THE NORTHEAST PASSING NEAR THE BENCHMARK ON THURSDAY. GIVEN THAT THIS SYSTEM HAS CLOSED MID LEVEL CIRCULATIONS...WERE EXPECTING A BREAK DOWN IN PRECIPITATION FIELDS THAT WE OFTEN SEE DURING WINTER STORMS. 1) HEAVY RAIN POTENTIAL: IN A NUTSHELL...PERIODS OF HEAVY RAIN ARE EXPECTED TONIGHT ACROSS THE ENTIRE REGION. THE BIGGEST UNCERTAINTY IS TRYING TO LOCATE WHERE THE HEAVIEST RAIN BANDS WILL SET UP. THERE ARE A LOT OF MOVING PARTS TO THIS FORECAST...WHICH MAKES THIS A DIFFICULT TASK. WE EXPECT HEAVY RAIN TO INITIALLY OVERSPREAD SOUTHEAST NEW ENGLAND AND WORK NORTHWARD ACROSS THE REST OF THE REGION THIS EVENING. THE MID LEVEL DRY SLOT WILL THEN APPROACH SOUTHEAST NEW ENGLAND BY LATE EVENING. THIS MAY RESULT IN THE PRECIPITATION FIELD MORE SCATTERED AT TIMES ACROSS SOUTHEAST SECTIONS OVERNIGHT...BUT ALSO MORE CONVECTIVE GIVEN SOME ELEVATED CAPE. SO WHILE WE MAY SEE SOME BREAKS IN THE PRECIPITATION SHIELD ACROSS SOUTHEAST SECTIONS...ISOLATED THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL WILL ALSO BE POSSIBLE. IN ADDITION...WE PROBABLY WILL SEE A SUBTLE COASTAL FRONT SET UP ACROSS SOUTHEAST MA LATE TONIGHT INTO THURSDAY MORNING SO SOME ENHANCEMENT IS POSSIBLE. WILL ALSO HAVE TO WATCH FOR A SECOND AREA OF HEAVIER PRECIPITATION IN ASSOCIATION WITH THE MID LEVEL DEFORMATION ZONE/BACK BENT WARM FRONT. LOCATION OF THIS IS TRICKY BUT PERHAPS FURTHER BACK INTO THE INTERIOR ACROSS SOUTHERN NH AND EAST SLOPES OF BERKSHIRES? FINALLY IN BETWEEN THE TWO BANDS OF HEAVIEST RAIN THERE WILL LIKELY BE A MINIMUM. SO BASICALLY...A WIDESPREAD 1 TO 2.50 INCHES OF RAIN IS EXPECTED FOR MUCH OF THE REGION...BUT LOCALIZED 4+ INCH AMOUNTS ARE CERTAINLY POSSIBLE ACROSS A PORTION OF THE REGION. WILL JUST HAVE TO CONTINUE TO MONITOR RADAR/SATELLITE TRENDS OVERNIGHT AND FINE TUNE OUR QPF FORECAST. THE FLOOD WATCH IS IN EFFECT ACROSS EASTERN NEW ENGLAND FOR THE POTENTIAL FOR LOCALIZED FLOODING IF THE HIGHER AMOUNTS ARE REALIZED. 2) TIMING: HEAVY RAIN OVER SPREADS THE REGION FROM SOUTHEAST TO NORTHWEST THIS EVENING. PERIODS OF HEAVY RAIN WILL OCCUR TONIGHT INTO THURSDAY MORNING...WHICH WILL LIKELY IMPACT THE MORNING RUSH HOUR. ISOLATED THUNDERSTORMS ARE POSSIBLE TONIGHT INTO THURSDAY MORNING ACROSS SOUTHEAST NEW ENGLAND NEAR THE DRY SLOT. THE STEADIEST RAIN SHOULD BE OVER BY THURSDAY AFTERNOON...BUT SCATTERED SHOWERS WILL CONTINUE. 3) STRONG WIND POTENTIAL: NORTHEAST LOW LEVEL JET OVER 50 KNOTS WILL IMPINGE ON EASTERN NEW ENGLAND THROUGH EARLY THURSDAY MORNING. IN FACT...BUFKIT SOUNDINGS SHOWING SOME PRETTY IMPRESSIVE WIND FIELDS BELOW 1000 FEET. THE UNCERTAINTY IS THAT AN INVERSION WILL ATTEMPT TO KEEP THE STRONGEST WINDS JUST OFF THE DECK. HOWEVER...HEAVY RAIN BANDS MAY BE ABLE TO PULL BRIEF STRONG WIND GUSTS TO THE GROUND. THE WIND ADVISORY CONTINUES FOR NORTHEAST MA INTO COASTAL PLYMOUTH COUNTY. PROBLEMS MAY BE EXACERBATED GIVEN THE MANY FULLY LEAFED TREES...RESULTING IN SOME DOWNED TREE LIMBS AND EVEN ISOLATED POWER OUTAGES. THERE IS THE CHANCE THAT THE WIND ADVISORY MAY NEED TO BE EXPANDED FURTHER NORTHWEST...BUT AGAIN ITS UNCERTAIN HOW MUCH WIND WILL MIX DOWN. THE WINDS SHOULD DIMINISH BY MID MORNING ON THURSDAY AS THE LOW LEVEL JET WEAKENS.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... * LINGERING SHOWERS POSSIBLE ON FRIDAY * SHOWERS POSSIBLE AGAIN SATURDAY AS LOW PRES MOVES INTO QUEBEC * MAINLY DRY AND SEASONABLE WEATHER EARLY NEXT WEEK OVERALL THE 12Z MODEL SUITE IS IN FAIRLY GOOD AGREEMENT THROUGH THE LONG TERM. THERE ARE SOME DISCREPANCIES IN THE MESOSCALE DETAILS BUT OTHERWISE THEY ARE IN GOOD AGREEMENT. AFTER THE COASTAL STORM CURRENTLY AFFECTING THE REGION MOVES AWAY FROM SOUTHERN NEW ENGLAND...THE WEATHER STARTS TO DRY OUT AND BECOME MORE SEASONABLE. THERE ARE A COUPLE OF COLD FRONTS EXPECTED TO MOVE THROUGH THE REGION AND EACH OF THESE MAY BRING SOME SHOWERS WITH THEM. THURSDAY NIGHT AND FRIDAY...LOW PRESSURE SLOWLY MOVES INTO THE GULF OF MAINE AND THEN THE MARITIMES FRIDAY. WHILE THE BULK OF THE RAIN WILL BE ENDING BY THURSDAY NIGHT...COULD SEE SOME LINGERING SHOWERS. HOWEVER...WINDS SHIFT TO THE NORTHWEST EARLY FRIDAY BRINGING SOMEWHAT DRIER AIR INTO THE REGION. OVERALL EXPECT DRIER WEATHER AND A GRADUAL IMPROVEMENT AS WE MOVE INTO FRIDAY AFTERNOON. SATURDAY...ANOTHER UPPER LEVEL TROUGH MOVES OVER THE NORTHEAST WITH LOW PRESSURE MOVING THROUGH SOUTHERN QUEBEC AND INTO THE MARITIMES. THE MODELS DON/T SHOW A WHOLE LOT OF MOISTURE OR A BIG WIND SHIFT WITH THIS FRONT BUT WE COULD SEE SOME SHOWERS. THE GFS HAS A STRONGER LOW LEVEL JET THAN THE ECMWF WHICH COULD ENHANCE THE AMOUNT OF RAINFALL BUT THERE IS STILL MUCH TO BE SEEN WITH THIS SYSTEM. SUNDAY THROUGH TUESDAY...HIGH PRESSURE STARTS TO BUILD INTO SOUTHERN NEW ENGLAND BRINGING DRY AND SEASONABLE WEATHER. TEMPERATURES BEGIN TO CLIMB AND MAY WARM TO WELL ABOVE NORMAL BY TUESDAY. WEDNESDAY...LOW PRESSURE MOVING THROUGH THE GREAT LAKES AND INTO QUEBEC MAY BRING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND. ANOTHER CHANCE OF SOME SHOWERS POSSIBLE WITH THIS FRONT BUT PLENTY OF UNCERTAINTY. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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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/... THRU 12Z... BAND OF HEAVY SHOWERS WITH EMBEDDED T-STORMS OVER CAPE COD NORTHWEST INTO WESTERN MA WILL CONTINUE TO SLOWLY PIVOT NORTHWARD WITH TIME. STRONG NE WINDS CONTINUE WITH HIGHEST GUSTS OVER NORTHEAST MA. IFR PERSIST ALONG THE COAST WITH MVFR ELSEWHERE. AFTER 12Z... BAND OF HEAVY RAIN WITH EMBEDDED T-STORMS SHOULD BE ACROSS NORTHERN MA INTO SOUTHERN NH AND SLOWLY LIFTING NORTHWARD. MARGINAL IFR/MVFR CONDITIONS CONTINUE. GUSTY NE WINDS CONTINUE WITH STRONGEST WINDS FOCUSED ACROSS NORTHEAST MA. TONIGHT... IFR EASTERN MA WITH MVFR ELSEWHERE. SLOW IMPROVEMENT WITH SHOWERS BECOMING LESS NUMEROUS AND WINDS SLOWLY EASING. FRIDAY... MVFR BUT TRENDING TOWARD VFR LATE. SCATTERED SHOWERS BECOMING LESS NUMEROUS AS THE DAY PROGRESSES. NNW WINDS 10-20 KT. KBOS...HIGH CONFIDENCE IN TAF ON TRENDS BUT LOWER CONFIDENCE ON EXACT TIMING OF DETAILS. KBDL...HIGH CONFIDENCE IN TAF ON TRENDS BUT LOWER CONFIDENCE ON EXACT TIMING OF DETAILS. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... SATURDAY THROUGH MONDAY...MODERATE CONFIDENCE. VFR. LOW PROBABILITY OF SCATTERED SHOWERS SATURDAY.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/... ***20 FOOT SEAS AND STORM FORCE NORTHEAST WIND GUSTS CONTINUE INTO THURSDAY ACROSS THE EASTERN MASSACHUSETTS WATERS*** LOW LEVEL JET WILL CONTINUE TO RESULT IN NORTHEAST WIND GUSTS OF 40 TO 50 KNOTS ACROSS THE NORTHERN MASSACHUSETTS WATERS INCLUDING BOSTON HARBOR THROUGH THURSDAY MORNING BEFORE GRADUALLY DIMINISHING. STRONG WINDS AND LONG NORTHEAST FETCH WILL RESULT IN 20 FOOT SEAS ACROSS PORTIONS OF OUR NORTHERN MASSACHUSETTS WATERS. GALE FORCE NORTHEAST WIND GUSTS WILL CONTINUE ACROSS THE SOUTHERN WATERS THROUGH THURSDAY MORNING. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY... THURSDAY NIGHT AND FRIDAY...HIGH CONFIDENCE. 8 TO 11 FOOT SEAS WILL SLOWLY DIMINISH AS LOW PRESSURE MOVES INTO THE MARITIMES. NORTHEAST WINDS GUSTING TO NEAR 30 KTS WILL DIMINISH AND SHIFT TO THE NORTHWEST. VISIBILITIES MAY BE REDUCED IN SCATTERED SHOWERS. 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. MONDAY...MODERATE CONFIDENCE. WINDS AND SEAS DIMINISH AS HIGH PRESSURE BUILDS OVER THE WATERS. && .TIDES/COASTAL FLOODING... DESPITE RATHER LOW ASTRONOMICAL HIGH TIDE CYCLES LATE TONIGHT AND AGAIN MIDDAY THURSDAY...OPTED TO ISSUE A COASTAL FLOOD ADVISORY FOR A PORTION OF THE EASTERN MA COAST. THIS IS MAINLY FOR THE AREA NORTH OF CAPE ANN AND THE SCITUATE AREA. A LONG DURATION OF NORTHEAST WINDS COMBINED WITH 15 TO 20 FOOT SEAS ACROSS OUR NORTHERN MA WATERS MAY YIELD POCKETS OF SPLASH OVER AND POCKETS OF MINOR COASTAL FLOODING. CERTAINLY NOT EXPECTING A SIGNIFICANT COASTAL FLOOD EVENT...BUT FELT IT WAS WORTH AN ADVISORY. IN ADDITION...THERE IS POTENTIAL FOR SIGNIFICANT BEACH EROSION ALONG THE EXPOSED BEACHES FROM SALISBURY TO PLUM ISLAND. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...WIND ADVISORY UNTIL 8 AM EDT THIS MORNING FOR CTZ004. MA...HIGH WIND WARNING UNTIL 8 AM EDT THIS MORNING FOR MAZ007- 014>016-019. FLOOD WATCH UNTIL 11 AM EDT THIS MORNING FOR MAZ005>007- 013>022-026. COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR MAZ007-019. WIND ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MAZ005-006-012- 013-017-018-020-021. NH...FLOOD WATCH UNTIL 11 AM EDT THIS MORNING FOR NHZ012-015. WIND ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NHZ012. RI...WIND ADVISORY UNTIL 8 AM EDT THIS MORNING FOR RIZ001>007. MARINE...GALE WARNING UNTIL 5 AM EDT EARLY THIS MORNING FOR ANZ231>237- 254>256. STORM WARNING UNTIL 5 AM EDT EARLY THIS MORNING FOR ANZ230. STORM WARNING UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ250-251.
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&& $$ SYNOPSIS...NOCERA NEAR TERM...FRANK/RLG SHORT TERM...FRANK/NOCERA LONG TERM...RLG AVIATION...NOCERA/RLG MARINE...FRANK/RLG TIDES/COASTAL FLOODING...

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