Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 052330 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 730 PM EDT THU MAY 5 2016 .SYNOPSIS... CLOUDY...DREARY AND COOL WEATHER CONTINUES THROUGH FRIDAY WITH PERIODS OF RAIN AS WAVES OF LOW PRESSURE TRACK SOUTH OF SOUTHERN NEW ENGLAND. DESPITE SOME SHOWERS POSSIBLE THIS WEEKEND THERE WILL BE MANY HOURS OF DRY WEATHER ALONG WITH MODERATING TEMPERATURES. SIGNIFICANT IMPROVEMENT WILL LIKELY OCCUR EARLY TO MIDDLE OF NEXT WEEK AS HIGH PRESSURE BUILDS IN WITH MUCH MILDER TEMPERATURES. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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7 PM UPDATE... NOTING THAT THE SHALLOW DZ FIELD CONTINUES TO EXPAND WEST WHILE THE HEAVIER RAIN IS WRAPPING CLOSER TO THE DEEPENING LOW TO THE SE. THEREFORE...EXPECT A GRADUAL EASTWARD SHIFT OF ALL STEADY RAINFALL THROUGH 04-06Z. AREAS OF DZ LIKELY TO FOLLOW FOR SOME TIME UNTIL DRIER AIR AND SOME MIXING BEGINS AFTER DAYBREAK. OTHERWISE...ANOTHER DAMP/CLOUDY NIGHT. TWEAKED POPS TIMING SLIGHTLY AND TEMPS TOWARD LATEST MET GUIDANCE WHICH IS HANDLING TRENDS WELL. PREVIOUS DISCUSSION... LOW PRESSURE SEVERAL HUNDRED MILES SOUTH OF NANTUCKET WAS PROGRESSING TO THE NORTHEAST EARLY THIS EVENING. IT IS FORECAST TO REACH THE BAY OF FUNDI BY DAYBREAK. RAIN...LOCALLY MODERATE TO HEAVY...WAS OCCURRING OVER SOUTHEAST MA. THE WESTERN EDGE OF THIS RAIN SHIELD IS EXPECTED TO PROGRESS SLIGHTLY FARTHER TO THE WEST EARLY TONIGHT...REACHING THE I-495 CORRIDOR AND TO NEAR THE RI/CT BORDER. THEN IT SHOULD HEAD OFF THE COAST AROUND OR AFTER MIDNIGHT. WITH THE MOIST NORTHEAST FLOW...AREAS OF DRIZZLE AND FOG CAN ALSO BE EXPECTED ANYWHERE IN SOUTHERN NEW ENGLAND OVERNIGHT... BUT MOST LIKELY IN CENTRAL AND EASTERN SECTIONS. MESOSCALE MODELS SHOW THE LOW LEVEL JET INCREASING FOR A FEW HOURS BETWEEN NOW AND ABOUT 10 PM...SO NORTHEAST GUSTS TO 25-35 MPH WILL CONTINUE THIS EVENING IN RI AND EASTERN MA. WINDS WILL DIMINISH ACROSS THE REGION AFTER MIDNIGHT. THERE IS THE LIKELIHOOD OF MINOR COASTAL FLOODING AT THE TIME OF HIGH TIDE TONIGHT. PLEASE REFER TO THE COASTAL FLOODING SECTION BELOW FOR MORE INFORMATION. LOWS TONIGHT WILL BE IN THE 40S.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... 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. && .LONG TERM /SATURDAY THROUGH THURSDAY/... */ HIGHLIGHTS... - DREARY WEATHER OF LIGHT RAIN / DRIZZLE SATURDAY - COLD FRONT AND BEST CHANCES OF RAIN ON SUNDAY - QUICK BLAST OF COLDER AIR MONDAY MORNING BEHIND THE FRONT...DRY - POSSIBLE PROLONGED PERIOD OF UNSETTLED WEATHER THRU THE WEEK OVERVIEW AND MODEL PREFERENCES... FINAL BREAKDOWN OF THE AMPLIFIED FLOW PATTERN ACROSS THE CONUS BEGINS LATE SAT INTO SUN AS ARCTIC VORT MAX WITHIN THE NRN STREAM IS FINALLY ABLE TO SHIFT THE STUBBORN CUTOFF E OF THE REGION. THIS WILL COME WITH SOME CONSEQUENCE IN THE FORM OF A COLD FRONTAL PASSAGE ON SUN...BUT AT THE VERY LEAST...SOME MODERATION IN TYPES AND DRYING OF THE COLUMN IS EXPECTED. BEYOND THE WEEKEND...CONFIDENCE IN THE FORECAST WAINS. AT ISSUE IS THE DEVELOPMENT OF YET ANOTHER CUTOFF DEVELOPS TO THE N AS THE NRN STREAM VORT MAX PHASES WITH SRN STREAM ENERGY EARLY IN THE WEEK. THE RESULTING CUTOFF COULD END UP ANYWHERE FROM ONTARIO TO S OF GREENLAND...AND THIS LOCATION WILL ULTIMATELY HELP TO DEFINE THE DAILY SENSIBLE WX ACROSS SRN NEW ENGLAND. AGREE WITH THE PREVIOUS FORECASTER THAT AN ENSEMBLE APPROACH IS BEST HERE...AND GIVEN WPC/S LEANING ON AN ECENS ENSEMBLE MEAN...WILL BE FOLLOWING SUIT WITH THIS UPDATE. THE OVERALL RESULT WILL BE THE RISK FOR MORE WET/GRAY CONDITIONS MID-LATE WEEK AS A BAROCLINIC ZONE SETTLES NEAR NEW ENGLAND S OF THE THE DEVELOPING CUTOFF. DETAILS... SAT AND SAT NIGHT... FILLING OCCLUSION WILL BE SHIFTING E OF THE REGION AND GRADUALLY ALLOWING MORE DRY AIR THROUGH THE COLUMN. AFTER A DAMP/SHOWERY/DRIZZLE START TO THE DAY...SOME BREAKS ARE EXPECTED IN THE AFTERNOON AND EVENING...WITH EVEN THE LOW POSSIBILITY OF A FEW PEAKS OF SUN. WITH FLOW SHIFTING S...TEMPS WILL BE MODERATING ALLOWING FOR A FEW MORE 50S AND LOW 60S THAN PREVIOUS DAYS WITH LOWS NOW FALLING INTO THE 40S. SUN... STRONG COLD FRONT WILL SWEEP THROUGH THE REGION DURING THE MID DAY PERIOD. THE COMBINATION OF PWATS APPROACHING AN INCH WITH A MODEST ELEVATED UNSTABLE LAYER BETWEEN H9 AND H7 SUGGESTS SOME SHRA COULD BE BRIEFLY HEAVY AT TIMES...PARTICULARLY ACROSS THE NRN HALF OF THE AREA...CLOSER TO THE INFLUENCE OF A LLJ. SOME WETTING PRECIP EXPECTED ACROSS ALL OF SRN NEW ENGLAND HOWEVER...WITH HIGHEST TOTALS MAINLY N OF THE MASS PIKE IN THE 0.25-0.50 RANGE WITH LOCALLY HIGHER AMOUNTS. MON... BRIEF REPRIEVE FROM EXPECTED RAINFALL WITH COLD FRONT SHIFTING E OF THE REGION...ALLOWING A DRIER...BUT COLDER AIRMASS TO SPILL ACROSS SRN NEW ENGLAND. BREEZY NW FLOW EXPECTED WITH SOME CLOUD COVER...THE RESULT OF A SECONDARY SHORTWAVE MOVING THROUGH LATE IN THE DAY. TEMPS MAINLY NEAR TO BELOW SEASONAL NORMALS. TUE... CONFIDENCE IN THE FORECAST DROPS RAPIDLY AT THIS POINT DUE TO A WIDE ARRAY OF POSSIBILITIES FOR A BAROCLINIC ZONE AND UPPER LVL CUTOFF. FOR NOW...FEEL THAT WITH A DRY COLUMN TO START...TUE WILL ITSELF BE MAINLY DRY BUT TRANSITIONING BACK TO GRAY/DAMP CONDITIONS LATE. ECENS/GEFS PROBABILITIES FOR PRECIP ARE RATHER LOW...HENCE THE DECISION TO LEAN CLOSER TO A DRY FORECAST FOR TUE. TEMPS WILL BE DETERMINED BY THE FINAL LOCATION OF THE BAROCLINIC ZONE. LATE WEEK... ALTHOUGH NOT LIKELY AS PERSISTENTLY GRAY AND DAMP AS THIS WEEK...A SHIFT IN THE PATTERN SUGGESTS THAT SEVERAL WAVES ACTING ALONG THE BAROCLINIC ZONE COULD PROVIDE PERIODS OF RAIN AND EVEN SOME POSSIBLE THUNDER. OVERALL..NOT AS COLD AS THIS WEEK THANKS TO INFLUENCE OF THE SRN STREAM WITH THIS FEATURE. && .AVIATION /00Z 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. 2030Z UPDATE... SHORT TERM /THROUGH FRIDAY NIGHT/... OVERNIGHT...MODERATE CONFIDENCE. IFR AND LOWER END MVFR CIGS CONTINUE...BUT GRADUALLY RISE TO UPPER END IFR AND UPPER END MVFR BY THE EARLY MORNING HOURS. AREAS OF FOG AND DRIZZLE ESPECIALLY IN EASTERN AND CENTRAL SECTIONS. WINDS SLOWLY DIMINISHING. RAIN HEADS NORTHEAST AND OFF THE COAST AROUND OR SHORTLY AFTER MIDNIGHT. FRIDAY...AREA OF IFR WITH POSSIBLE DRIZZLE EARLY. THEN CONDITIONS IMPROVING TO MVFR. SHOWERS LIKELY IN CT AND WESTERN MA IN THE AFTERNOON WITH A CHANCE OF SHOWERS ELSEWHERE. ENE WINDS BECOMING E OR ESE LATE...GUSTING TO 20-25 KT ALONG THE SOUTH COAST LATE. FRIDAY NIGHT...MORE OF THE SAME. IFR AND LOW-END MVFR WITH SCATTERED SHOWERS EAST AND SHOWERS LIKELY WEST. CANNOT RULE OUT AN ISOLATED THUNDERSTORM SOMEWHERE ACROSS THE REGION. KBOS TERMINAL...MODERATE CONFIDENCE CONCERNING THE TAF. IFR IN RAIN THROUGH ABOUT 02-03Z THEN RAIN ENDING AND CONDITIONS SLOWLY IMPROVING TO MVFR CIGS TOWARD DAYBREAK...CONTINUING THROUGH FRI. KBDL TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF. MVFR CIGS. RAIN EXPECTED TO REMAIN TO THE EAST TONIGHT BUT SHOWERS DEVELOPING AFTER NOON ON FRI. CANNOT RULE OUT AN ISOLATED THUNDERSTORM FRI NIGHT. OUTLOOK /SATURDAY THROUGH TUESDAY/... SAT...HIGH CONFIDENCE. MIX OF MVFR/IFR GIVES WAY TO MORE WIDESPREAD VFR LATER IN THE DAY AS RAIN/DRIZZLE COMES TO AN END. LOW RISK OF A MID DAY TS. SUN...MODERATE CONFIDENCE. VFR TO START THE DAY...BUT MIX OF SHOWERS WITH MVFR CONDITIONS THROUGH MID AFTERNOON WITH A COLD FRONTAL PASSAGE. VFR FOLLOWS INTO SUN NIGHT. MON AND TUE...HIGH CONFIDENCE. MAINLY VFR WITH BRIEF RIDGE OF HIGH PRES.
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&& .MARINE... 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 THROUGH TUESDAY/...MODERATE CONFIDENCE. SAT AND SUN... ALTHOUGH WINDS WILL BE SHIFTING TO THE S AND RECEDING...LINGERING SWELL ON THE OCEAN WATERS REMAINS NEAR 5-6FT. THEREFORE...SMALL CRAFT ADVISORIES ARE LIKELY TO LINGER FOR AT LEAST SEAS. MON AND TUE... HIGH PRES BRIEFLY BUILDS OVER THE WATERS BUT WITH SUSTAINED NW FLOW SEAS HOLD NEAR 5 FT ON THE OCEAN WATERS. QUIETER BOATING WEATHER CLOSER TO SHORE. && .TIDES/COASTAL FLOODING... 430 PM UPDATE... 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 UNTIL 1 AM EDT FRIDAY FOR MAZ007-015- 016-019-022-024. RI...NONE. MARINE...GALE WARNING UNTIL 5 AM EDT FRIDAY FOR ANZ231>235-237-250-251- 254>256. GALE WARNING UNTIL 2 AM EDT FRIDAY FOR ANZ230-236.
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&& $$ SYNOPSIS...DOODY/GAF NEAR TERM...DOODY/GAF SHORT TERM...GAF LONG TERM...DOODY AVIATION...DOODY/GAF MARINE...DOODY/GAF TIDES/COASTAL FLOODING...

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