Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 040636 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 236 AM EDT WED MAY 4 2016 .SYNOPSIS... CLOUDY...DREARY AND COOL WEATHER CONTINUES THROUGH FRIDAY WITH PERIODS OF RAIN AS WEAK WAVES OF LOW PRESSURE PASS SOUTH AND EAST OF OUR REGION. SOME SHOWERS ARE STILL POSSIBLE AT TIMES THIS WEEKEND...BUT TEMPERATURES WILL BEGIN TO MODERATE. SIGNIFICANT IMPROVEMENT WILL LIKELY OCCUR EARLY TO MIDDLE OF NEXT WEEK AS HIGH PRESSURE BUILDS IN WITH MUCH MILDER TEMPERATURES. && .NEAR TERM /THROUGH TODAY/...
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230 AM UPDATE... *** STEADY RAIN DEVELOPS LATE AFTERNOON-EARLY EVENING TODAY *** ANOTHER COOL MORNING IN PROGRESS ACROSS THE REGION HOWEVER CONDITIONS REMAIN DRY. WATER VAPOR IMAGERY DEPICTS A NOTABLE SHORT WAVE TROUGH OVER TN AND KY EARLY THIS MORNING...MOVING NORTHEAST TOWARD THE MID ATLC STATES. WELL IN ADVANCE OF THIS SYSTEM THERE IS SOME WEAK SHORT WAVE RIDGING AND ASSOCIATED SUBSIDENCE ACROSS SOUTHERN NEW ENGLAND. THIS WILL YIELD MOSTLY DRY CONDITIONS THIS MORNING ACROSS THE AREA. HOWEVER BY AFTERNOON AND ESPECIALLY AFTER 5 PM THE SHORT WAVE CURRENTLY OVER TN/KY APPROACHES THE AREA AND INDUCES A COASTAL LOW OFF THE MID ATLC COAST. AS THE LOW TRACKS NORTHEAST THIS WILL RESULT IN AN INCREASE IN ONSHORE ENE WINDS YIELDING ANOTHER DAY OF COOL CONDITIONS. AS THIS SHORT WAVE APPROACHES IT BACKS THE MID LEVEL FLOW ALONG THE EASTERN SEABOARD AND CAPTURES A SUBTROPICAL PLUME OF MOISTURE JUST OFFSHORE WITH PWATS OVER 1 INCH. THIS WILL RESULT IN A SHIELD OF RAIN OVERSPREADING THE AREA BETWEEN 18Z AND 00Z. THERE IS SOME ELEVATED INSTABILITY OVER RI AND SOUTHEAST MA THAT MAY RESULT IN A FEW T-STORMS WITH LOCALLY HEAVY RAINFALL HERE.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/...
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TONIGHT ... WIDESPREAD RAIN LIKELY DURING THE EVENING BUT THEN SHOULD TRANSITION TO SPOTTY LIGHT RAIN/DRIZZLE LATE EVENING AND OVERNIGHT AS DRY SLOT OVERSPREADS THE AREA. HOWEVER DAMP/RAW NORTHEAST FLOW CONTINUES AND MAINTAINS COOL TEMPS. THURSDAY ... FORECAST UNCERTAINTY HINGES ON LOCATION OF WARM CONVEYOR BELT /WCB/ AND CORRESPONDING DRY SLOT. ALL NON NAM SOLUTIONS SUPPORT DEEP LAYER MOISTURE ASSOCIATED WITH WCB REMAINING JUST OFFSHORE AND ONLY CLIPPING EXTREME EASTERN MA. THUS GREATEST RISK FOR APPRECIABLE RAINFALL IS OVER EASTERN MA AND SOUTHEAST MA. ELSEWHERE ANOTHER DREARY DAY WITH MOIST AND COOL NORTHEAST WINDS AS NEXT FRONTAL WAVE APPROACHES FROM THE SOUTH.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... BIG PICTURE... LONGWAVE SCALE HAS A TROUGH OVER THE EASTERN USA WITH AXIS CENTERED OVER THE GREAT LAKES. LONGWAVE RIDGE OVER THE WEST COAST. CLOSED UPPER LOW WITHIN THE LONGWAVE TROUGH LINGERS OVER THE EAST COAST THURSDAY THROUGH SATURDAY. NORTHERN STREAM SHORTWAVE THEN DIVES SOUTHEAST INTO THE NORTHEAST USA SUNDAY...KICKING THE OFFSHORE LOW OUT TO SEA. THE SHORTWAVE FORMS A NEW CUTOFF LOW THAT MIGRATES FROM NORTHERN NEW ENGLAND TO NEWFOUNDLAND EARLY NEXT WEEK. THE DAILIES... THURSDAY-FRIDAY... CLOSED UPPER LOW AND ASSOCIATED COLD POOL OVER THE APPALACHIANS SHIFT EAST. UPPER FLOW OVER NEW ENGLAND IS SOUTHERLY AND DIFLUENT. GFS INDICATES ONE DEPARTING JET STREAK IN THIS FLOW AT 12Z THURSDAY...A SECOND STREAK APPROACHING FROM THE SOUTH MIDDAY. ADDITIONAL STREAKS MOVE PAST US DURING FRIDAY AS WELL. MEANWHILE COLD ADVECTION FROM THE ADVANCING COLD POOL WILL FURTHER DESTABILIZE THE AIRMASS. THIS WILL MAINTAIN A CHANCE OF SHOWERS BOTH DAYS...WITH FOG AND DRIZZLE IN BETWEEN ANY SHOWERS. EAST-NORTHEAST LOW LEVEL FLOW OFF THE GULF OF MAINE/MASS BAY WILL MAINTAIN COOL MOIST AIR NEAR THE SURFACE WITH DAY TEMPS IN THE UPPER 40S AND 50S WHILE DEW POINTS IN THE 40S WILL ALLOW MIN TEMPS IN THE 40S. WE WILL TREND A COUPLE OF DEGREES COOLER THAN GUIDENCE ON FRIDAY MAX TEMPS. SATURDAY-SUNDAY... UPPER TROUGH AND COLD POOL STILL OVERHEAD BUT JET SUPPORT MOVES OFF FARTHER EAST. PROBABILITY OF SHOWERS WILL BE LESS...BUT STILL A LOT OF LOW LEVEL MOISTURE SO LINGERING SCATTERED TO WIDELY SCATTERED SHOWERS. WITH THE EAST-NORTHEAST FLOW DIMINISHING...DAYTIME TEMPS SHOULD REACH A LITTLE MILDER. MIXING DEPTHS SUPPORT MAX SFC TEMPS MID 60S EACH DAY. NORTHERN STREAM SHORTWAVE PUSHES SOUTHEAST FROM ONTARIO SUNDAY. THIS WILL BRING A BETTER CHANCE OF SHOWERS AS A COLD FRONT SWINGS THROUGH NEW ENGLAND. SOME SIGNS OF NORTHWEST GUSTS TO 30 KNOTS IN COLD ADVECTION BEHIND THE COLD FRONT. MONDAY-TUESDAY... HIGH PRESSURE BUILDS OVER THE REGION. LINGERING COLD POOL MOISTURE ALOFT MAY BRING DIURNAL CLOUDS MONDAY...OTHERWISE A FAIR PERIOD. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 230 AM UPDATE ... SHORT TERM /THROUGH THURSDAY/... HIGH FORECAST CONFIDENCE ON TRENDS BUT LOWER ON EXACT DETAILS. TODAY ... A COMBINATION OF IFR AND MVFR BUT MAINLY DRY WEATHER. TREND TOWARD LOWER CIGS/VSBYS AFTER 21Z AS RAIN OVERSPREADS THE AREA. NE WINDS INCREASE THIS AFTERNOON 15 TO 20 KT WITH A FEW GUSTS UP TO 25 KT EASTERN MA. TONIGHT ... IFR AND LIFR IN WIDESPREAD RAIN THIS EVENING...THEN RAIN BECOMING LESS NUMEROUS OVERNIGHT. MODEST NE WIND 15 TO 20 KT WITH A FEW GUSTS UP TO 25 KT EASTERN MA. THURSDAY ... GREATEST RISK FOR STEADY RAIN WILL BE OVER EXTREME EASTERN MA. OTHERWISE NUISANCE TYPE SPOTTY LIGHT RAIN/DRIZZLE YIELDING LIFR AND IFR TRENDING TOWARD MFR IN THE AFTERNOON. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...MODERATE CONFIDENCE THURSDAY-FRIDAY...MIXED IFR/MVFR IN SHOWERS AND FOG. LOW LEVEL EAST- NORTHEAST FLOW UP THROUGH 3000 FEET WITH GUSTS TO 25 KNOTS ALONG THE EAST MASS SHORE. SATURDAY-SUNDAY... MIXED MVFR/IFR SATURDAY. WINDS BECOMING SOUTH WITH IMPROVEMENT TO VFR BY SUNDAY...THEN SCATTERED MVFR/IFR IN SHOWERS AS A COLD FRONT MOVES THROUGH. WINDS TURN FROM THE NORTHWEST SUNDAY AFTERNOON WITH GUSTS 20 TO 25 KNOTS.
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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. 945 PM UPDATE ... NOT MUCH CHANGE FROM PREVIOUS FORECAST. A DRYING TREND STILL EXPECTED OVERNIGHT WITH RAIN BECOMING LESS NUMEROUS. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. TONIGHT AND WEDNESDAY...PERSISTENT NORTHEAST FLOW WILL BUILD SEAS TO BETWEEN 3 AND 5 FEET ACROSS OUR SOUTHERN OUTER-WATERS. SO WHILE WIND SPEEDS WILL GENERALLY NOT EXCEED 20 KNOTS THROUGH MIDDAY WEDNESDAY...WILL STILL NEED SMALL CRAFT HEADLINES FOR SOME 5 FOOT SEAS. PATCHY FOG POSSIBLE AT TIMES AS WELL. WEDNESDAY NIGHT...PRESSURE GRADIENT INCREASES AS WAVE OF LOW PRESSURE APPROACHES FROM THE SOUTH AND COMBINES WITH HIGH PRESSURE OVER THE CANADIAN MARITIMES. NORTHEAST WIND GUSTS TO 25 KNOTS MAY DEVELOP ACROSS A GOOD CHUNK OF OUR WATERS ALONG WITH SEAS BUILDING TO BETWEEN 4 AND 7 FEET. ADDITIONAL SCA HEADLINES WILL LIKELY BE NEEDED...BUT SINCE ITS 3RD PERIOD WILL WAIT UNTIL THE NEXT SHIFT GETS A LOOK AT IT. OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...MODERATE CONFIDENCE... NORTHEAST WIND GUSTING 20 TO 25 KNOTS THURSDAY...BEST CHANCE ALONG THE WATERS EAST OF MASS. WINDS TURN FROM SOUTH SATURDAY AND SUNDAY MORNING...THEN FROM NORTHWEST SUNDAY AFTERNOON AFTER A COLD FRONT MOVES THROUGH. NORTHWEST GUSTS BEHIND THE COLD FRONT MAY REACH 25 KNOTS. SEAS 5 TO 7 FEET MUCH OF THE PERIOD. SMALL CRAFT ADVISORY MAY BE NEEDED.
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&& .TIDES/COASTAL FLOODING... HIGH ASTRONOMICAL TIDES ARE EXPECTED...WITH PRIME CONCERN ON THE HIGHER OF THE TWO HIGH TIDE CYCLES THURSDAY NIGHT AND FRIDAY NIGHT. ASTRO HEIGHTS ARE PROJECTED JUST BELOW 12 FEET AT BOSTON BOTH NIGHTS. ASTRO HEIGHTS NEAR PROVIDENCE ARE PROJECTED AT 6 FEET THURSDAY NIGHT AND 6.5 FEET FRIDAY NIGHT. IT WON/T TAKE MUCH OF A SURGE ON TOP OF THOSE ASTRO HEIGHTS TO CAUSE SOME SPLASHOVER OR EVEN POSSIBLY SOME MINOR COASTAL FLOODING. PERSISTANT NORTHEAST WINDS AGAINST THE EAST MASSACHUSETTS COAST WILL ADD TO POTENTIAL FOR SURGE ALONG THAT COASTLINE. THIS WILL NEED TO BE MONITORED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ254>256. && $$ SYNOPSIS...NOCERA NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...WTB AVIATION...WTB/NOCERA MARINE...WTB/NOCERA TIDES/COASTAL FLOODING...

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