Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 181047 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 647 AM EDT SAT APR 18 2015 .SYNOPSIS...
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MILDER WEATHER RETURNS TODAY AHEAD OF A DRY COLD FRONT WHICH MOVES THROUGH DURING THE AFTERNOON. CANADIAN HIGH PRESSURE BRINGS MUCH COOLER WEATHER TONIGHT AND SUNDAY. THEN A COASTAL LOW DELIVERS A WIND SWEPT SOAKING RAIN TO THE REGION MON AFTERNOON AND NIGHT. MILD WEATHER TUE ALONG WITH A DRYING TREND. THEN MID TO LATE WEEK THE TREND WILL BE TOWARD MUCH COOLER WEATHER ALONG WITH THE RISK OF SCATTERED SHOWERS...MAINLY IN THE AFTERNOON AND EVENING.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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650 AM UPDATE... LARGE TEMP DIFFERENCES ACROSS THE REGION AT SUNRISE. LOCATIONS WITH CALM OR LIGHT WINDS HAVE TEMPS IN THE 30S ALONG WITH PATCHY FOG. MEANWHILE HIGHER ELEVATIONS INCLUDING URBAN AREAS REMAIN WELL MIXED WITH SURFACE WINDS KEEPING TEMPS IN THE U40S TO L50S! THUS COOL AIR IS VERY SHALLOW AND WILL MIX OUT QUICKLY WITHIN THE NEXT FEW HOURS AS STRONG MID APRIL SUNSHINE GOES TO WORK. THEREFORE EXPECT RAPID TEMP RISES THIS MORNING INTO THE AFTERNOON WITH INLAND LOCATIONS SEEING HIGHS IN THE LOW TO MID 70S! THIS IS WELL COVERED BY PREVIOUS FORECAST SO ONLY CHANGE WITH THIS UPDATE WAS TO ADJUST HOURLY TEMPS TO BETTER REFLECT CURRENT CONDITIONS. EARLIER DISCUSSION BELOW. ==================================================================== YESTERDAYS CONVECTIVE FORECAST SURELY NOT PLAYING OUT ACROSS NE MA AS THE CONSENSUS OF FORECAST GUIDANCE HAS NUDGED THE SE SWEEPING POTENT MID-LEVEL IMPULSE FURTHER NE ACROSS NH/ME. THIS TAKES THE BETTER INSTABILITY AND MOISTURE OUT OF THE EQUATION ALONG WITH THE LIKELIHOOD OF WET WEATHER. WILL STILL KEEP WITH CHANCE POPS FOR N/NE MA. OTHERWISE FOCUS IS ALONG COLD FRONT PARENT TO SE SWEEPING IMPULSE AND THE ELEVATED FIRE WEATHER POTENTIAL. THE FRONT ANTICIPATED TO SWEEP S NEW ENGLAND DURING THE AFTERNOON HOURS WILL BE ACCOMPANIED BY COOLER AND DRIER AIR USHERED BY BLUSTERY NW-WINDS. WITH THE LOCAL ENVIRONMENT ALONG AND AHEAD WARMING INTO THE LOW-70S AT THE SURFACE...EXPECT THE BOUNDARY-LAYER TO BECOME WELL-MIXED UP TO H7 ALLOWING FOR THE MIX-DOWN OF DRIER AIR AND FASTER MOMENTUM TO THE SURFACE WITH AFTERNOON FRONTAL PASSAGE. SUBSEQUENTLY...EXPECTING MINIMUM RELATIVE HUMIDITY TO DROP AS LOW AS 20 PERCENT AS SUSTAINED WINDS APPROACH 20 MPH /ESPECIALLY ALONG THE HIGH TERRAIN/ WITH GUSTS UP TO 30 MPH. SEA-BREEZES ALONG THE E-COAST PRIOR TO COLD FRONTAL PASSAGE SHOULD BE EASILY SCOURED OUT BY THE STRONG NW-FLOW...BUT THAT TAKING PLACE CLOSER TO EVENING. SO BETTER CHANCES FOR ELEVATED FIRE WEATHER POTENTIAL IS ACROSS THE REGION WHICH WAS IN THE FIRE WEATHER WATCH WHICH HAS NOW BEEN CONVERTED TO A RED FLAG WARNING FOR THE STATE OF CT...WITH A SPECIAL WX STATEMENT FOR ALL OTHER LOCALES PREVIOUSLY ADDRESSED IN THE WATCH. PLEASE SEE THE FIRE WX DISCUSSION BELOW FOR MORE DETAILS. HIGHS ACROSS THE REGION AROUND THE LOW-70S WITH WARMEST CONDITIONS OVER THE LOWER CT-VALLEY WITH HIGHS AROUND THE MID-70S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... SATURDAY NIGHT... N/NW-WINDS DIMINISHING DIMINISHING AS HIGH PRESSURE BUILDS ACROSS THE REGION. EARLIER H925 +14C TEMPERATURES DROP TO NEAR THE FREEZING MARK OVERNIGHT. BECOMING MOSTLY CLEAR...EXPECT A CHILLY NIGHT WITH LOWS DROPPING DOWN TO AROUND THE UPPER-30S TO LOW-40S. EXPECT ACROSS THE HIGH TERRAIN FOR LOWS TO DROP INTO THE LOW-30S. SUNDAY... HIGH PRESSURE PUSHES THROUGH THE REGION AND OFFSHORE. COOLER AIRMASS STILL IN PLACE WITH H925 TEMPERATURES +4-6C. DESPITE THIN HIGH CLOUD INCREASING TOWARDS THE LATER HALF OF THE DAY AHEAD OF MONDAYS WET WX EXPECT HIGHS ACROSS THE INTERIOR INTO THE LOW-60S...COOLER ALONG THE SHORES WITH ANTICIPATED VEERING E/SE ONSHORE FLOW OFF THE CHILLY WATERS. HIGHS AROUND THE MID-50S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * MON/MON NGT...WIND SWEPT SOAKING RAIN * TUE...DRYING TREND AND MILD * WED-FRI...COOLER WITH PERIODS OF SHOWERS MID TO LATE NEXT WEEK SYNOPTIC OVERVIEW... BOTH GEFS AND EPS ENSEMBLE TELECONNECTIONS SUPPORT A TYPICAL SPRING- LIKE BLOCKY UPPER AIR PATTERN NEXT WEEK WITH NAO AND AO BECOMING FAIRLY NEGATIVE ESPECIALLY THE NAO. IN ADDITION THE PNA REMAINS POSITIVE BUT MORE IMPORTANTLY THE EPO BECOMES VERY NEGATIVE. THUS A VERY STRONG SIGNAL FOR A TREND TOWARD COOLER AND UNSETTLED WEATHER HERE IN NEW ENGLAND MID TO LATE NEXT WEEK. THIS PATTERN CHANGE WILL KICK-OFF WITH STREAMS MERGING LATE SUN/SUN NGT...SENDING SOUTHERN STREAM MOISTURE UP THE EASTERN SEABOARD MON/MON NGT INTO NEW ENGLAND. ANOMALOUS PWAT AND WIND ANOMALIES WITHIN THIS MOIST/WARM CONVEYOR BELT WILL RESULT IN A PERIOD OF HEAVY WIND SWEPT RAIN AS TRIPLE POINT LOW RIDES THE COASTLINE. DAILY DETAILS... * SUNDAY NIGHT...RIDGING OVER THE AREA SLOWLY RETREATS OFFSHORE. DRY WEATHER PREVAILS BUT INCREASING CLOUDS. * MONDAY...NAM...GFS AND GEFS HAVE SPED UP ONSET OF PRECIP WITH RAIN OVERSPREADING THE AREA DURING THE MORNING. HOWEVER NON NCEP MODELS SUCH AS ECENS ENSEMBLES ALONG WITH EC AND UKMET ARE SLOWER WITH PRECIP ARRIVING LATE MORNING/EARLY AFTERNOON FROM WEST TO EAST. GIVEN AMPLIFYING UPPER AIR PATTERN A SLOWER ONSET SEEMS REASONABLE. GIVEN TIME RANGE A MODEL BLEND OF POPS APPEARS PRUDENT. THUS THINKING MARATHON BEGINS DRY BUT INCREASING CHANCES OF RAIN FROM MIDDAY ONWARD. A SOAKING WIND SWEPT RAIN REMAINS LIKELY AS TRIPLE POINT LOW MOVES UP THE COASTLINE ACTING ON PWATS +2 STANDARD DEVIATIONS /SD/ ABOVE CLIMO ALONG WITH STRONG ATLC INFLOW WITH WIND ANOMALIES +3 SD FROM CLIMO. THIS WILL YIELD A HIGH PROBABILITY FOR A WIDESPREAD RAINFALL APPROACHING 1" WITH A LOW TO MODERATE PROBABILITY OF RAINFALL UP TO 1.5". AS FOR WINDS...SOUNDINGS BECOME INVERTED WITH STRONG LOW LEVEL WARM AIR ADVECTION. HOWEVER BEFORE THIS OCCURS BLYR IS INITIALLY COOL DURING THE MORNING AND MODEL SOUNDINGS SUGGEST SE WINDS IN THE MORNING COULD GUSTS UP TO 40 MPH. * TUESDAY...COULD TURN OUT TO BE A DECENT AFTERNOON PENDING EXACT TIMING ON DEPARTURE OF MID LEVEL TROUGH AND ASSOCIATED DEEP LAYER MOISTURE. APPEARS RISK OF MORNING SHOWERS WITH COLUMN DRYING DURING THE AFTERNOON FROM SOUTH TO NORTH. COLD AIR ADVECTION HOLDS OFF TIL LATE IN THE DAY OR AT NIGHT. THUS IF SUNSHINE BREAKS OUT IN THE AFTN COULD SEE TEMPS JUMP WELL INTO THE 60S TO NEAR 70. * WEDNESDAY THRU FRIDAY...MUCH COOLER AS GREAT LAKES MID LEVEL LOW TRAVERSES EASTWARD INTO NORTHERN NEW ENGLAND. COLD POOL COMBINED WITH CYCLONIC FLOW ALOFT WILL YIELD A RISK OF SHOWERS AT TIMES ESPECIALLY DIURNALLY DRIVEN. NOT EXPECTING RAIN ALL THE TIME. THUS WILL BE PERIODS OF DRY WEATHER AS WELL. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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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 SUNDAY/... 650 AM UPDATE... NOT MUCH CHANGE FROM 06Z TAFS. EARLIER DISCUSSION BELOW. =============================================================== * INTO MORNING...PATCHY IFR-LIFR CIGS / VSBYS FOR SE MA ERODE TOWARDS MORNING. VFR ALL OTHER LOCALES. * TODAY...VFR. SEA-BREEZE ACROSS THE E. INCREASING W/NW-WINDS OVER THE INTERIOR IN WAKE OF A COLD FRONT. SUSTAINED 10-15 KTS WITH GUSTS UP TO 30 KTS. BEST CHANCE OF LOW-END VFR CIGS AND -SHRA ACROSS NE MA. * TONIGHT...VFR. WINDS DIMINISHING. * SUNDAY...VFR. WINDS VEERING TURING E/SE AND ONSHORE. INCREASING LATE ALONG WITH HIGH CLOUDS. * KBOS TAF...HIGH CONFIDENCE. SEABREEZE DEVELOPING TOWARDS MIDDAY...ERODING AS IT IS PUSHED OFFSHORE BY STRONG W/NW-WINDS BY EVENING. * KBDL TAF...MODERATE CONFIDENCE. COLD FRONTAL PASSAGE FOLLOWED BY STRONGER NW-WINDS EXPECTED BY AFTERNOON. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... * SUN NIGHT...VFR AND LIGHT WINDS. HIGH CONFIDENCE. * MON...MVFR/IFR DEVELOPING IN RAIN/FOG BY AFTERNOON. LIFR POSSIBLE TOWARD 00Z. E/SE WIND GUSTING TO 25-30KT NEAR COAST. MODERATE CONFIDENCE. * TUE...LIFR/IFR TRENDING TOWARD MVFR/VFR IN THE AFTERNOON. SHOWERS MOST NUMEROUS IN THE MORNING. MODERATE CONFIDENCE. * WED...MAINLY VFR WITH SCT MVFR IN DIURNAL CU/SHOWERS. MODERATE CONFIDENCE.
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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 SUNDAY/...HIGH CONFIDENCE. ONSHORE FLOW AROUND 10 KTS THROUGH THE DAY AS SEAS REMAIN BELOW 5-FEET. LOW CLOUDS AND PERHAPS PATCHY FOG MAY LINGER. COLD FRONT APPROACHING THE WATERS TOWARDS EVENING BEHIND WHICH W/NW-FLOW INCREASES WITH THE POTENTIAL FOR SUSTAINED WINDS UP TO 15 KTS AND GUSTS AROUND 25 KTS. SUBSEQUENT WIND STRESS COULD RESULT IN SEAS BUILDING IN EXCESS OF 5-FEET FOR THE OVERNIGHT PERIOD INTO THE EARLY HALF OF SUNDAY BY WHICH POINT HIGH PRESSURE WILL SETTLE ACROSS THE REGION ALLOWING WINDS AND WAVES TO RELAX. WILL ALLOW THE DAY-SHIFT TO EVALUATE AND MAKE THE CALL AS TO WHETHER SMALL- CRAFTS SHOULD BE ISSUED. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUNDAY NIGHT...HIGH CONFIDENCE. LIGHT WINDS AND NEAR CALM SEAS. MONDAY...MODERATE CONFIDENCE. INCREASING E/SE WINDS EXPECTED MON WITH BUILDING SEAS...PROBABLY REQUIRING SCA WITH GUSTS REACHING 25-30KT. OUTSIDE CHANCE OF REACHING MARGINAL GALES /35KT/. SEAS COULD REACH AS HIGH AS 8-11 FT ON OUTER WATERS MON NIGHT. RAIN AND FOG WILL LIMIT VSBY MON AFTERNOON AND AND MON NIGHT. TUESDAY...MODERATE CONFIDENCE. LEFT OVER HIGH SEAS IN THE FORM OF SE SWELLS. WINDS DIMINISH AS LOW PRES MOVES OVERHEAD. LOW VSBY IN MORNING FOG AND SHOWERS IMPROVES DURING THE AFTERNOON. WEDNESDAY...MODERATE CONFIDENCE. SEAS AND WIND WILL SLOWLY SUBSIDE. && .FIRE WEATHER... THERE IS THE POTENTIAL FOR ELEVATED FIRE WEATHER CONDITIONS TODAY MAINLY ACROSS THE INTERIOR AND AWAY FROM THE SHORES WHICH ARE LIKELY TO SEA-BREEZE WITH AN ONSHORE MOIST FLOW /OUTLINED BY THE PRIOR FIRE WEATHER WATCH/. FOCUS IS ALONG A COLD FRONT WHICH SWEEPS ACROSS THE REGION DURING THE AFTERNOON HOURS. CONDITIONS WARM AHEAD OF THE FRONT AROUND THE LOW-70S ALLOWING FOR DEEP-LAYER MIXING AND MIX-DOWN OF DRIER AIR AND FASTER MOMENTUM TO THE SURFACE. EXPECTING NW-WINDS SUSTAINED AROUND 15 MPH WITH GUSTS AROUND 30 MPH /STRONGER ACROSS THE HIGH TERRAIN/ IMMEDIATELY BEHIND THE COLD FRONT AS THE RELATIVE HUMIDITY DROPS CLOSE TO 20 PERCENT. THIS IS NOT HELPFUL TO AN ENVIRONMENT IN WHERE FRIDAYS WET WEATHER WAS NOTHING OF A WASHOUT. ONLY A TENTH OR TWO OF RAINFALL WAS OBSERVED. SO EXPECT IT TO BE CONSIDERABLY DRY. BUT WITH THE BULK OF CONDITIONS THAT MEET FIRE WEATHER PARAMETERS OCCURRING DURING THE AFTERNOON INTO EVENING HOURS...THE SHORT-LIVED EVENT WITH SUSTAINED WINDS BELOW 20 MPH MAKE THIS A MARGINAL EVENT. PER COLLABORATION WITH SURROUNDING WFOS AND FIRE WEATHER OFFICIALS FROM THE STATE OF MA...WILL REVERT THE FIRE WEATHER WATCH TO A RED FLAG WARNING FOR THE STATE OF CT...WHILE ISSUING A SPECIAL WEATHER STATEMENT FOR THE REMAINDER OF THE WATCH ENCOMPASSING CENTRAL AND INTERIOR E MA...AS WELL AS NW RI. HIGH PRESSURE MOVES IN ON SUNDAY KEEPING THE WINDS GUSTS AT BAY... BUT ALLOWING FOR RH/S TO DROP NEAR 25 PERCENT AGAIN. CONDITIONS WILL TURN MORE WET BY NEXT WEEK WITH SEVERAL CHANCES OF SHOWERS AND COOLER WEATHER THROUGHOUT THE WORK WEEK. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...RED FLAG WARNING FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR CTZ002>004. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA/SIPPRELL SHORT TERM...SIPPRELL LONG TERM...NOCERA AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL FIRE WEATHER...

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