Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 252000 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 400 PM EDT SAT APR 25 2015 .SYNOPSIS... UNSEASONABLY COOL WEATHER CONTINUES THROUGH THIS WEEKEND WITH SPOTTY SHOWERS OR SPRINKLES. PERIODS OF UNSETTLED WEATHER AND BELOW NORMAL TEMPERATURES WILL CONTINUE THROUGH MOST OF NEXT WEEK AS WELL. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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330 PM UPDATE...CLOUDS HAVE STREAMED DOWN THE EAST COAST OF MASSACHUSETTS THIS AFTERNOON. THIS IS IN RESPONSE TO A SHORTWAVE SLOWLY ROTATING ITS WAY AROUND THE BASE OF THE UPPER LOW WHICH IS EAST OF MASSACHUSETTS. OTHERWISE...TEMPERATURES REMAIN IN THE MID 50S FOR MUCH OF THE AREA...WITH COOLER TEMPERATURES NEAR THE COAST. TONIGHT...LIGHT WINDS AND MOSTLY CLEAR SKIES WILL RESULT IN EXCELLENT RADIATIONAL COOLING OVERNIGHT. THIS WILL DROP MANY LOCATIONS INTO BELOW FREEZING ACROSS THE INTERIOR. TEMPERATURES WILL FALL INTO THE LOW TO MID 30S ACROSS NORTHERN CONNECTICUT... RHODE ISLAND...AND SOUTHEASTERN MASSACHUSETTS. BECAUSE THE GROWING SEASON HAS BEGUN ACROSS THESE AREAS...WILL ISSUE A FROST ADVISORY FOR THIS REGION. THERE IS ALSO A LOW PROBABILITY OF FROST OCCURRING ALONG THE EAST COAST OF MASSACHUSETTS. HOWEVER...CONFIDENCE IS LOWER THERE SO HAVE HELD OFF ON ISSUING AN ADVISORY.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
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SUNDAY...THE UPPER LOW IS EXPECTED TO MOVE SLIGHTLY CLOSER TO OUR REGION. THUS WE WILL BE IN A MORE FAVORABLE POSITION FOR DIURNAL CLOUDS AND SHOWERS. SKIES SHOULD START OFF PARTLY TO MOSTLY SUNNY THEN CLOUDS DEVELOP ALONG WITH A FEW SPOTTY SHOWERS. THESE SHOWERS ARE MORE LIKELY TO OCCUR NORTH OF THE MASS PIKE. HIGH TEMPERATURES SHOULD BE IN THE 50S ONCE AGAIN...THOUGH IF ENOUGH SUN PEEKS THROUGH THE CLOUDS...COULD SEE TEMPS NEAR 60 THROUGH THE CONNECTICUT VALLEY AND IN PARTS OF RHODE ISLAND AND SOUTHEASTERN MASSACHUSETTS. SUNDAY NIGHT...SCATTERED SHOWERS WILL CONTINUE TO AFFECT SOUTHERN NEW ENGLAND WITH THE UPPER LOW JUST EAST OF THE AREA. WITH CLOUDY SKIES AND RAIN SHOWERS...EXPECT TEMPERATURES TO BE A BIT WARMER THAN EITHER OF THE PREVIOUS TWO NIGHTS WITH LOWS IN THE UPPER 30S TO THE LOWER 40S.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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HIGHLIGHTS... * RISK FOR SHOWERS AT TIMES BUT DRY MOST OF PERIOD * LOW CONFIDENCE AFTER WEDNESDAY OVERVIEW... PERSISTENT UPPER TROF OVER MARITIMES RETROGRADES EARLY IN THE WEEK BEFORE MOVING BACK OFFSHORE. SOUTHERN STREAM ENERGY WHICH CAME ASHORE LAST NIGHT IN CA MAY PHASE WITH NORTHERN STREAM ENERGY LATE IN THE WEEK. OPERATIONAL GFS DOES NOT SHOW PHASING. THE 12Z ECMWF DOES SHOW PHASING LIKE ITS PREDECESSOR...BUT ALSO LIKE ITS PRIOR RUN...STILL TAKES THE SURFACE LOW WELL SOUTH OF NEW ENGLAND. THE ECMWF HAS SHOWN BETTER RUN TO RUN CONTINUITY AND ITS 12Z OPERATIONAL RUN SEEMS FAIRLY CONSISTENT WITH ITS 00Z ENSEMBLE MEAN. THE OPERATIONAL GFS RUNS SHOW LITTLE RUN TO RUN CONTINUITY...AND ITS ENSEMBLES ARE WIDELY DISPERSED WITH MANY MEMBERS SHOWING NO SURFACE LOW OFF THE MID ATLC COAST AND A FEW OTHERS DEPICTING AN INTENSE COASTAL LOW JUST SE OF NEW ENGLAND. ALTHOUGH OVERALL CONFIDENCE IS LOW AFTER WEDNESDAY...TEND TO HAVE A LITTLE MORE CONFIDENCE IN THE ECMWF SOLUTION AT THIS TIME GIVEN ITS BETTER INTERNAL CONSISTENCY. DETAILS... MONDAY...UPPER LOW RETROGRADES TO THE WEST AND INDUCES SOME LOW LEVEL MOISTURE CONVERGENCE AND A COLD POOL ALOFT THAT SUPPORTS SHOWERS. HAVE POPS GENERALLY AROUND 40 PERCENT BUT THINKING THAT FUTURE SHIFTS MAY WISH TO INCREASE THOSE IF FUTURE MODEL RUNS REMAIN CONSISTENT. NOTED THAT TOTAL TOTALS WERE NEAR 50...REFLECTIVE OF THE COLD POOL ALOFT. MONDAY NIGHT...MAY SEE SHOWERS LINGER INTO THE EVENING HOURS BEFORE GRADUALLY DISSIPATING AND UPPER TROF STARTS TO SHIFT SE IN ADDITION TO LOSS OF DAYTIME HEATING. TUESDAY...HAVE KEPT SLIGHT CHANCE OF SHOWERS FOR THE AFTERNOON IN THE EAST GIVEN SOME LINGERING MOISTURE...CYCLONIC FLOW AND PROXIMITY OF COLD POOL ALOFT. WEDNESDAY AND THURSDAY...WEDNESDAY IS LOOKING DRY FOR NOW. GFS BRINGS UPPER SHORT WAVE TOWARD NEW ENGLAND LATE IN DAY/EVENING BUT ECMWF HOLDS IT BACK. ENOUGH UNCERTAINTY THAT HAVE JUST LOW END SLIGHT CHANCE POPS FOR THURSDAY. THURSDAY NIGHT THROUGH SATURDAY...A LOT OF UNCERTAINTY FOR THIS PERIOD DEPENDENT UPON EVOLUTION OF PROBABLE LOW DEVELOPMENT OFF THE MID ATLC COAST. THE ECMWF SHOWS BEST CONSISTENCY RUN TO RUN AND WITH ITS ENSEMBLES SO LEANING IN THAT DIRECTION FOR THE MOMENT. THIS WOULD SUGGEST THE POTENTIAL OF A SIGNIFICANT SURFACE LOW FORMING NEAR THE MID ATLC COAST BUT PROBABLY REMAINING SE OF NEW ENGLAND. IT IS POSSIBLE THAT BY SATURDAY WILL SEE BUILDING HEIGHTS ALOFT AND INCREASING THICKNESSES AS A RIDGE AMPLIFIES OVER THE OH VALLEY AND ATTEMPTS TO BUILD TOWARD NEW ENGLAND. THIS MAY SIGNAL THE START OF A WARMER PERIOD FOR THE AREA.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH 00Z...HIGH CONFIDENCE. VFR. NW WINDS GUSTING AROUND 20 KNOTS. TONIGHT...HIGH CONFIDENCE. VFR WITH LIGHT WINDS. SUNDAY...HIGH CONFIDENCE. VFR WITH LIGHT WINDS. SEA BREEZES LIKELY. POSSIBLE BRIEF MVFR IN SPOTTY SHOWERS. SUNDAY NIGHT...HIGH CONFIDENCE. VFR WITH LIGHT WINDS. POSSIBLE BRIEF MVFR IN SPOTTY SHOWERS. KBOS TAF...HIGH CONFIDENCE IN OVERALL TAF. LOW CONFIDENCE IN LATE SEA BREEZE DEVELOPMENT. KBDL TAF...HIGH CONFIDENCE IN OVERALL TAF. OUTLOOK...MONDAY THOUGH THURSDAY... MONDAY INTO MONDAY NIGHT...VFR MOST OF THE TIME BUT AREAS OF MVFR CIGS/VSBYS IN SCATTERED SHOWERS. TUESDAY THROUGH THURSDAY...VFR CONDITIONS APPEAR LIKELY AT THIS TIME.
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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. HIGH CONFIDENCE. QUIET BOATING WEATHER EXPECTED THROUGHOUT THE PERIOD WITH WINDS AND SEAS REMAINING BELOW SMALL CRAFT ADVISORY CRITERIA. WINDS WILL SHIFT FROM TIME TO TIME THROUGH SUNDAY NIGHT BUT SHOULD BE OUT OF THE NORTHWEST FOR MUCH OF THE TIME. OUTLOOK...MONDAY THOUGHT THURSDAY... MODERATE TO HIGH CONFIDENCE. ENOUGH NORTHERLY GRADIENT ANTICIPATED MON NIGHT INTO TUE MORNING THAT SMALL CRAFT ADVISORY CONDITIONS MIGHT BE MET...ESPECIALLY COASTAL WATERS TO THE EAST. MAY TAKE UNTIL TUE EVENING BEFORE SEAS SUBSIDE BACK BELOW 5 FEET. OFFSHORE LOW MAY BRING INCREASING WINDS AND SEAS...PERHAPS NEAR OR ABOVE SMALL CRAFT ADVISORY THRESHOLDS...TO THE OUTER SOUTH COASTAL WATERS LATE THU OR THU NIGHT...BUT CONFIDENCE IS LOW ON THE EVOLUTION OF THE WIND FIELD FOR THAT TIME FRAME GIVEN HIGHER THAN AVERAGE NUMERICAL WEATHER PREDICTION MODEL UNCERTAINTIES.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR CTZ002>004. MA...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR MAZ017-018. RI...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR RIZ001-003. MARINE...NONE.
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&& $$ SYNOPSIS...RLG/THOMPSON NEAR TERM...RLG SHORT TERM...RLG LONG TERM...THOMPSON AVIATION...RLG/THOMPSON MARINE...RLG/THOMPSON

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