Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280042 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 842 PM EDT WED MAY 27 2015 .SYNOPSIS...
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SHOWERS AND ISOLATED THUNDERSTORMS WILL DIMINISH THIS EVENING...WITH MAINLY DRY CONDITIONS EXPECTED AFTER MIDNIGHT. A COLD FRONT MAY BRING A FEW STRONG THUNDERSTORMS TO THE REGION THURSDAY AFTERNOON BUT A WIDESPREAD/SOAKING RAINFALL IS NOT EXPECTED. DURING FRIDAY HIGH PRESSURE WILL BRING DRY CONDITIONS. FOR THIS WEEKEND...A SLOW MOVING FRONT WILL BRING THE CHANCE FOR SHOWERS AND SOME THUNDERSTORMS. THIS FRONT MAY LINGER NEAR OUR AREA INTO THE BEGINNING OF THE NEXT WORKWEEK...WITH HIGH PRESSURE RETURNING BY MIDWEEK.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY/...
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830 PM UPDATE... INTENSITY OF CONVECTION HAD DIMINISHED CONSIDERABLY OVER THE PAST HOUR...AND THE SEVERE THUNDERSTORM WATCH THAT WAS PREVIOUSLY IN EFFECT FOR WESTERN PORTIONS OF OUR AREA HAS BEEN CANCELED. THE LINGERING PRECIPITATION IS MAINLY SHOWERS...ALTHOUGH ISOLATED THUNDER IS STILL POSSIBLE THRU 02Z. BECAUSE OF THE EXTENT OF CONVECTION THAT DEVELOPED...EXPANDED THE CHANCES FOR PRECIP EASTWARD INTO THE I495/I95 CORRIDOR...TO JUST TOUCH THE BOSTON AREA THIS EVENING. HOWEVER LIGHTNING IS NOT EXPECTED TO MAKE IT EAST OF THE I95 CORRDIOR THIS EVENING. UPDATED SKY GRIDS TO ACCOUNT FOR CONVECTIVE DEBRIS AS WELL AS MARINE STRATUS IN SOUTH COASTAL LOCALES...SO MOSTLY CLOUDY SKIES EXPECTED THRU THIS EVENING. AFTER MIDNIGHT...SHOULD SEE LOW CLOUDS INCREASE OVERNIGHT BUT AREAL COVERAGE IS VERY UNCERTAIN WITH HIGHEST RISK ACROSS SOUTH OF MA PIKE. WINDS DO NOT TOTALLY DECOUPLE IN MOST LOCATIONS...SO WHILE SOME FOG PATCHES ARE POSSIBLE ESPECIALLY NEAR THE SOUTH COAST ITS EXTENT SHOULD BE LIMITED TO SOME DEGREE. LOW TEMPS WILL NOT DROP BELOW 65 DEGREES IN MANY LOCATIONS AS A RESULT OF INCREASING LOW LEVEL MOISTURE.
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&& .SHORT TERM /6 AM THROUGH 6 PM THURSDAY/...
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*** A FEW STRONG TO MARGINALLY SEVERE THUNDERSTORMS POSSIBLE THURSDAY AFTERNOON/EARLY EVENING BUT A WIDESPREAD OUTBREAK IS NOT EXPECTED *** THURSDAY... ANY LOW CLOUDS AND FOG PATCHES SHOULD MIX OUT ACROSS MOST OF THE REGION BY LATE MORNING. THIS A RESULT OF WINDS VEERING AT LEAST A BIT AHEAD OF A PRE-FRONTAL TROUGH/COLD FRONT. THE EXCEPTION TO THIS WILL BE THE SOUTH COAST/CAPE/ISLANDS...WHERE MARINE INFLUENCE MAY ALLOW LOW CLOUDS/FOG PATCHES TO HANG ON MUCH OF THE AFTERNOON. OTHERWISE...SHOULD SEE PARTIAL SUNSHINE EMERGE. MILD START AND WITH 850 MB TEMPS AROUND +15C TO +16C SHOULD ALLOW HIGHS TO REACH INTO THE MIDDLE TO UPPER 80S NORTHWEST OF BOS TO PVD LINE. IN FACT...MAY SEE A FEW LOCATIONS NEAR 90 IN THE MERRIMACK RIVER VALLEY. TEMPS WILL BE COOLER SOUTHEAST OF A BOS TO PVD LINE GIVEN THE MARINE INFLUENCE ON GUSTY SOUTHWEST WINDS. THE MAIN CONCERN THURSDAY AFTERNOON AND EARLY EVENING WILL THE POTENTIAL FOR A FEW STRONG TO MARGINALLY SEVERE THUNDERSTORMS. CAPES SHOULD INCREASE ON THE ORDER OF 1000 TO 2000 J/KG AHEAD OF AN APPROACHING PRE-FRONTAL TROUGH/COLD FRONT. IN ADDITIONAL...0 TO 6 KM SHEAR ON THE ORDER OF 30 TO 35 KNOTS WITH MID LEVEL LAPSE RATES STEEPENING A LAPSE RATES SHOULD ALLOW SOME SCATTERED SHOWERS/THUNDERSTORMS TO DEVELOP DURING THE AFTERNOON. THIS WILL FIRST OCCUR IN THE INTERIOR AND THEN MAKE THEIR WAY TOWARDS THE COASTAL PLAIN LATER IN THE AFTERNOON/EARLY EVENING WITH THE PRE- FRONTAL TROUGH COLD FRONT. ENOUGH 0 TO 6 KM SHEAR AND 500 MB TEMPS DROPPING TO AROUND -12C...MAY ALLOW FOR A FEW STRONG TO SEVERE THUNDERSTORMS. WHILE WE ARE NOT EXPECTING A WIDESPREAD/HIGH END OUTBREAK...A FEW STORMS MAY CONTAIN LOCALLY STRONG TO DAMAGING WIND GUSTS AND HAIL. LOCALLY HEAVY RAINFALL WILL ALSO BE A CONCERN...AS IT TYPICALLY IS WITH THUNDERSTORMS.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... DETAILS... THURSDAY NIGHT...COLD FRONT MOVES OFFSHORE THURSDAY EVENING. SLIGHT CHANCE OF SHOWERS/THUNDER EARLY ACROSS EAST AND SOUTH COASTAL AREAS WITH THE FRONT...THEN PRECIP CHANCES COME TO AN END AND HIGH PRESSURE STARTS TO BUILD INTO OUR AREA. THE POTENTIAL EXISTS FOR AREAS OF FOG TO DEVELOP ALONG SOUTH COASTAL MA AND RI. FRIDAY...UPPER LEVEL RIDGING AND PASSING SURFACE HIGH PRESSURE BRING A MAINLY DRY DAY TO SOUTHERN NEW ENGLAND. A BIT LESS WARM WITH HIGHS IN THE UPPER 70S TO LOW 80S...EXCEPT ONSHORE WINDS KEEP TEMPS LOWER CLOSE TO THE SHORELINE. SATURDAY...SURFACE HIGH PRESSURE SLIDES OFFSHORE...ENABLING SOUTHWEST FLOW TO BRING INCREASING MOISTURE/HUMIDITY TOWARDS OUR AREA. LATE IN THE DAY A COLD FRONT APPROACHES OUR REGION FROM THE WEST...EMERGING FROM THE EASTERN GREAT LAKES REGION AND QUEBEC. WE COULD SEE SCATTERED SHOWERS/THUNDERSTORMS DURING SATURDAY AFTERNOON IN WESTERN MA AND NORTHERN CT...WITH SHOWER/THUNDERSTORM CHANCES EXTENDING EASTWARD SATURDAY EVENING AS THE COLD FRONT PUSHES INTO OUR AREA. WITH PRECIPITABLE WATER INCREASING TO OVER 1.5 INCHES AHEAD OF THE FRONT...LOCALLY HEAVY DOWNPOURS WILL BE POSSIBLE. SUNDAY... COLD FRONT SLOWLY MOVES THROUGH OUR REGION DURING SUNDAY. EXPECTING SHOWERS TO CROSS OUR AREA DURING THE DAY...LOWER CHANCE FOR THUNDERSTORMS. THE FRONT MAY REACH THE SOUTH COAST BY SUNDAY NIGHT...BUT THERE IS SOME UNCERTAINTY AS TO WHETHER THE FRONT HANGS UP IN OUR AREA FOR A PERIOD OF TIME. AT THIS TIME WILL CONTINUE WITH HIGH CHANCE TO LIKELY POPS ON SUNDAY...THEN CHANCE POPS THRU SUNDAY NIGHT. MONDAY AND TUESDAY...THERE CONTINUES TO BE UNCERTAINTY ON HOW FAR SOUTH THE FRONT TRACKS EVEN INTO THIS TIMEFRAME...WHETHER IT STALLS NEAR THE SOUTH COAST OR FURTHER OFFSHORE. THIS WILL AFFECT OUR CHANCES FOR SHOWERS. 00Z ECMWF WAS LEAST PROGRESSIVE WITH THE FRONT...BUT THE 12Z ECMWF IS MORE PROGRESSIVE...NUDGING THE FRONT SOUTH OF OUR AREA FOR MONDAY EVENING. 12Z GFS HAS OUR AREA MAINLY DRY ON MONDAY. AT THIS TIME WILL CONTINUE WITH SLIGHT CHANCE TO CHANCE POPS FOR MONDAY...AND TUESDAY GOING MAINLY DRY...WITH THE HIGHEST POPS ALONG SOUTH COASTAL LOCALES. THUNDER LOOKS LESS PROBABLE FOR THIS TIMEFRAME. WEDNESDAY...MODELS ARE SHOWING SURFACE HIGH PRESSURE AND UPPER LEVEL RIDGING BRINGING MAINLY DRY CONDITIONS TO OUR AREA. && .AVIATION /01Z 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. THIS EVENING...LOW TO MODERATE CONFIDENCE. MIX OF VFR AND MVFR CONDITIONS FOR THIS EVENING...WITH THE LOWER CIGS/VSBYS OVER THE INTERIOR IN SCATTERED SHOWERS/ISOLATED THUNDERSTORMS...AND MVFR CIGS SOUTH COASTAL MA AND RI IN STRATUS. TONIGHT...LOW CLOUDS SHOULD ADVANCE FURTHER NORTH TONIGHT..BUT HOW FAR NORTH THE LOW CLOUDS GET AND THEIR EXTENT REMAINS UNCERTAIN. CIGS SHOULD BECOMING MAINLY MVFR...EXCEPT IFR SOUTH COASTAL MA AND RI. WINDS PROBABLY DO NOT COMPLETELY DECOUPLE OVERNIGHT IN MOST LOCATIONS...SO EXTENT OF FOG MAY BE LIMITED BUT SOME STILL POSSIBLE ESPECIALLY ALONG AREAS OF THE SOUTH COAST/CAPE/ISLANDS. THURSDAY...MODERATE CONFIDENCE. ANY LOWER CLOUDS AND FOG PATCHES SHOULD BURN OFF BY LATE MORNING...EXCEPT FOR THE SOUTH COAST/CAPE/ISLANDS WHERE MAY HANG TOUGH THROUGH THE AFTERNOON. OTHERWISE...VFR BUT A COLD FRONT/PRE-FRONTAL TROUGH MAY BRING A FEW STRONG THUNDERSTORMS DURING THE AFTERNOON RESULTING IN BRIEFLY LOWER CONDITIONS. KBOS TERMINAL...CONFIDENCE IN TAF DETERIORATES LATE THIS EVENING AND OVERNIGHT. VFR INTO THIS EVENING. LOW CONFIDENCE IF IFR OR LOW END MVFR CIGS CAN MAKE IT AS FAR NORTH AS THE BOS TERMINAL. KBDL TERMINAL...LOW CONFIDENCE IN TAF. AN AREA OF SHOWERS/THUNDERSTORMS CROSSING THRU BDL THRU 02Z OR SO WILL PRODUCE VARIABLE CIGS/VSBYS. OTHERWISE...IMPROVEMENT TO VFR IS PROBABLE LATE THIS EVENING...UNTIL LOWER CIGS MAY INVADE DURING THE OVERNIGHT HOURS. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY...VFR. MAY SEE LOCAL MVFR-IFR CONDITIONS EARLY MORNING ALONG S COAST IN PATCHY FOG...THEN MAY LOWER AGAIN LATE FRI NIGHT TO MVFR- IFR. SATURDAY...PATCHY EARLY MORNING FOG WITH MVFR-IFR CONDITIONS... WILL IMPROVE. SCT SHRA/TSRA SAT AFTERNOON THROUGH SAT NIGHT... WITH LOCAL MVFR-IFR CONDITIONS. SUNDAY...SCT SHOWERS LINGER WITH ISOLD TSTMS POSSIBLE DURING THE DAY. MAY SEE BRIEF MVFR CONDITIONS. MONDAY...CONDITIONS MAINLY VFR...EXCEPT MVFR WITH SCT SHOWERS SOUTH COASTAL MA/RI.
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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. SHORT TERM /TONIGHT AND THURSDAY/... TONIGHT...MODERATE TO HIGH CONFIDENCE. NEAR SHORE SMALL CRAFT WIND GUSTS DIMINISH AS THE EVENING PROGRESSES. HOWEVER...SCA CONTINUE FOR THE OUTER- WATERS OVERNIGHT FOR MARGINAL 5 FOOT SEAS. AREAS OF FOG MAY DEVELOP OVERNIGHT...BUT WINDS MAY BE A BIT TOO STRONG FOR WIDESPREAD DENSE FOG. THURSDAY...MODERATE TO HIGH CONFIDENCE. ANOTHER ROUND OF NEAR SHORE SOUTHWEST WIND GUSTS OF 25 KNOTS EXPECTED THURSDAY AFTERNOON. LATER SHIFTS WILL LIKELY HAVE TO HOIST MORE SMALL CRAFT ADVISORIES TO COVER THIS POTENTIAL. IN ADDITION...A FEW STRONG THUNDERSTORMS WITH GUSTY WINDS AND HAIL ARE POSSIBLE LATE THURSDAY AFTERNOON AND EVENING. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY...LIGHT N-NE WINDS BECOME E DURING THE DAY...THEN SHIFT TO S- SW FRI NIGHT. EXPECT WINDS AND SEAS BELOW SMALL CRAFT CRITERIA. SATURDAY-SUNDAY...SW WINDS MAY BRIEFLY GUST TO 25 KT DURING SAT ON THE EASTERN WATERS...AS A COLD FRONT APPROACHES THE WATERS. OTHERWISE...EXPECTING GUSTS UP TO 20 KT. SEAS BUILD AGAIN TO AROUND 5 FT ACROSS THE OUTER WATERS. MONDAY...COLD FRONT MAY LINGER NEAR THE WATERS DURING THIS TIMEFRAME...WITH SEAS UP TO 5 FEET AND GUSTS TO 20 KT.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ231>235- 237-251. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ230- 236. SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ250- 254>256. && $$ SYNOPSIS...FRANK/NMB NEAR TERM...FRANK/NMB SHORT TERM...FRANK LONG TERM...NMB AVIATION...FRANK/NMB MARINE...FRANK/NMB

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