Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 272153 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 553 PM EDT WED MAY 27 2015 .SYNOPSIS... A FEW STRONG THUNDERSTORMS ARE POSSIBLE ACROSS WESTERN MASSACHUSETTS AND NORTHERN CONNECTICUT THIS EVENING...WHILE IT REMAINS DRY ELSEWHERE. 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. && .NEAR TERM /UNTIL 10 PM THIS EVENING/...
-- Changed Discussion --
***SEVERE THUNDERSTORM WATCH UNTIL 10 PM FOR NORTHERN CT AND CENTRAL/WESTERN MA ZONES*** 545 PM UPDATE... UPDATED GRIDS/FCST TO INLUDE SEVERE THUNDERSTORM WATCH 232 UNTIL 10 PM THIS EVENING FOR NORTHERN CT AND CENTRAL/WESTERN MA ZONES. INCREASED POPS EASTWARD TO ENCOMPASS THE WATCH AREA...AND EXPANDED POPS FOR SHOWERS/TSTMS INTO MIDDLESEX COUNTY MA SOUTHWARD INTO NORTHWEST RI. PREVIOUS DISCUSSION FOLLOWS... A CLUSTER OF SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ACROSS EASTERN NY IN RESPONSE TO AN APPROACHING SHORTWAVE AND ITS ASSOCIATED INSTABILITY. SPC MESO-ANALYSIS SHOWING CAPES ON THE ORDER OF 1500 TO 2000 J/KG HAVE DEVELOPED ACROSS WESTERN MA/NORTHWEST CT. HOWEVER...AS IS USUALLY CASE THERE ARE SOME LIMITING FACTORS IN OUR REGION. MID LEVEL LAPSE RATES ARE MARGINAL AND OUR WESTERN ZONES ARE ON THE FRINGE OF THE BETTER INSTABILITY/FORCING. THE ACTIVITY WILL ALSO BE ENTERING OUR REGION AFTER PEAK HEATING. SO ALL IN ALL...IT LOOKS LIKE SCATTERED SHOWERS/THUNDERSTORMS WILL MOVE INTO WESTERN MA/NORTHWEST CT SOMEWHERE BETWEEN 6 AND 10 PM THIS EVENING. PRIMARY THREAT WILL BE LOCALLY HEAVY RAINFALL AND DANGEROUS CLOUD TO GROUND LIGHTNING. HOWEVER...A FEW STRONG TO PERHAPS A MARGINALLY SEVERE THUNDERSTORM OR TWO ARE POSSIBLE GIVEN DECENT INSTABILITY AND 30 TO 35 KNOTS OF SHEAR. THE BIGGEST THREAT WOULD BE VERY LOCALIZED STRONG TO DAMAGING WIND GUSTS WITH HAIL A SECONDARY CONCERN. ACTIVITY SHOULD QUICKLY WEAKEN TO MAINLY SCATTERED SHOWERS AS IT ATTEMPTS TO ENTER CENTRAL MA LATER IN THE EVENING WITH WANING INSTABILITY AND LESS DYNAMICS/FORCING. ITS UNCERTAIN IF ANY SHOWERS EVEN GET INTO CENTRAL MA AND EXTREMELY UNLIKELY TO MAKE IT INTO EASTERN NEW ENGLAND.
-- End Changed Discussion --
&& .SHORT TERM /10 PM THIS EVENING THROUGH 6 PM THURSDAY/... *** A FEW STRONG TO MARGINALLY SEVERE THUNDERSTORMS POSSIBLE THURSDAY AFTERNOON/EARLY EVENING BUT A WIDESPREAD OUTBREAK IS NOT EXPECTED *** LATE THIS EVENING AND OVERNIGHT... OTHERWISE...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. 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. && .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 /22Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THIS AFTERNOON AND TONIGHT...LOW TO MODERATE CONFIDENCE. VFR CONDITIONS EXCEPT FOR MAINLY MVFR CIGS ACROSS RI/SOUTHEAST MA. LOW CLOUDS SHOULD ADVANCE FURTHER NORTH TONIGHT...BUT HOW FAR NORTH AND THEIR EXTENT REMAIN UNCERTAIN. 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. OTHERWISE...THERE IS THE RISK FOR A FEW STRONG THUNDERSTORMS BETWEEN 22Z AND 02Z ACROSS WESTERN MA AND NORTHERN CT. THIS ACTIVITY SHOULD QUICKLY WEAKEN AND FALL APART AS IT TRIES TO ENTER CENTRAL MA LATER THIS EVENING. 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...MODERATE CONFIDENCE IN TAF. A THUNDERSTORM IS POSSIBLE BETWEEN 22Z AND 02Z. OTHERWISE...VFR UNTIL LOWER CIGS MAY INVADE LATER IN THE EVENING AND INTO THE OVERNIGHT HOUR 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. && .MARINE... 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 THIS EVENING. 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. && .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

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.