Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 282021 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 421 PM EDT TUE JUL 28 2015 .SYNOPSIS...
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ISOLATED TO SCATTERED THUNDERSTORMS WILL COME TO AN END THIS EVENING. OTHERWISE...HOT AND HUMID CONDITIONS EXPECTED THROUGH THURSDAY. A COLD FRONT MAY BRING SCATTERED THUNDERSTORMS LATE THURSDAY AND THURSDAY NIGHT. WARM BUT DRIER AND LESS HUMID WEATHER IS EXPECTED FRIDAY INTO NEXT WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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***A FEW STRONG TO SEVERE THUNDERSTORMS THROUGH EARLY EVENING MAINLY CENTRAL/SOUTHEAST MA INTO RHODE ISLAND AND PERHAPS FAR EASTERN CT*** ISOLATED TO SCATTERED THUNDERSTORMS HAVE DEVELOPED LATE THIS AFTERNOON. THIS IN RESPONSE TO DIURNAL HEATING RESULTING IN MLCAPES OF 1500 TO 2000...SOME SEA BREEZE/OUTFLOW INTERSECTIONS AND A SHORTWAVE PASSING EAST OF THE REGION. WHILE ISOLATED THUNDERSTORMS OCCURRED ACROSS OUR FAR WESTERN ZONES EARLIER...MAIN FOCUS FOR ACTIVITY SHOULD BE IN CENTRAL AND SOUTHEAST MA...AS WELL AS RHODE ISLAND AND PERHAPS INTO FAR EASTERN CT. THIS FROM SEA BREEZE AND OUTFLOW BOUNDARIES ALONG WITH TERRAIN INFLUENCES. A FEW OF THESE STORMS MAY BECOME STRONG TO SEVERE AND PRODUCE ISOLATED STRONG WIND GUSTS AND HAIL THROUGH EARLY EVENING. ACTIVITY SHOULD WIND DOWN BY 7 OR 8 PM OR SO THIS EVENING AS SHORTWAVE DEPARTS...HEIGHTS RISE AND INSTABILITY DIMINISHES. OTHERWISE...DRY WEATHER PREVAILS FOR THE REST OF TONIGHT. WILL LIKELY SEE PATCHY FOG DEVELOP ESPECIALLY IN AREAS THAT RECEIVED RAIN THIS AFTERNOON AND EARLY EVENING. LOW TEMPS WILL RANGE FROM THE LOWER TO MIDDLE 60S IN THE OUTLYING LOCATIONS WITH UPPER 60S TO LOWER 70S IN THE URBAN HEAT ISLANDS OF DOWNTOWN BOSTON AND PROVIDENCE.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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***HOT BUT DRY WEATHER ON WEDNESDAY*** UPPER LEVEL RIDING WILL BUILD ACROSS SOUTHERN NEW ENGLAND. THIS SHOULD RESULT IN PARTLY TO MOSTLY SUNNY SKIES...DESPITE SOME DIURNAL CUMULUS CLOUDS. 850 MB TEMPS AROUND +18C WILL YIELD HIGHS BETWEEN 90 AND 95 ACROSS MOST OF THE REGION. WEAK PRESSURE GRADIENT WILL RESULT IN TEMPS A BIT COOLER ALONG PORTIONS OF THE COAST. WHILE THERE IS A LOW RISK OF A VERY ISOLATED SHOWER/THUNDERSTORM...GIVEN UPPER LEVEL RIDGING OPTED FOR A DRY FORECAST. EVEN IF ONE WERE TO HAPPEN IT PROBABLY WOULD BE VERY BRIEF AND COVER SUCH A SMALL AREA OF OUR REGION...NOT WORTH A MENTION AT THIS POINT.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... 350 AM UPDATE... HIGHLIGHTS... * VERY WARM AND HUMID THU * SCATTERED STORMS POSSIBLE LATE THU/THU NIGHT * DRIER/LESS HUMID FRI THRU MON BUT STILL WARM WED NIGHT/THU/THU NIGHT... GOOD MODEL AGREEMENT ON SHORT WAVE RIDGING OVER THE AREA WED NIGHT INTO THU. THUS DRY WEATHER TO START THIS PERIOD HOWEVER THE RISK OF SHOWERS/T-STORMS INCREASES LATE THU INTO THU NIGHT AS POTENT NORTHERN STREAM TROUGH CURRENTLY EXITING THE NORTHERN ROCKIES INTO THE HIGH PLAINS BEGINS TO APPROACH NEW ENGLAND FROM THE WEST. APPEARS TIMING OF THE FRONT COMES THROUGH OVERNIGHT...WELL AFTER PEAKING HEATING. THIS COMBINED WITH MARGINAL SHEAR KEEPS THE RISK LOW FOR STRONG CONVECTION LATE THU INTO THU NIGHT. HOWEVER GOOD SYNOPTIC SCALE LIFT WITH THIS TROUGH SUGGEST AT LEAST SHOWERS SHOULD BE ABLE TO HOLD TOGETHER AND MOVE ACROSS THE AREA LATE THU AND THU NIGHT. PWATS ABOVE NORMAL AND DEW PTS 65 TO 70 WILL INCREASE THE RISK FOR HEAVY DOWNPOURS. ALTHOUGH STILL 2 DAYS AWAY WILL NEED TO MONITOR LATER MODEL TRENDS. OTHERWISE VERY WARM AND HUMID CONDITIONS THU AHEAD OF APPROACHING COLD FRONT. A MODEL BLEND OFFERS HIGHS U80S TO L90S. FRIDAY THROUGH MONDAY... ANOMALOUS CLOSED LOW/VORTEX SETS UP OVER HUDSON/JAMES BAY THIS TIME PERIOD. THIS RESULTS IN BELOW NORMAL HEIGHTS AND MEAN TROUGH OVER THE GREAT LAKES INTO THE NORTHEAST. THIS WILL KEEP TEMPERATURES NEAR NORMAL /HIGHS MU80S/ AND LOWS IN THE 60S ALONG WITH TOLERABLE HUMIDITY AS DEW PTS AVERAGE IN THE 50S DURING THE DAYLIGHT HOURS. HOWEVER WITH THE NORTHERN STREAM JET SUPPRESSED SOUTHWARD INTO THE GREAT LAKES AND NORTHEAST THERE WILL BE THE RISK OF SCATTERED DIURNAL SHOWERS/T-STORMS JUST ABOUT EVERY DAY. TOO DIFFICULT AT THIS TIME RANGE TO TIME INDIVIDUAL SHORT WAVES. NOT A WASHOUT BUT THE RISK OF CONVECTION FROM TIME TO TIME. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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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 WEDNESDAY AFTERNOON/... LATE THIS AFTERNOON...MODERATE TO HIGH CONFIDENCE EXCEPT FOR SOME LOW CLOUDS AND FOG PATCHES ON THE ISLANDS. MAINLY VFR CONDITIONS BUT HIT AND MISS SHOWERS/THUNDERSTORMS EXPECTED THROUGH EARLY EVENING WILL RESULT IN LOCALIZED LOWER CONDITIONS. ACTIVITY WILL BE ISOLATED TO SCATTERED...SO MUCH OF THE REGION WILL REMAIN DRY. BULK OF ACTION SHOULD BE ACROSS CENTRAL/SOUTHEAST MA...RHODE ISLAND AND PERHAPS FAR EASTERN CT. TONIGHT...MODERATE CONFIDENCE. ANY ISOLATED TO SCATTERED CONVECTION SHOULD COME TO AN END BY 7 OR 8 PM. OTHERWISE...VFR FOR MOST SITES EXCEPT FOR SOME PATCHY FOG IN THE TYPICALLY PRONE LOCATIONS. ALSO...CANNOT RULE OUT IFR IN STRATUS AND FOG ACROSS FAR SE MASS INCLUDING THE CAPE AND ISLANDS...BUT CONFIDENCE IN THAT IS LOW. WEDNESDAY...HIGH CONFIDENCE IN VFR CONDITIONS. KBOS TERMINAL...HIGH CONFIDENCE IN MAINLY VFR THROUGH TONIGHT. CONVECTION WILL LIKELY REMAIN WEST OF THE BOSTON TERMINAL...BUT STILL A LOW RISK THAT SOMETHING COULD DEVELOP THROUGH 8 PM KBDL TERMINAL...HIGH CONFIDENCE IN MAINLY VFR THROUGH TONIGHT. VERY LOW RISK OF AN ISOLATED THROUGH 8 PM. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... 350 AM UPDATE... WED NGT/THU...PATCHY MVFR/IFR IN FOG WED NGT BUT QUICKLY IMPROVING TO VFR THU MORNING. LOW PROB THAT MVFR/IFR IN STRATUS LINGERS ALONG THE SOUTH COAST THU. THEN UNCERTAINTY ON HOW QUICK THIS FOG/STRATUS BURNS OFF SOUTH COAST. THU NIGHT...VFR-MVFR IN SCATTERED SHOWERS/T-STORMS. SOME UNCERTAINTY ON HOW WIDESPREAD PRECIP WILL BE. FRI AND SAT...VFR LIKELY. HIGH FORECAST CONFIDENCE.
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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 THROUGH WEDNESDAY AFTERNOON/...HIGH CONFIDENCE. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH WEDNESDAY AFTERNOON. MAIN CONCERN WILL BE A FEW STRONG TO SEVERE STORMS ACROSS THE ADJACENT SOUTH COASTAL WATERS THROUGH 7 OR 8 PM. LOCALLY STRONG WIND GUSTS AND PERHAPS ISOLATED HAIL ARE THE MAIN CONCERNS. ALSO...SOME PATCHY FOG IS POSSIBLE THIS EVENING NEAR THE ISLANDS BUT VISIBILITIES SHOULD IMPROVE AFTER MIDNIGHT AS WINDS TURN WEST. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... 350 AM UPDATE... WED NIGHT AND THU...FAIRLY TRANQUIL WIND AND SEAS. POSSIBLE PATCHY FOG IN HUMID AIRMASS. THU NIGHT...MODEST SSW WIND AHEAD OF APPROACHING COLD FRONT. SCATTERED SHOWERS WITH EMBEDDED THUNDER POSSIBLE. FRI AND SAT...COLD FRONT SLOWLY MOVES OFFSHORE. ANOTHER WEAK FRONT MAY ENTER THE WATERS SAT. WSW WINDS EXPECTED.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT WEDNESDAY FOR MAZ017>024. RI...AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT WEDNESDAY FOR RIZ005>008. MARINE...NONE.
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&& $$ SYNOPSIS...FRANK NEAR TERM...FRANK SHORT TERM...FRANK LONG TERM...NOCERA AVIATION...FRANK/NOCERA MARINE...FRANK/NOCERA

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