Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 260558 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 158 AM EDT SAT JUL 26 2014 .SYNOPSIS... HIGH PRESSURE NEARBY WILL RESULT IN DRY AND BEAUTIFUL WEATHER INTO SATURDAY AFTERNOON. SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED AT TIMES SUNDAY INTO MONDAY ALONG WITH A RETURN TO THE HUMIDITY AHEAD OF THE NEXT COLD FRONT. THE COLD FRONT MOVES OFFSHORE TUESDAY WITH HIGH PRESSURE BUILDING IN BEHIND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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2 AM UPDATE... SEASONABLY COOL NIGHT IN PROGRESS WITH TEMPS AT 130 AM IN THE U50S TO L60S INLAND AND MU60S ALONG THE COAST AND THE URBAN AREAS. MOST LOCATIONS HAVEN`T DECOUPLED YET SO AREAS OF FOG ARE VERY LIMITED. SOME MID/HIGH CLOUD DEBRIS FROM UPSTREAM TROUGH APPROACHING WESTERN NEW ENGLAND...ALTHOUGH NO PRECIP ASSOCIATED WITH THIS LOW AMPLITUDE SHORT WAVE. PREVIOUS FORECAST CAPTURES THESE DETAILS WELL SO NO MAJOR CHANGES WITH THIS FORECAST UPDATE. PREVIOUS DISCUSSION BELOW. =================================================================== HIGH PRESSURE NEARBY WILL RESULT IN A TRANQUIL NIGHT ACROSS SOUTHERN NEW ENGLAND. MAINLY CLEAR SKIES EXPECTED OTHER THAN PERHAPS A BIT OF HIGH CLOUDS STREAMING INTO THE REGION LATE. THE RELATIVELY DRY AIRMASS IN PLACE AND LIGHT WINDS WILL ALLOW FOR A GOOD NIGHT OF RADIATIONAL COOLING. LOWS SHOULD BOTTOM OUT IN THE 50S ACROSS THE OUTLYING LOCATIONS...TO THE LOW TO MID 60S IN THE URBAN HEAT ISLANDS OF DOWNTOWN BOSTON/PROVIDENCE. LOW HUMIDITY WILL MAKE FOR A VERY COMFORTABLE NIGHT.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... SATURDAY... A BEAUTIFUL START TO THE WEEKEND IS ON TAP FOR THE REGION. HIGH PRESSURE MOVING OFF THE COAST WILL ALLOW FOR TEMPS TO BE A DEGREE OR TWO WARMER THAN TODAY. HIGHS SHOULD TOP OUT IN THE MIDDLE 80S ACROSS MUCH OF THE REGION...WITH READINGS A FEW DEGREES COOLER ACROSS THE HIGHER TERRAIN AND ON THE SOUTH COAST. WHILE DEWPOINTS WILL BE SEVERAL DEGREES HIGHER...IT CERTAINLY WON/T BE HUMID FOR JULY STANDARDS. A SOUTHWEST BREEZE OF 20 TO 25 MPH EXPECTED TO DEVELOP DURING THE AFTERNOON. WE WILL SEE A MIXTURE OF CLOUDS AND SUNSHINE...BUT DRY WEATHER WILL DOMINATE. LOW PROBABILITY OF A SPOT SHOWER/THUNDERSTORM LATE IN THE AFTERNOON/EARLY EVENING ACROSS THE DISTANT INTERIOR...BUT EVEN IF IT HAPPENS AREAL COVERAGE/DURATION SHOULD BE QUITE LIMITED. SATURDAY NIGHT... DRY WEATHER SHOULD DOMINATE FOR MOST OF THE NIGHT. AN APPROACHING SHORTWAVE FROM THE WEST ALONG WITH A BURST OF ELEVATED INSTABILITY SHOULD ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO MOVE INTO OUR WESTERN ZONES AFTER 4 OR 5 AM. IT DOES NOT APPEAR THERE WILL BE ENOUGH INSTABILITY FOR SEVERE WEATHER...BUT GUESS THERE IS A LOW PROBABILITY FOR A STRONG THUNDERSTORM OR TWO WITH MUCAPES ON THE ORDER OF 500 TO 1000 J/KG. GIVEN INCREASING LOW LEVEL MOISTURE...LOW TEMPS WILL BE MILDER THAN TONIGHT. LOW TEMPS BY DAYBREAK SUNDAY SHOULD ONLY BOTTOM OUT IN THE MIDDLE TO UPPER 60S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... * SHOWERS AND THUNDERSTORMS POSSIBLE OVER THE WEEKEND AND INTO EARLY NEXT WEEK * HIGH PRESSURE BUILDS IN BEHIND COLD FRONT FOR THE SECOND HALF OF THE WEEK ON A SYNOPTIC LEVEL...THE MODELS ARE IN DECENT AGREEMENT...INCLUDING THE ECMWF ENSEMBLE AND GEFS. HOWEVER...THERE ARE OF COURSE MANY DISCREPANCIES WHEN IT COMES TO THE MESOSCALE DETAILS. THE OVERALL PATTERN HAS AN ANOMALOUSLY STRONG PERSISTENT UPPER TROUGH OVER THE GREAT LAKES WITH PERSISTENT RIDGING OVER THE WESTERN CONUS. THIS BRINGS SOME TIMING CONCERNS AS THE PERSISTENT TROUGH IS LIKELY TO SLOW THE TRAVEL OF A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION LATE SUNDAY THROUGH TUESDAY. THE MAIN CONCERN FOR THIS PERIOD OF THE FORECAST WILL BE THE SUNDAY TO TUESDAY TIME FRAME WHEN SHOWERS AND THUNDERSTORMS ARE LIKELY. THERE IS A POTENTIAL FOR SEVERE THUNDERSTORMS SOMETIME DURING THIS TIME FRAME BUT THERE IS QUITE A BIT OF UNCERTAINTY WHEN IT COMES TO THE DETAILS AND TIMING OF THIS POTENTIAL. AFTER THE COLD FRONT MOVES OFFSHORE TUESDAY...EXPECT HIGH PRESSURE TO BUILD IN ACROSS SOUTHERN NEW ENGLAND. SUNDAY THROUGH TUESDAY...LOW PRESSURE MOVES THROUGH SOUTHEASTERN CANADA WITH A SECONDARY LOW DEVELOPING AND MOVING SOMEWHERE CLOSE TO...IF NOT OVER...SOUTHERN NEW ENGLAND. EVENTUALLY THIS SYSTEM ALONG WITH A COLD FRONT MOVES THROUGH SOUTHERN NEW ENGLAND. HOWEVER...THE FRONT DOES NOT PUSH OFFSHORE UNTIL SOMETIME TUESDAY OR EVEN TUESDAY NIGHT. A SERIES OF SHORTWAVES ROTATING AROUND THE BASE OF THE UPPER TROUGH WILL BRING SEVERAL CHANCES FOR SHOWERS AND THUNDERSTORMS TO DEVELOP. INCREASINGLY WARMER AND MORE HUMID AIR WILL MOVE INTO THE REGION ON SOUTHWESTERLY WINDS. ALL OF THIS WILL COME TOGETHER RESULTING IN A RATHER UNSTABLE ENVIRONMENT WITH MULTIPLE POTENTIAL TRIGGERS FOR SHOWERS AND THUNDERSTORMS. THE MODELS STRAY IN THE DETAILS OF COURSE...WITH THE OPERATIONAL ECMWF CLOSEST TO THE ENSEMBLE MEANS OF BOTH THE ECMWF AND GEFS. WHILE SB CAPES ARE FORECAST TO BE OVER 1000 J/KG AND 0 TO 6 KM BULK SHEAR IS FORECAST TO BE UPWARDS OF 30 TO 40 KTS DURING THIS TIME... THERE ARE CONCERNS THAT A QUICK INSTABILITY BURST EARLY SUNDAY MORNING MAY RESULT IN DRIER AIR AND SUBSIDENCE PRECLUDING ANY STORMS FROM DEVELOPING LATER SUNDAY AFTERNOON AND EVENING. HOWEVER...WE WILL HAVE TO WAIT AND SEE HOW THINGS COME TOGETHER SUNDAY MORNING BEFORE WE CAN RULE OUT ANYTHING HAPPENING LATER SUNDAY. STORMS ARE POSSIBLE AGAIN MONDAY AND TUESDAY AS THE FRONT NEARS AND THEN CROSSES INTO SOUTHERN NEW ENGLAND. WEDNESDAY THROUGH FRIDAY...HIGH PRESSURE BUILDS IN OVER SOUTHERN NEW ENGLAND WEDNESDAY AND SLIDES SLOWLY OFFSHORE TOWARDS THE END OF THE WORK WEEK. && .AVIATION /06Z 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. 2 AM UPDATE... CIGS AND VSBYS MAINLY A BLEND OF GFS AND ITS MAVMOS OUTPUT. SHORT TERM /TODAY THROUGH SUNDAY/...HIGH CONFIDENCE THROUGH THIS EVENING THEN LOWERING CONFIDENCE LATE TONIGHT INTO SUNDAY ON SPECIFIC TIMING OF LOWER CIGS/VSBYS ASSOCIATED WITH SHOWERS/T-STORMS. THRU 12Z...DRY WEATHER ALONG WITH VFR CONDITIONS. EXCEPTION WILL BE IN A FEW SPOTS INLAND WHERE PATCHY GROUND FOG POSSIBLE. AFTER 12Z...DRY WEATHER CONTINUES ALONG WITH VFR CONDITIONS. SW WINDS 15-20 KT WITH A FEW GUSTS UP TO 25 KT POSSIBLE OVER SOUTHEAST MA THIS AFTERNOON. TONIGHT...DRY WITH VFR TO START THEN LOWERING TO MARGINAL VFR/MVFR TOWARD MORNING ALONG WITH A LOW PROB OF IFR CIGS WELL INLAND. SCATTERED SHOWERS AND T-STORMS ENTER WESTERN NEW ENGLAND LATE. SUNDAY...MARGINAL MVFR/VFR IN SCATTERED SHOWERS AND T-STORMS... MOST NUMEROUS IN THE MORNING. KBOS TAF...HIGH CONFIDENCE THROUGH THIS EVENING THEN LOWER CONFIDENCE ON EXACT TIMING OF SHOWERS/T-STORMS LATE TONIGHT INTO SUNDAY. MODEST SW WIND TODAY WITH SPEEDS OF 15-20 KT. KBDL TAF...HIGH CONFIDENCE THRU THIS EVENING THEN LOWER CONFIDENCE ON EXACT TIMING OF SHOWERS/T-STORMS LATE TONIGHT INTO SUNDAY. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUNDAY NIGHT THROUGH TUESDAY...MODERATE CONFIDENCE. MAINLY VFR. PERIODS OF MVFR/IFR LIKELY IN SHRA/TSRA. WEDNESDAY...MODERATE CONFIDENCE. VFR.
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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 /TONIGHT THROUGH SATURDAY NIGHT...HIGH CONFIDENCE. TONIGHT...HIGH PRESSURE IN CONTROL WILL KEEP WINDS/SEAS WELL BELOW SCA THRESHOLDS. VISIBILITIES WILL REMAIN EXCELLENT. SATURDAY...HIGH PRESSURE MOVING OFF THE COAST WILL RESULT IN SOUTH TO SOUTHWEST WINDS AROUND 15 KNOTS. GUSTS TO BETWEEN 20 AND 25 KNOTS ARE EXPECTED DURING THE AFTERNOON. THE HIGHEST WIND GUSTS ARE EXPECTED NEAR SHORE. ITS MARGINAL AND SINCE ITS 2ND PERIOD WILL HOLD OFF ON SCA HEADLINES FOR NOW...BUT THE NEXT SHIFT MAY HAVE TO CONSIDER ISSUANCE FOR THE NEAR SHORE WATERS. SATURDAY NIGHT... SOUTH TO SOUTHWEST WINDS OF 10 TO 20 KNOTS WILL CONTINUE ACROSS THE WATERS WITH HIGH PRESSURE OFF THE COAST. LONG SOUTH TO SOUTHWEST FETCH MAY ALLOW MARGINAL 5 FOOT SEAS TO DEVELOP ACROSS THE SOUTHERN OUTER-WATERS TOWARDS 12Z SUNDAY. OUTLOOK...SUNDAY THROUGH WEDNESDAY... MODERATE CONFIDENCE. SOUTHWESTERLY WINDS AND SEAS INCREASE GRADUALLY AS A COLD FRONT SLOWLY APPROACHES THE WATERS. SHOWERS AND THUNDERSTORMS ARE POSSIBLE SUNDAY THROUGH TUESDAY OVER THE WATERS. SMALL CRAFT ADVISORIES WILL BE NECESSARY SUNDAY THROUGH TUESDAY FOR SEAS AND SUNDAY FOR WINDS GUSTING TO AROUND 25 KTS. WINDS AND SEAS DIMINISH WEDNESDAY AS HIGH PRESSURE BUILDS OVER THE WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANK/RLG NEAR TERM...NOCERA SHORT TERM...FRANK LONG TERM...RLG AVIATION...NOCERA/RLG MARINE...FRANK/RLG

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