Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271426 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1025 AM EDT WED MAY 27 2015 .SYNOPSIS... WARM AND MUGGY CONDITIONS WILL INCREASE THROUGH TOMORROW. A FEW SHOWERS AND THUNDERSTORMS ARE EXPECTED EACH DAY...BUT VAST MAJORITY OF THE TIME WILL FEATURE DRY WEATHER. COOLER AND LESS HUMID CONDITIONS ARRIVE LATE THIS WEEKEND INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ***A FEW STRONG TO PERHAPS EVEN A MARGINALLY SEVERE THUNDERSTORM OR TWO POSSIBLE ACROSS WESTERN MA/NORTHERN CT BETWEEN 4 AND 10 PM THIS EVENING*** 1021 AM UPDATE... ANOTHER VERY WARM AND MAINLY DRY DAY ON TAP FOR THE REGION. 850 MB TEMPERATURES AROUND +16C SHOULD ALLOW HIGH TEMPS TO REACH WELL INTO THE 80S ACROSS MUCH OF SOUTHERN NEW ENGLAND. THE WARMEST TEMPS WILL BE FOUND IN THE LOWER CT RIVER VALLEY AND MERRIMACK VALLEY...WHERE HIGHS SHOULD REACH INTO THE UPPER 80S. MEANWHILE...SOUTH TO SOUTHWEST FLOW OFF THE COOL OCEAN WILL HOLD HIGH TEMPS IN THE UPPER 60S AND THE 70S ALONG THE SOUTH COAST. GOOD MIXING SHOULD SUPPORT 25 TO 35 MPH WIND GUSTS ACROSS MOST LOCATIONS THIS AFTERNOON. WHILE MOST OF THE DAY WILL BE DRY...A SHORTWAVE WILL APPROACH OUR WESTERN ZONES LATE IN THE AFTERNOON AND EVENING. GIVEN DEWPOINTS OVER 60 DEGREES...CAPES ON THE ORDER OF 1000 TO 2000 J/KG WILL DEVELOP ALONG WITH 0 TO 6 KM SHEAR VALUES OF 30 TO 35 KNOTS. HOWEVER...AS IS USUALLY THE CASE THERE ARE SOME LIMITING FACTORS. MID LEVEL LAPSE RATES ARE FAIRLY WEAK WHICH WILL LIMIT UPDRAFTS TO SOME DEGREE AND THE PEAK TIME OF THE ACTIVITY IS A BIT LATER THAN WE LIKE TO SEE...BETWEEN 4 AND 10 PM. ALSO...BETTER DYNAMICS WILL BE TO OUR NORTH AND WEST. SO ALL IN ALL...IT LOOKS LIKE SCATTERED SHOWERS/THUNDERSTORMS WILL AFFECT WESTERN MA/NORTHERN CT LATE THIS AFTERNOON AND ESPECIALLY THIS EVENING. PRIMARY THREAT WILL BE HEAVY RAINFALL AND DANGEROUS CLOUD TO GROUND LIGHTNING. HOWEVER...A FEW STRONG TO PERHAPS A MARGINALLY SEVERE THUNDERSTORM OR TWO ARE POSSIBLE. THE BIGGEST THREAT WOULD BE VERY LOCALIZED STRONG TO DAMAGING WIND GUSTS WITH HAIL A SECONDARY CONCERN. ACTIVITY SHOULD WEAKEN TO MAINLY SCATTERED SHOWERS AS IT ATTEMPTS TO ENTER CENTRAL MA LATER IN THE EVENING WITH WANING INSTABILITY AND LESS DYNAMICS. IT PROBABLY NEVER EVEN MAKES IT INTO EASTERN MA/RHODE ISLAND. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... MUGGY CONDITIONS WILL CONTINUE OVERNIGHT...WITH THE POTENTIAL FOR AREAS OF FOG ESPECIALLY ACROSS THE SOUTH COAST/CAPE AND ISLANDS. SOME LOCATIONS COULD SEE LOCALLY DENSE FOG. POPS DO SLOWLY INCREASE TO LOW CHANCE FOR THE WESTERN PORTIONS OF THE REGION OVERNIGHT AS THE PRE-FRONTAL TROUGH REMAINS NEARBY AND ELEVATED INSTABILITY COULD PROMOTE DEVELOPMENT OF A FEW SHOWERS/STORMS. TOMORROW... UPPER LEVEL SHORTWAVE WILL PASS THROUGH NORTHERN NEW ENGLAND ON THURSDAY PUSHING A COLD FRONT ACROSS THE REGION. 00Z GUIDANCE SHOWS THE FRONT PUSHING THROUGH BY THE AFTERNOON/EVENING HOURS WHICH COULD BE A SOURCE OF LIFT FOR ANY CONVECTION. HOWEVER APPEARS THAT THE BETTER DYNAMICS WILL BE NORTH OF THE REGION...IN MAINE AND NEW HAMPSHIRE. STILL CANT RULE OUT A FEW SCT SHOWERS/THUNDERSTORMS AS GUIDANCE SUGGESTS A NARROW CORRIDOR OF HEATING WITH DESCENT SHEAR BETWEEN 25-30 KTS AND MARGINAL MID-LEVEL LAPSE RATES. PWAT VALUES ARE STILL HIGH...AROUND 1.6 INCHES WHICH MAY YIELD TO THE POTENTIAL FOR HEAVY RAINFALL WITHIN ANY STRONG THUNDERSTORM. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... OVERVIEW AND MODEL PREFERENCES... NOT MUCH CHANGE FROM PREVIOUS GUIDANCE RUNS. MAIN SYNOPTIC PATTERN REMAINS LARGELY IN PLACE THROUGH THE REST OF THIS WEEK...WITH A DEEP RIDGE IN PLACE OVER THE ATLANTIC OCEAN. THIS WILL KEEP THE HEAT AND HUMIDITY IN PLACE. WILL LIKELY HAVE TO WAIT UNTIL LATE THIS WEEKEND OR EARLY NEXT WEEK FOR A REPRIEVE...AS THIS RIDGE GRADUALLY MOVES FARTHER OFFSHORE. GENERALLY FAVORED A CONSENSUS BLEND OF THE GUIDANCE TO SMOOTH OVER THE RELATIVELY MINOR DIFFERENCES INTO THIS WEEKEND. THESE DIFFERENCES BECOME MORE SIGNIFICANT MONDAY INTO TUESDAY. STILL FAVORED A CONSENSUS BLEND TO DEAL WITH THE UNCERTAINTY. DETAILS... THURSDAY NIGHT...WILL SEE AREAS OF FOG...LOCALLY DENSE...DEVELOP ACROSS SOUTH COASTAL AREAS. ISOLATED TO SCATTERED SHOWERS END FROM WEST TO EAST. FRIDAY...EXPECTING A MAINLY DRY DAY...AS OUR REGION IS BETWEEN TWO SYSTEMS...WITH WEAK SURFACE RIDGING. IT SHOULD BE SLIGHTLY LESS HUMID...BUT STILL MUGGY. SATURDAY...HIGH PRESSURE REPOSITIONS OFF THE EASTERN SEABOARD...SO SW WINDS INCREASE AGAIN...BRINGING A RETURN OF MORE HUMID AIR. ANOTHER COLD FRONT STARTS TO APPROACH OUT OF GREAT LAKES AND WESTERN QUEBEC. ALSO NOTING INCREASING INSTABILITY PARAMETERS AHEAD OF THIS FRONT. WE COULD SEE SOME THUNDERSTORMS SATURDAY AFTERNOON...WHICH COULD LAST THOUGH SAT NIGHT. WITH THE HUMIDITY ALREADY IN PLACE...HEAVIER DOWNPOURS ARE POSSIBLE WITH ANY CONVECTION. SUNDAY...COLD FRONT SLOWLY MOVES ACROSS THE REGION SUNDAY MORNING...THEN REACHES THE SOUTH COAST BY SUNDAY NIGHT. EXPECTING AT LEAST A CHANCE FOR SHOWERS AND THUNDERSTORMS. WITH THE SLOW MOVEMENT OF THIS FRONT...EXPECTING SCT RAINFALL TO CONTINUE THROUGH SUNDAY NIGHT. MONDAY-TUESDAY...SOMEWHAT LOWER CONFIDENCE DUE TO TIMING AND PLACEMENT DIFFERENCES WITH A FRONT...AND WHETHER IT STALLS NEAR THE SOUTH COAST OR OFFSHORE. AT THIS POINT...KEPT CHANCE POPS ACROSS CENTRAL AND SOUTHERN AREAS THROUGH MONDAY AFTERNOON. LOW PROBABILITY FOR THUNDERSTORMS EARLY...THEN INSTABILITY WORKS OFFSHORE. HAVE KEPT SLIGHT CHANCE POPS GOING FOR SOUTHERN AREAS INTO TUESDAY AS FRONT LOOKS TO LINGER NEARBY...THEN MAY TRY TO MAKE A RUN BACK NE AS THE HIGH PUSHES OFF INTO THE GULF OF MAINE. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY...MODERATE CONFIDENCE. VFR TO START. WESTERN SITES COULD DROP TO MVFR WITHIN ANY -SHRA/-TSRA THAT DEVELOPS LATE THIS AFTERNOON OR PERHAPS NOT UNTIL THIS EVENING. EXPECT SW WINDS TO GUST UP TO 20-30 KT AT TIMES. THE BIG QUESTION WILL BE THE POTENTIAL DEVELOPMENT OF IFR/MVFR STRATUS ALONG THE SOUTH COAST. THIS IS THE LOWEST CONFIDENCE PORTION OF THE FORECAST. TONIGHT...MODERATE CONFIDENCE. CONDITIONS DETERIORATE TO IFR ALONG THE SOUTH COAST...CAPE...AND ISLANDS AS MARITIME FOG AND STRATUS ROLL IN. THURSDAY...MODERATE CONFIDENCE. COLD FRONT WILL PASS ACROSS THE REGION SWITCHING THE SOUTHERLY WINDS TO THE WEST DURING THE DAY. IFR...FOG AND STRATUS IS POSSIBLE BEFORE FRONTAL PASSAGE ALONG SE TAF SITES. CANNOT RULE OUT A FEW SHOWERS/T-STORMS ALONG THE FRONT DROPPING CONDITIONS TO MVFR. OTHERWISE VFR WILL PREVAIL. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SOUTHWEST WIND GUSTS UP TO 30 KNOTS THIS AFTERNOON. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. A THUNDERSTORM MAY AFFECT THE TERMINAL SOMETIME BETWEEN 21Z AND 02Z...BUT THAT IS OF LOW CONFIDENCE. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...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. SW WINDS GUSTING TO 20-25 KT MAINLY ALONG THE COAST SAT AFTERNOON/EVENING. SUNDAY...SCT SHOWERS/TSTMS LINGER...BUT SHOULD END LATE SUNDAY NIGHT. MAY SEE BRIEF MVFR CONDITIONS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. NEW SET OF SMALL CRAFT ADVISORIES ARE UP TODAY AND INTO TONIGHT. EXPECT NEAR SHORE WATERS TO SEE GUSTS NEAR 30 KTS THIS AFTERNOON AND PERHAPS EVEN A BIT HIGHER IN A FEW LOCATIONS. OTHERWISE SOUTHERLY SWELL WILL CONTINUE TO BUILD INCREASING OUTER WATER SEAS TO 5FT. IN ADDITION...AREAS OF DENSE FOG ARE LIKELY TO DEVELOP ON THE WATERS LATER TODAY AND TONIGHT...SUBSTANTIALLY REDUCING VISIBILITIES. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ231>234. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230- 236. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ235- 237-251. SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ250- 254>256. && $$ SYNOPSIS...BELK/DUNTEN NEAR TERM...FRANK SHORT TERM...DUNTEN LONG TERM...BELK AVIATION...FRANK/BELK/DUNTEN MARINE...FRANK/BELK/DUNTEN

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