Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271140 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 740 AM EDT WED MAY 27 2015 .SYNOPSIS... WARM AND MUGGY CONDITIONS WILL INCREASE THROUGH TOMORROW. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED EACH DAY... WITH TODAY AND TOMORROW HAVING THE HIGHER POTENTIAL FOR STRONG STORMS. COOLER AND LESS HUMID CONDITIONS ARRIVE LATE THIS WEEKEND INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 740 AM UPDATE... HAVE UPDATED THE FORECAST MAINLY FOR VSBYS AND FOG POTENTIAL AS IT IS NOT AS WIDESPREAD AS PREVIOUSLY ADVERTISED. IN FACT...ONLY THE VINEYARD SHOWS VSBYS BELOW 5 SM. OTHERWISE THE BULK OF THE FORECAST REMAINS ON TRACK. BROUGHT NEAR-TERM CONDITIONS BACK IN LINE WITH OBSERVED TRENDS. STARTING TO HAVE CONCERNS MARINE STRATUS ALONG THE SOUTH COAST WILL NOT DEVELOP AS QUICKLY AS PREVIOUSLY THOUGHT. LATEST GUIDANCE HAS STARTED TO SLOW THE TIMING. THIS WILL NEED TO BE MONITORED THROUGH THE MORNING HOURS. TODAY... WARM...MUGGY CONDITIONS CONTINUE FOR TODAY. SOUTHWESTERLY WINDS WILL GUST BETWEEN 20-30 KTS AS HIGH TEMPS WARM INTO THE UPPER 70S TO MID 80S. UPPER LEVEL RIDGE CONTINUES TO DOMINATE THE REGION THROUGH MUCH OF THE DAY AS A COLD FRONT SLOWLY WORKS IT WAY EASTWARD ACROSS THE GREAT LAKES. FEEL TODAY HAS THE BETTER POTENTIAL TO SEE A FEW STRONG THUNDERSTORMS WITHIN THE PRE-FRONTAL TROUGH AND MODEST SOUTHERLY FLOW...ESPECIALLY ACROSS CT AND WESTERN MA. ASIDE FROM THE ABUNDANT MOISTURE...CAPE VALUES WILL RANGE BETWEEN 1500-2000 J/KG WITH ABOUT 25 KTS OF SHEAR. PWAT VALUES WILL BE ABOUT 1.5 INCHES...COMBINED WITH A DESCENT SOUTHERLY LLJ AND WARM CLOUD PROCESSES PER BUFKIT SOUNDINGS...ANY THUNDERSTORM HAS THE POTENTIAL TO PRODUCE VERY HEAVY RAIN. HAVE CONTINUED ENHANCED WORDING TO THE FORECAST FOR HEAVY RAIN. COULD SEE SOME STRONG WINDS GUSTS AS WELL...ESP ACROSS FRANKLIN COUNTY. SHOWERS AND STORMS SHOULD DEVELOP BY THE LATE AFTERNOON AND LINGER INTO THE EVENING HOURS. SPC HAS THE PIONEER VALLEY IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS. AN ISOLATED SEVERE WIND GUST CANNOT BE RULED OUT...BUT OVERALL FEEL IS THAT STORMS SHOULD REMAIN BELOW SEVERE LIMITS WITH THE POTENTIAL FOR HEAVY RAINFALL. THE QUESTION FOR THIS EVENING IS HOW FAR EAST THE CONVECTION WILL GET. BELIEVE THAT THE MARINE INFLUENCE AND PROXIMITY OF THE UPPER RIDGE WILL MOST LIKELY WEAKEN THE STORMS CONSIDERABLY AS THEY MOVE NEAR THE CENTRAL HILL OF WORCESTER COUNTY. IN FACT BELIEVE PRECIP WILL STRUGGLE AFTER 3/4Z. AREAS OF FOG ARE EXPECTED TO DEVELOP ALONG THE SOUTH COAST BY THE EVENING HOURS LIMITING VISIBILITIES. DENSE FOG ADVISORY MAY BE NEEDED. && .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 /12Z 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. EXPECT SW WINDS TO GUST UP TO 20-30 KT AT TIMES MAINLY ACROSS RI/SE MA. 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. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. COULD SEE CONDITIONS DROP TO MVFR WITHIN ANY THUNDERSTORM TODAY. 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 25 KTS...JUST LIKE YESTERDAY. 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 FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR ANZ230-236. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ235- 237-251. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 8 AM EDT THURSDAY FOR ANZ250-254>256. && $$ SYNOPSIS...BELK/DUNTEN NEAR TERM...BELK/DUNTEN SHORT TERM...DUNTEN LONG TERM...BELK AVIATION...BELK/DUNTEN MARINE...BELK/DUNTEN

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