Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 312028 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 428 PM EDT FRI JUL 31 2015 .SYNOPSIS...
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SEASONABLY WARM THIS WEEKEND WITH A RISK OF SCATTERED SHOWERS AND WIDELY SCATTERED THUNDERSTORMS MID TO LATE SATURDAY AFTERNOON. WARM WEATHER CONTINUES INTO EARLY NEXT WEEK ALONG WITH THE RISK OF THUNDERSTORMS BOTH MON AND TUE. NOT AS WARM AND LESS HUMID CONDITIONS ARRIVE MID TO LATE NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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ALTHOUGH EVIDENCE OF A WEAK SHORT WAVE...THINK ACTIVITY NOW OVER WESTERN NY WILL NOT BE ABLE TO OVERCOME DRY AIR OVER OUR REGION ALONG WITH ANY FORCING OF CONSEQUENCE STAYING NORTH. THUS...HAVE GONE WITH A DRY FORECAST THROUGH TONIGHT. HAVE STAYED WITH A MODEL CONSENSUS FOR TEMPERATURES TONIGHT. DEWPOINTS GIVE SOME SPACE FOR RADIATIONAL COOLING BUT STARTING THE DESCENT AT RATHER HIGH VALUES...UPPER 80S MOST AREAS...AND SO EXPECT LOWS NEAR TO A LITTLE ABOVE AVERAGE FOR TONIGHT. WINDS HAVE BEEN A BIT GUSTY OVER LAND TO 25 TO 30 MPH BUT SHOULD SETTLE DOWN FAIRLY QUICKLY WITH SUNSET.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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MAIN ISSUE FOR THIS TIME PERIOD IS WHETHER OR NOT WE WILL SEE ANY CONVECTION SATURDAY AFTERNOON/EARLY EVENING. A SHORT WAVE TROF AND RELATIVELY WEAK SURFACE COLD FRONT WILL HAVE A MARGINALLY UNSTABLE AIR MASS TO WORK WITH AND FAIRLY NOTABLE VERTICAL WIND SHEAR OF 40 TO 50 KT. THINK THE NAM IS A LITTLE TOO ROBUST WITH ITS INSTABILITY AS IS A COMMON BIAS BUT NONETHELESS OTHER MODELS...INCLUDING THE HIGHER RESOLUTION ARW AND NMM...PROVIDE AT LEAST SOME SUPPORT FOR WIDELY SCATTERED THUNDERSTORMS. THINK WE MAY LACK SUFFICIENT MOISTURE BUT MOST MODELS DO TRY TO PRODUCE AT LEAST A LITTLE QPF. RELATIVELY COOL 500 MB TEMPERATURES ARE A CONCERN. EXPERIENCE HAS SHOWN THAT WE HAVE A TENDENCY TO OVERPRODUCE AT THIS TIME OF YEAR WITH COLD TEMPERATURES ALOFT. THE VERTICAL WIND SHEAR OF 40 TO 50 KT SUGGESTS THAT ITS NOT OUT OF THE QUESTION THAT ONE OR TWO STORMS...IF THEY ARE ABLE TO GET GOING...COULD PRODUCE LOCALLY STRONG WIND GUSTS AND HAIL. ALTHOUGH SOME VARIATION FROM MODEL TO MODEL...INCLINED TO THINK BEST INSTABILITY AND CHANCE FOR CONVECTION WILL BE ACROSS SE MA...S CENTRAL MA ALONG AND S OF THE MASSPIKE...NORTHERN RI AND NE CT. HAVE GONE WIDELY SCATTERED TO SCATTERED. THIS IS A RELATIVELY LOW CONFIDENCE SITUATION AND FOR THE MOST PART SATURDAY SHOULD BE A DRY SUMMER DAY WITH TEMPERATURES IN THE 80S. HAVE GONE WITH MODEL CONSENSUS FOR SATURDAY TEMPERATURES.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... * SEASONABLE TEMPS AND LOWER HUMIDITY FOR THE FIRST HALF OF THE WEEK * PATTERN CHANGE BY MID WEEK BRINGING BELOW AVG TEMPS * HIT OR MISS SHOWERS/TSTORMS THROUGH THE PERIOD OVERVIEW... 00Z GUIDANCE IS IN GOOD AGREEMENT FOR MOST OF THE PERIOD. ISSUES LIE WITHIN THE SMALL SCALE AND TIMING. STRONG UPPER LEVEL LOW WILL CONTINUE TO SPIN OVER HUDSON BAY KEEPING THE NORTHEAST IN SOUTHWESTERLY FLOW FROM ELONGATED TROUGH. SEVERAL WAVES WILL MOVE THROUGH THIS FLOW KEEPING THE CHANCE FOR SHOWERS AND THUNDERSTORMS IN THE FORECAST. UPPER LEVEL LOW WILL BEGIN TO SHIFT EASTWARD DUE TO AMPLIFIED RIDGE OVER THE CENTRAL CONUS AND NORTHWESTERLY LOW STRENGTHENING. THIS SHIFT IN THE PATTERN WILL DROP HEIGHTS AND TEMPS ACROSS THE NORTHEAST...LEADING TO BELOW AVERAGE TEMPERATURES. DAILIES... SUNDAY THROUGH WEDNESDAY...MODERATE CONFIDENCE. MID-LEVEL RIDGE WILL BUILD ACROSS THE REGION SUNDAY INTO MONDAY. MOST OF THE AREA SHOULD REMAIN DRY BUT CANNOT RULE OUT A FEW SPOT SHOWERS OR AIRMASS THUNDERSTORMS. BEST REGION WILL BE ACROSS NORTHWEST ZONES DUE TO THE HIGHER TERRAIN. OTHERWISE TEMPERATURES WILL AT OR SLIGHTLY ABOVE AVERAGE. HIGHS WILL BE NEAR 85F TO 90F WITH LOWS BETWEEN 60-70F. POTENT SHORTWAVE WILL MOVE THROUGH THE FLOW ON TUESDAY. ANTICIPATE SHOWERS AND THUNDERSTORMS TO DEVELOP AHEAD OF THE WAVE ACROSS UPSTATE NY ON MONDAY AND OVER SNE MONDAY NIGHT INTO TUESDAY. SOME MODEST INSTABILITY AND LI VALUES BELOW -4C LEADS TO THE POTENTIAL FOR OVERNIGHT THUNDERSTORMS. LOW CONFIDENCE ON STRONG TO SEVERE. TEMPERATURES ON TUESDAY WILL BE SLIGHTLY COOLER BUT STILL NEAR SEASONABLE AS DRY AIR FROM THE WEST MOVES INTO THE AREA. WEDNESDAY AND BEYOND...HIGH CONFIDENCE IN TEMPS...LOW CONFIDENCE IN PRECIP. CLOSED LOW ALOFT WILL SHIFT EASTWARD PUSHING A POTENT SHORTWAVE OVER THE REGION. THIS WAVE WILL DEVELOP A COASTAL LOW OVER THE MID- ATLANTIC AND MOVE CLOSE TO THE BENCHMARK....GRAZING THE SOUTH COAST WITH PRECIP. HOWEVER EXACT PLACEMENT CAN CHANGE...DEPENDING ON IF PATTERN AMPLIFIES MORE. OTHERWISE ANTICIPATE COOLER CONDITIONS AS UPPER LEVEL TROUGH TAKES HOLD OVER THE NORTHEAST SENDING SEVERAL WAVES TO REINFORCE THE COOLER AIRMASS. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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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 SATURDAY/...HIGH CONFIDENCE EXCEPT ONLY LOW TO MODERATE CONFIDENCE IN DEVELOPMENT OF ANY CONVECTION SATURDAY AFTERNOON. REST OF THIS AFTERNOON...VFR FOR ALL TERMINALS. TONIGHT...VFR WITH PERHAPS JUST A LITTLE PATCHY FOG IN A FEW INTERIOR LOW SPOTS. SATURDAY...VFR BUT RISK OF WIDELY SCATTERED THUNDERSTORMS IN THE AFTERNOON...WITH HIGHEST CHANCE ACROSS INTERIOR SE MA...S CENTRAL MA ALONG AND S OF MASSPIKE...NORTHERN RI AND NE CT. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SFC WIND SHOULD DIMINISH TOWARD SUNSET. FOR SATURDAY AFTERNOON...WIDELY SCATTERED TSTMS MAY DEVELOP ACROSS BOS AREA LATE SATURDAY AFTERNOON BUT NOT ENOUGH CONFIDENCE TO REFLECT IN TAF AT THIS TIME. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. ISOLATED THUNDERSTORM NOT OUT OF THE QUESTION SATURDAY AFTERNOON. OUTLOOK /SUNDAY THROUGH TUESDAY/...MODERATE CONFIDENCE. VFR MUCH OF THE TIME WITH A RISK FOR SCATTERED SHOWERS AND TSTMS MONDAY INTO TUESDAY MORNING. A FEW TSTMS COULD BE STRONG LATE MON AFTERNOON/EVENING...ESPECIALLY WEST OF A AFN-ORH-IJD LINE.
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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 /THROUGH SATURDAY NIGHT/...MODERATE CONFIDENCE. TONIGHT...TRANQUIL CONDITIONS WITH GENERALLY GOOD VSBY AND LIGHT SW WIND. SATURDAY AND SATURDAY NIGHT...ENOUGH OF A SW FETCH AHEAD OF A COLD FRONT THAT SEAS ARE PROJECTED TO BUILD TO NEAR 5 FEET ACROSS THE OUTER S COASTAL WATERS. THINK THAT THE WAVE GUIDANCE IS OVERDONE BUT NONETHELESS PROBABLY STILL ENOUGH FETCH AHEAD OF A WEAK COLD FRONT TO GET THOSE 5 FOOT SEAS AND HENCE HAVE RAISED A SMALL CRAFT ADVISORY FROM LATE SATURDAY MORNING TO SATURDAY NIGHT. ALSO...ISOLATED THUNDERSTORMS ARE POSSIBLE SATURDAY EVENING AHEAD OF THE COLD FRONT. OTHER ISSUE FOR SATURDAY AFTERNOON IS THAT THERE LOOKS TO BE ENOUGH IN WAY OF INCOMING SEAS TO PRODUCE POCKETS OF MODERATE RIP CURRENT ACTIVITY ACROSS THE EXPOSED SOUTHERN RI SHORELINE...ESPECIALLY BLOCK ISLAND. OUTLOOK /SUNDAY THROUGH TUESDAY/... FAIRLY TRANQUIL BOATING WEATHER THIS PERIOD WITH MODEST SW WINDS...GOOD VSBY AND MAINLY DRY WEATHER. LOW RISK OF SCATTERED SHOWERS AND T-STORMS LATE MONDAY.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 11 AM SATURDAY TO 2 AM EDT SUNDAY FOR ANZ255-256.
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&& $$ SYNOPSIS...DUNTEN/THOMPSON NEAR TERM...THOMPSON SHORT TERM...THOMPSON LONG TERM...DUNTEN AVIATION...DUNTEN/THOMPSON MARINE...DUNTEN/THOMPSON

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