Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 041152 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 752 AM EDT TUE AUG 4 2015 .SYNOPSIS... THUNDERSTORMS ARE ONCE AGAIN EXPECTED TODAY...BUT MAINLY ACROSS THE EASTERN HALF OF THE AREA. SOME OF THESE MAY BECOME SEVERE. DRY...WARM AND LESS HUMID WEATHER ARRIVES THURSDAY. A PERIOD OF UNSETTLED WEATHER IS POSSIBLE THURSDAY NIGHT INTO SATURDAY...BUT CONFIDENCE IS LOW REGARDING THE TIMING AND COVERAGE OF ANY POTENTIAL WET WEATHER. && .NEAR TERM /THROUGH WEDNESDAY/... 745 AM UPDATE... A LINE OF STRONG TO SEVERE THUNDERSTORMS WAS MOVING OFF THE EAST COAST OF MA...BUT WILL CONTINUE TO IMPACT CAPE COD AND THE ISLANDS...AS WELL AS THE MA COASTAL WATERS...FOR THE NEXT 2 HOURS OR SO. THEN ATTENTION TURNS TO THE POSSIBILITY FOR MORE SHOWERS AND THUNDERSTORMS LATER TODAY. WITH THE ONGOING CONVECTION...MAINLY MINOR CHANGES TO THE FORECAST THIS MORNING. PREVIOUS DISCUSSION... CONVECTION DEVELOPING IN PA AND SE NY CONTINUES TO DIMINISH AS IT APPROACHES THE NE...WHERE DRY AIR AND SOME SUBSIDENCE CONTINUES TO LIMIT THE CONVECTION AS IT APPROACHES. ONLY SOME SHOWERS JUST NOW ENTERING THE LOWER CT VALLEY. STRONGER STORMS ARE STAYING TO THE S...MAINLY WHERE THE HIGHEST CAPE VALUES ARE PER LATEST MESO- ANALYSIS. THEREFORE...OUTSIDE OF A SHOWER...OR MAINLY AN ISOLATED RUMBLE OF THUNDER IN THE W SUSPECT MOST OF THE MORNING TO REMAIN QUIET. THE REST OF THE DAY...STILL REMAINS SOMEWHAT UNCERTAIN. AT ODDS IS THE ABILITY TO GENERATE SFC INSTABILITY AS A COLD FRONT SWEEPS THROUGH FROM ABOUT 14Z - 22Z. UPPER LVL INSTABILITY IS LIKELY SOMEWHERE BETWEEN THE MOIST NAM AND THE DRIER GFS...BUT WITH A MODIFIED EML AND 6.0-7.0C/KM LAPSE RATES AND AROUND 2000J/KG OF MU CAPE...THERE IS PLENTY AVAILABLE. SHEAR INCREASES AS THE FRONT APPROACHES AS WELL. SREF PROBS CONTINUE TO HIGHLIGHT GREATER THAN 50 PERCENT PROBABILITY OF MUCAPES GREATER THANK 2000/SHEAR GREATER THAN 40 KT...ESPECIALLY ACROSS THE ERN 2/3 OF THE REGION...WHERE SPC HAS UPGRADED TO A SLIGHT RISK. THE SFC CONNECTION...WILL BE BASED ON THE AMOUNT OF CLOUD COVER THAT REMAINS OVER THE AREA FROM THE WEAKENED CONVECTION THIS MORNING AND LOW STRATUS ACROSS SE MASS. LATEST QPF ON MESOSCALE GUIDANCE IS HIGHER THAN PREVIOUS RUNS...WHICH INCREASES CONFIDENCE THAT BETTER DESTABILIZATION WILL OCCUR LATER IN THE DAY IN SPITE OF THE EARLY CLOUD COVER...THEREFORE...WILL INCREASE AFTERNOON/EVENING POPS...AND BE ADDING ENHANCED/SEVERE WORDING WITH THIS UPDATE. SOME DRY AIR AT THE SFC...AND SHEAR SUGGEST THAT STRONG WINDS AND DOWNDRAFTS ARE THE PRIMARY CONCERN. SOME HAIL POSSIBLE ESPECIALLY GIVEN NAM SHOWS HAIL CAPES APPROACHING 500+. PWATS INCREASING TO NEAR 2.0 INCHES WILL ONCE AGAIN SUPPORT HEAVY RAIN...BUT STORMS SHOULD BE MOVING. SHEAR ALSO HIGH ENOUGH TO SUPPORT THE RISK OF A WEAK TORNADO...REFLECTING CURRENT THINKING BY SPC. THEREFORE...STAY TUNED TO UPDATES THROUGH THE DAY. OTHERWISE...HEAT AND HUMIDITY REMAINS TODAY AHEAD OF THE FRONT...WITH DWPTS IN THE UPPER 6OS TO NEAR 70. HIGHS MAINLY IN THE MID-UPPER 80S. && .SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/... OVERNIGHT... COLD FRONT WILL BE SLOWING TO A NEAR STALL BETWEEN 00Z AND 04Z THIS EVENING JUST OFFSHORE. THIS WILL ALLOW A CONTINUATION OF T-STORM RISK MAINLY ACROSS COASTAL REGIONS UNTIL DRIER AIR MOVES IN FROM THE NW AND CONVECTION SHIFTS S TOWARD BETTER INSTABILITY. THEREFORE...GRADUAL IMPROVEMENT EXPECTED. SOME FOG POSSIBLE WHERE RAINFALL OCCURS. OTHERWISE...TEMPS A LITTLE COOLER...MAINLY IN THE LOWER 60S ACROSS THE AREA...OR EVEN IN THE 50S ACROSS NW MA. WEDNESDAY... CYCLONICALLY CURVED FLOW REMAINS IN PLACE ACROSS THE REGION COMBINED WITH H5 TEMPS ABNORMALLY COLD...AROUND -13C. STALLED FRONTAL BOUNDARY REMAINS TO THE S...BUT ONE FINAL SHORTWAVE WILL BE ROTATING THROUGH TO THE N. THIS MAY LEAD TO SOME SCT SHOWERS/T-STORMS MAINLY N OF THE MASS PIKE. WITH THE VERY COLD H5 TEMPERATURES...THERE IS A RISK FOR HAIL AS WELL. KEY WILL BE HOW MUCH DRY AIR BUILDS THROUGH THE COLUMN. NOT EXPECTING SHOWERS/STORMS TO BE AS WIDESPREAD AS TODAY...BUT SOME LOW CHANCE OR AT LEAST SLIGHT CHANCE POPS ARE NEEDED TO REFLECT THE RISK. WARMER TEMPS REMAIN IN PLACE...MAINLY THE LOW-MID 80S. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * UNSETTLED WEATHER POSSIBLE FRIDAY * TEMPERATURES TRENDING BELOW NORMAL DURING THIS PERIOD OVERALL...THE MODELS CONTINUE TO HAVE RATHER POOR AGREEMENT ON THE DETAILS THROUGH THIS PORTION OF THE FORECAST. THERE IS SOME AGREEMENT ON THE OVERALL PATTERN TREND...WITH A CLOSED MID LEVEL LOW OVER EASTERN CANADA...MOVING INTO THE MARITIMES LATE THIS WEEK. LOOKING AT A PERIOD OF UNSETTLED WEATHER WITH TEMPERATURES TRENDING BELOW NORMAL THROUGH MUCH OF THIS TIME PERIOD. THURSDAY...MUCH OF THE DAY LOOKS TO BE DRY WITH HIGH PRESSURE BUILDING INTO THE AREA. THURSDAY NIGHT THROUGH SATURDAY...THIS LOOKS TO BE THE MOST UNSETTLED TIME WITH A LOW PRESSURE MOVING INTO THE MID ATLANTIC STATES...THEN POSSIBLY UP THE EAST COAST OVER THE 40/70 BENCHMARK SOUTHEAST OF SOUTHERN NEW ENGLAND. THE ECMWF REMAINS MORE BULLISH THAN THE GFS...AND HAS A FASTER TIMING AS WELL. THE GFS ALSO HAS A MORE SOUTHERN TRACK THAN THE GFS. GIVEN THE UNCERTAINTY IN THE DETAILS...WILL KEEP AT LEAST A CHANCE OF RAINFALL...WITH THE GREATEST POPS TOWARD THE SOUTH COAST OF NEW ENGLAND. WITH MOSTLY CLOUDY TO OVERCAST SKIES FOR MUCH OF THIS TIME...EXPECTING BELOW NORMAL TEMPERATURES. SUNDAY AND MONDAY...MUCH OF THIS FORECAST WILL DEPEND ON HOW THE PATTERN FOR FRIDAY AND SATURDAY DEVELOP. IN GENERAL THOUGH... EXPECTING DRIER WEATHER WITH REBOUNDING TEMPERATURES. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH WEDNESDAY/... TODAY...MODERATE CONFIDENCE. DEPENDING ON SUNSHINE...EXPECTING MORE THUNDERSTORMS AND SHOWERS TO REDEVELOP MID DAY...AND CONTINUE FROM W-E INTO THE EVENING HOURS. SOME OF THESE STORMS MAY BE SEVERE...WITH STRONG WINDS AND HAIL...AS WELL AS BRIEF MVFR/IFR CONDITIONS. TONIGHT INTO WEDNESDAY...HIGH CONFIDENCE. AFTER STORMS/RAIN SWEEPS OFFSHORE LATE THIS EVENING...EXPECT IMPROVEMENT TO VFR WHICH WILL LINGER INTO THE DAYLIGHT HOURS ON WED. AN ISOLATED SHOWER OR THUNDERSTORM IS THEN POSSIBLE MAINLY N OF THE MASS PIKE ON WED...BUT NOT AS WIDESPREAD AS TUE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. LOWER CONFIDENCE IN TIMING OF ANY AFTERNOON STORMS. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. LOWER CONFIDENCE IN TIMING OF ANY AFTERNOON STORMS. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... WEDNESDAY NIGHT THROUGH THURSDAY...HIGH CONFIDENCE. VFR. LOW PROBABILITY OF A FEW SHOWERS/STORMS ACROSS NW MA WEDNESDAY. ANY STORMS THAT DEVELOP MAY HAVE MVFR/IFR CONDITIONS. THURSDAY NIGHT THROUGH SATURDAY...LOW CONFIDENCE ON TIMING...HIGHER CONFIDENCE ON TRENDS. MVFR/IFR CONDITIONS IN WIDESPREAD RAIN LIKELY SOMETIME DURING THIS PERIOD. VFR BEFORE AND AFTER PERIODS OF RAIN. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH TUESDAY NIGHT/... THROUGH TODAY...MODERATE CONFIDENCE. SW WINDS REMAIN IN PLACE AND WITH SOME GUSTS POTENTIALLY APPROACHING 25-30 KT AT TIMES. GUSTS COULD APPROACH 45 KT IN AND NEAR THE STRONGER THUNDERSTORMS. THIS WILL ALLOW SEAS...WHICH ARE ALREADY RUNNING AROUND 5 FT ON THE S WATERS TO INCREASE...POSSIBLY INCREASING TO AS HIGH AS 7 FT BY THE EVENING. SMALL CRAFT ADVISORIES CURRENTLY OUT REFLECT THIS...SO NO CHANGES. TONIGHT INTO WEDNESDAY...MODERATE CONFIDENCE. FRONT MOVES FURTHER OFFSHORE...OUTSIDE OF ANY STORMS/SHOWERS...WINDS AND SEAS WILL GRADUALLY DIMINISH...SO EXPECT THESE SMALL CRAFT ADVISORIES TO GRADUALLY BE DROPPED THROUGH THE PERIOD. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...MODERATE CONFIDENCE. WEDNESDAY NIGHT THROUGH FRIDAY...HIGH CONFIDENCE. QUIET BOATING WEATHER WITH LIGHT WINDS AND SEAS BELOW 5 FEET EXPECTED. RAIN IS LIKELY AT TIMES THURSDAY NIGHT THROUGH FRIDAY...LIMITING VISIBILITIES AT TIMES. FRIDAY NIGHT AND SATURDAY...MODERATE CONFIDENCE. EASTERLY WINDS AND SEAS INCREASE AS LOW PRESSURE PASSES SOUTH OF THE WATERS. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED FOR THE OUTER WATERS. RAIN IS LIKELY FRIDAY NIGHT INTO SATURDAY...LIMITING VISIBILITIES AT TIMES. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230>234-236-250-251. SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR ANZ235-237- 254>256. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK/DOODY SHORT TERM...DOODY LONG TERM...BELK AVIATION...BELK/DOODY MARINE...BELK/DOODY

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