Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 042012 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 412 PM EDT SAT JUL 4 2015 .SYNOPSIS... LOW PRESSURE RACES SOUTH OF NEW ENGLAND THIS AFTERNOON AND EVENING BRINGING SCATTERED POCKETS OF LIGHT RAIN. HIGH PRESSURE RETURNS SUNDAY AND LINGERS THROUGH MONDAY. BECOMING MORE HUMID TUESDAY AND WEDNESDAY. A CHANCE OF SHOWERS AND THUNDERSTORMS ALONG AND WEST OF THE CONNECTICUT RIVER VALLEY ON TUESDAY AND MORE GENERALLY ACROSS THE AREA ON WEDNESDAY. LOCAL HEAVY DOWNPOURS POSSIBLE ON WEDNESDAY. BECOMING DRY THE REST OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... THROUGH 8 PM...MAIN AREA OF CONCERN IS OVER WESTERN MASS/CONNECTICUT. RADAR SHOWS PATCHY YELLOWS AND ORANGES WHILE OBSERVATIONS SHOW VSBYS AROUND 10 MILES...EXCEPT 4-5 MILES IN THE BERKSHIRES. WITH CLOUD BASES 9-10 THOUSAND FEET...EXPECT MUCH OF THE RAIN ON RADAR IS EVAPORATING ON THE WAY DOWN. WE WILL CONTINUE WITH LIGHT SHOWERS THROUGH THE AFTERNOON IN OUR WESTERN AND CENTRAL AREAS...SCATTERED SPRINKLES IN THE EAST. EARLY AFTERNOON OBSERVED TEMPERATURES SHOW A RANGE OF 65 TO 75. UPPER 60S AND 70S SHOULD COVER THE AFTERNOON MAX TEMPS. TONIGHT... COASTAL LOW PRESSURE MOVES OUT TO SEA. UPPER SHORTWAVE SWINGS OVER NEW ENGLAND. RIGHT ENTRANCE REGION OF THE SUPPORTING UPPER JET WILL BE RIGHT OVER US AT 00Z/8 PM CREATING UPPER VENTING. IF SUFFICIENT MOISTURE LINGERS THEN WE MAY CONTINUE TO SEE WIDELY SCATTERED LIGHT SHOWERS/SPRINKLES FOR A COUPLE OF HOURS. BUT THE AMOUNT OF EVAPORATION IN PROGRESS SUGGESTS A FACTOR COUNTERACTING ANY LINGERING SHOWERS. WE WILL MAKE OUR FINAL CALL ON EVENING POPS BASED ON THE RADAR DISPLAY BETWEEN 3 AND 4 PM. BUT THE TREND ON THE FORECAST IS FOR DIMINISHING CHANCE OF SHOWERS. THE UNCERTAINTY IS WHETHER IT WILL BE STARTING AT 70 PERCENT OR 20 PERCENT OR 5 PERCENT. THE UPPER SHORTWAVE AXIS SWEEPS EAST OF OUR AREA BY MORNING...SO EXPECT A TREND TO CLEARING SKIES AFTER MIDNIGHT. DEW POINTS UPSTREAM ARE IN THE 50S...THIS SHOULD ALLOW MIN SFC TEMPS IN THE 50S AND LOWER 60S. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... HIGH PRESSURE FROM THE PLAINS BUILDS EAST OVER NEW ENGLAND SUNDAY. CROSS SECTIONS OF RH SHOW DRY AIR ABOVE 800 MB...AND A MOIST LAYER AT 800-850 MB. MIXING SHOULD REACH ABOVE 850 MB. THIS SUGGESTS SOME DIURNAL CUMULUS DEVELOPING SUNDAY AND DISSIPATING SUNDAY EVENING. TEMPERTURES AT THE TOP OF THE MIXED LAYER WOULD SUPPORT MAX SURFACE TEMPS OF 80-85. FAIR SKIES SUNDAY NIGHT WITH LIGHT WINDS AND RADIATIONAL COOLING. DEW POINTS RISE A LITTLE TO AROUND 60. EXPECT MIN SURFACE TEMPS IN THE UPPER 50S AND LOWER 60S. THIS MAY SUPPORT PATCHES OF FOG DEVELOPING LATE AT NIGHT...ESPECIALLY IN WESTERN MASS. && .LONG TERM /MONDAY THROUGH SATURDAY/... HIGHLIGHTS... * WARM FRONT MAY TRIGGER SCATTERED SHOWERS/THUNDERSTORMS IN WEST TUE * LOCALLY EXCESSIVE RAIN POSSIBLE WITH SHOWERS/THUNDERSTORMS ON WED OVERVIEW...SEVERAL PLAYERS INFLUENCE THE WEATHER PATTERN AFFECTING SOUTHERN NEW ENGLAND THIS COMING WEEK. OUR AREA WILL BE SUSCEPTIBLE TO SHORT WAVE ENERGY ROTATING ABOUT STRONG EASTWARD MOVING TROUGH ACROSS NORTH CENTRAL CANADA AND EJECTING FROM CLOSED LOW SLOWLY APPROACHING CA. AS IS TYPICAL FOR THIS TIME OF YEAR...H50 HEIGHTS ARE RELATIVELY HIGH...BUT AT THE SAME TIME THE LARGE SCALE FLOW IS CHARACTERIZED BY BROAD CYCLONIC FLOW WITH SUSCEPTIBILITY FOR TROUGHING ACROSS THE E CENTRAL CONUS. MAIN FOCUS FOR THIS FORECAST PERIOD IS ON THE MID WEEK PERIOD WHEN A SLOW MOVING COLD FRONT THROUGH A HIGH PRECIPITABLE WATER OR PWAT ENVIRONMENT MAY SET THE STAGE FOR CONVECTIVE HEAVY RAIN BANDS. MODELS HAVE COME INTO BETTER AGREEMENT FOR THIS PERIOD. THE LATTER PART OF THE WEEK INTO THE WEEKEND WILL PROBABLY FEATURE RIDGING AND DRY CONDITIONS...BUT CONFIDENCE IS LOWER DUE TO CHALLENGE OF RESOLVING SHORT WAVE TROFS IN THE LARGE SCALE FLOW THAT FAR OUT. ALSO...AS NOTED IN THE PRIOR FORECAST DISCUSSION...NEW ENGLAND MAY AT SOME POINT BY NEXT WEEKEND OR A LITTLE BEYOND BE SITUATED ON THE PERIPERY OF A RIDGE ACROSS THE SOUTHERN/CENTRAL CONUS AND BE SUSCEPTIBLE TO ANY MCS ACTIVITY ON THAT PERIPHERY. DETAILS... MONDAY...HIGH CONFIDENCE OF DRY CONDITIONS AS MODELS AGREE UPON SHORT WAVE RIDGING BOTH ALOFT AND AT THE SURFACE. H85 TEMPERATURE PROJECTIONS COMBINED WITH AMPLE SUNSHINE SUPPORT CURRENT FORECASTS OF TEMPS IN THE MID TO UPPER 80S ACROSS THE INTERIOR. TUESDAY...SHORT WAVE TROF AND WARM FRONT USHER IN HIGHER DEWPOINT AIR AND MUCH HIGHER PWATS. WILL INDICATE CHANCE POPS ROUGHLY W OF AN AFN-ORH-IJD LINE ON TUE WHERE K INDICES RISE TO ABOVE 30 FOR A TIME AND SUGGESTIVE FOR SCATTERED SHOWERS/TSTMS. AIR MASS LOOKS DRIER AND MORE STABLE FURTHER EAST WHERE WILL CONTINUE WITH SLIGHT CHANCE OR LESS POPS. IN DEFERENCE TO SOME INSTABILITY NOTED ON THE LATEST GFS...WILL INDICATE SOME SLIGHT CHANCE POPS TUE NIGHT NEAR THE VT AND NH BORDERS. WEDNESDAY...THERE IS A CONCERN OF ONE OR BANDS OF SIGNIFICANT TO EXCESSIVE RAFL SETTING UP AS COLD FRONT DEACCELERATES ACROSS THE REGION WITH PWATS OVER 2 INCHES. MODEL CONSENSUS ALSO INDICATES K INDICES IN THE MID 30S. ISOBARS BECOME BAGGY AT THE SURFACE AS A WEAK WAVE ATTEMPTS TO FORM ALONG THE FRONT NEAR THE SOUTH COAST OF NEW ENGLAND...AND THE H70 AND H50 FLOWS ARE PARALLEL DURING THE AFTERNOON AND EVENING. THERE IS EVEN A HINT OF DIVERGENCE WITH THE 1000-500 MB THICKNESS. ALL OF THIS IN THE SYNOPTIC PATTERN SUGGEST A POTENTIAL FOR HEAVY DOWNPOURS AND POSSIBLY TRAINING OF CELLS. THE INSTABILIY AND WIND SHEAR LOOK QUITE MODEST AND SO THE SEVERE POTENTIAL LOOKS LOW. THE SIGNAL FOR LOCALIZED HEAVY/EXCESSIVE RAIN LOOKS STRONG ENOUGH...HOWEVER...TO MENTION IN THE HWO. THURSDAY...MODELS HAVE CHANGED POSITIONS FROM 24 HOURS AGO WITH THE GFS HANGING RAFL OVER THE AREA FOR A TIME WITH A WAVE WHEREAS THE ECMWF IS NOW MORE PROGRESSIVE. FOR THE POPS HAVE GONE WITH A MODEL BLEND WITH A SLIGHT LEANING TOWARD THE GFS WHICH SEEMS TO HAVE BEEN DEMONSTRATING A LITTLE MORE RUN TO RUN CONTINUITY THAN THE ECMWF. ANTICIPATING LOWER DEWPOINTS AND SEASONABLE TEMPS. FRIDAY THROUGH SATURDAY...CONFIDENCE LOWER SINCE DIFFICULT TO RESOLVE SHORT WAVE TROFS DAYS 6 AND 7 ESPECIALLY IN THE WARM SEASON. MODEL CONSENSUS IS FOR A DRY FORECAST FOR THIS PART OF THE FORECAST PERIOD WITH TEMPS NOT TOO FAR FROM THE LONG TERM AVERAGES FOR THIS TIME OF YEAR. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH FRIDAY NIGHT/... THROUGH 8 PM...MODERATE TO HIGH CONFIDENCE. LARGE AREA OF RAIN ON RADAR BUT ONLY LIGHT AMOUNTS REACHING THE GROUND. EXPECT CONDITIONS TO REMAIN VFR THROUGH EVENING. THERE IS SOME POTENTIAL FOR MVFR CIGS/VSBYS BUT MAINLY IN NORTHWEST MASSACHUSETTS WHERE 1000-1500 FOOT CIGS AND 4-5 MILE VSBYS ARE POSSIBLE IN ANY HEAVIER SHOWERS. TONIGHT...HIGH CONFIDENCE. ANY LINGERING RAIN TAPERS OFF EARLY IN THE NIGHT. PATCHES OF MVFR CIGS/VSBYS ARE POSSIBLE...BUT WE THINK DRY AIR BELOW 5000 FEET WILL OVERCOME MOST OF THE POTENTIAL FOR MVFR. DRIER AIR MOVING IN AFTER MIDNIGHT WILL BRING CLEARING SKIES BY MORNING. LIGHT WINDS TREND TO WEST/NORTHWEST TOWARD MORNING. SUNDAY...HIGH CONFIDENCE. VFR SUNDAY NIGHT...HIGH CONFIDENCE. VFR. PATCHES OF IFR IN LATE NIGHT FOG POSSIBLE IN THE CT VALLEY OF MASSACHUSETTS. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /MONDAY THROUGH THURSDAY/... MONDAY...HIGH CONFIDENCE. VFR EXPECTED. TUESDAY...MODERATE TO HIGH CONFIDENCE. MOSTLY VFR CONDITIONS EXCEPT AREAS OF MVFR IN SCT SHOWERS/TSTMS W OF AFN-ORH-IJD LINE. TUESDAY NIGHT...MODERATE CONFIDENCE. MVFR CIGS/VSBYS WITH AREAS OF IFR CIGS/VSBYS IN FOG ALONG THE S COAST. ELSEWHERE...MOSTLY VFR. WEDNESDAY...MODERATE CONFIDENCE. AREAS OF MVFR CIGS/VSBYS IN SHOWERS/TSTMS. POCKETS OF IFR CONDITIONS POSSIBLE IN HEAVIER SHOWERS/TSTMS AS WELL AS IN FOG PATCHES ALONG THE S COAST. WEDNESDAY NIGHT...MODERATE CONFIDENCE. IMPROVING TO VFR EXCEPT MVFR CIGS/VSBYS MAY PERSIST IN SHOWERS AND FOG ALONG SE COASTAL AREAS. THURSDAY...MODERATE CONFIDENCE. VFR OR BECOMING VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TONIGHT...HIGH CONFIDENCE. LOW PRESSURE PASSES SOUTH OF THE WATERS AND MOVES OFF SOUTH OF NOVA SCOTIA TONIGHT. WINDS SHIFT FROM EAST TO NORTH AFTER THE PASSAGE OF THE LOW...BUT WILL REMAIN BELOW 25 KNOTS. EXPECT SEAS TO BUILD A LITTLE WITH HEIGHTS AROUND 5 FEET ON THE SOUTHERN OUTER WATERS. TIMING ON THE ADVISORY HAS BEEN ADJUSTED TO A LATER START TIME BUT OTHERWISE THE HEADLINE REMAINS THE SAME. SUNDAY AND SUNDAY NIGHT...HIGH CONFIDENCE. HIGH PRESSURE BUILDS OVER THE WATERS WITH LIGHT WIND AND DIMINISHING SWELL. THE SMALL CRAFT ADVISORY WILL END AROUND MIDDAY. OUTLOOK /MONDAY THROUGH THURSDAY/... MODERATE TO HIGH CONFIDENCE. WINDS AND SEAS EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD. AREAS OF FOG WITH POCKECTS OF VISIBILITY A MILE OR LESS POSSIBLE TUE NIGHT AND WED MORNING...MAINLY ALONG SOUTH COASTAL WATERS. POSSIBLY AREAS OF FOG AGAIN WED NIGHT ALONG THE S COAST. SCATTERED TSTMS MAY OCCUR LATE WED AFTERNOON AND EVENING OVER THE WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 AM TO 5 PM EDT SUNDAY FOR ANZ255-256. && $$ SYNOPSIS...WTB/THOMPSON NEAR TERM...WTB SHORT TERM...WTB LONG TERM...THOMPSON AVIATION...WTB/THOMPSON MARINE...WTB/THOMPSON

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