Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250222 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1022 PM EDT MON AUG 24 2015 .SYNOPSIS... COLD FRONT APPROACHES FROM THE WEST TONIGHT AND CROSSES NEW ENGLAND TUESDAY NIGHT. SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG AND AHEAD OF THIS FRONT. MAINLY DRY AND SEASONABLE WEATHER WITH COMFORTABLE HUMIDITY LEVELS FOLLOWS WEDNESDAY THROUGH SATURDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 1015 PM UPDATE... WIDELY SCT SHOWERS/TSTMS CONFINED TO THE WEST OF NEW ENG FROM E NY TO NE PA. ACTIVITY IS NOT MAKING MUCH PROGRESS EAST AS IT TRACKS SLOWLY NE. HRRR AND HIRES ARW BRING SOME ELEVATED CONVECTION INTO FAR W NEW ENG VERY LATE TONIGHT. IN ADDITION...WATCHING AREA OF SHOWERS WELL TO THE S ASSOCD WITH HIGHER THETA-E AIR AND SOME ELEVATED INSTABILITY. MODELS BRING THIS NWD ACROSS CAPE/ISLANDS LATE TONIGHT SO CANT RULE AN ISOLD SHOWER HERE OVERNIGHT AS WELL. OTHERWISE...MAINLY DRY OVERNIGHT. CURRENTLY WE HAVE 1000-1500 J/KG OF SBCAPE OFFSHORE TO THE S. MODELS BRING UP TO 1000 J/KG ACROSS SE NEW ENG TOWARD 12Z SO WILL HAVE TO WATCH FOR POSSIBLE DEVELOPMENT NEAR THE S COAST BUT THERE IS NO FORCING MECHANISM. STRATUS HAS DEVELOPED ALONG THE S COAST AND WITH LIGHT SOUTHERLY FLOW MAY SEE THIS ADVECT FURTHER NWD ACROSS SNE. PATCHY FOG POSSIBLE AS WELL...ESPECIALLY NEAR THE S COAST. A WARM AND HUMID NIGHT WITH MINS UPPER 60S TO AROUND 70 WITH SIMILAR DEWPOINTS. && .SHORT TERM /6 AM TUESDAY THROUGH 6 AM TUESDAY/... CLOSED UPPER LOW MOVES TO EASTERN CANADA WITH CYCLONIC FLOW ACROSS THE EASTERN USA. SURFACE COLD FRONT IS FORECAST IN/NEAR THE HUDSON VALLEY AND ROUGHLY PARALLEL TO THE UPPER FLOW. THE GFS IS A LITTLE MORE PROGRESSIVE THAN THE ECMWF BUT BOTH HOLD THE FRONT EITHER SIDE OF THE NEW ENGLAND BORDER TUESDAY EVENING. BOTH MODELS THEN SWEEP THE FRONT EAST ACROSS NEW ENGLAND TUESDAY NIGHT. STABILITY PARAMETERS ARE FAVORABLE FOR CONVECTION WITH TOTALS MID TO UPPER 40S/LI AROUND ZERO/SBCAPE 1000-3000 J/KG. WIND FIELDS ALOFT ALSO PICK UP WITH SPEEDS NEAR 20 KNOTS AT 850 MB AND 40 KNOTS AT 500 MB. THE MOST FAVORABLE AREA FOR CONVECTION WOULD BE WESTERN/CENTRAL MASS AND POSSIBLY PARTS OF NORTHERN CT. THE BEST MODE OF DAMAGING WEATHER WOULD BE STRONG WIND GUSTS. WILL THERE BE A MORNING ROUND OF SHOWERS/TSTMS? BOTH THE GFS AND ECMWF INDICATE INCREASED SBCAPE OVER RI AND SOUTHEAST MASS AT 12Z. COULD BE A QUICK MORNING BURST. MAIN EVENT SHOULD BE FARTHER WEST IN THE AFTERNOON/EVENING. COLD FRONT THEN SLIPS THROUGH DURING TUESDAY NIGHT WITH SHOWERS/TSTMS ENDING...AND DRIER AIR FILTERING IN FROM THE WEST. PRECIPITABLE WATER VALUES WILL BE 1.5 TO 1.75 INCHES...SO LOCALLY HEAVY DOWNPOURS POSSIBLE. TEMPS AT 900 MB ARE EQUIV TO 13C AT 850 MB...MAX SFC TEMPS IN THE LOW TO MID 80S EXCEPT COOLER ALONG THE COAST AND IN THE HIGHER HILLS. MIN SFC TEMPS SHOULD REMAIN IN THE 60S IN THE EAST BUT WILL REACH THE UPPER 50S IN WESTERN MASS. && .LONG TERM /TUESDAY THROUGH MONDAY/... HIGHLIGHTS... * MAINLY DRY/SEASONABLE WITH COMFORTABLE HUMIDITY WED THROUGH SAT * ABOVE NORMAL TEMPS AND HUMIDITY LOOKS TO RETURN EARLY NEXT WEEK OVERVIEW AND MODEL PREFERENCES... 24.12Z MODEL GUIDANCE IS SHOWING LITTLE DIFFERENCE THROUGH MUCH OF THE LONG TERM. AT THE VERY LEAST ANY DIFFERENCES ARE MINIMAL ENOUGH SO AS NOT TO IMPACT THE FORECAST SIGNIFICANTLY. AT THE VERY LEAST...THE PATTERN SHIFT WE HAVE BEEN WAITING FOR NOW FOR ALMOST A WEEK IS AT HAND. UPPER LVL CUTOFF MOVES INTO QUEBEC/LABRADOR ALTHOUGH WITH A SLIGHT REMNANT OF THE ATTENDANT TROF ACROSS THE NE CONUS THROUGH THE END OF THE WEEK. A ZONAL FLOW PATTERN WILL FINALLY DEFINE MUCH OF THE NRN PERIPHERY OF THE CONUS...WITH DRIER CP AIRMASS DRAW INTO NEW ENGLAND. NOTING A SLIGHT SLACKENING OF THE MASS FIELDS TO THE S BY LATE IN THE WEEKEND...WHICH COULD SHIFT THE FLOW PATTERN INCREASING TEMPS/DWPTS AND A RISK FOR SCT PRECIPITATION. WITH THE AGREEMENT...A BLEND OF OPERATIONAL GUIDANCE WILL BE USED. DETAILS... WED... MODELS CONTINUE TO INDICATE THE POSSIBILITY OF WEAK CYCLOGENESIS IN THE GULF OF MAINE ALONG THE SLOW MOVING COLD FRONT. COMBINE THIS WITH STRONG CYCLONIC/COLD UPPER FLOW WITH THE UPPER LVL CUTOFF MAKING IT/S CLOSEST PASS...AND WILL LIKELY SEE A FAIR AMOUNT OF DIURNAL AND LEFTOVER CLOUD COVER THROUGH THE DAY...ALTHOUGH IT WILL LIKELY REMAIN DRY. A SPOT SHOWER CAN/T BE RULED OUT AS BUFKIT DATA SUPPORTS A WEAK UNSTABLE LATER NEAR THE TOP OF THE BL WHICH COULD BE JUST ENOUGH TO SQUEEZE OUT WHAT LITTLE MOISTURE IS THERE. IN SPITE OF THE -10 TO -11C H5 TEMPERATURES...FEEL RISK FOR SMALL HAIL IS LOW IN SPITE OF THE GOOD SETUP AS THERE IS A FAIRLY PRONOUNCED WARM LAYER BETWEEN H8 AND H6. H85 TEMPERATURES BETWEEN 12 AND 14C SHOULD BE REALIZED AT LEAST...SO TEMPERATURES NEAR SEASONAL LEVELS /UPPER 70S AND LOW 80S/ ARE EXPECTED. THE BEST NEWS...DWPTS MAINLY IN THE 50S. THU AND FRI... PLEASANT CONDITIONS. LITTLE CHANGE IN MID LEVEL TEMPERATURES SUGGEST HIGHS REMAIN NEAR NORMAL. LOW DWPTS IN THE 50S...AND MAY EVEN DIP INTO THE 40S LOCALLY. OVERNIGHT MINS IN THE 50S. SAT AND SUN... ZONAL FLOW BUT WITH SRN NEW ENGLAND ON THE ANTICYCLONIC SHEAR SIDE. THEREFORE...FEEL THAT GFS IS A BIT OVERDONE TRYING TO BRING ABOUT SHRA ACTIVITY EACH AFTERNOON. FOR NOW WILL CONTINUE WITH NIL POPS. INCREASING MID LVL TEMPS AND MOISTURE ARE EXPECTED...ALTHOUGH ONLY SLIGHTLY THROUGH THE WEEKEND. EARLY NEXT WEEK... A STRONGER SHORTWAVE WILL ATTEMPT TO PHASE WITH THE SLACKENED MASS FIELDS S OF THE REGION. THIS MAY LEAD TO A SHIFT IN THE PATTERN SUCH THAT WARMING/MOISTENING IS EXPECTED. THE SFC REFLECTION LOOKS TO BE A WEAK WARM FRONT...WHICH COULD INCREASE THE RISK FOR SHRA/TSTORMS BY THIS TIME PERIOD. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THIS AFTERNOON THROUGH TONIGHT/... 00Z UPDATE...NO SIGNIFICANT CHANGES. MAY BE A BIT MORE VFR THAN PREVIOUSLY FORECAST. BUT EXPECT SOME MVFR/IFR CONDITIONS LATE. TONIGHT...MODERATE CONFIDENCE. IFR CIGS ALONG THE SOUTH COAST MAY LOWER TO MVFR/IFR ELSEWHERE BUT CONFIDENCE IS LOWER FURTHER INLAND. PATCHY FOG POSSIBLE AS WELL. WIDELY SCT SHOWERS/TSTMS IN NEW YORK WILL MOVE INTO WESTERN SECTIONS WELL AFTER MIDNIGHT. TUESDAY...LOW CLOUDS AND FOG IN THE MORNING ESPECIALLY ON THE ISLANDS AND SOUTH COAST. A FEW MORNING SHOWERS/TSTM WILL ALSO BRING BRIEF MVFR/IFR CONDITIONS. SHOWERS/TSTMS WILL REFIRE IN THE AFTERNOON...WITH BEST CHANCES IN HFD-SPRINGFIELD-WORCESTER AND NORTHERN MASS. OTHERWISE VFR. TUESDAY NIGHT...COLD FRONT MOVES THROUGH OVERNIGHT WITH A WIND SHIFT FROM SOUTH TO WEST. EVENING SHOWERS/TSTMS SHOULD TAPER OFF. MVFR IN ANY SHOWERS/TSTMS AND IFR IN ANY PATCHY GROUND FOG OVERNIGHT. OTHERWISE VFR. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK /WEDNESDAY THROUGH SATURDAY/... WEDNESDAY THROUGH SATURDAY...HIGH CONFIDENCE. VFR CONDITIONS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...MODERATE TO HIGH CONFIDENCE. TONIGHT...HIGH CONFIDENCE. SOUTH TO SOUTH WINDS 10-15 KT OR LESS. SEAS BELOW 5 FT. AREAS OF FOG WITH POOR VISIBILITY. SHOWERS/SCATTERED TSTMS MAY REACH THE WATERS TOWARD MORNING. TUESDAY...WINDS IN ANY TSTMS MAY GUST TO NEAR 35 KNOTS. LOCALLY POOR VSBYS IN MORNING FOG. OTHERWISE WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS. OUTLOOK /WEDNESDAY THROUGH SATURDAY/...HIGH CONFIDENCE. A PERIOD OF QUIET BOATING WEATHER IS EXPECTED THANKS TO SLOW MOVING HIGH PRES WHICH WILL GRADUALLY BUILD OVER THE WATERS THROUGH THE PERIOD. WINDS OUT OF THE W-NW THROUGH FRI...SHIFTING TO THE S SOMEWHAT BY SAT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/DOODY NEAR TERM...KJC SHORT TERM...WTB LONG TERM...DOODY AVIATION...WTB/KJC/DOODY MARINE...WTB/DOODY

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