Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251058 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 658 AM EDT TUE AUG 25 2015 .SYNOPSIS... A COLD FRONT WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS TODAY AS IT STALLS IN EASTERN NEW YORK. THE FRONT CROSSES SOUTHERN NEW ENGLAND TONIGHT MOVING OFFSHORE WEDNESDAY. MAINLY DRY AND SEASONABLE WEATHER WITH COMFORTABLE HUMIDITY LEVELS IS EXPECTED WEDNESDAY THROUGH SATURDAY. HUMIDITY AND ABOVE AVERAGE TEMPS RETURN FOR THE BEGINNING OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... *** A FEW STRONG TO SEVERE THUNDERSTORMS POSSIBLE IN INTERIOR SNE TODAY *** 700 AM UPDATE... COLD FRONT IS STILL SITUATED WELL OUT BY BGM THIS MORNING AND WILL SLOWLY MOVE EASTWARD TODAY. OTHERWISE A BATCH OF SHOWERS AND THUNDERSTORMS HAS DEVELOPED ACROSS THE BERKSHIRES AND WILL MOVE NORTHEAST INTO NEW HAMPSHIRE. CAPE VALUES HAVE STARTED TO INCREASE ACROSS THE CT VALLEY AND WITH K VALUES WELL ABOVE 34 ANTICIPATE THUNDERSTORMS TO CONTINUE TO DEVELOP...IE BACK BUILD FROM CURRENT CONVECTION. IN FACT THE LATEST HRRR KEEPS PRECIP GOING ACROSS THE WESTERN PORTION OF THE CWA OVER THE NEXT FEW HOURS. ALTHOUGH PWATS ARE AROUND 1.5 INCHES...IF THESE STORMS BACKBUILD...COULD SEE FLOODING ISSUES. CURRENTLY THE STORMS ACROSS FRANKLIN AND HAMPSHIRE COUNTY IS SHOWING OVER 2 INCHES HAS FALLEN WITHIN AN HOUR! INSTABILITY IS PROGGED TO INCREASE OVER THE NEXT FEW HOURS SO ANTICIPATE STRONG TO SEVERE STORM POTENTIAL CLOSER TO 10-11 AM AND LAST THROUGH MUCH OF THE DAY. PREVIOUS DISCUSSION... TODAY...CLOSED UPPER LOW S OF JAMES BAY WITH MEAN TROF ACROSS GT LAKES AND SW CYCLONIC FLOW ACROSS NEW ENG. SFC COLD FRONT EXPECTED TO STALL INVOF HUDSON VALLEY AS IT IS PARALLEL TO UPPER FLOW. MAIN CONCERN FOR TODAY IS THE POTENTIAL FOR STRONG TO SEVERE TSTMS. MODELS SHOW A RAPID INCREASE IN INSTABILITY AFTER 12Z WITH CAPES 1000-2000 J/KG DEVELOPING...FOCUSED ACROSS THE INTERIOR. 0-6KM SHEAR INCREASES TO 35-40 KT SO EXPECT A FEW STRONG TO SEVERE TSTMS TO DEVELOP WITH POTENTIAL FOR ORGANIZED SEVERE WEATHER AND POSSIBLY A FEW SUPERCELLS GIVEN MAGNITUDE OF SHEAR/INSTABILITY. 0-1KM HELICITY IS NOT IMPRESSIVE BUT UPPER LEVEL PATTERN OF CLOSED LOW OVER SE CANADA FITS CLIMATOLOGY OF WEAK SNE TORNADOES SO CANT RULE OUT AN ISOLD BRIEF SPINUP. HI-RES GUIDANCE SHOWS ACTIVITY INCREASING DURING THE MORNING ACROSS W MA AND N CT THEN MOVING E INTO THE AFTERNOON. WHILE WE CANT RULE OUT A SHOWER OR TSTM IN THE COASTAL PLAIN...IT APPEARS MOST OF THE CONVECTION WILL REMAIN WEST OF BOS-PVD CORRIDOR TODAY. THE UNCERTAINTY FOR THE AFTERNOON IS THE EXTENT OF A POSSIBLE SECOND ROUND OF CONVECTION DEVELOPING IN W NEW ENG AS MID LEVEL DRYING WILL BE MOVING IN FROM THE WEST AND THIS COULD SUPPRESS ACTIVITY LATER IN THE AFTERNOON. LOWER CONFIDENCE ON POSSIBLE LATE DAY CONVECTION. IT WILL BE A RATHER HUMID DAY WITH DEWPOINTS INTO THE UPPER 60S TO LOWER 70S. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... COLD FRONT WILL BE MOVING EAST ACROSS SNE TONIGHT. MODELS SHOW INSTABILITY PERSISTING THROUGH THE NIGHT AND EVENTUALLY BECOMING FOCUSED ACROSS E NEW ENG LATE TONIGHT. A FEW EVENING STORMS POSSIBLE...BUT MID LEVEL DRYING MOVING IN FROM THE WEST AND RAPIDLY DECREASING KI WILL SUPPRESS ACTIVITY WITH ANY CONVECTION AFTER MIDNIGHT BEING CONFINED TO E NEW ENG IN HIGHER KI AXIS. PATCHY LATE NIGHT FOG EXPECTED. MIN TEMPS MOSTLY IN THE 60S...WITH SOME UPPER 50S W MA. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * MAINLY DRY/SEASONABLE WITH COMFORTABLE HUMIDITY WED THROUGH SAT * ABOVE NORMAL TEMPS AND HUMIDITY LOOKS TO RETURN EARLY NEXT WEEK OVERVIEW... 00Z GUIDANCE IS IN GOOD AGREEMENT FOR THIS PORTION OF THE FORECAST. THERE ARE SOME UNCERTAINTY WITH REGARDS TO THE STRENGTH OF A FEW PASSING SHORTWAVES BUT THIS SHOULD NOT IMPACT THE OVERALL TREND IN THE FORECAST. HIGH PRESSURE WILL REMAIN OVER THE REGION UNTIL SUNDAY BEFORE MOVING OFFSHORE. A WEAK WAVE ON SUNDAY MAY BRING A FEW SHOWERS WHILE HIGH PRESSURE WILL BUILD RIGHT BEHIND THIS WAVE. DAILIES... WEDNESDAY INTO SATURDAY...HIGH CONFIDENCE. BULK OF THE PRECIP TUESDAY/TUESDAY NIGHT WILL BE OFFSHORE BY WEDNESDAY MORNING. HOWEVER...BECAUSE THIS FRONT IS SLOW MOVING AND WITH CYCLONIC FLOW ALOFT...COULD SEE LINGERING SHOWERS ACROSS EASTERN MASS DURING THE DAY. COLD FRONT SHOULD BE OFFSHORE BY THE LATE AFTERNOON AND BEHIND IT COMFORTABLE TEMPS AND HUMIDITY. UPPER LEVEL PATTERN WILL TURN FROM TROUGH TO ZONAL AS SURFACE HIGH PRESSURE BUILDS ACROSS THE NORTHEAST. THIS WILL KEEP NEAR NORMAL TEMPS AND LOW HUMIDITY THROUGH THE REMAINDER OF THE PERIOD. SUNDAY AND BEYOND...LOW CONFIDENCE. GUIDANCE BEGINS TO DIVERGE DURING THIS PERIOD AS THERE ARE SOME UNCERTAINTIES ON THE STRENGTHS OF EACH SHORTWAVE MOVING THROUGH THE FLOW. FOR NOW APPEARS THAT A STRETCHED SHORTWAVE WILL PASS SOUTHERN NEW ENGLAND...AND COMBINED WITH SOUTHERLY WINDS/INCREASING HUMIDITY THIS COULD TRIGGER A FEW LIGHT SHOWERS LATE SATURDAY NIGHT INTO SUNDAY. TEMPERATURES WILL BEGIN TO TREND ABOVE AVERAGE STARTING ON SUNDAY AND INTO THE FIRST WEEK OF SCHOOL FOR SOME. BOTH MODELS AND ENSEMBLES ARE HINTING AT UPPER 80S TO LOW 90S FOR THE WORK-WEEK AS UPPER LEVEL RIDGE TRIES TO BUILD. && .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 TONIGHT/... TODAY...MODERATE CONFIDENCE. AREAS OF MVFR/IFR STRATUS WILL IMPROVE TO VFR AROUND 13/14Z. SCT SHOWERS/TSTMS WITH BRIEF MVFR/IFR EXPECTED IN THE MORNING W MA AND N CT...WITH A SECOND ROUND OF ACTIVITY POSSIBLE IN THE AFTERNOON...MAINLY INTERIOR. TONIGHT...MODERATE CONFIDENCE. EVENING SHOWERS/TSTMS WITH BRIEF MVFR/IFR POSSIBLE. MAY SEE SOME CONVECTION LINGER ACROSS E NEW ENG OVERNIGHT. PATCHY FOG DEVELOPING OVERNIGHT. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK /WEDNESDAY THROUGH SATURDAY/... WEDNESDAY THROUGH SATURDAY...VFR CONDITIONS. COULD SEE WEAK SEA BREEZES ALONG THE COASTLINES. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TONIGHT/...HIGH CONFIDENCE. TODAY...S WINDS LESS THAN 20 KT WITH SEAS BELOW SCA. LOCALLY POOR VSBYS IN MORNING FOG. SCT SHOWERS AND ISOLD TSTMS SE WATERS THIS MORNING. TONIGHT...LIGHT S WINDS WITH SEAS BELOW SCA. VSBYS REDUCED IN PATCHY FOG. OUTLOOK /WEDNESDAY THROUGH SATURDAY/...HIGH CONFIDENCE. A PERIOD OF QUIET BOATING WEATHER IS EXPECTED THANKS TO BUILDING HIGH PRES. WINDS OUT OF THE W-NW THROUGH FRI...SHIFTING TO THE S BY SAT OR SUN. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...KJC/DUNTEN NEAR TERM...KJC/DUNTEN SHORT TERM...KJC LONG TERM...DUNTEN AVIATION...KJC/DUNTEN MARINE...KJC/DUNTEN

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