Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 010729 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 329 AM EDT WED JUL 1 2015 .SYNOPSIS... A FRONTAL SYSTEM WILL BRING SHOWERS...AND A CHANCE FOR STRONG TO SEVERE THUNDERSTORMS...INTO THIS AFTERNOON. THIS FRONT STALLS NEAR THE SOUTH COAST THURSDAY...BEFORE MOVING OFFSHORE THURSDAY NIGHT. ASIDE FROM A SPOT SHOWER POSSIBLE SATURDAY...MAINLY DRY AND SEASONABLE WEATHER IS EXPECTED INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... A POTENT MID LEVEL SHORTWAVE AND ITS ASSOCIATED COLD POOL ALOFT WILL APPROACH SOUTHERN NEW ENGLAND EARLY THIS MORNING. THIS WILL BE ENOUGH TO INITIATE SOME SHOWERS. SURFACE INSTABILITY REMAINS LACKING DURING THIS TIME. HOWEVER...THERE IS SOME ELEVATED INSTABILITY LEADING TO A FEW THUNDERSTORMS ACROSS WESTERN NEW ENGLAND. RECENT TRENDS HAVE BEEN FOR THESE THUNDERSTORMS TO WEAKEN AS THE MOVE FARTHER EAST. THE LARGER QUESTION WILL BE HOW QUICKLY DEEPER INSTABILITY CAN BE DEVELOPED THIS MORNING. GUIDANCE CONTINUES TO ADVERTISE A QUICK INCREASE OF CAPE TO AROUND 1000 J/KG. WE ALSO NOTED THE ARRIVAL OF RATHER STRONG LOW LEVEL SHEAR...WHICH WILL ONLY HELP TO FOCUS THIS ENERGY. THAT SAID...WE DO NOT SEEM TO MAXIMIZE THE SHEAR AND INSTABILITY AT THE SAME TIME. THUS...NOT EXPECTING WIDESPREAD SEVERE WEATHER AT THIS TIME. THINKING IS FOR A FEW STRONG TO SEVERE THUNDERSTORMS...WITH THE MAIN THREAT BEING DAMAGING WINDS AND/OR HAIL. PRECIPITABLE WATER VALUES REMAIN NEAR 2.0 INCHES INTO EARLY AFTERNOON. COUPLED WITH THE STRONG LOW LEVEL JET...THIS IS A RECIPE FOR HEAVY RAINFALL WITHIN THE SHOWERS AND THUNDERSTORMS. A QUICK INCH OF RAIN IN LESS THAN AN HOUR IS NOT UNREASONABLE. THIS COULD RESULT IN POOR DRAINAGE AND URBAN FLOODING. THE BENEFIT OF THE STRONG LOW LEVEL JET IS STORMS SHOULD MOVE ALONG AT A FAIRLY GOOD SPEED. THIS WILL REDUCE THE LIKELIHOOD OF FLOODING SOMEWHAT. MAIN FLOODING THREAT WILL BE WITH ANY TRAINING THUNDERSTORMS. && .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/... A FEW LEFTOVER SHOWERS...AND PERHAPS A THUNDERSTORM OR TWO...ARE STILL POSSIBLE EARLY THIS EVENING. OTHERWISE EXPECTING DRY CONDITIONS FOR MOST OF TONIGHT. A COLD FRONT WILL BE SLOWLY CROSSING OUR REGION TONIGHT...LIKELY STALLING NEAR THE SOUTH COAST OF NEW ENGLAND FOR A TIME LATE TONIGHT INTO THURSDAY. LATEST GUIDANCE CONTINUES TO ADVERTISE A DRY ATMOSPHERE...SO EXPECTING MOST OF THURSDAY. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * SEASONABLE TO SLIGHTLY ABOVE SEASONABLE TEMPERATURES EXPECTED. * LOW CHANCE OF A SHOWER MAINLY ON THE 4TH. OVERVIEW AND MODEL PREFERENCES...MODELS CONTINUE TO INDICATE A SHIFT IN THE OVERALL PATTERN FROM A HIGHLY AMPLIFIED REGIME TO ONE THAT IS MORE PROGRESSIVE AND ZONAL. THIS IS IN SPITE OF THE FAIRLY ROBUST RIDGES IN PLACE ACROSS THE E PACIFIC AND THE BERMUDA HIGH N OF THE ANTILLES. ALTHOUGH THIS MORE ZONAL FLOW PATTERN DOES TAKE ON A LONGWAVE TROF FEATURE BETWEEN THE TWO RIDGES...IT IS NOT OVERLY DEEP/SHARP. THIS ALLOWS THE RIDGING ASSOCIATED WITH THE BERMUDA HIGH TO BECOME THE DOMINANT PLAYER FOR OUR SENSIBLE WX INTO EARLY NEXT WEEK. AT THIS POINT A MUCH DEEPER NRN STREAM VORTEX WILL BE IN PLAY...AND WILL TRANSITION THE DRIER AND MORE STABLE REGIME ACROSS THE NE CONUS TO A MORE UNSETTLED PATTERN. THE ONLY FLY IN THE OINTMENT IS ON THE 4TH UNFORTUNATELY...BUT MORE ON THAT BELOW. DETAILS... THU NIGHT INTO FRI...THE FIRST IN A SERIES OF MID LVL RIDGES WILL BE MOVING THROUGH THE ZONAL FLOW PATTERN DURING THIS PERIOD. THIS INTRODUCES A MAINLY DRY PERIOD WITH WEAK HIGH PRES IN PLACE ACROSS SRN NEW ENGLAND. THERE REMAINS A FRONT STALLED TO THE S...WITH SOME UPPER LVL MOISTURE SUGGESTING SOME PARTLY CLOUDY CONDITIONS. OTHERWISE...H85 TEMPS BETWEEN +10C AND +12C SUGGEST HIGHS NEAR TO SLIGHTLY ABOVE SEASONAL NORMALS ACROSS THE REGION AWAY FROM THE COAST WERE SEA BREEZES ARE LIKELY. FRI NIGHT INTO SAT NIGHT...WITH THIS NEARLY ZONAL FLOW IN PLACE...IT/S NOT JUST RIDGING...BUT WEAK SHORTWAVES TO CONCERN OURSELVES WITH. MODELS CONTINUE TO INDICATE A WEAK PACKET OF ENERGY PASSING THROUGH THE REGION DURING THE EARLY WEEKEND. THE OVERALL COLUMN IS RELATIVELY DRY...WITH PWATS NEAR NORMAL FOR EARLY JULY. HOWEVER...WITH THE FRONT STALLED TO THE S...THE DEVELOPMENT OF A WEAK WAVE OF LOW PRES COULD BRING ABOUT MODEST LIFT ALONG THE SRN TIER OF SRN NEW ENGLAND DURING THE DAY SAT. THERE ARE TWO CAMPS HERE...GFS AND SOME ENSEMBLE MEMBERS WITH QPF ACROSS THE REGION...AND THE ECMWF AND OTHER ENSEMBLE MEMBERS WITHOUT. THEREFORE...CONFIDENCE NOT HIGH ON PRECIP CHANCES...BUT IT IS LIKELY TO NOT BE A WASHOUT IN EITHER CASE GIVEN HOW WEAK THE WAVE IS AND THE LACK OF MOISTURE. JUST A FEW PASSING SHOWERS TO CONTEND WITH. SUN INTO MON...AS DEEP ER WAVE FORMS ACROSS THE CANADIAN PRAIRIE LANDS...A SECONDARY RIDGE WILL AMPLIFY IN RESPONSE TO WARM ADVECTION FROM THE BERMUDA HIGH TO THE SE. THIS WILL YIELD ANOTHER PERIOD OF DRIER AND WARMER CONDITIONS ACROSS SRN NEW ENGLAND. BETTER CHANCES FOR TEMPS INCHING ABOVE NORMAL DURING THIS STRETCH...THANKS TO MORE INFLUENCE FROM THE SE. TOWARD MID WEEK...THE AFOREMENTIONED WAVE WILL BEGIN A SLIDE TO THE E. THIS PARTICULAR FEATURE IS MORE ROBUST THAN PREVIOUS WAVES...SO IT/S LIKELY A PERIOD OF WETTER AND UNSETTLED WX WILL RETURN BY THE MID PORTION OF NEXT WEEK. UNCERTAINTY IN EXACT TIMING. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH 12Z...MODERATE CONFIDENCE. TIMING ISSUES REMAIN THE LOWEST CONFIDENCE PART OF THE FORECAST. SHOWERS AND ISOLATED THUNDERSTORMS ALREADY MOVING INTO WESTERN NEW ENGLAND...WITH CONDITIONS LOWERING TO MVFR. TODAY...HIGH PROBABILITY FOR WIDESPREAD SHRA AND SCATTERED TSRA. RISK FOR A FEW STRONG STORMS AND HEAVY RAINFALL. IFR AND MVFR CONDITIONS LIKELY IN SHRA/TSRA. CONDITIONS IMPROVING TO VFR DURING THIS AFTERNOON...BUT SCT TSRA MAY REDEVELOP. TONIGHT...MODERATE CONFIDENCE. PATCHY MVFR/IFR STRATUS AND FOG DEVELOPING...OTHERWISE VFR. THU...HIGH CONFIDENCE. VFR. KBOS TERMINAL...HIGH CONFIDENCE IN TAF TRENDS. MODERATE CONFIDENCE IN TIMING. KBDL TERMINAL...HIGH CONFIDENCE IN TAF TRENDS. MODERATE CONFIDENCE IN TIMING. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... HIGH CONFIDENCE. MAINLY VFR. A FEW SHOWERS POSSIBLE ON SAT...BUT MAINLY DRY OTHERWISE. SEA BREEZES LIKELY MOST DAYS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. WINDS AND SEAS WILL INCREASE IN RESPONSE TO A FRONTAL SYSTEM APPROACHING THE WATERS LATER TODAY. SMALL CRAFT ADVISORIES HAVE BEEN EXTENDED FOR THE SOUTHERN OUTER WATERS AND RHODE ISLAND AND BLOCK ISLAND SOUNDS. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THU NIGHT INTO FRI...HIGH CONFIDENCE. WEAK RIDGE OF HIGH PRES WILL BE MOVING OVER THE WATERS THROUGH THE PERIOD. ANY LINGERING SWELL ABOVE 5 FT WILL RECEDE OVERNIGHT WITH QUIET BOATING WX EXPECTED THROUGH THE REST OF FRI. SAT AND SUNDAY...MODERATE CONFIDENCE. THIS PERIOD WILL BE DEPENDENT ON HOW CLOSELY A WEAK WAVE OF LOW PRES PASSES TO THE S COAST ON SAT. IF IT PASSES CLOSE ENOUGH...A PERIOD OF SWELLS EXCEEDING 5 FT IS POSSIBLE. OTHERWISE...MAINLY QUIET BOATING WEATHER WILL CONTINUE ESPECIALLY AS HIGH PRES RETURNS SUNDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 AM EDT THURSDAY FOR ANZ254>256. SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT THURSDAY FOR ANZ235-237. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY

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