Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 301501 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 1101 AM EDT THU JUL 30 2015 .SYNOPSIS...
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WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AS A COLD FRONT MOVES ACROSS THE REGION. A FEW OF THESE THUNDERSTORMS HAVE THE POTENTIAL TO BECOME STRONG TO SEVERE THIS AFTERNOON GUSTY WINDS AND HEAVY DOWNPOURS. COOLER WEATHER RETURNS ON FRIDAY AS THE COLD FRONT EXITS THE AREA.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 11 AM EDT THURSDAY...QUICK UPDATE TO ADJUST FOR HOURLY TEMP TRENDS (A TAD COOLER BECAUSE OF CLOUD COVER), OTHERWISE FORECAST IS IN GOOD SHAPE. THE QUESTION RIGHT NOW IS HOW MUCH WILL THE SHOWERS MOVING ACROSS NY PUT THE DAMPER ON CONVECTIVE POTENTIAL THIS AFTEROON. STILL CARRYING THE POTENTIAL FOR GUSTY WINDS AND HEAVY RAIN DURING THE AFTERNOON, BUT THE QUESTION RIGHT NOW WILL THE ATMOSPHERE DESTABILIZE SUFFICIENTLY BEFORE THE FRONT PUSHES THROUGH MID TO LATE AFTERNOON. SEEING ONLY 500 J/KG MUCAPE RIGHT FROM THE 12Z ALY AND BUF SOUNDINGS BUT GETTING UP TO 1500 J/KG MU/SBCAPE FROM CWMW MODIFIED FOR SFC TEMPS IN THE LOWER TO MID 80S. STILL SEEING 70 DEGREE DEW POINTS PUSHING UP THE HUDSON VALLEY AND OVER THE ST. LAWRENCE VALLEY AS FAR WEST AT CYOW, SO IT`S POSSIBLE TO SEE THE NAM`S 1000+ J/KG CAPE JUST AHEAD OF THE FRONT NEAR BTV AROUND 20-21Z AND ALONG WITH 30+ KT 0-6KM BULK SHEAR WILL HAVE TO WATCH ANY STORMS THAT DO DEVELOP. ADDITIONALLY CORFIDI VECTORS SMALL THIS AFTERNOON WITH LOW LEVEL JET PARALLEL TO THE MEAN CLOUD LAYER, SO HEAVY RAINS STILL POSSIBLE IN A FEW SPOTS DESPITE OVERALL PROGRESSIVE MOVEMENT OF THE SYSTEM. PREVIOUS DISCUSSION...FORECAST REMAINS ON TRACK FOR THE POTENTIAL FOR STRONG TO SEVERE STORMS TODAY AS A COLD FRONT SHIFTS THROUGH THE REGION. CURRENT RADAR AND SURFACE ANALYSIS SHOW THE BOUNDARY CURRENTLY OVER THE WESTERN TIP OF LAKE ERIE WHILE CONVECTION IS FIRING UP ON THE EASTERN SHORE. DOESN`T MATTER WHICH MODEL YOU PICK, THEY ALL SHOW JUST ABOUT THE SAME TIMING FOR CONVECTION SHIFTING INTO THE BTV CWA TODAY. CURRENT ARRIVAL/EXIT TIMING LOOKS TO BE 13-17Z IN THE SAINT LAWRENCE VALLEY AND NORTHERN ADIRONDACKS, 16-20Z IN THE CHAMPLAIN VALLEY, AND 17-21Z ACROSS CENTRAL AND EASTERN VERMONT. WITH THIS TIMING IN MIND, THE GREATEST THREAT FOR ANY SEVERE STORMS WILL BE FROM THE CHAMPLAIN VALLEY AND POINTS EASTWARD WHERE THE BEST SURFACE HEATING WILL TAKE PLACE. STILL LOOKING AT ROUGHLY 1000-2000 J/KG OF CAPE DEVELOPING BY MID-DAY FROM THE CHAMPLAIN EASTWARD, WITH 0-6KM SHEAR OF ABOUT 30-40 KNOTS WHICH SHOULD BE ENOUGH TO DEVELOP A NARROW BAND OF ORGANIZED THUNDERSTORMS. WIND SHEAR IS MOSTLY UNI- DIRECTIONAL FROM THE SOUTHWEST AND PARALLEL TO THE FRONT, SO THE PRIMARY SEVERE THREAT WILL BE DAMAGING WINDS FROM BOWING SEGMENTS WITH A FAIRLY MINIMAL HAIL THREAT DUE TO HIGH FREEZING LEVELS. SECONDARY THREAT WILL BE THE POTENTIAL FOR HEAVY DOWNPOURS WITH PWATS PUSHING CLOSE TO 2", BUT STORMS SHOULD BE MOVING QUICK ENOUGH TO MITIGATE ANY FLASH FLOOD CONCERNS. HIGHS TODAY WILL RANGE THROUGH THE 80S TO NEAR 90 IN SOME PLACES. BASED ON CONVECTIVE TIMING, HIGH TEMPS ARE EXPECTED TO BE REACHED AROUND MID-DAY ACROSS VERMONT, AND LATE AFTERNOON ACROSS NORTHERN NEW YORK.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... AS OF 410 AM EDT THURSDAY...AS THE AFOREMENTIONED SURFACE FRONT CLEARS THE REGION TO OUR EAST CONVECTION WILL QUICKLY DIE OFF THIS EVENING WITH CLEARING SKIES EXPECTED AFTER 00Z. SOUTHWEST FLOW CONTINUES ALOFT AS A LARGE-SCALE CLOSED LOW TAKES RESIDENCE OVER JAMES BAY RESULTING IN A SLOW ARRIVAL OF THE COOLER POST-FRONTAL AIR. OVERNIGHT LOWS WILL REMAIN ABOVE NORMAL BUT COOLER THAN THE PREVIOUS 2 NIGHTS WITH TEMPS FALLING INTO THE 60S FOR MOST, EXCEPT SOME 50S IN THE ADIRONDACKS. FOR FRIDAY AND SATURDAY THE CLOSED LOW OVER JAMES BAY REMAINS THE DOMINANT WEATHER MAKER ACROSS THE NORTH COUNTRY WITH SEVERAL PIECES OF SHORTWAVE ENERGY MOVING THROUGH THE GENERALLY WEST/SOUTHWEST FLOW ALOFT. FIRST PIECE OF WEAK ENERGY SHIFTS THROUGH FRIDAY WITH A FEW ISOLATED SHOWERS POSSIBLE ACROSS THE NORTHERN TIER OF THE CWA, BUT MORE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE SATURDAY AS A STRONGER SHORTWAVE SHIFTS EAST FROM THE GREAT LAKES. HIGHS BOTH DAYS WILL BE VERY SEASONAL IN THE UPPER 70S TO MID 80S, WITH FRIDAY NIGHT LOWS IN THE MID 50S TO LOW 60S. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 312 AM EDT THURSDAY...THIS MORNING`S GLOBAL OPERATIONAL RUNS AND SUPPORTING ENSEMBLE MEMBERS REMAIN IN OVERALL GOOD AGREEMENT ON THE LARGE-SCALE SYNOPTIC FEATURES FROM SUNDAY ONWARD. THIS WILL FEATURE A SLOWLY EVOLVING AND BROAD UPPER TROUGH ACROSS THE NORTHERN GREAT LAKES AND CANADIAN PRAIRIES EASTWARD INTO THE NORTHEASTERN TIER OF THE COUNTRY INTO EAST-CENTRAL CANADA. NORTHERN NEW YORK AND NEW ENGLAND WILL GENERALLY LIE ON THE SOUTHERN PERIPHERY OF THIS FEATURE WITH A RATHER ACTIVE WEATHER PATTERN TAKING SHAPE AS FAST FLOW ALOFT BRINGS SEVERAL SHORTWAVES AND CHANCES OF SHOWERS/STORMS TO THE REGION. NO WIDESPREAD SEVERE WEATHER IS EXPECTED, BUT CONFIDENCE ON TIMING AND STRENGTH OF INDIVIDUAL SHORTWAVE FEATURES IS MODEST AT BEST, TYPICAL UNDER SUCH SCENARIOS. IN GENERAL THE BEST THREAT OF PRECIPITATION WILL OCCUR DURING THE AFTERNOON AND EARLY EVENING HOURS WHEN WEAK TO MODEST INSTABILITY WILL EXIST. WITH LOW TO MID LEVEL FLOW REMAINING WEST TO SOUTHWESTERLY, NEAR SEASONAL TEMPERATURES AND TOLERABLE HUMIDITY LEVELS ARE EXPECTED WITH A SLIGHT COOLDOWN BY THE MIDDLE OF NEXT WEEK AS UPPER TROUGH MAKES ITS FURTHEST INROADS SOUTH. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... THROUGH 12Z FRIDAY...MAINLY VFR. FRONTAL BOUNDARY PUSHES THROUGH THE AREA WITH SHOWERS/STORMS POSSIBLE FROM WEST TO EAST IN THE 13-21Z TIME FRAME. A FEW STORMS MAY TREND STRONG TO LOCALLY SEVERE WITH TURBULENCE/GUSTY WINDS FROM KPBG/KBTV AND POINTS EAST. BRIEF IFR VISIBILITY/MVFR CIGS POSSIBLE WITH THIS ACTIVITY. SHOWERS/STORMS TO CLEAR EASTERN TERMINALS BY 21Z. WINDS SOUTHERLY FROM 6-12 KTS AND OCCASIONALLY GUSTY THROUGH 00Z, TRENDING LIGHT AFTERWARD. SOME POSSIBILITY OF PATCHY IFR IN BR/FG AFTER06Z FRIDAY BUT LOW CONFIDENCE AT THIS TIME. OUTLOOK 12Z FRIDAY THROUGH MONDAY... 12Z FRI - 12Z SAT: MAINLY VFR. CHANCE MVFR/IFR FOG MAINLY AT MPV/SLK 06/12Z SAT. 12Z SAT ONWARD: MAINLY VFR, THOUGH DAILY CHANCES OF SHRA/TSRA WITH BRIEF MVFR/IFR POSSIBLE IN HEAVIER CONVECTIVE DOWNPOURS. && .MARINE... AS OF 410 AM EDT THURSDAY...BOATERS SHOULD EXERCISE CAUTION IF PLANNING ON RECREATING ON LAKE CHAMPLAIN TODAY AS A COLD FRONT SHIFTING THROUGH THE REGION WILL PRODUCE A LINE OF POTENTIALLY STRONG THUNDERSTORMS. WE CURRENTLY EXPECT STORMS TO IMPACT THE LAKE CHAMPLAIN BASIN BETWEEN NOON AND 4 PM WHERE THE GREATEST THREAT WILL BE STRONG TO LOCALLY DAMAGING WINDS IN EXCESS OF 50 MPH. WINDS OF THIS MAGNITUDE CAN EASILY OVERTURN VESSELS SO BE PREPARED TO SEEK SAFE HARBOR SHOULD SEVERE THUNDERSTORMS DEVELOP. MONITOR NOAA WEATHER RADIO FOR UPDATES THROUGH THE MORNING. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...LAHIFF/SISSON NEAR TERM...LAHIFF/SISSON SHORT TERM...LAHIFF LONG TERM...JMG AVIATION...JMG MARINE...LAHIFF

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