Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 271607 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 1207 PM EDT SUN JUL 27 2014 .SYNOPSIS... ACTIVE PERIOD OF WEATHER IS EXPECTED ACROSS THE NORTH COUNTRY TODAY INTO MONDAY. INITIAL AREA OF SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE REGION THROUGH THE MORNING HOURS...WITH RE- DEVELOPMENT OF THUNDERSTORMS...SOME STRONG...DURING THE AFTERNOON. A POTENT MID-SUMMER LOW WILL TRACK ACROSS THE NORTH COUNTRY ON MONDAY WITH A WETTING RAINFALL TO THE REGION WITH POTENTIAL FOR THUNDERSTORMS ACROSS EASTERN VERMONT. GRADUALLY IMPROVING CONDITIONS TUESDAY INTO MIDWEEK...WITH HIGH TEMPERATURES BEING A FEW DEGREES BELOW NORMAL THROUGH MIDWEEK. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... AS OF 1200 PM EDT SUNDAY...EARLY AFTN UPDATE TO CAPTURE LATEST TRENDS IN BAND OF RAIN MOVING ACRS EXTREME EASTERN VT AND POTENTIAL FOR ADDITIONAL ACTIVITY THIS AFTN. I HAVE CUT POPS TO CHC ACRS ENTIRE CWA AS STEADIER PRECIP WL BE EAST OF OUR CWA VERY SHORTLY. LATEST LAPS DATA SHOWS SFC INSTABILITY DEVELOPING ACRS NORTHERN NY WITH VALUES BTWN 800 AND 1200 J/KG...ASSOCIATED WITH SOME CLRING IN THE VIS SATL. THIS HAS HELPED WARM TEMPS INTO THE 70S...WITH DWPTS IN THE MID 60S...CREATING THIS INSTABILITY. THIS CLEARING AND INSTABILITY WL SHIFT INTO THE CPV AND PARTS OF VT THIS AFTN...BUT ULVL FORCING IS PRETTY LIMITED. THIS COMBINED WITH MINIMAL INSTABILITY WL RESULT IN WIDELY SCATTERED ACTIVITY DEVELOPING THIS AFTN...MAINLY ACRS NORTHERN NY INTO PARTS OF CENTRAL/NORTHERN VT. THE SHEAR/INSTABILITY PARAMETERS SUPPORT PULSE LIKE ACTIVITY WITH NO REAL ORGANIZATION. WL CONT TO MENTION CHC POPS FOR THIS POTENTIAL AND KEEP TEMPS MAINLY IN THE 70S...WITH A FEW READINGS NEAR 80 POSSIBLE IN THE WARMER VALLEYS. && .SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY/... AS OF 437 AM EDT SUNDAY...ACTIVE PERIOD OF WEATHER THEN CONTINUES LATER SUNDAY NIGHT AND ESPECIALLY ON MONDAY. MORE GRADUAL IMPROVEMENT FOR TUESDAY BUT STILL GENERALLY UNSETTLED WITH THE NORTH COUNTRY UNDER A WELL-ADVERTISED 500 MB TROUGH. TONIGHT: STILL CAN`T RULE OUT AN ISOLATED STRONGER STORM EARLY EVENING BUT ALREADY LIMITED INSTABILITY WILL BECOME EVEN MORE SO BY DARK. THE STRONG...POSITIVELY TILTED SHORTWAVE TROUGH ASSUMES A NEGATIVE TILT BY 12Z MONDAY AND INDUCES SFC LOW DEVELOPMENT NEAR CENTRAL PA LATER TONIGHT. THERE`S SOME QUESTION MARKS AS TO THIS LOW`S EXACT TRACK ESPECIALLY IN LIGHT OF POTENTIAL MASS FIELD CHANGES GIVEN A POTENTIAL SEVERE WEATHER EVENT IN THE MID-ATLANTIC /APPALACHIANS TODAY. THERE APPEARS TO BE BETTER AGREEMENT ON A MORE INTERIOR TRACK (LOW ROUGHLY CENTERED OVER THE HUDSON VALLEY REGION BY 12Z MONDAY) - AND THERE ARE GOOD SIGNALS IN HIGH RES MODELS OF A BAND OF MODERATE RAIN ON THE NORTHWEST PERIPHERY OF SFC LOW`S TRACK. THAT BAND OF MODERATE RAIN LOOKS TO OVERSPREAD SOUTHERN VERMONT INTO THE ADIRONDACKS THROUGH 12Z MONDAY. INITIALLY KEPT POPS AROUND CHANCE CATEGORY BUT BEGIN TO TREND UPWARD AFTER MIDNIGHT TO LIKELY/LOW CATEGORICAL BY THE PRE-DAWN HOURS. LOWS UNLIKELY TO FALL MUCH UNDER OVERCAST SKIES...UPPER 50S TO MID 60S GENERALLY A DEGREE OR TWO WARMER THAN MAV OR MET MOS GUIDANCE. MONDAY & MONDAY NIGHT: SFC LOW THEN TRACKS UP THE CHAMPLAIN VALLEY/GREEN MOUNTAINS THROUGH 00Z TUESDAY...500 MB TROUGH ALSO PIVOTS NORTHWARD BUT APPEARS TO CLOSE OFF BY MONDAY EVENING. WITH THAT EXPECTED LOW TRACK...IT LEAVES CENTRAL/EASTERN VERMONT IN THE WARM SECTOR. FAVORABLE WIND SHEAR PARAMETERS FOR STRONG THUNDERSTORMS IF GREATER INSTABILITY CAN BE REALIZED (GENERALLY IS HIGHEST IN THE 00Z GFS) IN THIS CORRIDOR. NORTHWEST OF THE LOW TRACK...MORE STRATIFORM MODERATE RAIN WILL PIVOT NORTH-NORTHEASTWARD ACROSS NORTHERN NY AND THE NORTHERN CHAMPLAIN VALLEY. I`VE INDICATED CHANCE THUNDER FOR CENTRAL AND EASTERN VERMONT IN PROGGED WARM SECTOR...BUT HAVE OTHERWISE KEPT THUNDER OUT ELSEWHERE WHERE IT`S LIKELY TO BE MORE RAIN-COOLED/STABLE. CATEGORICAL POPS OFFERED MONDAY WITH GRADUAL TAPER TO HIGH CHANCE/LIKELY THROUGH MONDAY EVENING. TEMPS ARE TRICKY/DEPENDENT ON LOW TRACK...BUT LIKELY TO BE BELOW NORMAL AND CLOSER TO NORMAL IF WARM SECTOR CAN GET ESTABLISHED. HIGHS IN NORTHERN NY MAY STRUGGLE TO REACH 70 DEGREES IN A CLOUDY/RAINY DAY...AND CLOSER TO THE MID/UPPER 70S IN CENTRAL AND EASTERN VERMONT. QPF MONDAY RANGES FROM LESS THAN A HALF-INCH FOR THE SAINT LAWRENCE VALLEY... .75-1" FOR MUCH OF VERMONT TO JUST A TICK OVER AN INCH FOR THE ADIRONDACKS. NOT ANTICIPATING ANY HYDRO ISSUES FROM THIS AMOUNT OF RAIN GIVEN HOW DRY IT HAS BEEN. TUESDAY: UPPER TROUGH EXITS WITH STILL SOME LINGERING SHOWERS PARTICULARLY ACROSS HIGHER TERRAIN. NORTHWEST FLOW...MDT COLD ADVECTION (850 TEMPS DURING TUESDAY PLUNGE TO +6 TO +8C) AND PARTLY CLOUDY SKIES PRODUCES BELOW NORMAL HIGHS IN THE 60S TO THE LOWER 70S. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... AS OF 421 AM EDT SUNDAY... A SLOW WARMING TREND TO NEAR NORMAL TEMPERATURES IS EXPECTED BY THE END OF THE WEEK WITH THE HIGHEST CHANCE OF SHOWERS AND THUNDERSTORMS ON THURSDAY. MODELS IN GOOD AGREEMENT THAT A DEEP LARGE SCALE TROUGH WILL REMAIN OVER THE EASTERN US CENTERED NEAR 80 DEG W WITH A RIDGE OVER THE INTER-MOUNTAIN WEST THROUGHOUT THE PERIOD...THOUGH WEAKENING WITH RISING HEIGHTS. THOUGH A SHOWER CAN`T BE COMPLETELY RULED OUT ANY AFTERNOON DURING THIS PERIOD WITH THE UPPER TROUGH JUST OFF TO THE WEST...THE BEST CHANCE FOR SEEING SHOWERS AND THUNDERSTORMS WILL BE THURSDAY AFTERNOON AS A SHORT WAVE WITH COLD AIR ALOFT SWINGS ACROSS THE AREA WITH SOME INSTABILITY AND SOME QG FORCING. THE UPPER TROUGH WEAKENS BUT REMAINS IN PLACE FRIDAY INTO THE WEEKEND BUT RETROGRADES A FEW DEGREES WESTWARD IN RESPONSE TO A BUILDING ATLANTIC RIDGE ALOFT, RISING HEIGHTS OVER THE EAST COAST WITH A BERMUDA HIGH STRENGTHENING AT THE SURFACE...WHICH IS FAIRLY TYPICAL FOR LATE SUMMER. SOME SMALL CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE EACH DAY AS AREA REMAINS LOCKED INTO THE EASTERN SIDE OF THE UPPER TROF. SLIGHTLY BELOW NORMAL MAX TEMPS ARE EXPECTED WEDNESDAY WITH PARTLY SUNNY SKIES. HIGHS TEMPS MAINLY IN THE 70S WITH 850 TEMPS ONLY AROUND 8-10C. 850 MB TEMPS WARM A COUPLE DEGREES EACH DAY SO THAT BY THURSDAY THROUGH SATURDAY SHOULD BE 12-14C. WITH PARTIAL SUN UNDER DIURNAL CUMULUS CLOUDS EXPECT HIGHS MODERATING TO NEAR NORMAL - UPPER 70S LOWER 80S. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... THROUGH 06Z MONDAY..MVFR LCL IFR 12-16Z THIS MORNING WITH SHOWERS AND THUNDERSTORMS AS A WEAK WARM FRONT PUSHES THROUGH THE REGION. CHANCE OF SHOWERS ARE NEAR 80 PERCENT THROUGH ABOUT 16Z TODAY THEN DECREASE. CHANCES OF THUNDER INCREASING ESPECIALLY PBG BTV RUT MPV MOVING WEST TO EAST 12-16Z. VISIBILITIES EXPECTED TO REMAIN MAINLY VFR...EXCEPT SOME BRIEF REDUCTIONS TO MVFR/IFR POSSIBLE IN ANY HEAVIER SHOWERS OR ISOLATED THUNDERSTORMS. PERIODS OF MVFR ARE LIKELY ON BACK SIDE OF RAIN SHOWERS...LASTING UNTIL LATE MORNING WHEN SHOWER THREAT DECREASES. CEILINGS LIFT BACK TO VFR THIS AFTERNOON. ISOLATED THUNDERSTORM DEVELOPMENT POSSIBLE AGAIN THIS AFTERNOON/EVENING AHEAD OF A SLOW SOUTHWARD MOVING COLD FRONT IN CANADA BUT POBABILITIES ONLY 20-30 PERCENT SO HAVE LEFT OUT ALL BUT SLK WHERE TERRAIN MAY HELP. SHOWER AND THUNDER CHANCES DROP THIS EVENING UNDER VFR CONDITIONS. COULD BE SOME FG/BR CHANCES LATER TONIGHT IF CLEARING SKIES AND LIGHT WINDS PREVAIL AS FRONTAL SYSTEM STALLS TO OUR NORTH WHEN 09-12Z MORE SHOWERS AND POSSIBLE THUNDER RETURN ALONG WITH A MVFR/IFR. SOUTH/SOUTHWEST WINDS 5 TO 10 KNOTS TODAY. SOME GUSTS TO 20 KNOTS POSSIBLE. OUTLOOK 12Z MONDAY THROUGH THURSDAY... 12Z MON - 12Z TUE...PERIODS OF MVFR IN RAIN AND ISOLATED THUNDERSTORMS. LOCAL IFR POSSIBLE IN HEAVIER RAIN. 12Z TUE - 12Z THU...TRENDING VFR. POSSIBLE IFR/LOWER VISIBILITY IN OVERNIGHT FOG/MIST MPV AND SLK. 12Z THU ONWARD...MAINLY VFR ALTHOUGH BRIEF PERIODS OF MVFR POSSIBLE IN SCATTERED SHOWERS...MAINLY SLK/MSS. && .MARINE... AS OF 550 AM EDT SUNDAY...A LAKE THUNDERSTORM ADVISORY IS NOW IN EFFECT FOR LAKE CHAMPLAIN. A LINE OF THUNDERSTORMS HAS DEVELOPED OVERNIGHT AND NOW EXTENDS FROM ST. LAWRENCE COUNTY TO THE EASTERN SHORE OF LAKE ONTARIO. WHILE THERE IS NO IMMEDIATE THREAT OF LIGHTNING ON LAKE CHAMPLAIN...EXPECT THESE STORMS TO APPROACH LAKE CHAMPLAIN BY MID-MORNING. BOATERS AND OTHERS NEAR THE LAKE SHOULD BE PREPARED TO SEEK SAFE HARBOR AS THESE STORMS MOVE THROUGH...WITH OCCASIONAL TO FREQUENT LIGHTNING...HEAVY DOWNPOURS PRODUCING BRIEFLY LOWERED VISIBILITY...AND ROUGH SEAS. ADDITIONAL THUNDERSTORMS MAY DEVELOP AGAIN LATER THIS AFTERNOON. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...LOCONTO NEAR TERM...TABER/LOCONTO SHORT TERM...LOCONTO LONG TERM...SISSON AVIATION...SISSON MARINE...LOCONTO

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