Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 201145 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 745 AM EDT WED AUG 20 2014 .SYNOPSIS... A RIDGE OF HIGH PRESSURE WILL MOVE EAST OF THE REGION THIS AFTERNOON. A LOW PRESSURE AREA OVER THE WESTERN GREAT LAKES WILL BRING INCREASING CLOUDS TO THE NORTH COUNTRY TODAY...WITH A CHANCE OF SHOWERS AND A POSSIBLE THUNDERSTORM ACROSS NORTHERN NEW YORK LATE THIS AFTERNOON. SKIES WILL BECOME CLOUDY ACROSS NORTH COUNTRY TONIGHT WITH THE BEST CHANCE FOR SHOWERS AND POSSIBLE THUNDERSTORMS ACROSS NORTHERN NEW YORK. SHOWERS WILL OVERSPREAD THE REMAINDER OF THE REGION ON THURSDAY...WITH A CHANCE OF THUNDERSTORMS ACROSS NORTHERN NEW YORK ON THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 745 AM EDT WEDNESDAY...CURRENT FORECAST IN GOOD SHAPE...SO NO CHANGES MADE. PREVIOUS DISCUSSION FROM 451 AM EDT WEDNESDAY...PATCHY DENSE FOG IN THE SHELTERED VALLEYS OF EASTERN AND NORTH CENTRAL VERMONT WILL BURN OFF BY MID MORNING. EXPECTING SKIES TO START OUT PARTLY TO MOSTLY SUNNY ACROSS THE REGION THIS MORNING...BUT EXPECTING INCREASING CLOUDS ACROSS THE REGION DURING THE DAY. MODELS DIFFER ON TIMING OF PRECIPITATION ACROSS NORTHERN NEW YORK LATE THIS AFTERNOON...WITH THE ECMWF AND CANADIAN GLOBAL MODELS HOLD OFF ANY SHOWER ACTIVITY UNTIL TONIGHT. THE GFS AND NAM WANT TO BRING SHOWERS INTO NORTHERN NEW YORK LATE THIS AFTERNOON. HAVE OPTED TO GO WITH CHANCE POPS FOR SHOWERS ACROSS NORTHERN NEW YORK LATE THIS AFTERNOON. COMPOSITE RADAR LOOP SHOWING SHOWER ACTIVITY ACROSS EXTREME WESTERN NEW YORK STATE HAS BEEN VERY SLOW TO MOVE EASTWARD. THIS IS LIKELY A RESULT OF THE CLOSED UPPER LOW OVER THE GULF OF SAINT LAWRENCE THIS MORNING...COMBINED WITH THE UPPER RIDGE OVER THE REGION AND CLOSED UPPER LOW OVER THE WESTERN GREAT LAKES WHICH PUTS THE REGION IN A BLOCKING PATTERN. GIVEN THIS...FORECASTER CONFIDENCE FOR SHOWERS ACROSS NORTHERN NEW YORK THIS AFTERNOON IS LOW...AND WOULD ALSO EXPLAIN THE TIMING DIFFERENCES IN THE VARIOUS MODEL GUIDANCE. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... AS OF 450 AM EDT WEDNESDAY...MODELS IN SOMEWHAT BETTER AGREEMENT TONIGHT IN BRINGING SHOWERS AND POSSIBLE THUNDERSTORMS INTO NORTHERN NEW YORK TONIGHT. MOS POPS LOOK TOO HIGH ACROSS VERMONT TONIGHT...SO HAVE GONE BELOW MOS GUIDANCE FROM THE CHAMPLAIN VALLEY EASTWARD. THUS...HAVE A SHARP POP GRADIENT FROM THE CONNECTICUT VALLEY TO THE SAINT LAWRENCE VALLEY TONIGHT. THE LOWEST POPS OVER EASTERN VERMONT WITH THE HIGHEST POPS ACROSS THE ADIRONDACKS AND SAINT LAWRENCE VALLEY IN NORTHERN NEW YORK. MODELS IN BETTER AGREEMENT IN BRINGING SHOWERS INTO VERMONT ON THURSDAY. THUS...HAVE INCREASED POPS ACROSS VERMONT ON THURSDAY. HAVE KEPT IN A CHANCE OF THUNDERSTORMS ACROSS NORTHERN NEW YORK ON THURSDAY...AS THIS IS WHERE THE BEST INSTABILITY WILL BE. ON FRIDAY...UPPER LOW SLIDES SOUTH OF THE REGION WITH AN UPPER RIDGE BUILDING SOUTH FROM QUEBEC. THUS...DECREASING CHANCE FOR SHOWERS ON FRIDAY. HAVE JUST GONE WITH SLIGHT CHANCE POPS ON FRIDAY. THE UPPER RIDGE BUILDING SOUTH FROM CANADA ON FRIDAY MARKS THE START OF A REX BLOCK DEVELOPING ACROSS THE REGION FOR THIS WEEKEND. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 400 AM EDT WEDNESDAY...LARGE SCALE PATTERN WL FEATURE A BLOCKING TYPE SCENARIO DEVELOPING ACRS THE EASTERN CONUS. BOTH ECMWF/GFS SHOWS A DEVELOPING CLOSED 5H CYCLONIC CIRCULATION OVER THE WESTERN ATLANTIC AND BUILDING HGHT RIDGE ACRS THE CENTRAL CONUS INTO THE GREAT LAKES BY SUNDAY. THIS PATTERN WL RESULT IN MAINLY DRY CONDITIONS FOR DAYS 4 THRU 7 WITH NEAR TO SLIGHTLY ABOVE NORMAL TEMPS. SFC HIGH PRES BUILDING DOWN FROM EASTERN CANADA WL PUSH SLIGHTLY COOLER TEMPS INTO OUR CENTRAL/EASTERN CWA OVER THE WEEKEND...ASSOCIATED WITH EASTERLY FLOW AND 85H TEMPS BTWN 8-10C. THESE TEMPS SUPPORT HIGHS MAINLY IN THE 70S ACRS OUR REGION WITH THIS COOLER MARITIME AIR WL HAVE THE GREATEST IMPACTS ON EASTERN VT...ASSOCIATED WITH LLVL EASTERLY FLW. SFC HIGH PRES REMAINS NEARLY STATIONARY INTO NEXT WEEK...WITH BUILDING HGHTS ALOFT. THIS WL SLOWLY ALLOW TEMPS TO CLIMB...WITH BEST THERMAL RIDGE AND WARMEST LLVL TEMPS ACRS THE CENTRAL PLAINS INTO THE OHIO VALLEY. THIS VERY WARM AIR MASS...HAS DIFFICULTIES ADVECTING INTO OUR CWA...GIVEN PLACEMENT OF SFC RIDGE AND NW FLW ALOFT...BUT SHOULD BY THE MID TO END OF NEXT WEEK. PROGGED 85H TEMPS WL WARM BTWN 12-14C BY NEXT WEDS...WITH HIGHS IN THE M/U 70S MTNS/NEK TO L80S WARMER VALLEYS. WL CONT TO KEEP FCST DRY AS BEST ULVL SUPPORT AND MID LVL MOISTURE IS LOCATED TO OUR WEST THRU THE MIDDLE OF NEXT WEEK. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... THROUGH 12Z THURSDAY....LIFR IN FOG WL PREVAIL AT MPV UNTIL 13Z...BEFORE GRADUALLY DISSIPATING. MID/UPPER LVL CLOUDS WL SPREAD FROM WEST TO EAST ACRS OUR TAF SITES THIS MORNING AHEAD OF AN APPROACHING WARM FRNT. THESE CLOUDS WL PRODUCE SCATTERED SHOWERS ACRS NORTHERN NEW YORK TAF SITES BY 21Z TODAY...AND SPREAD INTO VT BY THIS EVENING. INITIALLY GIVEN THE VERY DRY LLVLS...EXPECTING SOME OF THE MOISTURE TO FALL AS VIRGA. SOME MVFR CIGS COULD DEVELOP AT SLK BY THIS EVENING...AS MOISTURE INCREASES ON SOUTHERLY WINDS. OTHERWISE...LOOK FOR LIGHT TRRN DRIVEN WINDS THIS MORNING...TO BECOME SOUTH/SOUTHEAST AT 4 TO 8 KNOTS TODAY...WITH EASTERLY FLW AT MSS. OUTLOOK 12Z THURSDAY THROUGH SUNDAY... ADDITIONAL SHOWERS ARE LIKELY INTO THURSDAY WITH PERIODS OF MVFR CIGS/VIS...ESPECIALLY AT SLK/MPV. FOG/BR WL BE LIMITED BY THE INCREASING CLOUDS AND THREAT FOR SHOWERS. SFC HIGH PRES ACRS NORTHERN MAINE WL BUILD INTO OUR TAF SITES ON SATURDAY INTO SUNDAY WITH VFR CONDITIONS LIKELY. THE COMBINATION OF CLR SKIES AND LIGHT WINDS WL RESULT IN FOG/BR AT SLK/MPV BOTH SAT AND SUN MORNINGS WITH IFR CONDITIONS LIKELY. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...WGH NEAR TERM...WGH SHORT TERM...WGH LONG TERM...TABER AVIATION...TABER

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