Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 180533 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 133 AM EDT THU SEP 18 2014 .SYNOPSIS... A COLD FRONT ACROSS ONTARIO AND SOUTHWESTERN QUEBEC WILL TRANSLATE SOUTHEASTWARD TONIGHT BRINGING A PERIOD OF CLOUDY CONDITIONS OVERNIGHT INTO EARLY THURSDAY MORNING...ALONG WITH A FEW LIGHT RAIN SHOWERS OR SPRINKLES...MAINLY OVER THE MOUNTAINS. WINDS TURN NORTHERLY BEHIND THE FRONT RESULTING IN FALL-LIKE AFTERNOON TEMPERATURES ON THURSDAY. STRONG HIGH PRESSURE BUILDS IN THURSDAY NIGHT AND FRIDAY...SETTING UP A WIDESPREAD FROST THURSDAY NIGHT WITH TEMPERATURES NEAR TO BELOW FREEZING IN MOST SECTIONS AWAY FROM LAKE CHAMPLAIN. FAIR AND SEASONABLY COOL CONDITIONS CONTINUE ON FRIDAY...FOLLOWED BY BREEZY AND WARMER WEATHER FOR SATURDAY. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... AS OF 108 AM EDT THURSDAY...GOING FORECAST REMAINS IN GOOD SHAPE. NO REAL CHANGES NEEDED...ONLY MINOR ADJUSTMENTS MADE TO HOURLY PARAMETERS TO REFLECT LATEST CONDITIONS AND TRENDS. FRONT NOW SOUTH OF OTTAWA OF OTTAWA AND MONTREAL...AND CONTINUES TO PUSH SOUTH TOWARDS FORECAST AREA. WIDELY SCATTERED LIGHT RAIN SHOWERS/SPRINKLES POSSIBLE OVER NORTHERN AREAS OVERNIGHT. CURRENT POPS OF 20-30 PERCENT LOOK REASONABLE. EARLIER DISCUSSION FROM 721 PM WEDNESDAY... UPPER TROUGH AND SURFACE COLD FRONT CONTINUE TO APPROACH THE REGION THIS EVENING WITH SOUTH/SOUTHWEST FLOW ACROSS THE AREA OUT AHEAD OF THE FRONT...SHIFTING TO NORTH/NORTHWEST BEHIND FRONT IN SOUTHERN CANADA. CLOUDS WILL INCREASE AREA-WIDE THIS EVENING WITH A FEW SCATTERED RAIN SHOWERS POSSIBLE OVERNIGHT WITH FRONTAL PASSAGE...AND THEN PERHAPS A FEW LINGERING INTO THURSDAY MORNING WITH RESIDUAL MOISTURE AND NORTHWEST FLOW. FRONTAL PASSAGE TIMES SHOULD BE AROUND 06Z IN THE SAINT LAWRENCE VALLEY...09Z CHAMPLAIN VALLEY...AND THROUGH THE ENTIRE REGION BY 12Z. AREAS THAT START CLEAR THIS EVENING WILL DROP RAPIDLY AT FIRST...BUT OVERALL MINIMUM TEMPERATURES WON`T BE MET UNTIL LATE AFTER FRONT PASSES...GENERALLY IN THE 40S FOR MOST. && .SHORT TERM /7 AM THIS MORNING THROUGH FRIDAY NIGHT/... AS OF 320 PM EDT WEDNESDAY...LOOK FOR A NORTHERLY WIND SHIFT AS THE FRONT PASSES FROM NORTH TO SOUTH THROUGH THE REGION THURSDAY MORNING. SKIES WILL GRADUALLY CLEAR BY EARLY THURSDAY AFTERNOON BEHIND THE FRONT WITH INCREASING SUBSIDENCE. THE REINFORCING SURGE OF COOL CANADIAN AIR WILL ALSO DRIVE DEWPOINTS DOWN INTO THE UPR 30S THURSDAY AFTERNOON...SO IT WILL FEEL A BIT CRISP. HIGHS THURSDAY OF MID-UPR 50S NRN AREAS...AND LOCALLY IN THE LOW-MID 60S AROUND SPRINGFIELD VT WITH SOME DOWNSLOPE EFFECTS AND LATER ARRIVAL OF LOW-LEVEL COLD AIR ADVECTION EAST OF THE GREEN MOUNTAINS. CONDITIONS ARE IDEAL FOR A WIDESPREAD FROST/FREEZE EVENT THURSDAY NIGHT...AS STRONG HIGH PRESSURE SETTLES SOUTHEASTWARD ACROSS THE REGION FROM ONTARIO AND SWRN QUEBEC. 1000-500MB RH VALUES DROP BELOW 30 PERCENT...AND ANTICIPATE GENERALLY CLEAR SKIES WITH LIGHT WINDS. HAVE ISSUED A FREEZE WATCH FOR ALL ZONES EXCEPT GRAND ISLE COUNTY (CHAMPLAIN ISLANDS)...WHERE THE MODERATING INFLUENCE OF THE WARMER LAKE WATERS SHOULD LOCALLY PRECLUDE A FREEZE. TEMPS WILL RANGE FROM 31-35F FOR MOST OF THE CHAMPLAIN VALLEY (JUST A FROST IN SOME LOCATIONS NEAR THE LAKE)...AND GENERALLY MID 20S TO LOWER 30S ELSEWHERE ACROSS NRN NY AND VERMONT. THE FREEZE WILL BE CLIMATOLOGICALLY EARLY BY 1-2 WEEKS IN MANY AREAS OF CENTRAL/ERN VT AND THE ST. LAWRENCE VALLEY OF NY. WILL ALSO SEE SOME LOCALLY DENSE NOCTURNAL FOG IN THE FAVORED RIVER VALLEYS OF CENTRAL AND EASTERN VERMONT AFTER 04Z FRIDAY. IT MAY TAKE UNTIL 14-15Z FRIDAY FOR THE FOG TO DISSIPATE GIVEN EXPECTED STRENGTH OF THE NOCTURNAL INVERSION. AFTER A FROSTY START WITH SOME VALLEY FOG...FRIDAY SHOULD FEATURE RESPLENDENT BLUE SKIES AS SURFACE ANTICYCLONE REMAINS IN CONTROL...DRIFTING SEWD ACROSS NORTHERN NEW ENGLAND INTO THE GULF OF MAINE. WINDS WILL BECOME LIGHT SE-S DURING THE AFTERNOON HOURS. HIGH TEMPERATURES WILL CONTINUE BELOW NORMAL BY SEVERAL DEGREES...WITH HIGHS GENERALLY 55-60F IN MOST SECTIONS. SURFACE HIGH ELONGATES FROM SW-NE EAST OF NEW ENGLAND WITH INCREASING SOUTH TO SOUTHWEST WINDS DURING THE OVERNIGHT HOURS. WILL PROBABLY NEED A LAKE WIND ADVISORY OVER LAKE CHAMPLAIN AS WINDS REACH 20-25 KTS DURING THE PRE-DAWN HOURS. COMBINATION OF INCREASING GRADIENT FLOW AND MID-UPPER CLOUDS MOVING IN FROM THE WEST WILL KEEP TEMPERATURES ABOUT 10F WARMER THAN EXPECTED LOWS FOR FRIDAY MORNING. LOWS FRIDAY NIGHT GENERALLY LOW-MID 40S. MAY STILL SEE SOME PATCHY FOG IN THE DEEPER RIVER VALLEYS EAST OF THE GREENS MOUNTAINS. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 313 PM EDT WEDNESDAY...THERE APPEARS TO BE A LITTLE MORE AGREEMENT BETWEEN 12 UTC GLOBAL SOLUTIONS THAN PRIOR MODEL CYCLES. INITIAL PERIOD OF MILDER THAN NORMAL TEMPS SATURDAY/SATURDAY NIGHT BEFORE A STRONG COLD FRONT MOVES THROUGH LATE IN THE WEEKEND USHERING IN COOLER THAN NORMAL TEMPS. WARM FRONT ASSOCIATED WITH NORTHERN STREAM DISTURBANCE MOVING ACROSS SPREADS ACROSS THE NORTH COUNTRY EARLY SATURDAY WITH CLOUDS AND CHANCES FOR LIGHT SHOWERS. WARM-SECTOR AIRMASS ASSOCIATED WITH 850 MB TEMPS OF +13 TO +15C BECOMES BRIEFLY ENTRENCHED SATURDAY NIGHT/SUNDAY...LEADING TO DAYTIME HIGHS NEARING THE MID 70S AND LOWS IN THE 50S. PRIMARY FOCUS FOR POPS /LIKELY/ HOWEVER IS LATER SUNDAY INTO SUNDAY NIGHT WITH COLD FRONTAL PASSAGE. BELOW-NORMAL TEMPERATURES THEN EXPECTED FOR EARLY NEXT WEEK WITH FRONTAL PASSAGE AS 850 MB TEMPS CRASH BACK TO THE +5 TO +7C RANGE MONDAY NIGHT INTO TUESDAY UNDER NORTHWEST FLOW. BOTH GFS AND ECMWF SHOW A SECONDARY SHORTWAVE DIVING SOUTHEASTWARD MONDAY INTO TUESDAY...BUT COLD FRONT AND ASSOCIATED THERMAL GRADIENT SHIFTS FAR ENOUGH EAST TO KEEP ANY SFC LOW DEVELOPMENT ALONG THE BOUNDARY OFFSHORE. EARLIER 00Z ECMWF HAD SHOWN MORE DEVELOPMENT ALONG THE SAGGING BAROCLINIC ZONE AND WAS MORE UNSETTLED THAN THE GFS. STRONG RIDGE OF HIGH PRESSURE THEN BUILDS IN FOR TUESDAY/TUESDAY NIGHT WITH THERMAL TROUGHING STILL IN PLACE ALOFT. PRIMARILY HAVE STUCK WITH SUPERBLEND GUIDANCE THROUGH MIDWEEK. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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THROUGH 06Z FRIDAY...SURFACE COLD FRONT SHIFTING INTO THE REGION EARLY THIS MORNING WITH SCT-OVC VFR CIGS AHEAD OF THE FRONT GRADUALLY LOWERING TO MVFR FOR A BRIEF PERIOD BEHIND THE FRONT BEFORE RETURNING TO VFR BY MID-DAY. CURRENT RADAR COVERAGE SHOWS WIDELY SCATTERED SPRINKLES ALONG THE INTL BORDER WITH SURFACE OBS SHOWING NO RESTRICTIONS TO VSBY. FEEL THIS WASN`T EVEN WORTH MENTIONING IN THE TAF. HIGH PRESSURE BEGINS TO BUILD BACK INTO THE AREA THIS AFTERNOON/EVENING WITH SKIES CLEARING OUT AFTER 00Z. LIGHT SOUTH/SOUTHWEST FLOW SHIFTS TO NORTH/NORTHWEST (NORTHEAST FOR A TIME AT PBG AND MSS) FOR THURSDAY FROM 5-10 KNOTS. OUTLOOK 06Z FRIDAY THROUGH MONDAY... 06Z FRIDAY THROUGH 12Z SUNDAY...MAINLY VFR UNDER HIGH PRESSURE. IFR IN EARLY MORNING FOG ALSO LIKELY EACH NIGHT...MAINLY FOR KSLK AND KMPV. 12Z SUNDAY THROUGH 12Z MONDAY...VFR TRENDING TO MVFR IN SHOWERS FROM WEST TO EAST AS A COLD FRONT TRACKS THROUGH THE REGION. 12Z MONDAY THROUGH 00Z TUESDAY...MORNING MVFR WITH LINGERING POST- FRONTAL SHOWERS POSSIBLE...TRENDING TO VFR LATE IN THE DAY AS HIGH PRESSURE RETURNS.
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&& .CLIMATE... AS OF 150 PM EDT WEDNESDAY... FOLLOWING ARE THE RECORD LOWS FOR FRIDAY MORNING SEPT 19TH. GIVEN THE EXPECTED BLAST OF CHILLY AIR, WE MAY BE APPROACHING RECORDS AT SOME LOCATIONS. LOCATION...............RECORD...YEAR MT MANSFIELD (MMNV1)...24F 1979 RUTLAND (RUTV1)........27F 1990 MONTPELIER (MPV).......29F 1959 ST JOHNSBURY (SJBV1)...29F 1943 MASSENA (MSS)..........30F 2008 BURLINGTON (BTV).......32F 1959 && .BTV WATCHES/WARNINGS/ADVISORIES... VT...FREEZE WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR VTZ002>012-016>019. NY...FREEZE WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR NYZ026>031-034-035-087. && $$ SYNOPSIS...BANACOS NEAR TERM...RJS/MUCCILLI SHORT TERM...BANACOS LONG TERM...LOCONTO AVIATION...LAHIFF CLIMATE...NASH

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