Area Forecast Discussion
Issued by NWS Burlington, VT

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511 FXUS61 KBTV 180240 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1040 PM EDT Thu Aug 17 2017 .SYNOPSIS... High pressure will shift east tonight as a warm front approaches from the southwest. Showers and thunderstorms are possible with the warm front after midnight tonight into Friday, especially in northern New York. Showers will taper off Friday night, and remain possible on Saturday mainly over the higher terrain. Sunday will be warm, a little less humid, with no rain forecast. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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As of 1038 PM EDT Thursday...Current forecast is in good shape as leading edge of warm advection rainfall/showers has reached St. Lawrence county as of 02Z. Surface ridge across central New England will continue to shift eastward overnight, allowing a warm front to lift northeast into the region from the eastern Great Lakes. Leading edge of warm and noticeably more moist air to push into mainly the New York side of the forecast area during the overnight hrs. Surface dewpoints in the 50s to be replaced by 60s dewpoints. Precipitable water rises with the surge of warm moist air, 1.5" across most of the region to near 2 inches in the south of the forecast area. Sharp gradient of Showalter Index values moves into northern New York after midnight and this will enhance the potential for elevated convection. The 18Z NAM indicates elevated CAPE approaching 800-1000 J/Kg for parcels lifted from 875mb in vicinity of srn St. Lawrence County around 09Z Friday. Thus, some embedded convective elements and thunder possible toward daybreak for the far wrn portion of the CWA, but tstm potl mostly holds off til daylight hrs Friday. Overnight lows will see an early drop, then start to rise around midnight in northern NY and early morning hours in the Champlain Valley. Green Mountains and eastward will experience normal diurnal trend in temps. Lows will mainly be in the mid to upper 50s, except lower 60s expected in the Champlain and St. Lawrence Valleys.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... As of 349 PM EDT Thursday...For Friday the warm front lifts through the rest of the forecast area and showers and increasing chances for thunderstorms as atmosphere destabilizes. Shortwave ridging at 500 mb shifts east, and by mid day Friday upper flow becomes diffluent ahead of approaching shortwave trough moving through the Great Lakes Region. Warm moist airmass remains in place through the period with dewpoints remaining well into the 60s. Forecast CAPE 500-1000 j/kg, not great but enough to support some thunder. With high PWATS and warm cloud depth nearing 12,000 feet looking for efficient rainfall production and heavy rainfall rates, however storms should keep moving along to mitigate flooding risk. Highs Friday in the 70s to near 80, and lows Friday night hold in the 60s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 318 PM EDT Thursday...Mainly dry weather is expected from Saturday night through Tuesday morning. Surface ridge builds over the region Sunday keeping things quiet through early Tuesday. A shortwave will cross the area Saturday and Sunday. As the ridge slides to the east Tuesday moisture and warm advection will increase on southwest winds bringing more humid and unstable air to the region, with precipitation chances returning. Deepening low pressure will move from the northern Great Lakes will move up the St. Lawrence seaway by Wednesday bringing unsettled weather once again. Greatest precipitation chances look to be Tuesday night and early Wednesday. Drier weather returns to the region Thursday. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Through 00Z Saturday...VFR conditions this evening will deteriorate as showers along approaching warm front lower cigs and vis to MVFR after 06z northern NY, 10-13 UTC in Champlain Valley and Vermont. Some embedded thunderstorms are possible at KMSS due to elevated CAPE in the area. Low level jet of 30-40kts around 2kft will produce LLWS at KSLK mainly between 08z-13z. Elsewhere, expect the jet to not be as strong. Surface winds will increase out of the south early morning Friday and throughout the mid-day. SE component of surface winds could lead to periods of VFR conditions at KRUT and KBTV through at least the mid morning hours. Showers and embedded thunderstorms continue throughout much of Friday, becoming less numerous during the late afternoon. Cigs may rise to VFR conditions as skinny dry slot moves across the North Country in the afternoon hours, ahead of main frontal boundary. Outlook... Friday Night: VFR/MVFR. Chance SHRA...Slight Chance TSRA. Saturday: VFR. Breezy. Slight Chance SHRA. Saturday Night: VFR. Slight Chance SHRA. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Chance SHRA...Slight Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Hanson NEAR TERM...Banacos/Hanson SHORT TERM...Hanson LONG TERM...Manning AVIATION...KGM

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