Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 191800 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 200 PM EDT Mon Jun 19 2017 .SYNOPSIS... Showers and thunderstorms with very heavy rainfall will form today, mainly in Vermont and the Champlain Valley of northern New York. A flash flood watch is in effect this afternoon and evening. Small hail and gusty winds are also possible in the stronger storms. The threat for heavy rainfall and wind will lessen after tonight, however the weather will remain unsettled this week as a trough of low pressure slowly moves through the area. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 1232 PM EDT Monday...Sent a quick update to adjust enhanced wording in the forecast due to new severe thunderstorm watch for all but far northwest Vermont. Deep layer shear has increased over the area and will do so for the next several hours. Instability not as great as yesterday...but numerous breaks in the clouds is helping to further destabilize the atmosphere. Much of northern New York to remain in the clouds and thus limit threat for organized storms. Still feel best threat for storms will be south and east of Burlington this afternoon and evening. Previous Discussion... Starting to see indications of where threat for organized storms may exist this afternoon. Clearing just to the east of a pronounced southwest to northeast band of clouds from west central Pennsylvania north-northeast into northeast New York. This puts a good portion of the Champlain Valley and points east in the region where destabilization may be best this afternoon. This is also where the axis of highest precipitable water will exist and where leading edge of stronger deep layer shear will try to move over. Have fine tuned grids to keep any showers over most of northern New York today in the showery mode and no thunder while maintaining stronger storm wording generally east of a line from Ticonderoga-Burlington-Highgate line although most favorable locations will likely be south of Montpelier where greatest clearing should take place. Previous Discussion... Pops decrease tonight with loss of surface heating, however with proximity of upper low to west and weak shortwaves kicking out can`t rule out continued showers entirely. Drier surface air works into the area on the southwest low level flow, reducing dewpoints from upper 60s to low 70s down into the 60s for a little relief from the humidity. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... As of 432 AM EDT Monday...Large upper trough extending from Eastern Canada down into the Great Lakes will be the dominant feature in the short period. The axis of deeper moisture shifts east but area remains in southwest flow aloft with upper trough still to the west leading to potential for showers and possible thunderstorms, especially terrain enhanced activity through the early evening of Tuesday. Another round of mainly terrain driven showers is expected for Wednesday as the trough axis passes over the region. An afternoon rumble of thunder can`t also be ruled out as well. Highs for Tuesday will be in the 70s to low 80s with lows in the upper 50s to 60. Wednesday will see highs in the upper 60s to 70s. && .LONG TERM /THURSDAY THROUGH SUNDAY/...
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As of 200 PM EDT Monday...Overall an active pattern with temperatures expected to be above normal through the weekend. Thursday will start off dry, under ridging at the surface and aloft. Embedded ripple of vorticity will approach the North Country late in the day, increasing chance for showers. Thursday night into Friday, a front will bring precipitation to the region but take its time moving across the region as upper level support in the form of mid- level vorticity will be lagging behind. GFS and ECMWF show boundary and associated precipitation affecting the North Country through Friday evening. Brief break in precip expected Friday night before the possibility of another wave bringing rain Saturday. Models diverge on next area of low pressure evolution and track for Sunday.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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Through 18Z Tuesday...VFR conditions to start the period with scattered showers and thunderstorms moving north northeastward into the forecast area. These showers and thunderstorms will produce brief periods of heavy downpours and deteriorate conditions to MVFR/IFR. Areas most likely to see thunderstorms this afternoon will be the Champlain Valley and areas east, especially at KRUT - which has a cluster of thunderstorms approaching from Hudson Valley and southern VT. Thunderstorms will produce strong gusty winds, heavy rain, gust fronts, possible turbulence and potentially small hail. Expect thunderstorm threat to diminish after sunset. Have lingering showers but not thunder after 03Z. With plentiful moisture still over the region heading into this evening, expect MVFR/IFR conditions to develop overnight. Chance for scattered light rain showers remains through the morning hours. Outlook... Tuesday Night: VFR. Chance scattered SHRA. Wednesday: VFR. Chance SHRA...Slight Chance TSRA. Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR. Slight Chance SHRA. Thursday Night: VFR. Chance SHRA. Friday: VFR/MVFR. Likely SHRA...Slight Chance TSRA. Friday Night: VFR. Chance SHRA...Slight Chance TSRA. Saturday: VFR. Chance SHRA.
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&& .HYDROLOGY... A flash flood watch continues from noon today through this evening for the potential for flash flooding associated with very heavy rainfall rates in thunderstorms across Clinton and Essex counties in New York and all of Vermont. High rainfall rates of 1 to 2 inches per hour with isolated higher amounts possible in the stronger convective elements will increase the potential for flash flooding this afternoon and night. The greatest potential for flash flooding will be across the higher terrain and urban areas with poor drainage, and areas that have received rainfall in the past week, including Washington, Orange, and Windsor counties in Vermont. Small streams in those areas continue to run above normal for this time of year, and can be quickly overcome by excessive rainfall. Rapid rises on smaller streams and rivers are possible in areas of the most persistent showers and thunderstorms. We also tend to see washouts of ditches and the edges of unpaved roads in steeper terrain in storms with very high rainfall rates of 2-3 inches per hour, even if they are short lived. && .MARINE... A Lake Thunderstorm Advisory is in effect through this evening. The threat for thunderstorms will be increase as the afternoon wears on and any of the storms will have the potential to produce strong wind gusts...hail...frequent lightning...and very heavy downpours. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Flash Flood Watch until midnight EDT tonight for VTZ001>012- 016>019. NY...Flash Flood Watch until midnight EDT tonight for NYZ028-031- 034-035. && $$ SYNOPSIS...Hanson NEAR TERM...Evenson/Hanson SHORT TERM...MV LONG TERM...KGM AVIATION...KGM HYDROLOGY...Hanson MARINE...Evenson

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