Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 202302 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 702 PM EDT Sun Jun 20 2021 .SYNOPSIS... Active weather is expected across the North Country Monday afternoon and evening as the potential for strong to severe thunderstorms are possible. Storms are expected to form over northern New York in the afternoon and then move east into Vermont during the late afternoon and evening hours. Gusty winds, hail, heavy rain, and frequent lightning will be the main threats with any of the thunderstorms. Above normal temperatures are expected on Monday with highs in the mid 80s to lower 90s. Cooler and drier weather is expected by the middle part of the week. && .NEAR TERM /THROUGH MONDAY NIGHT/...
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As of 651 PM EDT Sunday...Did make some adjustments to pops for late tonight into Monday morning, based on expected warm frnt and associated precip lifting from southwest to northeast acrs our fa. Have mention chc across much of VT and northern NY with low likely for the SLV btwn 10z-15z on Monday. Guidance continues to show ribbon of deeper moisture, favorable synoptic scale lift from 5h vort, and developing instability surging north on southwest flow to support idea of showers with a few embedded rumbles of thunder. We should experience a break in precip with some clearing btwn 15z-20z on Monday, which wl quickly help to destabilize atmosphere for next round of strong to severe storms to develop. Pre-storm environmental parameters still look very favorable for convection with some organized/rotating cells possible, given the combination of shear/instability and llvl convergence provided by pre-frontal trof. General consensus is for convection to fire btwn 17z-19z acrs the SLV and expand in areal coverage/intensity thru the aftn/evening hours, with axis of best instability located over the CPV around 21z. Should be an active and interesting day. Previous discussion below: Dry weather is expected for the first half of the night. As the flow aloft turns to the southwest later tonight some showers and isolated storms are expected during the early morning hours, especially across northern New York. Lows will generally be in the 60s with upper 50s in the mountains. Forecast remains on track for Monday with the potential for strong to severe thunderstorms during the afternoon and evening hours. Clouds and some showers should be lifting north of the area just before midday and sunshine should develop over most of the area. Thermal axis at 850 millibars will be right over the area and thus expecting highs in the mid 80s to lower 90s. Increasing south to southwest flow in the low levels will bring dew points into the 60s and this should result in an increasing unstable atmosphere during the afternoon hours. Looking at CAPE values in the 1500 to 2000 J/kg range ahead of a pre-frontal trough moving into the Saint Lawrence Valley of New York by mid-afternoon. This feature plus differential heating along any areas just to the east of more persistent cloud cover should also help to focus convective development. At this time storms should form out near Saint Lawrence and Franklin counties in New York in the 2-4 pm time period. Favorable deep layer shear will be over this area with strongest shear lagging back to the west. This should allow for storms to become organized and have the potential to become strong or severe. Strong wind gusts, hail, heavy downpours, and frequent lightning will be the main threats as the storms move across the northern Adirondacks during the mid-afternoon hours and across the Champlain Valley and points east during the late afternoon and evening hours. Threat of organized convection should come to an end overnight Monday night, but showers should still be rather prevalent.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 327 PM EDT Sunday...Have trended drier with the forecast for Tuesday as models are now indicating the front almost clearing our area by 12z. Have just a mention for chance of showers Tuesday morning, then the pops drop off for the afternoon and we`ll see increasing sunshine. High temperatures on Tuesday will reach the 60s to around 70, warmest in the Champlain valley. A large ridge of surface high pressure will then build into the region and remain through much of the week. Upper level trough will approach the region Tuesday night, but will mainly just see a slight increase in clouds with this feature. Minimum temperatures will be in the 40s to around 50. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 327 PM EDT Sunday...Dry weather is forecast from Wednesday through Friday as large ridge of surface high pressure settles over the region, but begins to slide eastward on Thursday. Our weather will turn more active on Saturday and Sunday as a low pressure system tracks from the Ohio river valley northeastward towards our region. Warm front and shortwave energy lifts across our area Saturday and spreads showers across the region. Surface low, upper level trough and another upper level shortwave moves across the area on Sunday bringing more showers to the region. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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Through 00Z Tuesday...VFR conditions wl prevail for the next 6 to 12 hours acrs all our taf sites with south/southwest winds of 5 to 10 knots. Expect scattered showers with embedded rumbles of thunder possible btwn 09z-15z on Monday with brief mvfr cigs/vis possible in the heavier convection. Additional strong to severe thunderstorms develop btwn 17z-19z acrs the SLV on Monday and move thru northern NY/western VT thru 00z Tues. Expect localized strong/gusty erratic winds, brief heavy down pours, and frequent lighting, with areas of turbulence and shear likely in and around any convection. Winds increase from the south/southwest at 15 to 25 knots on Monday. Outlook... Monday Night: VFR. Likely SHRA, Chance TSRA. Tuesday: Mainly VFR, with local MVFR possible. Chance SHRA. Tuesday Night: VFR. Slight chance SHRA. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX.
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&& .MARINE... Active weather is expected across Lake Champlain Monday and Monday night. First winds will be from the south at 15 to 25 knots, especially during the afternoon hours. Choppy conditions are expected, especially over the northern portions of the lake. From mid-afternoon through the evening hours showers and thunderstorms will move from west to east across the lake and any storms will have the potential to produce strong wind gusts, hail, heavy downpours, and frequent lightning. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson/Taber SHORT TERM...Neiles LONG TERM...Neiles AVIATION...Taber MARINE...Evenson

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