Area Forecast Discussion
Issued by NWS Burlington, VT

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361 FXUS61 KBTV 101945 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 345 PM EDT Mon Jun 10 2024 .SYNOPSIS...
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Plenty of clouds will prevail overnight with areas of patchy drizzle and fog, especially across the higher terrain. Temperatures will slowly cool back into the 40s to mid 50s. Tuesday will feature a few more breaks in the cloud cover with temperatures warming back into the mid 60s to mid 70s. A few widely scattered showers are possible on Wednesday, especially eastern Vermont, before a brief dry spell with warmer temperatures return for Thursday.
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&& .NEAR TERM /THROUGH TUESDAY NIGHT/...
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As of 344 PM EDT Monday...Upper air analysis shows closed cyclonic circulation is located over northern Maine this aftn with mid/upper lvl trof axis extending back into northern NY. Plenty of clouds are anticipated overnight associated with moist/cyclonic upslope flow as moisture is trapped below developing subsidence inversion. Given sounding profiles and webcams today, anticipate areas of fog/patchy drizzle is likely above 1500 feet tonight, especially northern/central Greens and northern Dacks. As subsidence layer continues to push toward the sfc, expect low cigs to produce areas of fog especially mtn valleys by early Tues morning. Temps remain mostly steady in the mid 40s to mid 50s acrs our cwa with light trrn driven winds. Tuesday mid/upper lvl trof axis prevails with slightly less deep layer moisture overhead. Expecting northwest downslope regions of the western CPV and lower CT River Valley near VSF to see increasing amounts of sunshine, along with parts of the SLV. Areas that see some breaks in the overcast should warm back into the l/m 70s, while mtn towns hold in the upper 50s to mid 60s. A spot light shower or pocket of drizzle is still possible, but overall probability of measurable precip is <15% on Tues. Tue night is dry with no impactful wx anticipated. If areas of clearing develop, especially mtn valleys patchy fog is possible as temps reach cross over values, but probability attm is <20% and confidence in this scenario is low. Lows generally in the l/m 40s to mid 50s again with light trrn driven winds.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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As of 344 PM EDT Monday...One last day under the influence of a decaying upper level low will support at least some shower chances, especially in the eastern half of Vermont. Forecast soundings show meager instability focused below the hail growth zone, so it will be hard to see any thunderstorm development. Temperatures should tick up a few degrees from Tuesday, especially if we wind up being partly to mostly sunny. That being said, forecast highs have trended downward a hair compared to the previous forecast, with highs ranging through the 70s. Overnight precipitation chances drop to nil as ridging starts to nudge in from the west. With light winds, there could be patchy fog where it rains during the afternoon/early evening hours but overall very quiet weather is expected with seasonable temperatures.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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As of 344 PM EDT Monday...Thursday looks seasonably warm and dry with weak upper level ridging. Temperatures should climb into the low to mid 80s for most locations and based on low spread in high temperatures from NBM guidance, this is a high confidence forecast. With low level flow turning from westerly to southwesterly, there should be a modest increase in humidity but overall due to relatively dry air upstream, dew points should still remain in the 50s. With mid and upper level westerly flow, we may see some high clouds stream in from remnant showers and thunderstorms that were in the western Great Lakes region Wednesday night, but at this time it does not look like we`ll have a trigger for showers and thunderstorms during the day on Thursday. That will change Thursday night as we will see a moderately strong cold front move through the region. The moist southerly flow ahead of the front will make for a mild night, with the ECMWF Extreme Forecast Index highlighting unusually warm conditions. The surface convergence ahead of the front will lead to numerous showers, with greatest chances as you head northward. Trends in the data seem to suggest most of this activity stays north of the International Border, with more coverage of showers north and west of the Adirondacks. With the system`s low pressure area tracking through northern portions of Canada and progressive nature of the front, any heavy showers will be short lived and thunder chances look minimal. In contrast, more widespread shower activity is expected during the day Friday as a wave of low pressure passes along the front right through our region. Timing and location of this precipitation is hard to pin down, but mean onset timing currently is roughly from 6 AM in northern/western areas to mid morning in the central/southern Champlain Valley to the early afternoon in southeastern Vermont. The early morning timing of the frontal passage is a limiter to thunderstorm chances. The more active scenario for Friday, which features at least 500 J/kg CAPE in the southern half of Vermont Friday afternoon, is shown by only 20% of the latest global model guidance and is consistent with the GEPS overall showing a slower frontal passage. Due to the frontal passage, high temperature Friday are much more uncertain than on Thursday. In fact, the forecast has changed substantially just since this last morning. Our whole region may be on the cool side of the front during the day, so it would not be surprising to see temperatures top out in the 60s and 70s for most locations on Friday. Rainfall also is rather uncertain, but ingredients for at least some rain are on the table even if amounts are not more than a quarter to half an inch. For now, likely (generally 55-70%) PoPs peaking between 2 and 8 PM looks reasonable. With upper height falls, some showers also could be capable of producing thunder if there is enough surface heating. Given the generally uncertain forecast, a slight chance of thunder areawide is offered for those afternoon/evening hours before sharply drier air arrives. The dry air mass looks to arrive and sustain itself over our region for the entire weekend with crisp air with a large ridge of seasonably strong high pressure working in from the northwest. When it sits right overhead Saturday night, temperatures will get down right chilly in the low to mid 40s by daybreak Sunday. Abundant sun will help temperatures surge well into the 70s or low 80s by Sunday afternoon, a few to several degrees warmer than Saturday. Enjoy the weekend`s weather if you can, as signals for very hot weather are showing up, especially just beyond this forecast period, next Tuesday through Thursday. There is a near certainty (greater than 80% chance) of heat concerns for our region during at least part of that time frame.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... Through 18Z Tuesday...A wide range of conditions this aftn from intervals of IFR at MPV/SLK to VFR at BTV/PBG, while rest of taf sites are experiencing MVFR conditions. Have used a 1 hour tempo group for SLK/MPV to cover IFR cigs potential, but feel conditions should trend toward MVFR in the next 1 to 2 hours. Utilizing the AvnFPS cigs/vis climo trend tool indicates based on crnt obs at 17z at SLK, probability of IFR/LIFR conditions increases to 30-40% by 02z and 50-60% by 05z, so have trended toward IFR by 02z with potential LIFR conditions by 06z. A similar type scenario, but delayed by a few hours is expected at MPV. Otherwise, a combination of VFR/MVFR cigs are anticipated at the other taf sites, with highest probability of VFR at PBG and MSS thru the period. Conditions slowly improve to VFR at all sites by 15z Tuesday. Winds west/northwest 5 to 10 knots become light and variable tonight. Outlook... Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Slight chance SHRA. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. Slight chance SHRA. Thursday Night: VFR. Chance SHRA. Friday: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA. Saturday: VFR. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...Kutikoff LONG TERM...Kutikoff AVIATION...Taber