Area Forecast Discussion
Issued by NWS Burlington, VT
Issued by NWS Burlington, VT
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984 FXUS61 KBTV 040242 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1042 PM EDT Mon Jun 3 2024 .SYNOPSIS... Increasing moisture is expected. Isolated showers, coverage more scattered over high terrain, will begin to develop with a few rumbles of thunder. The weather pattern will begin to shift over the later part of the week as an upper low approaches from the west. This will bring cooler temperatures from 80s back to mid 70s and lower 80s. The upper low will also bring more widespread rain chances across the region. && .NEAR TERM /THROUGH WEDNESDAY/... As of 1035 PM EDT Monday...Following a delightful early summer day across North Country with low humidity and plentiful sunshine, a quiet night of weather is on tap. With clear skies, light winds and broad surface high pressure in place, temperatures have fallen into the low to mid 60s, with the exception of low 50s in colder hollows like SLK and around 70 for urban heat islands in the Champlain Valley like BTV. A backdoor cool front associated with an upper low pressure system off Nova Scotia has cleared the White Mountains, but appears washed out across the Connecticut River Valley owing to the strength of the subsidence inversion across our area. High clouds associated with an approaching shortwave trough from the Great Lakes should start overspreading the region from west to east, but those have a higher probability of creating a vibrant sunrise than stunting the radiational cooling. Overnight lows are still on track to fall into the upper 40s to mid 50s, except mid 40s in the typically colder hollows and upper 50s to low 60s in the immediate Champlain valley. Overall, forecast remains in good shape. PREVIOUS DISCUSSION... Temperatures are running about 10 degrees above normal this afternoon under very dry, subsident air beneath a broad upper ridge. Outside some terrain driven cumulus, it`s mostly clear. For tonight, dry conditions are expected, but radiational cooling doesn`t appear as strong with slowly increasing moisture. Cool hollows will likely still fall into the 40s, but most locations should stay in the 50s with perhaps a few spot readings of 60 in the Champlain Valley. For tomorrow, 925 hPa temperatures are about a degree or two warmer, and so the forecast is for max temperatures to creep just a bit higher. BTV and MSS are forecast to reach 88 at present. Ensemble forecasts are about 10 to 30 percent chance of reaching 90. So it`s not out of the realm of possibility. In eastern Vermont, it appears there could be a backdoor cold front that slides into the area, which will be reinforced by a developing sea breeze, and that could help keep temperatures somewhat cooler in far eastern Vermont. With a bit more moisture on the ground, greater heating, and the presence of a subtle boundary in eastern Vermont, there should be enough forcing to break a capping inversion, at least across the mountain ranges. Since there`s still plenty of dry air underneath the upper ridge still in place with little to no shear present, only garden variety showers are anticipated across the Adirondacks and eastern Vermont. A rumble of thunder would be most likely in the Dacks. Overnight, a subtle theta e ridge axis will shift east in conjunction with the development of a weak surface trough and tiny embedded upper trough. It`s not much, but it appears to be enough with 300 to 500 J/kg of elevated CAPE that high resolution guidance is developing hit-or-miss showers in the Champlain Valley. The HREF paintball briefly shows several members with this type of development. So have refined the forecast to highlight some of those details with a 20 to 30 PoP in and around the Champlain Valley overnight. Not anticipating the activity will be strong enough for thunder at the moment. Increasing south flow and additional moisture will result in a humid conditions Tuesday night into early Wednesday with mid 50s to mid 60s. && .SHORT TERM /WEDNESDAY NIGHT/... As of 300 PM EDT Monday...Wednesday will be another warm day with highs reaching the mid to upper 80s. The humidity will also be higher as dew points will be in the low 60s. Diurnal heating will cause some instability to develop, but with minimal flow aloft, it will be mostly terrain driven pulse-type thunderstorms. Scattered showers and storms will likely develop in the mountains during the early afternoon and may spread a bit into the broad valleys later in the afternoon, but the coverage will be more isolated there. Some guidance is suggesting up to 1500 J/KG of CAPE will be in place but with limited shear, there is no severe threat with these storms. The showers will decrease in coverage overnight without the diurnal heating but a cold front will reach northern New York and cause some shower chances there to increase there later in the night. With the increased humidity and some lingering clouds, lows will only fall into the 60s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM EDT Monday...An unsettled pattern will be in place during much of this period as a closed off low will be lingering for several days. An initial cold front will come through Thursday into Thursday night and bring some steadier rain. There is still high model uncertainty with the exact timing of the front and how much moisture it will be able to bring up into the area, but there is good consensus that the front will be through by Friday morning. However, there is no real consensus on QPF. Looking at a Euro, GEFS and Canadian ensemble mixture, there is a roughly a 25 percent chance that the region sees over an inch of rain while there is around a 50 percent chance that the region sees under a half inch. With model guidance trending toward slightly less precipitation, conservatively went with around 0.25-0.50 inches for the region. Areas that see heavier convective showers will see locally more. The WPC put the region in a marginal risk ERO for flash flooding but with dry antecedent conditions, that would likely require the higher end synoptic-driven rain totals and training storms to occur in the areas that see the most synoptic-driven rain. Therefore, flooding looks unlikely at this time. After the front moves through, an upper level low will be situated over the region and bring some shower chances every day. There will be some embedded shortwaves that pivot around it that will increase shower coverage during a few periods. Temperatures will also drop back to or slightly below average with the cooler airmass and increased clouds and showers. The shower chances look to continue to the middle of next week at the moment. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... Through 00Z Wednesday...VFR conditions will continue at all sites. Fair weather cumulus dissipate with sunset and mostly clear skies are expected overnight tonight. Winds become light and variable outside of southeast drainage flow at KRUT overnight tonight. No fog is anticipated tonight. Winds will become southeast to southwest after 13z around 5 knots. Mid- level clouds of 5-8k ft increase towards the end of the TAF period with the slight chance of showers after 18z Tuesday but TAF conditions are expected to remain VFR. Outlook... Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Chance SHRA, Slight chance TSRA. Wednesday Night: VFR. Chance SHRA, Slight chance TSRA. Thursday: Mainly VFR, with local MVFR possible. Likely SHRA, Slight chance TSRA. Thursday Night: Mainly VFR, with local IFR possible. Chance SHRA. Friday: MVFR/IFR conditions possible. Chance SHRA, Slight chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Haynes NEAR TERM...Chai/Haynes SHORT TERM...Myskowski LONG TERM...Myskowski AVIATION...Chai