Area Forecast Discussion
Issued by NWS Burlington, VT
Issued by NWS Burlington, VT
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282 FXUS61 KBTV 070746 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 346 AM EDT Sun Jul 7 2024 .SYNOPSIS... Surface high pressure building east from the Great Lakes will provide the North Country and Vermont with dry weather through Monday. Humidity will be slightly more comfortable as well, while high temperatures in the 80s to near 90 will persist. A weak frontal boundary may provide some showers and thunderstorms on Tuesday, then our attention turns to the potential for heavy rain Wednesday into Thursday associated with the remnants of Hurricane Beryl. && .NEAR TERM /THROUGH MONDAY/... As of 345 AM EDT Sunday...We`ve got a nice break from active weather forecast for the next 36 hours as surface high pressure builds east from the Great Lakes into the forecast area. Overnight dense river valley fog will lift into some fair weather cumulus today from midday through the afternoon, and while a weak shortwave aloft lifts northeastward along the international border this afternoon, soundings show a mid-level cap persisting so not expecting much of anything. It`s not a non-zero chance though that something very isolated could develop, so have maintained some 5-10% PoPs along the northern tier zones. Humidity will be slightly better today as well, despite 925mb temps around +21C supporting similar highs to yesterday in the mid-80s to near 90. Afternoon dewpoints should fall into the low 60s, compared to yesterdays low 70s, so we`ll knock down the muggy meter just a little bit. Afternoon clouds should dissipate to mainly clear skies again tonight, setting the stage again for more dense river valley fog to form. Lows will be slightly cooler than the previous night as well with some mid 50s possible in the Adirondacks to low/mid 60s elsewhere. Monday should be a beautiful start to the week with abundant sunshine, dewpoints just a smidgen cooler in the upper 50s to low 60s, and highs once again above normal in the mid-80s to around 90. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 345 AM EDT Sunday...By Monday night, winds will shift to the south as an upper level disturbance approaches from the Great Lake with overnight lows generally in the 60s. Upper ridging starts to break down on Tuesday as a positively tilted upper level trough approaches from the Great Lakes. As such, shower and thunderstorm chances do return on Tuesday. There remains plenty of timing differences amongst the models on the timing of potential convection. If they do come through at night, the threat for severe weather will likely be greatly diminished. For now, have kept PoPs at 40-50 percent chance category. Accordingly, WPC Day 3 Excessive Rainfall Outlook (ERO) has stayed at the marginal risk category (level 1 of 4) for now. The hydrologic situation does quite a bit more concerning heading into Wednesday. More on that in the long term discussion. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 345 AM EDT Sunday...A year ago, the North Country was dealing with an unprecedented flood event on July 9-11. We are getting increasingly concerned about a potentially significant hydrologic episode right on the 1 year anniversary of last year`s flooding. To be clear, there are important differences between July 2023 and July 2024. Last year`s flooding was not tropical in nature. But there are also many similarities. According to the Northeast Regional Climate Center data, much of our forecast area with the exception of Windsor county saw 125-200 percent of normal monthly rainfall in June. And July has been wet so far. Grounds are saturated and dry stretches have been hard to come by. In coordination with the WPC and neighboring offices, the Day 4 Excessive Rainfall Outlook (Wednesday 8 AM to Thursday 8 AM) was upgraded to Slight risk (level 2 of 4). Bear in mind that Slight risk is 15-40 percent probability of rainfall exceeding flash flood guidance within 25 miles of a point. PWATs, which are already AOA 90th percentile, will be enhanced even further past maximum of SPC sounding climatology due to the moisture from Tropical Cyclone Beryl. PWATs of 2.3 to 2.5 inches are 3 to 4 standard deviations above normal. With slow-moving surface boundaries and generally a lack of atmospheric forcing to push out the tropical air mass, rounds of heavy rainfall and embedded thunderstorms will greatly the risk of flash flooding given the grounds are becoming saturated. The greatest sources of uncertainty right now are the areal placement of the richest PWAT plumes and timing of convection. It is certainly plausible that our region escapes next week relatively unscathed. But it is important to be prepared for the reasonable worst case scenario, which is for scattered to numerous flash flooding if we do get repeated rounds of heavy rainfall and storms to tap into the abnormally moist atmosphere. Please stay up to date with the latest forecast. As we head into Friday and next weekend, a cold front should push the richest PWAT plume (200+ percent of normal) into southern New England and the mid Atlantic states which will allow for slightly drier albeit still seasonably moist air mass to potentially give the North Country a break from the rainfall. Some of the more pessimistic guidance shows potential for the cold front to lift back north as a warm front and bring the risk for more heavy rainfall into the North Country next weekend. But that is a low probability scenario at this time so generally went with a blend of guidance for this portion of the forecast. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Through 06Z Monday...Outside of IFR fog at KMPV, KEFK, and possibly at KSLK overnight through 11-13Z, VFR conditions will prevail with mainly clear skies overnight trending to FEW-SCT fair weather cumulus during the day. Light and variable winds will trend southwesterly at 4-8kts from midday through the afternoon, with the exception being at KPBG where the wind direction will be more southeasterly due to the lake breeze. Outlook... Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Chance SHRA, Chance TSRA. Tuesday Night: VFR. Likely SHRA, Likely TSRA. Wednesday: VFR. Chance SHRA, Chance TSRA. Wednesday Night: MVFR/IFR conditions possible. Slight chance SHRA. Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...Chai LONG TERM...Chai AVIATION...Lahiff