289 FXUS61 KBTV 291120 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 720 AM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... As of 226 AM EDT Monday... Dangerous heat and humidity is still on track for Wednesday through at least Thursday, and perhaps into Friday. The threat for severe thunderstorms has increased for Tuesday night and Wednesday. && .KEY MESSAGES... As of 226 AM EDT Monday... 1. Dangerous heat and humidity are expected for mid to late week. Heat headlines will likely need to be issued by subsequent shifts. 2. Strong to severe thunderstorms are possible Tuesday and Wednesday. 3. Dangerously hot and humid conditions will linger into the holiday weekend along with daily chances of showers and thunderstorms. && .DISCUSSION... As of 226 AM EDT Monday... KEY MESSAGE 1: Today starts a gradual warming trend that will continue into the latter half of the week. High pressure will build eastward from the Ohio River Valley, while a warm front lifts toward and eventually across our region Tuesday into Wednesday. While today will remain fairly comfortable, humidity will increase markedly as the front moves through, making for very muggy conditions by late Tuesday into Tuesday night. Guidance continues to keep Tuesday a touch colder than previous runs owing to cloud cover and precipitation chances (more on that below), so while it will be hot and humid, expect heat index values to generally remain at or below 90F. Heat builds on Wednesday, with 925mb temperatures approaching 26-28C, and perhaps even warmer if the GFS holds true. As such, we expect this will be the first day to warrant heat headlines, particularly since dewpoints will be 70F or better across much of the region. However, there's still considerable spread in shower/thunderstorm timing/placement/coverage on Wednesday, which could potentially impact high temperatures. Regardless, the heat will continue into Thursday and perhaps beyond, with dewpoints remaining in the upper 60s to low 70s. If precipitation holds off and everything comes together just right, heat index values of 95 to 105 are very much possible both Wednesday and Thursday. And there will be little relief overnight as muggy conditions will keep lows close to or above 70F. Given that the core of the heat is still 48+ hours away and there's some uncertainty how Wednesday's temperatures will play out, have opted to not issue any heat headlines at this time. However, please use this time to prepare for potentially dangerous heat later this week, and follow forecast updates closely. KEY MESSAGE 2: We'll remain on the northeastern periphery of an upper level which which will be centered near/over the Ohio River Valley. Model guidance continues to indicate the potential for several shortwaves/ridge rollers to ride over the top of the ridge and down through the northwest flow that will be in place over New England. As these disturbances move along the upper flow, we also look to be influenced by waves of an EML, either right overhead or moving just off to our west. This will increase instability, even into the overnight hours, thus aiding any night time convection. Timing these sorts of ridge rolling systems is notoriously difficult, but at this time, guidance seems to be keying in one moving through northern/western New England and NY sometime later Tuesday into Tuesday night, with another one potentially following sometime Wednesday. If convection moves in during daylight hours, SB CAPE will be ample, generally 500-1500+ J/kg from the Champlain Valley westward on Tuesday. This would become more widespread and increase on Wednesday, with SB CAPE an impressive 1000-2000+ J/kg across much of the area (note both the NAM and GFS have values as high as 3000 J/kg, though placement differs between the models). Shear both days will be a respectable 35-50 kt. Hence, if convection does develop during the daylight hours, strong to severe thunderstorms capable of large hail, damaging winds, especially in any supercells. Any overnight storms would be elevated but still capable of some small hail. And any storms would be capable of producing very heavy rainfall, with PWATs 1.5 to 2+ inches and warm cloud depths 10-12+ kft. This thinking is reinforced by both SPC, which has us included in a Marginal Risk (level 1 of 5) for Tuesday and Tuesday night, while WPC likewise has a Marginal Risk (level 1 of 4) of excessive rainfall over our region. This is a complex scenario and there's still plenty of uncertainty, so please stay tuned for future forecast updates, especially if you have outdoor plans. KEY MESSAGE 3: Prolonged heat will likely be ongoing into the end of the week with ample humidity, even as temperatures trend less extreme. While we show another day of high heat index values on Friday with peak values well into the 90s at elevations below 1000 feet, the potential for a mesoscale convective system and its effect on temperatures makes this forecast somewhat uncertain. Furthermore, some guidance is more amplified with the ridge centered to our southwest, which allow for more anomalous low level temperatures to remain in our area. The mean 925 millibar temperatures range from merely very warm (close to 20 Celsius) in the cooler scenario to hot (close to 26 celsius) in the hotter scenario, translating to high temperatures either mainly mid to upper 80s or mid to upper 90s in a mainly dry scenario. This spread continues on Saturday (July 4th) and Sunday, but the high end temperatures trend less hot as the ridge begins to break down. As such, the story for the weekend may be potential for flooding, as a surface boundary may eventually become stationary to our south with rounds of showers and thunderstorms moving across the Northeast. The details of this are rather unclear and due to the convective nature of precipitation the signals for widespread heavy rain are low, but this hazard alongside strong to severe thunderstorms over the weekend will need to be watched, especially where earlier week convection had occurred. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Through 12Z Tuesday...VFR conditions and light winds will continue amidst high pressure during the period. A brief period of dense fog did materialize at MPV around sunrise along with intermittent fog at SLK, but drier air is expected to reduce the potential such that a repeat tonight is unlikely. Outlook... Tuesday: VFR. Chance SHRA, Chance TSRA. Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Chance TSRA. Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance TSRA. Wednesday Night: VFR. Chance SHRA, Chance TSRA. Thursday: VFR. Slight chance SHRA, Slight chance TSRA. Thursday Night: VFR. Chance SHRA, Chance TSRA. Friday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance TSRA. && .CLIMATE... Extreme heat and humidity is possible later this week, especially on Wednesday and Thursday, which could lead to some daily records. Below are the current daily high and low temperature records in jeopardy at our area climate sites. Record High Temperatures: June 30: KBTV: 93/2018 July 1: KBTV: 96/2018 KMPV: 92/2018 KPBG: 94/1968 KMSS: 94/2018 July 2: KBTV: 97/2018 KMPV: 90/2018 KMSS: 94/2018 July 3: KMPV: 91/2002 Record High Minimum Temperatures: July 1: KBTV: 76/2018 KPBG: 73/1971 KSLK: 69/2018 July 2: KPBG: 77/2002 KSLK: 68/2002 July 3: KBTV: 76/1911 KPBG: 73/2002 July 4: KPBG: 71/1973 KSLK: 67/1952 && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ WHAT HAS CHANGED...Hastings DISCUSSION...Hastings/Kutikoff AVIATION...Kutikoff CLIMATE...NWS BTV