textproduct: Burlington

WHAT HAS CHANGED

As of 208 PM EDT Monday...

No significant changes have been made to the forecast at this time.

KEY MESSAGES

As of 208 PM EDT Monday...

1. Showers and thunderstorms expected this afternoon and evening.

2. Drier weather Tuesday and Wednesday with another round of showers and thunderstorms on Thursday.

3. Showers possible on Friday with drier weather expected Saturday and Sunday.

DISCUSSION

As of 208 PM EDT Monday...

KEY MESSAGE 1: A warm front lifting north across New York this morning will be the catalyst for showers and thunderstorm development as we head into the mid afternoon hours and well into the evening. The latest high-resolution guidance has slowed the onset of precipitation into our forecast area until around 5 PM across far western portions of northern New York with rain and thunderstorms not entering Vermont until after 8 PM. The best instability doesn't develop until after 00Z as mid-leve lapse rates begin to steepen. Anywhere from 1000 to 1500 J/kg of MLCAPE is forecasted to develop which will be coupled with 40 knots of 0-6km shear. This should help produce some strong to localized severe thunderstorms and SPC has placed a marginal risk for severe weather across northern New York and the northern half of Vermont due to the increasing instability. The lack of surface convergence should keep the areal coverage low but it wouldn't be surprising to see some stronger storms following sunset tonight. In addition, we could see some impressive instantaneous rainfall rates with PWATS above the 80th percentile so we can't rule out some ponding of water on roads to localized flooding. These storms will be moving quickly (40 knots of 0-6 shear) which will mitigate the flood threat but will also help to move these storms east of the Connecticut river shortly after midnight.

KEY MESSAGE 2: Outside of a start shower across the Adirondacks or Green Mountains, quiet and dry weather is expected on both Tuesday and Wednesday. Weak surface high pressure will try to build north but will generally be suppressed due to low pressure to our north and east. Nevertheless, we should see some clearing in the skies midweek with Wednesday showing partly to mostly sunny skies for the partial eclipse. Temperatures will be in the mid 70s to lower 80s with winds generally from the west/northwest at 10 mph or less. Patchy dense fog will be possible in the favorable river valleys Wednesday morning given the upcoming rainfall this afternoon, light winds, and clearing skies.

The next system will move through the region on Thursday as a strong cold front approaches the region. The frontal timing has slowed slightly in the last 24 hours with the frontal passage now expected to be closer to peak heating. This has caused both the AI and machine learning algorithms to slightly increase the severe potential for Thursday. We will once again be working with 1000 to 1500 J/kg of ML CAPE and 40 knots of 0-6 km shear which is more than sufficient to see organized convection capable of producing strong to locally severe storms.

KEY MESSAGE 3: The upper level low will close off to our east Friday morning which will help bring some recycled maritime into our region under an easterly flow regime. This will likely spark additional rain showers across the northern and western slopes of the Green Mountains with upslope conditions. However, it seems likely that most valley locations will generally be on the drier side on Friday. Deep layer ridging will build across the region late Friday through the weekend with dry, seasonably cool, and less humid air expected. Highs should top out in the mid to upper 70s with dewpoints dropping into the 40s each afternoon and plentiful sunshine.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday...A warm front and weak cold front will bring increasing chances of showers and thunderstorms this afternoon and evening with drier conditions late Tuesday. A few of these showers and storms could produce localized heavy rainfall, but flow will be progressive enough to keep the cells moving. About 30% chance of some showers spreading from west to east across northern New York and Vermont through 00Z Tuesday, becoming more widespread into the evening. Highest chance overall of precipitation will be from 22Z Monday through 04Z Tuesday, which could lower visibilities 3-5 miles, briefly lower in any heavier downpours. There is also the potential for thunderstorms during this period, most likely at BTV, SLK, MPV, and MSS. With and following these showers and storms early Tuesday morning, low level moisture is expected to linger at several sites, and any breaks in clouds could lead to quick radiational fog. Most likely site for IFR conditions is SLK from 06Z-13Z Tuesday, though MPV and EFK both have some potential for cig and vis degradations around this time as well. Much will depend on the strength of the inversion that develops in the subsidence behind the storms, and the spots that see more rainfall from the afternoon/evening storms will be more likely to have fog, especially those that have clearing skies and lighter winds. Winds this afternoon and into tonight will be mainly southwesterly, turning more west-northwesterly Tuesday morning, following the passage of the cold front. Some brief LLWS is possible Tuesday morning as winds aloft turn and increase more quickly than winds at the surface.

Outlook...

Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Slight chance SHRA, Slight chance TSRA. Wednesday Night: VFR. Chance SHRA, Slight chance TSRA. Thursday: VFR. Likely SHRA, Chance TSRA. Thursday Night: Mainly VFR, with local IFR possible. Chance SHRA. Friday: Mainly VFR, with areas MVFR possible. Slight chance SHRA. Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX.

MARINE

Channeled southerly winds in the 15 to 20 knot range will continue across much of Lake Champlain through 10 PM. A frontal passage late this afternoon will yield a quick increase in winds across the lake with gusts upwards to 30 knots between 7 PM and 10 PM. Waves will generally be in the 1-2 ft range this afternoon with an increase to 2-3 feet this evening. Winds and waves will quickly subside after midnight.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.