textproduct: Burlington

WHAT HAS CHANGED

As of 228 PM EDT Friday...

The potential for severe weather remains in place but is largely conditional as wildfire smoke may limit daytime heating in some locations. Should we have severe weather, gusty winds looks the primary and likely only mode of severe weather given tall/skinny CAPE profiles and strong deep layer shear.

KEY MESSAGES

As of 228 PM EDT Friday...

1. Smoke, showers, and thunderstorms, some strong to severe, expected Saturday afternoon and evening.

2. Drier weather expected Sunday and Monday.

3. Frontal passages bring chances for showers and thunderstorms on both Tuesday and Wednesday before high pressure dominates our weather on Thursday and Friday.

DISCUSSION

As of 228 PM EDT Friday...

KEY MESSAGE 1: As winds shift from the north to south Saturday morning, we will see wildfire smoke once again lift north into the North Country. The HRRR and RAP smoke analysis continue to show 50-100 micrograms per cubic meter by Saturday afternoon which will likely begin to degrade air quality. Should this trend continue, the issuance of an air quality alert is possible. This smoke will be the wild card in a potential severe weather event across northern New York and Vermont as the thick smoke cover could have an impact in insolation and limit diurnal heating (as with the previous event on Tuesday/Wednesday). However, models are handling this smoke much better than last time so we can say with decent confidence that multiple strong to severe thunderstorms will be possible.

The environment will be highlight by Strong deep layer shear of 40- 45 knots and CAPE values in the 500-1000 J/kg range. High PWAT values of 1.7-1.8 inches will keep thermodynamic profiles moist- adiabatic with modest lapse rates which is the key limitation to instability Saturday afternoon. Still with deep moisture and strong shear profiles, some storms could contain severe wind gusts and have the potential to produce a wet microburst. Hail looks rather unlikely given high freezing levels and limited CAPE in the hail growth layer. A tornado can't be ruled out but the low level lapse rates and low level helicity should severely limit that potential. These showers and thunderstorms will exit to the east Saturday night.

KEY MESSAGE 2: We will likely see a few lingering showers across eastern Vermont during daybreak on Sunday but drier air filtering in through the morning hours should put an end to those quickly. Clearing skies will accompany these drier conditions which will lead to a beautiful Sunday. Dry conditions will persist Sunday and Monday with seasonal temperatures, plenty of sunshine, and light winds.

KEY MESSAGE 3: Upper level low pressure will swing through Ontario on Monday night, though models continue to show timing discrepancies, and there remains disagreement on how close the surface low pressure will get to the US-Canadian border. We anticipate cloud coverage will increase Monday night, with precipitation likely beginning in northern New York Tuesday morning and spreading eastward throughout the day as low pressure edges into Quebec and a warm front treks across northern New York and Vermont. Tuesday afternoon, thunderstorms are possible as highs reach into the seasonable upper 70s to mid 80s, with highest instability in the St. Lawrence Valley and western Adirondacks paired with widespread modest shear. Nighttime lows in the 50s to mid 60s are anticipated for the early week. A cold frontal boundary is expected to cross the forecast area Tuesday night, bringing another round of showers with embedded thunderstorms, then deterministic models diverge sharply in their solutions. Some projections show another frontal boundary or an area of low pressure moving through the Northeast on Wednesday, while other suggest the upper trough becomes negatively tilted. General consensus suggests precipitation is likely outside of shadowed areas on Wednesday with thunderstorms again possible, then precip chances drop Wednesday night into Thursday under high pressure. We will be monitoring the midweek period for potential of strong or severe storms and also for heavy rainfall. Chances of a half an inch of rainfall within 24 hours runs around 50-80%, most likely Tuesday through Wednesday as modeled precipitable water values max out 1.50- 2.00 inches on Tuesday afternoon and evening. Highs for the mid and late week are expected to be around the 70s and lower 80s with lows in the upper 40s to lower 60s, though this may depend on how exactly the atmospheric pattern shapes up during this period.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18Z Saturday...VFR conditions are expected to prevail over the next 24 hours. Winds out of the northwest 5-10 knots with isolated gusts 15- 20 knots this afternoon are expected to decrease this evening and tonight, becoming light and variable, at times calm by 00Z Saturday. Some sites could even see a light south- southwesterly wind, mostly below 5-10 knots. We anticipate winds increase Saturday morning into the early afternoon out of the south and southwest with sustained 5- 15 knots likely, and higher gusts in the afternoon. A low level jet will cross the region starting around 12Z-14Z, so LLWS is forecast at MSS and SLK for a few hours before winds fully pick up at the surface. Vis restrictions from smoke was not included in the TAF, however, there is the potential for smoke to return to the surface early Saturday morning and last through the day. At this time, uncertainty on how that will impact visibilities is too high to include, but certainly something to monitor. Thunderstorms and heavy rain are likely Saturday afternoon and evening, but this is primarily after 18Z Saturday so was not included either.

Outlook...

Saturday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Sunday: Mainly VFR, with local MVFR possible. NO SIG WX. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: Mainly VFR, with areas MVFR possible. Likely SHRA, Chance TSRA. Tuesday Night: Mainly MVFR, with areas IFR possible. Definite SHRA, Slight chance TSRA. Wednesday: MVFR/IFR conditions possible. Likely SHRA, Slight chance TSRA.

BTV WATCHES/WARNINGS/ADVISORIES

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