textproduct: Burlington

WHAT HAS CHANGED

As of 240 PM EDT Saturday...

Risk of strong to severe thunderstorms has decreased for the rest of today, with lower thunderstorm chances as well.

KEY MESSAGES

As of 240 PM EDT Saturday...

1. While the threat of damaging winds in our area has decreased, rounds of showers with a few thunderstorms will continue into this evening. Meanwhile, near surface smoke has returned to much of our region but will be replaced by cleaner air and low humidity for Sunday and Monday.

2. Chances of showers and a few thunderstorms return for later Tuesday into Wednesday, otherwise mainly fair and seasonable weather is expected to end the work week.

DISCUSSION

As of 240 PM EDT Saturday...

KEY MESSAGE 1:

A vigorous shortwave trough diving southeastward over eastern Ontario alongside a moderately deep low pressure system is promoting widespread precipitation and areas of deep convection across the Northeastern US. The system's warm front is having a hard time pushing east/northeastward, such that isentropic lift has been generating steady rain with embedded downpours across northern New York and Vermont. As a result, the possibility of our region becoming destabilized via surface heating has greatly diminished today's potential severe weather event. The limited threat area is trending towards the St. Lawrence Valley where MLCAPE is progged to surge to near 1000 J/kg by 7 PM amidst partial clearing, which could be sufficient for localized damaging wind if there is some storm organization/linear convection in the late afternoon/early evening. This area is the most likely to see any thunderstorm activity as well, although some thunder can't quite be ruled out farther east into the Adirondacks and perhaps northern portions of Vermont given Otherwise, the rest of the day is shaping up to be merely showery and breezy, with rain-cooled air and thick clouds making for the coolest day we have seen since June.

As the system's cold front presses eastward through our region between about 9 PM and 1 AM, winds will shift westerly and trend northwesterly, ushering in a return to dry air. Relatedly, most of the wildfire smoke that has pushed northward into northern New York and Vermont, especially higher elevations, this afternoon will be steered out of the region. Unfortunately, a different plume of smoke from the northwest will likely push into northern New York overnight, which could once again degrade air quality. At this time, the concentrations look less significant than what we are seeing currently For now, Air Quality Alerts remain in effect today; the New York State Department of Environmental Conservation at https://on.ny.gov/nyaqi and Vermont Agency of Natural Resources web site at https://dec.vermont.gov/air- quality/local-air-quality-forecasts will have more information. Aside from any lingering smoke concerns, another extended stretch of high pressure and pleasant temperatures are anticipated Sunday through Tuesday morning.

KEY MESSAGE 2: Overall, deterministic solutions and their accompanying ensemble blends support a persistence forecast into the middle and latter portions of next week so I'll continue with this idea. The main weather feature of note will be the approach/passage of a frontal system later Tue/Wed. At this time, the best forcing looks to arrive in the overnight hours thus limiting the threat of severe weather. However, PWAT values do climb AOA 1.5 inches, so locally heavy downpours will be possible with any deeper convective cores. Behind the front, surface high pressure and a much drier airmass arrive for late week (Thu/Fri) with fair/dry wx returning. Model- averaged 925 hPa thermal profiles through the period support pleasantly seasonable mid-summer temperatures with daily highs in the mid 70s to lower 80s and overnight lows in the mid 50s to lower 60s.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18Z Sunday...Mainly VFR this afternoon with scattered thunderstorms as a warm front approaches. Some TSRA will continue to develop through the evening hours, mainly in the south and west portions of our CWA, as indicated by the PROB30s for RUT and SLK. Other terminals could see some locally heave downpours that bring down visibilities for a short period of time. Outside of the showers, we will see primarily southerly winds with gusts into the mid 20 knots. Showers will clear after 00z.

Outlook...

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

MARINE

Seasonably strong south-southeast winds have been mixing on Lake Champlain during the day today, resulting in observed winds at Colchester Reef as high as 27 knots sustained early this afternoon and likely large waves on both the broad lake and northern waters in the 2 to 4 foot range. Peak winds will persist in a 20-30 knot range on the broad lake through early evening before diminishing and then picking up tonight out of the northwest behind a cold front. These winds overnight will also potentially reach 25 knots and produce rough waves with a strong westerly component and deeper mixing will help produce gusty conditions. Gradually winds and waves will subside during the Sunday morning timeframe.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Air Quality Alert until 11 PM EDT this evening for VTZ001>011- 016>021. NY...Air Quality Alert until midnight EDT tonight for NYZ026>031- 034-035-087.