textproduct: Burlington

WHAT HAS CHANGED

As of 730 PM EDT Sunday...

Thunderstorm activity has begun to weaken. A rumble or two may take place in the Champlain Valley, but the severe threat is over for the evening. Quiet conditions are expected tonight.

KEY MESSAGES

As of 250 PM EDT Sunday...

1. Numerous showers and embedded thunderstorms will continue across the region this afternoon, with some isolated strong to severe thunderstorms possible.

2. Lingering showers will continue into the start of the week under broad cyclonic flow, with drier weather returning towards the middle of the week.

3. Showers with some thunderstorm potential to end the week will be followed by another tranquil period over the weekend.

DISCUSSION

As of 250 PM EDT Sunday...

KEY MESSAGE 1: Gusty showers continue to bubble up across the region this afternoon as a frontal boundary continues to move through the region. Some more embedded thunderstorms are expected to develop as the afternoon progresses, especially with clearing skies allowing for more instability over the next few hours. CAPE values are expected to reach around 1000-1500 J/kg this afternoon, which will help with the thunderstorm development, along with modest lapse rates and shear. SPC continues to show the entire forecast area in a Marginal Risk for severe weather this afternoon with the idea that a few isolated strong to severe thunderstorms are possible, with possible hail and strong winds as the primary threats. Storms looks to be progressive, limiting any hydro concerns at this time, especially given the dry weather the last few days. The current forecast still shows about 0.20 to 0.50 inches across much of the area, with lower totals expected across much of the Northeast Kingdom and some higher amounts possible within any thunderstorms that develop. Shower activity will gradually wane through this evening as the frontal boundary exits the region, although some showers may linger overnight, especially across northern New York. Some clearing may be possible tonight behind the system, which may lead to some fog/mist developing overnight, especially in locations that see rainfall today as there will be plenty of moisture, although winds may be enough to limit this potential. Overnight lows are expected to generally be in the upper 40s and 50s tonight, with temperatures near Lake Champlain near 60.

KEY MESSAGE 2: For the start of the week, the region will remain in broad cyclonic flow, will will allow for linger showers on Monday and Tuesday, especially across the higher terrain as the upper level low gradually shifts away from the region. This cyclonic flow will also lead to some lake effect showers off Lake Ontario, with increased shower chances expected across northern New York Monday into Tuesday. Temperatures will be on the cool side, with highs only climbing into the 70s, with some locations in the Adirondacks struggling to climb out of the upper 60s. A brief period of ridging looks to build into the region for Wednesday, bringing some drier weather conditions for the middle of the week.

KEY MESSAGE 3: A broad upper-level trough remains on track to progress into the eastern Great Lakes by Thursday afternoon, putting us in a favorable position for showers and thunderstorms. The probability of thunderstorms compared to 24 hours ago has trended quite a bit higher for this timeframe, with the latest NBM 6 hour thunder chances (2 PM to 8 PM) now in the 25 to 32% range across our region. Relatedly, forecast temperatures have ticked up with highs favored to reach the upper 70s to mid 80s amidst seasonably humid conditions with dewpoints in the low to mid 60s during peak heating. Generally the potential for stronger storms is low but appears to be slightly elevated in northern New York relative to Vermont where both CAPE and shear will likely be somewhat higher.

With a surface low and associated trough slow to push eastward, shower chances will continue through Thursday night into Friday morning, which makes the convective chances for Friday questionable. However, signals for higher instability relative to Thursday, especially in Vermont, still exists in many pieces of ensemble guidance. The large scale pattern with continued height falls and cold front still to our west suggests scattered showers and thunderstorms are a good bet for Friday afternoon, especially if there is enough surface heating. Given convective nature of a lot of the rain, rainfall amounts will likely be highly variable, but overall the potential for excessive rain is minimal at this time without particularly rich moisture. 48 hour probabilities of rainfall exceeding an inch per latest NBM are only as high as 22% and mainly under 10% in our region.

As the system's low pressure area occludes near Hudson Bay, a ridge of high pressure will build in to the south and expand across the northeastern US by Saturday morning, providing us with low humidity and seasonable conditions for the weekend. Perhaps by the end of the weekend the gyre will be forced southward and precipitation chances increase, but the predictability of such a scenario is low at this time.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Through 00Z Tuesday...Two strips of precipitation are crossing the Vermont-New Hampshire border and in the Champlain Valley. Portions of Vermont may see some showers for a couple more hours, but mostly quiet conditions are expected. There are mixed signals for fog tonight. Under the influence of cooler low pressure to our west, lake effect activity will stream into northern New York. This should bring some clouds over KSLK with ceilings around 2000-3000 ft agl, but KMPV and KRUT are the most likely to experience fog tonight, but there will be some light winds possible overnight and so 3SM is shown given the uncertainty. South to southeast winds are expected to trend towards 5 knots, and then after 14z, increase to 7 to 12 knots sustained with gusts 16 to 22 knots possible. Additional shower activity is likely Monday afternoon, first over KSLK about 15z-21z, and then 18z-23z for most others. Precipitation will be scattered, and so mainly PROB30s were used.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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