textproduct: Burlington

WHAT HAS CHANGED

As of 309 AM EDT Wednesday...

No significant changes were made. Isolated to scattered showers with a few embedded thunderstorms are expected today.

KEY MESSAGES

As of 309 AM EDT Wednesday...

1. Isolated to scattered showers are expected this afternoon with a few thunderstorms mixed in. Chances increase Thursday as a wave moves through with lingering showers Friday.

2. Tranquil weather on Saturday, then beneficial rain likely spreads in from the west Sunday afternoon and exits on Monday. Becoming seasonably warm and dry early next week.

DISCUSSION

As of 309 AM EDT Wednesday...

KEY MESSAGE 1: Maintained yesterday's forecast change of including some showers and very isolated convection today. Best chances of thunderstorms lie in the St Lawrence Valley where the CAPE gradient will be sharpest with around 500J/kg to work with. Otherwise, temperatures will be similar to yesterday with highs in the mid/upper 70s to low 80s today and Thursday. Shower and thunderstorm chances increase Thursday as low pressure moving through southern Canada pushes a boundary through the region. Around 500 J/kg of CAPE is projected to be in the region coincident with the weakening boundary with the strongest forcing towards the Canadian border(CAMs are highlighting potential for a bullseye of 1000+J/kg at max heating which may strafe our northern zones in Vermont - lower likelihood, but potentially impactful scenario where a couple stronger storms would be possible). Another trough is anticipated to move through Friday in broad northwest flow. Showers are mostly expected, but could see a few rumbles in southern Vermont where timing will play a roll in convective chances. Should the trough slow, surface instability will likely build enough for more showers and storms, but current timing of this wave supports mainly showers as the wave exists early afternoon. Some breezy conditions should be anticipated with this trough, especially on Lake Champlain and the peaks where gusts could approach or exceed 30 mph. Gusts 15 to 25 mph are probable at lower elevations away from Lake Champlain.

KEY MESSAGE 2: A mid-level ridge over the southeastern US will build northward a bit on Saturday, leaving us in northwesterly flow with dry air and no precipitation chances. This ridge will breakdown on Sunday, allowing a weak wave of low pressure originating in the foothills of the Colorado Rockies to zip eastward and bring us some overrunning/warm frontal type of rain. There is a slight chance of thunder indicated at this time Sunday night in much of Vermont, which would only be a factor if the low pressure system trended stronger and/or tracked farther north, such that our region got into the system's warm sector. Otherwise, a steady soaking rain looks favored, with current consensus timing from Sunday afternoon through Monday morning. Probabilities of event total rainfall exceeding 0.5" currently ranges from about 20% to 40%, tapering off generally towards the north. among the latest global ensemble scenarios, some solutions are a little slower to bring rain to an end on Monday with higher probabilities of rain into Monday evening than what the current forecast suggests. Given the uncertainties, the 10-30% chance of showers Monday afternoon looks reasonable at this time; some of this precipitation could be orographic, post-frontal showers.

Following this system it appears a ridge of high pressure may build in, which would provide us with generally quiet weather for Tuesday. There are weak signals for perhaps a terrain-driven shower in the Adirondacks or off of a lake breeze interface, which would make sense given a typical summertime heating scenario with lack of other forcing mechanisms for precipitation.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thursday...Dense fog at SLK will dissipate within the next hour leaving VFR conditions at all terminals through at least 18Z. Clusters of showers with a couple of thunderstorms are expected to develop in southern Canada this afternoon or early evening and move southeastward across portions of northern New York and Vermont. Have only used prevailing showers/MVFR conditions at MSS where stronger consensus of a direct hit exists, in which brief IFR conditions would also occur. Other sites fit more in the chance category for showers and PROB30s were used. Additional showers after 00Z are expected but beyond the timeframe to indicate in the TAF.

Aside from a thunderstorm or stronger shower winds will remain light; during the daytime, generally expect west/northwest winds, except terrain driven in the Champlain Valley (SE at PBG, N-NW at BTV). With these light winds, nocturnal fog redevelopment at SLK is anticipated but could be affected by coverage and timing of these showers lingering into the overnight hours. Evening precipitation would also aid in fog formation at MSS, and perhaps other sites that are less likely to see appreciable rain such as RUT, MPV, and EFK.

Outlook...

Thursday: VFR. Chance SHRA, Chance TSRA. Thursday Night: VFR. Slight chance SHRA. Friday: VFR. Slight chance SHRA. Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

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