textproduct: Burlington

WHAT HAS CHANGED

As of 248 PM EDT Monday...

No meaningful changes at this time. Aside from a few light showers across northernmost Vermont and New York this afternoon, weather remains dry and quiet across the area through midnight.

KEY MESSAGES

As of 248 PM EDT Monday...

1. An area of rain showers will expand into southern portions of Vermont and Adirondacks with light rainfall expected through Tuesday.

2. Showers and thunderstorms are likely Thursday afternoon/night.

3. A cold front moves through Friday morning.

DISCUSSION

As of 248 PM EDT Monday...

KEY MESSAGE 1: A large positively tilted trough over the Great Lakes is inducing a weak surface low pressure system with mid-level circulating tracking across western New York tonight and it will slide eastward into southern New England by morning. On the cool side of the boundary, there will be a sharp edge of clouds and showers. The latest model guidance has settled on southern Vermont being within this shield of light rainfall, likely in the 0.25" to 0.5" range. This rain may consist of briefly heavier elements, as showers overrun the boundary from the juicier air mass to the south. Meager and shallow instability will be present so we do not expect any thunder. As one goes northward into central Vermont, a shorter period of showers can be expected with low chances of even 0.1" of total rainfall. Much of northern New York and northern Vermont will see no precipitation. In fact, skies will be variably cloudy to mostly sunny by later in the day Tuesday.

KEY MESSAGE 2: Following another very quiet weather period Tuesday night through Thursday morning, our next round of active weather will begin during the day Thursday. The ECMWF Extreme Forecast Index does not show any signals in CAPE and shear for this event being particularly noteworthy in spite of heat and humidity in place ahead of a cold front - heat index values could peak in the lower 90s in the deeper valleys. In referencing some deterministic model guidance, it looks like a shortwave passing across the mid- Atlantic states out ahead of this front could interfere with the moisture feed northward into our region, but also may be separated enough in space/time to not make a difference in our convection. It looks like the moisture feed with a channel of anomalous PWAT stretched along the boundary will consist of modified southern Pacific Ocean moisture without the addition of Gulf or Atlantic moisture, reducing the residence time of the potential heavier rainfall rates. Accordingly, at this time we aren't seeing any signals for excessive rainfall despite ingredients for at least briefly heavy rainfall with some of the likely thunderstorm development.

While the upper level forcing will not be particularly strong, but the track of weak surface low pressure and the associated belt of stronger westerly winds appears to line up well for northern New York and Vermont for a risk of strong thunderstorms and perhaps a severe thunderstorm or two during the afternoon and especially evening hours based on the consensus timing. Would expect at least a marginal severe thunderstorm risk will be introduced from the Storm Prediction Center moving forward. Noted that the machine learning thunderstorm probabilities from the GEFS shows a regional maximum across northeastern New York (around 70% chance). Convection across southern Canada will shift south and eastward as the cold front moves eastward, with a couple of boundaries pushing through to eventually end the potential for showers on Friday. The risk of thunderstorms, given only modest instability (MUCAPE in the 1000- 1500 J/kg range) driven by diurnal heating and height falls with the incoming weak trough, should diminish overnight along with potential for any localized flash flooding as drier air works in aloft.

KEY MESSAGE 3: A cold front will sweep through the CWA Friday morning, bringing drier and seasonable temperatures to the region. Temperatures on Friday and Saturday will be in the upper 70s or lower 80s for most of our area. Similar to Thursday, we will see a chance of thunder and some widespread rain along the front on Friday. Temperatures look to rebound slightly for the second half of the weekend and beginning of next week.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Through 00Z Wednesday...Generally quiet aviation conditions are expected with relatively little change over the next 24 hours. Outside a few mid-level cumulus near KEFK, there are mostly high clouds at or above 20000 ft agl. Southeast winds overnight will be around 5 knots, but locally faster at KRUT around 7-10 knots. High clouds will track east with the St. Lawrence Valley clearing out, and guidance indicates some fog potential at KMSS. Since it's one of the less favored, decided to hold it to 3SM in a TEMPO from 06z-10z. Looking more closely at KRUT, the potential for LLWS appears lower and removed it. Although winds at 2000 ft agl will approach 25-30 knots, surface winds will stay elevated enough that it could be bumpy, but doesn't meet criteria. Showers are expected near KRUT, mainly between 09z and 13z, but did use PROB30s on either end due to some timing uncertainty. Lowering ceilings to 2500-4000 ft agl are expected at KRUT as precipitation moves in. Remaining TAF sites will likely avoid any rain and may just observe some lowering ceilings past 13z.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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