textproduct: Burlington

WHAT HAS CHANGED

As of 306 AM EDT Tuesday...

No significant changes have been made to the forecast, although chances for showers Wednesday afternoon/evening have increased slightly.

KEY MESSAGES

As of 306 AM EDT Tuesday...

1. Dry today, with next chance of a few showers and perhaps a thunderstorm late in the day on Wednesday.

2. A round of widespread showers with a few embedded thunderstorms is likely for later Thursday into Thursday night.

3. After a few showers on Friday, a beautiful weekend is setting up as a dry airmass moves into the region.

DISCUSSION

As of 306 AM EDT Tuesday...

KEY MESSAGE 1: Following an active evening of showers and thunderstorms, especially in northern portions of our region, today will be a reprieve with only modest wind gusts on the backside of departing low pressure. Northwesterly breezes will be somewhat refreshing with somewhat drier air being advected in from a heavily modified polar air mass, with some of the deeper mixing supporting a few gusts to around 25 MPH, although 850 millibar winds will decrease through the afternoon hours, limiting the magnitude of gusts despite steepening low level lapse rates. Meager instability and anti-cyclonic flow will yield near zero PoPs for our entire region.

By Wednesday afternoon, it appears some variety of trough will swing in from the northwest, and with a subtle surface trough out ahead of it in southern Canada, isolated showers will develop with greatest chances in northern New York. Instability downstream in our area looks fairly low (under 1000 J/kg), driven by steep low level lapse rates, while humidity near the surface and aloft remains muted compared to recent days along with poor mid-level lapse rates. Therefore, the threat of either heavy rainfall or severe weather is not evident at this time with any of the showers that develop, and with greater instability to our north, the greatest threat of locally strong thunderstorm wind gusts will be towards the International Border as thunderstorms track towards the southeast late in the day. The timing in the latest convection allowing models (CAMs) for any heavier variety of showers generally looks after 2 PM, with highest probabilities between around 5 and 8 PM. The swath for these showers currently is favored for northern New York and somewhat less likely in northern Vermont, with again little or no chance of rain in southern portions of Vermont. Overnight Wednesday the convective chances are a little more unclear, dependent on how widespread and intense any of the storms in southern Canada earlier in the day wind up being. Remnants of those storms would provide us with precipitation potentially Wednesday night, with otherwise quiet weather.

Temperatures through the next couple of days will remain rather seasonable with minimal change in 850 millibar temperatures, which look near the climatological normals, supporting highs each day in the mid 70s to low 80s and lows in the 50s for most locations.

KEY MESSAGE 2: A seasonably potent low pressure system will pass near or north of the region later Thursday into Friday. Widespread rain can be expected with this system, with convective weather more uncertain and relatively limited compared to recent events. Model consensus on the timing/track of the primary shortwave supports a cold frontal passage Thursday night. Generally the ingredients don't look particularly favorable for heavy rainfall ahead of the front, given the dominance of polar influence in the mid and upper air flow and westerly rather than southerly near surface winds, limiting deep moisture with lack of warm rain processes. With regards to severe weather, seasonably warm air and height falls still will support some CAPE, presenting a low CAPE, high shear scenario that will need to be monitored for low-topped convection, particularly in the vicinity of the system's warm front or effective warm front. The latest blend of models shows a swath of moderate rainfall (0.5" to 1") roughly from Franklin County, New York eastward to Franklin County, Vermont, with lesser amounts trending southward, which seems reasonable given global ensemble support for heavy rainfall is non- existent (probabilities of rainfall exceeding 1" are under 5% in 24 hours).

KEY MESSAGE 3: Models continue to favor the closing off of low pressure east of Vermont Friday. This will support a Northwest flow pattern likely resulting in a few upslope rain showers as maritime air wraps around the low. Heating in the afternoon could result in the triggering of a few thunderstorms.

Over the weekend, much drier air moves into the region as high pressure pushes the low along the longwave pattern. Conditions will likely be quite pleasant Saturday with dewpoints in the 40s and 50s with temperatures generally in the 70s. The ridge axis is projected to shift eastward Sunday and supports warmer highs for broad valleys to around 80 degrees while dew points dry further remaining more in the 40s. Overall, these conditions are shaping up to be near ideal weather for outdoor activities. The next wave that will bring precipitation to the Northeast will be early next week as zonal flow keeps the pattern progressive. Temperatures should warm a degree or Monday and Tuesday as low level flow turns southwesterly.

AVIATION /07Z TUESDAY THROUGH SATURDAY/

Through 06Z Wednesday...Rain and thunderstorms are tracking out of Vermont and northern New York with most locations becoming partially clear to clear after 07Z. With ample low level moisture and clearing skies, fog and stratus will become increasingly likely. IFR conditions will be most likely at SLK/MPV/EFK, but there is a 10-25% chance for CIGs to form below 1000ft for most terminals; note the 6sm due to BR and sct002- 004 in the TAFs for BTV/PBG/MSS. MVFR conditions are more likely at RUT by 08Z as BKN033 sags lower with decreasing winds aloft. After 12-15Z, conditions improve to VFR with some northwesterly breezes. Gusts will be 10-20kts. More IFR/MVFR conditions are expected after 00Z tonight but more of a question of when it will set up for each terminal in the 02-08Z time frame.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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