textproduct: Burlington

WHAT HAS CHANGED

As of 234 AM EST Wednesday...

Forecast snow totals have increased in the higher elevations for Thursday into Friday.

KEY MESSAGES

As of 234 AM EST Wednesday...

1. Increased confidence in impactful elevation-dependent snowfall Thursday into Friday.

2. Lingering upslope rain/snow showers possible on Sunday, followed by much quieter and warmer weather next week.

DISCUSSION

As of 234 AM EST Wednesday...

KEY MESSAGE 1: A gradually deepening surface low will track from the Ohio Valley east over southern New England before heading off into the Canadian Maritimes on Thursday into Friday. Despite a favorable storm track for snow, a marginally cold initial airmass will be in place at the onset, especially at the surface due to a lack of Canadian high pressure to the north. Precipitation looks to enter southwestern areas Thursday morning but very slowly make its way northeast during the day. By Thursday night, it should reach the Northeast Kingdom, but the heaviest rates may remain to the south. At the onset, surface temperatures will likely be in the 30s in most places, with low 40s possible in the warmest valleys. Steep lapse rates will exist with summit levels well below freezing, though a lack of a significantly dry layer will prevent significant wet-bulb cooling.

Precipitation will begin as rain in the valleys and snow at the summits. A first estimate of initial snow levels is around 1,500 ft. Light rates and daytime occurrence will prevent significant accumulations at the onset outside the mountains. A weak November sun angle will limit some of the warming effects though. Heading into Thursday night, heavier rates will likely enter the region, and darkness will end any solar radiation. The combination of lowering temperatures due to dynamical cooling and nighttime cooling will allow snow levels to drop a bit, and especially allow for more efficient accumulations at higher elevations with higher snow ratios. By Friday morning, snow levels should be around or below 1,000 ft. While brief periods of snow are possible in the low valleys like the Champlain Valley and Lower Connecticut Valley, temperatures may stay just above freezing and prevent accumulations other than some slush in grassy-type surfaces.

As the low tracks to the east heading through Friday, cyclonic northwest flow will develop and maintain some upslope snow showers in the higher terrain into Saturday. Boundary layer temperatures will reach their lowest values Saturday morning, with most areas likely seeing temperatures in the 20s. Warm Lake Champlain temperatures will probably further limit the already marginal accumulations in the immediate Champlain Valley, especially with northwest flow off the lake and downsloping along the eastern Adirondacks.

Overall, this is still a relatively low-confidence forecast. Our deterministic most-likely scenario has snow amounts in the 3-6 inch range for areas around and above 2,000 ft. One exception is northern Vermont, where the heaviest bands may not reach. Areas between 1,000- 2,000 ft look to be in the 1-3 inch range, and below 1,000 ft looks to be a slushy coating. However, the ensemble spread is still massive. The NBM 10th percentile is 2-4 inches above 2,000 ft and the 90th percentile is 10-18 inches. Deterministic models are all split. This is mostly due to QPF differences and not temperatures/ratios so any significant accumulations in the lower elevations like the Champlain Valley are unlikely at this point.

In higher end scenarios, there would be a power outage threat in the higher elevations. The snow will be a heavier, wetter snow, prone to sticking to trees and powerlines. It may end a bit drier with lower ratios in the Adirondacks if enough cooling occurs on the backside, but the exact details remain to be seen.

KEY MESSAGE 2: The cyclonic upslope flow from departing low pres wl produce a few light rain and mtn snow showers on Sunday, along with plenty of clouds. A building ridge of high pres both aloft and at the sfc is progged to expand acrs the Great Lakes/NE CONUS by next week. This wl result in much drier atmospheric profiles, with pw values btwn 0.20 and 0.40" by early next week. As 1035mb high pres builds directly overhead, expect large daily swings in temps from cool night-time lows to mild day-time highs, given the dry airmass and nightly inversions. No significant or impactful wx is anticipated for days 4 thru 7. Highs generally mid 40s to lower 50s and lows mid 20s to mid 30s.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thursday...Current observations indicate a mixture of MVFR and VFR conditions with across our 7 taf sites this morning. Any lingering MVFR cigs at MPV/EFK and SLK will improve by 15z this morning, while VFR conditions prevail across our lower elevation taf sites. Northwest winds will be 5 to 10 knots, before shifting to the northeast at MSS and southeast at RUT overnight. Cigs lower toward MVFR again after 06z tonight at SLK with a light mixture of snow and rain likely by sunrise on Thursday.

Outlook...

Thursday: MVFR/IFR conditions possible. Definite SN, Chance RA. Thursday Night: Mainly MVFR, with areas IFR possible. Definite SN, Definite RA. Friday: Mainly MVFR, with local IFR possible. Likely SN, Chance RA. Friday Night: Mainly MVFR, with local VFR possible. Chance SN, Chance RA. Saturday: MVFR. Chance RA, Chance SN. Saturday Night: Mainly MVFR, with areas VFR possible. Chance SHSN, Chance SHRA. Sunday: Mainly MVFR, with local VFR possible. Slight chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

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