Marine Weather and Tide Forecast for St. Albans, VT

NEAR TERM /THROUGH WEDNESDAY NIGHT/
As of 601 PM EST Tuesday...Winter wx advisory continues through 4 PM Weds for 3 to 7 inches of snow, with localized higher amounts for portions of northern NY and VT.

The forecast challenge continues to be snowfall totals associated with upslope snow overnight into Weds, as qpf wl be light but snow ratios wl be tricky.

Snow showers have begun to move down into the region from Canada and will continue to increase in coverage and intensity this evening. It has been taking some time for them to saturate the dry low levels of the atmosphere but light snow has been observed across much of northern Vermont and northern New York.
The showers will progress down into much of central Vermont this evening and become heavier in the upslope areas. While light snow has been falling in much of the Champlain Valley, relatively unblocked looks to keep the heavier snow in the Greens.

Previous Forecast...GOES-16 mid lvl water imagery shows a rather messy and disorganized pattern acrs the northeast CONUS with central of closed 5h circulation over northern Maine, while several weak s/w's and pockets of mid lvl moisture rotating toward our northern cwa. Weak sfc trof is helping to focus slightly better radar returns near the International Border this aftn, however sfc dwpts have dropped back into the single digits to near 10F and precip is having difficulties reaching the ground per webcams/obs. Radar shows ribbon of light snow, but upstream sfc obs show vis btwn 3-6SM in light snow with minimal accumulation so far.

As mid/upper lvl trof axis and associated sfc reflection swings acrs our cwa expect the areal coverage of snow showers to increase with a period of slightly higher rates anticipated btwn roughly 8 PM and 3 AM. Initially the Froude number is unblocked this evening with values btwn 1.0 and 1.5, but as winds shift to the northwest after midnight the flow becomes blocked with the Froude value lowering btwn 0.50 and 0.75 by 12z Weds. This general idea initially supports snowfall along and downwind of the northern Dacks/Greens, but as flow becomes blocked snowfall wl become along and upstream of the mtns/western slopes. This supports the highest totals from Mt Mansfield summit to Jay Peak with amounts dropping off on either side of the ridges. Very challenging to determine snow ratios, as thermal profiles suggest sweet spot with progged 850mb temps between -12C and -17C, with favorable moisture thru the DGZ, but lift is modest, per omega field cross sections on Bufkit soundings. Bottom line expect a window of better ratios in the 25/30 to 1 range this evening, before moisture/lift wane btwn 06-09z on Weds. A sharp elevational dependent snowfall gradient is anticipated from only a dusting to 2 inches SLV/CPV and Lower CT River Valley to 3 to 7 inches advisory area with localized higher amounts near summits.
Main impacts wl be localized hazardous Weds morning commute with snow covered and slippery roads. Given fluff factor some localized areas of blowing/drifting snow is expected, especially exposed mid slopes and summits. Locally here at BTV feel the best potential for a brief period of accumulating snow showers wl be with trof passage near midnight, as winds shift to the northwest and we experience some lake enhance moisture. Temps drop back into the upper teens valleys but near 0F as progged 850mb temps drop btwn -16C and -18C by 12z Weds. This combined with localized gusty west/northwest winds wl create wind chills -5F to -25F on the summits overnight into Weds. Soundings show inversion height near summit level on Weds with good mixing below inversion, supporting localized gusts 20 to 30 mph. Have trended toward the 90th percentile for winds based on lowering inversion helping to push stronger winds toward the sfc, especially east side of the Greens. Temps on Weds struggle in the mid teens to lower 20s with single digits in the mtns. Latest trends show deep layer moisture decreasing on Weds AM, so anticipate advisory could be dropped early, as accumulating snowfall tapers of by mid morning.

A quiet and chill night is anticipated on Weds night, could be much colder than crnt fcst if more clearing develops than anticipated, given the the chilly 925mb to 850mb thermal profiles. For now have lows 0 to 10F, but could be much cooler, especially areas with fresh snow pack.

SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
As of 327 PM EST Tuesday...A brief period of ridging looks to build overhead, bringing drier conditions to the region. The only exception to this may be some additional showers across northern New York, especially with some moisture enhancement off Lake Ontario.
Temperatures will continue to be on the cooler side for Thursday, with high temperatures in the upper teens to mid 20s. Overnight lows Thursday will be a few degrees warmer than climatological normals, generally in higher single digits to mid teens thanks to abundant cloud cover and increasing southerly flow.

LONG TERM /FRIDAY THROUGH TUESDAY/
As of 327 PM EST Tuesday...Temperatures look to trend warmer as we head towards the weekend with southwesterly flow, with high temperatures climbing into the 30s by Saturday. Low pressure centered over the Great Lakes will push northeastward this weekend, with the associated frontal boundary bringing widespread precipitation to the region Saturday evening into Sunday. With such mild temperatures, a mix of rain and snow looks likely in the broad valleys, with snow expected elsewhere although this will continue to depend on temperature profiles as we get closer to the weekend. An arctic airmass and much colder temperatures look to move into the region behind this weekend system, with 925mb temperatures between -20 and -25C by Monday afternoon.

AVIATION /23Z TUESDAY THROUGH SUNDAY/
Through 00Z Thursday...As snow showers increase in coverage across the forecast area this evening, visibilities will be up and down in accordance to location and timing of showers. Most likely spot to see IFR visibilities will be SLK, though this is not out of the question for any site tonight in heavier snow showers. Ceilings are expected to remain at MVFR level or higher throughout the overnight period, slowly lifting to mostly VFR tomorrow as snow showers end. Winds are a mix of north- and south-westerly this evening, with a few gusts to 20-25 knots in the Champlain Valley. Most, if not all sites will see a trend towards mainly northwesterly throughout the night tonight with gusts 15-20 knots possible.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES
VT...Winter Weather Advisory until 4 PM EST Wednesday for VTZ002- 003-006-016>018.
NY...Winter Weather Advisory until 4 PM EST Wednesday for NYZ029>031.