Marine Weather and Tide Forecast for St. Albans, VT

KEY MESSAGES
As of 225 AM EST Monday...

1. A widespread light to locally moderate long duration snowfall is expected Tues through Weds with storm total snowfall of 2 to 5 inches, except locally higher in the mountains. A quick burst of heavy snow could impact the Tuesday evening commute.

2. Temperatures will be seasonable through most of the week, then less cold over the weekend. Many locations are likely to reach 32 degrees for the first time in over three weeks.

3. A higher impact, lower probability winter storm continues to be monitored for Sunday into Monday.

DISCUSSION
As of 225 AM EST Monday...

KEY MESSAGE 1: Tonight the challenge is ribbon of mid/upper lvl clouds and potential impacts on temps, along with light south/southwest flow developing. Based on previous nights have trended toward the cooler MAV guidance again, especially given dry sfc dwpts and potential for mostly clear skies in the evening. Feel temps drop quickly before axis of mid/upper lvl clouds lift from southwest to northeast acrs our cwa. Lows generally 5F to -15F acrs our fa.

A widespread light to moderate long duration snowfall of 2 to 5 inches with localized higher amounts in the mountains is expected late Tues through Weds. Guidance continues to support a burst of heavy snowfall associated with waa lift btwn 2 PM and 10 PM Tues.
Soundings show deep uvv's from 2000 ft thru 20,000 ft, along with deepening moisture profiles, but a relative small DGZ zone around 10kft. The synoptic scale lift is produced by a ribbon of strong 850 to 700mb fgen forcing, a developing 850mb southwest jet of 30 to 45 knots , and left front quad of 250mb jet of 100-120 knots, wl promote strong ascent acrs our region on Tues aftn/evening. HRRR shows mean 1 hourly snowfall rates of 1.0 to 1.5", with probs of 70 to 90% of 1 inch per hour rates on Tues aftn/evening. This progged band is poorly timed for the Tues evening commute, especially locally here in the CPV. Expecting a 1 to 3 hour band of heavy snowfall to lift from southwest to northeast acrs our cwa, with a quick 1 to 3 inches anticipated.

After initial waa snowfall, mid/upper lvl dry slot tries to advect into our central/southern cwa, especially as closed 850 to 500mb cyclonic circulation and associated 1000mb sfc low pres tracks along and north of the International Border. In addition, brief window of southwest downslope winds develop, which wl result in mostly trrn driven precip with much less coverage on Tues night into Weds morning. As sfc low pres deepens in the Gulf of Maine, northwest upslope flow develops under moderate llvl caa by Weds. This combined with blocked flow with Froude number <0.5 supports intervals of snow showers with additional accumulation likely, especially northern Dacks into parts of the central/northern Greens and the eastern CPV. Feel GFS/NAM solutions are a bit aggressive with storm total qpf/snowfall given northern stream system and tendency to over forecast qpf associated with waa lift. Have trended toward a ECMWF/CMC and NBM blend, which support 0.15 to 0.25" valleys to 0.35 to 0.50" northern Dacks into the central/northern Greens. This would result in storm totals snowfall of 2 to 5 inches, except 4 to 8 inches northern Dacks and Greens of central/northern VT. NBM prob of qpf>0.5" is only 20 to 30%, while EPS mean is 0.30 to 0.45" and operational ECMWF is 0.35" to locally 0.50", which seems very reasonable. Temps warm into the 20s on Tues and mid 20s to lower 30s on Weds, with summits near 20F, while lows are mostly in the teens.
A winter weather advisory will probably be needed for most of the area.

KEY MESSAGE 2: In the longer range of the forecast, Thursday through Friday looks to continue temperatures near normal, supported by ensemble guidance 925 millibar temperatures in the 30-40th percentile. The trough axis will be to our east, which limits chances for widespread precipitation with any light snow being primarily in the northern Greens. A bump up in temperatures for the weekend is likely as heights rise ahead of a southern stream low pressure system. Probabilities of temperatures reaching 32 increase markedly over the weekend, mainly in the lowest elevations on Saturday to near 50%, and then into the 50-80% range on Sunday in most valley locations including those closer to 1500 feet elevation. If temperatures do not reach 32 earlier in the week, this thaw will end the longest deep freeze since the 2014-2015 winter. In Burlington, the last day with a temperature breaking 32 degrees was January 22nd; sub-freezing temperature streaks surpassing 21 days are fairly unusual in the Burlington area, last happening January- February 2015 and only occurring 20 times going back across the last 141 winter seasons.

KEY MESSAGE 3: We continue to monitor the potential for a more substantial storm that could track northeastward along the east coast early next week. A favorable track would lead to another period of widespread snow. The probability of such a storm track remains low, associated with poor run-to-run model consistency and large variability among guidance, especially between the GEFS and EPS. The grand ensemble probability of 24 hour precipitation greater than 0.25", a decent proxy for a significant snowfall, peaks roughly in the Sunday 7 PM through Monday 7 PM timeframe at about 20-30%, with highest values in our far western and southern areas. Of four model clusters which comprise this grand ensemble, precipitation chances vary substantially. The two most interesting ones include one model cluster, made up of almost half of the GEFS members, with chances of only 0.01" under 30%. However, in contrast to this dry scenario, a wet cluster produces a rather high snowfall, with a warning level storm total (widespread 7+ inches) indicated in its mean value. This cluster's 500 millibar pattern supports a slow and more amplified storm track and is made up of a small proportion of mainly EPS and GEPS members. Note the character of snow could be on the wetter side given the aforementioned less cold air in place ahead of this system. While unlikely, the potential for a heavier, wet snow does exist, so we'll keep on eye on this scenario moving forward.

AVIATION /12Z MONDAY THROUGH FRIDAY/
Through 12Z Tuesday...Main potential impact probably remains a marginal amount of LLWS persisting for up to a few more hours at RUT, where surface winds remain calm with persistent northwesterly flow close to 30 knots about 2000 feet above ground level. Otherwise this period will remain quiet as high pressure builds in. We are seeing a VFR cloud deck build southward towards the airspace which was not being modeled well; it will likely affect MSS later this morning but farther south and east confidence is lower in any ceilings. Terrain driven and light winds will dominate at all terminals. One exception with a bit more wind is at MPV through much of the daytime hours, where a modest, but favorable northwesterly gradient flow will be present.

Outlook...

Tuesday: Mainly VFR, with local MVFR and IFR possible. Definite SN.
Tuesday Night: Mainly MVFR, with local IFR possible. Definite SN, Chance SHSN.
Wednesday: Mainly MVFR, with local VFR possible. Chance SHSN.
Wednesday Night: Mainly MVFR, with areas VFR possible. Slight chance SN.
Thursday: VFR. NO SIG WX.
Thursday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Friday: Mainly VFR, with local MVFR possible. NO SIG WX.

EQUIPMENT
NOAA Weather Radio station WXM-44, transmitting from Mt.
Ascutney, Vermont, on frequency 162.475 MHz is non- operational at this time. NWS technicians have diagnosed the problem, but repairs will likely not be able to occur for quite some time due to circumstances beyond our control. Therefore, the time of return to service is currently unknown. The following NOAA Weather Radio transmitters may be able to provide service during this outage: WWG 50 from Burke Mtn, VT at 162.425 MHz and WNG 546 from Hanover, NH at 162.525 MHz.

The Colchester Reef meteorological station is out of service.
This site is not serviced by the NWS and there isn't an estimated return to service at present. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES
VT...None.
NY...None.