textproduct: Burlington

WHAT HAS CHANGED

As of 111 AM EST Thursday... An Extreme Cold Watch has been issued across the entire North Country, with arctic air mass and gusty northwest winds arriving on Saturday.

KEY MESSAGES

As of 111 AM EST Thursday...

1. Mainly quiet weather next 36 hours. Then, dry/light snowfall expected with arctic front Friday Night into Saturday. Minor travel impacts possible late Friday night and Saturday morning.

2. Dangerous cold with wind chills of 20 to 35 below zero expected over the weekend.

3. No significant impacts are expected through much of next week, though details on precipitation chances still remain uncertain.

DISCUSSION

As of 111 AM EST Thursday...

KEY MESSAGE 1: Weak surface high pressure building ewd from the Great Lakes will bring relatively quiet weather today through Friday. A couple of notes: (1) mid-level shortwave trough will bring some very light snow to northern NY and VT this morning. Air mass is quite dry with PW values only 0.10-0.15", however a coating to an inch of dry snow accumulation is possible, mainly across the northern Green Mountains. (2) Very cold temperatures and light winds are expected tonight. This may allow for the last bit of open water to freeze on Lake Champlain, so we could be looking at complete ice coverage by Friday AM. This would be the first complete freezing of Lake Champlain since March 8th, 2019.

Approaching arctic boundary Friday night is exceptionally sharp in deterministic NWP guidance (see next key message concerning frigid temperatures and low wind chills with this bndry). Despite lack of instability, appears frontogenesis and low-level convergence is quite strong, and will lead to a period of snow Friday night thru the first half of Saturday. Best frontal forcing is generally midnight to 7am Saturday. Thermal profiles support SLRs near 20:1, so expecting a light/fluffy 1-2" snowfall across the region, with higher summits amounts locally 2-4". The snowfall won't be particularly impactful because of the dry character, but reduced vsby and some slick spots Friday night and Saturday will present a minor concern for travelers during this time frame. May also see some blowing snow as NW winds pick up with the arctic frontal passage around 4am in the St. Lawrence valley and around 7am in the Champlain Valley based on current indications.

KEY MESSAGE 2: Another round of dangerously cold conditions is expected over the weekend. Temperatures will plummet late Friday night into Saturday as strong cold air advection follows the cold frontal passage. Northern NY will see the drastic cooling first, falling from the teens around midnight to the single digits below zero by daybreak Saturday. The cold air will be a little slower to arrive in those areas from the Champlain Valley eastward, but anticipate single digits areawide by mid afternoon Saturday. Brisk northwest winds of 10 to 20 mph with gusts to 30 mph will combine with the cold ambient temperatures to produce wind chills 15 to 25 below zero during the daylight hours Saturday. Winds will be slow to abate overnight Saturday night; while overnight lows will generally be 10 to 20 below zero, wind chills of 20 to 35 below are expected. High pressure will nose into the region Sunday, allowing winds to gradually subside. While it will still be very cold (highs will only be in the single digits), wind chills will improve through the afternoon. With this in mind, an Extreme Cold Watch has been issued for northern NY for Saturday, Saturday night, through Sunday morning. For areas from the Champlain Valley eastward, the Watch starts later Saturday due to the later arrival time of the coldest air, but it also runs through Sunday morning. At this time, the northern Adirondacks and portions of northern/central VT have the highest likelihood of the Watch being upgraded to a Warning (due to wind chills of -30F or colder), with an upgrade to Advisories elsewhere. We'll continue to refine the forecast going forward and headlines will be adjusted as needed. However, don't focus on Advisory vs Warning overly much; it's going to be dangerously cold, regardless. Anyone with outdoor plans should keep a close eye on future forecasts. If outdoor plans can't be delayed or altered, please make sure to dress for very cold conditions.

High pressure briefly builds overhead late Sunday into Sunday night, before moving east on Monday. As such winds will slacken, but giving way to better radiational cooling conditions. There are some indications that there could be lingering cloud cover over the higher terrain Sunday night/Monday morning which would limit cooling potential. Still, overnight lows are expected to be 5 to 15 below zero areawide, and can't rule out some locations approaching -20F. Additional cold headlines may be needed.

KEY MESSAGE 3: Lots of disagreement between the longer range forecast models through much of next week. Temperatures look to improve a little through the period, approaching normal by mid week. However, precipitation chances are harder to pin down. There is at least some consensus that ridging will keep the area dry through Tuesday, but solutions differ thereafter, specifically how quickly the ridge breaks down and how amplified an incoming shortwave trough becomes. The CMC holds the ridge more firmly through mid week, while the GFS/ECMWF are faster, bringing a swath of precipitation into the Northeast CONUS by Wednesday afternoon, though they differ on how the pattern will evolve and what processes will drive this precipitation. Have stayed close to the NBM from Monday onward, with slowly increasing PoPs and temperatures through mid week.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Through 18Z Friday...VFR conditions with light northerly winds are expected through the remainder of the day with winds beginning to switch to the south midday Friday. Some very localized IFR/VLIFR fog is expected overnight at KSLK and KMPV between 5Z and 12Z.

Outlook...

Friday: Mainly VFR, with local MVFR possible. NO SIG WX. Friday Night: Mainly MVFR and IFR, with areas VFR possible. Definite SHSN. Saturday: Mainly VFR, with local MVFR possible. Chance SHSN. Saturday Night: VFR. NO SIG WX. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Monday: VFR. 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...Extreme Cold Watch from Saturday evening through Sunday afternoon for VTZ001>011-016>021. NY...Extreme Cold Watch from Saturday morning through Sunday afternoon for NYZ026-027-029>031-034-087. Extreme Cold Watch from Saturday evening through Sunday afternoon for NYZ028-035.