textproduct: Burlington

WHAT HAS CHANGED

As of 814 PM EST Saturday...

Snow showers continue to persist across portions of the Adirondacks, Champlain Valley, and northern Vermont this evening, so have increased PoPs to reflect this. Snow showers should be ending over the next several hours.

KEY MESSAGES

As of 206 PM EST Saturday...

1. Dangerous cold with wind chills of 20 to 40 below zero expected through Sunday Night.

2. A potential clipper low pressure system is possible Tuesday into Tuesday Night with potentially accumulating light snow.

3. No significant or impactful weather expected Tuesday night through next weekend with temperatures trending toward mid-February normals.

DISCUSSION

As of 206 PM EST Saturday...

KEY MESSAGE 1: Dangerous cold will continue today as northwest winds associated with an approaching ridge slides east behind the arctic cold front from this morning. Much of the area is already experiencing below zero wind chills as wind gusts increase to 20 to 30 mph, with all of northern New York already below zero for actual air temperatures. An Extreme Cold Warning remains in effect for the Adirondacks and St. Lawrence Valley in New York until 1 PM Sunday for wind chills between -20F and -40F, with a Cold Advisory for the rest of the region across the Champlain Valley and northern and central Vermont from 6 PM tonight through 1 PM Sunday for wind chills between -20F and -30F. If you must be outdoors, please make sure to dress for very cold conditions. Frostbite can start to affect exposed skin in as little as 10 minutes in these sorts of wind chill ranges, so hats, gloves/mittens, and warm layers for your core will be crucial.Strong caa from the northwest will continue to steepen lapse rates through this evening into tonight resulting in good vertical mixing and continue gusty conditions, primarily across the Adirondacks, the Champlain Valley, and along the spine of the Greens. Temperatures tonight will continue to fall overnight with air temperatures bottoming out in the minus teens across northern New York, and the minus single digits in Vermont, with minus teens in the higher terrain. The coldest wind chills will occur close to sunrise Sunday when radiative cooling peaks with wind chills near -20F to -25F in Vermont, and near -30F to -40F in northern New York and the spine of the Greens. Anyone with outdoor plans should consider altering and/or delaying outdoor activities this weekend.

Winds will weaken slightly for the day Sunday, but only down to 10 to 20 mph, which will keep wind chills below zero for the entire day. Wind chills will slightly "improve" to -5F to -15F during Sunday afternoon, but will return to dangerous cold levels Sunday night. While the Extreme Cold Warning and Cold Advisory expire tomorrow early afternoon, additional Cold Advisories may be needed for Sunday night. Northwest winds will continue Sunday night, but a steep inversion near 1000-1500ft agl may develop overnight, which would lead to colder valley floors as compared to mountain summits. Sunday night lows may be near -5F to -15F in the valleys, but only 0F to -5F above 1500ft agl. Adding to the complex temperature forecast, winds will slacken across the valleys, and become limited to the higher terrain (15 to 25 mph), as well as some models suggesting lingering lower clouds, especially over the high terrain. If the inversion were to develop, it would likely trap low clouds across the higher terrain, reducing the radiative cooling processes, but a fresh snowpack and sinking air from the higher terrain could be enough to counteract the inversion. Regardless, Sunday night into Monday will remain cold with high pressure building, resulting in wind chills returning to near -20F to -25F, with additional Cold Advisories possibly needed. KEY MESSAGE 2: A potential clipper like low pressure system will move through the area Tuesday into Tuesday night with chances for accumulating light snow. The system will be moving into a very dry air mass left behind by the high responsible for our cold this weekend, which will limit the overall snow potential. That being said, there will be some marginal frontogenesis, particularly over the Champlain Valley with some waa snow showers. The DGZ base in the current GFS soundings is notably high up to 8000ft, however, it is only a few thousand feet thick which would lead to more needle-like snow, and smaller flakes. Additionally, the forcing rapidly shifts east Tuesday night, along with any associated moisture. NBM probabilistic guidance denotes a 40-60% chance for most of the region of seeing 2 inches of snow or more, but only up to a 20% chance of 4 inches or more, mainly in the upslope regions of the northern Greens. The snow becomes more orographically driven along the upslope regions of the northern Greens by late Tuesday night.

KEY MESSAGE 3: Medium range deterministic, ensemble and AI guidance is coming into better agreement with the overall synoptic pattern for mid-week through next weekend featuring the continuation of a broad upper trough over the Northeast and ridging over the central CONUS through Friday, with the ridge shifting over the east coast on the weekend. Upslope snow showers across the central/northern Greens/Dacks will likely linger Wednesday into Thursday morning before surface high pressure builds in and dominates the regions weather through the end of the forecast period on Saturday with dry conditions expected. Temperatures finally look to trend towards mid- February normals with highs generally mid-20s to low-30s and lows in the low/mid teens above zero.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00Z Monday...Strong cold air advection from the northwest will continue to steepen lapse rates through this evening into tonight, resulting in good vertical mixing and continued breezy conditions, primarily across the Adirondacks, the Champlain Valley, and along the spine of the Greens.

Winds are expected to be strongest over the next six hours out of the northwest across Vermont and out of the west to west- southwest across northern New York. Most sites are reporting sustained winds 3-10 knots with some gusts at KMPV and KRUT 15 to 20 knots, and other sites could see winds 10-15 knots over the next few hours. After about 06Z-08Z Sunday, we'll see high pressure nose into the region from the Midwest, but most sites stay mixed for much of the night. This should result in winds staying mostly below 10 knots for the remainder of the night and into the Sunday morning daylight hours. Then, around 15Z-18Z Sunday, daytime mixing will help increase winds again, with highest probability of northwesterly gusts 15-20 knots at KRUT.

Low FROUDE numbers and snow showers will likely result in a mix of VFR and MVFR conditions over the next 3 to 6 hours, depending on the site. Generally, ceilings will be on the increase, though a scattered layer of cloud around 2000-3000 feet above ground level may cause periodic drops in flight category across northern New York and Vermont. KSLK is most likely to hold onto sustained low ceilings longest with low clouds persisting there until around 14Z-16Z Sunday. Visibilities should remain 4+ miles at any site, but the odd heavier snow shower could produce brief IFR vis during the early portion of the night tonight.

Outlook...

Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: Mainly VFR, with local MVFR possible. Chance SHSN. Tuesday Night: Mainly MVFR, with local IFR possible. Chance SN. Wednesday: Mainly MVFR, with local IFR possible. Slight chance SN. Wednesday Night: Mainly MVFR, with local VFR possible. Slight chance SN. Thursday: Mainly MVFR, with areas VFR 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...Cold Weather Advisory until 1 PM EST Sunday for VTZ001>011- 016>021. NY...Extreme Cold Warning until 1 PM EST Sunday for NYZ026-027- 029>031-034-087. Cold Weather Advisory until 1 PM EST Sunday for NYZ028-035.