textproduct: Burlington

WHAT HAS CHANGED

As of 233 PM EST Friday...

Winter Storm Warnings were expanded into Grand Isle and Washington counties in Vermont. Confidence has increased in very heavy snowfall rates of 1 to 2" per hour coinciding with the evening commute for much of the region.

KEY MESSAGES

As of 212 PM EST Friday...

1. A period of heavy, wet snow this evening will cause treacherous travel, with additional lighter snow continuing overnight before gradually ending tomorrow.

2. Low pressure system will track from the North Carolina coast northeastward towards the Gulf of Maine by Monday evening. This system will have little impact on our area with just a chance for light snow across southern Vermont.

3. Light snow with a clipper low expected Wednesday into Wednesday night.

DISCUSSION

As of 212 PM EST Friday...

KEY MESSAGE 1: Discussion: A dynamic low pressure system is bringing us a potent, short duration snowstorm today. As a large, laterally translating snowband continues to move northward across the entire region this evening, intense precipitation will support a changeover of any light rain and wintry mix in portions of southern St. Lawrence County, and southern portions of the Champlain and Upper Valleys. GOES-16 day cloud phase satellite imagery shows unusually widespread glaciated cloud tops normally seen in winter weather within snow squalls rather than frontal precipitation. The associated elevated instability with these tall clouds supports very heavy precipitation rates, which has been observed to our south in Albany early this afternoon where 2" fell within an hour. As of this writing webcam images show roads quickly going from wet to snowy with visibilities falling to a 1/2 mile in the Rutland area, and these conditions can be expected to continue expanding northward to make the afternoon and evening commute very hazardous. Regardless of Advisory or Warning, difficult travel due to low visibilities and slippery roads is expected tonight while the heaviest snowfall occurs. Widespread 4 to 10 inches of snow are expected by tomorrow morning; areas that see closer to 10 inches may see isolated power outages, but snow ratios are expected to be greater than 10:1 for enough of the event that these impacts should be limited.

The bulk of the snow will gradually wind down from southwest to northeast tonight following a roughly 6 hour period of moderate to heavy snowfall rates. Shallow east/southeast flow during at least the early part of the event will produce some terrain-driven effects with enhancement of precipitation on east facing slopes and shadowing in the western slopes, but this effect should diminish when the closed upper level low approaches from the west. One interesting feature of this event will be the sharply cooling temperatures late tonight primarily in our northern areas as north/northeasterly flow strengthens. This temperature gradient and the cold air advection during the day on Saturday will lead to some drying but also steep lapse rates near the surface to support snow showers chances after widespread snow ends. The colder air mass will set the stage for a seasonably chilly Saturday night as temperatures slip back into the teens and single digits.

KEY MESSAGE 2: Low pressure will track along the New England coast Sunday into Monday. Precipitation will stay pretty close to the low center, therefore only expect an increase in clouds for our region along with some light snow possible in southern Vermont. High temperatures Sunday and Monday will be in the lower 30s, with lows in the teens.

KEY MESSAGE 3: Next low pressure clipper system to bring chances for light snow to our region will pass through Wednesday into Wednesday night. This snow will be a bit more widespread, but at this time looks to only bring light accumulations. Temperatures over the next week will feature highs in the 20s and 30s, with lows in the single digits and teens with exception of Wednesday night which will only dip into the 20s with clouds and light snow ongoing.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Through 00Z Sunday...Widespread IFR/LIFR to dominate through about the first 12 hours of the TAF period in moderate to heavy snow. Currently seeing ceilings 500 to 1500 ft with visibilities 1/4SM to 1.5SM, and this will persist through 04z or so. The heaviest snow starts to wane thereafter with some slight visibility improvements, but ceilings will likely remain AOB 1000 ft through 12z. Clouds then slowly lift through MVFR and eventually VFR at all terminals by late in the TAF period. Any snow beyond flurries will likewise be ended by 12-14z. Winds generally light and variable overnight except locally stronger at KBTV with a SE wind around 10 kt gusting to 20 kt and at KMSS with an NE wind 10-15 kt with gusts to 25 kt through 06z.

Outlook...

Saturday Night: VFR. Slight chance SN. Sunday: VFR. Slight chance SN. Sunday Night: Mainly VFR, with local MVFR possible. Slight chance SN. Monday: VFR. Slight chance SN. Monday Night: Mainly VFR, with areas MVFR possible. Slight chance SN. Tuesday: Mainly VFR, with local MVFR possible. Slight chance SN. Tuesday Night: VFR. NO SIG WX. Wednesday: Mainly VFR, with local MVFR possible. Slight chance SN.

EQUIPMENT

The KMPV ASOS has suffered a communications failure. The issue has been diagnosed, but there is currently no estimated time of return to service. Terminal Aerodrome Forecasts will continue, but amendments to those forecasts will be suspended.

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...Winter Storm Warning until 10 AM EST Saturday for VTZ001-008- 010-018>021. Winter Weather Advisory until 10 AM EST Saturday for VTZ002>007-009-011-016-017. NY...Winter Storm Warning until 10 AM EST Saturday for NYZ026-028- 030-031-034-035. Winter Weather Advisory until 10 AM EST Saturday for NYZ027- 029-087.