textproduct: Burlington

WHAT HAS CHANGED

As of 100 PM EST Sunday...Winter Weather Advisory for lake effect snow issued for southern St Lawrence County from Monday afternoon through Tuesday morning.

KEY MESSAGES

As of 100 PM EST Sunday...

1. Lake effect snow will impact southern St Lawrence county from Monday through Tuesday. Snow squalls will also be possible Monday evening, especially across northern New York.

2. Dangerously cold weather is likely next weekend, especially by Sunday. Probabilities of temperatures and/or wind chills falling below -20 degrees are over 50% in much of northern New York and portions of northern Vermont.

3. Impacts to travel due to scattered snow showers and snow squalls will be possible at times, especially on Thursday and possibly over the weekend.

DISCUSSION

As of 100 PM EST Sunday...

.KEY MESSAGE 1: Lake effect snow band will continue off of Lake Ontario and impact parts of northern New York. This band will wave north and south over the next few periods, but become most persistent over southern St Lawrence county Monday afternoon into the overnight, winding down on Tuesday as the band sinks south of our area. Have issued a winter weather advisory for that area with 3 to 6 inches of snow expected, and locally higher amounts possible. There will also be a chance for snow squalls Monday afternoon into the evening ahead of an approaching cold front. Winds will be brisk out of the south southwest, with some decent surface based instability. Best chance for squall activity will be from 21z Mon to 03z Tue across northern New York.

.KEY MESSAGE 2: A large chunk of extreme cold, Arctic air will be across southern portions of Canada during the upcoming week. The teleconnections (defined global weather patterns) are strongly favoring a highly negative Arctic Oscillation and negative (but trending neutral) Pacific North American Oscillation, which sets up a pattern for persistent cold in our region with low chance of significant snowstorms. While only a piece of the truly bitter cold is forecast to enter the region late Thursday into Friday, more notable cold is possible over the weekend some of the colder air is forced southeastward on the eastern flank of an anomalously strong high pressure system. There is uncertainty in timing, however, which leads to a somewhat muted signal in the ensemble mean anomalies for low level temperatures. The mixed signals are somewhat related to the intensity of cold but also as to whether the extreme cold arrives on Saturday or is delayed until Saturday night. As of now, Saturday night/Sunday looks more favored for extreme cold, which is consistent with the NBM.

The current forecast high of 7 degrees on Sunday here at BTV would be the lowest maximum temperature we have seen since January 2022. During one Arctic outbreak that month, wind chills were below -30 and analyzed 925 millibar temperatures in the -26 to -28 Celsius range. The latest run of the machine learning/AI-GFS supports the coldest air settling in Saturday night when mean 925 millibar temperatures are down to -28 Celsius in northernmost Vermont. It should be noted this is near the 10th percentile of its ensemble, so not necessarily the most likely scenario at this point. As a consensus, lowest forecast wind chills during this event are still quite cold right now, ranging from -15 to -25 in most of our region. All together, expect Cold Weather Watches may be needed for portions of northern New York and Vermont.

.KEY MESSAGE 3: Ahead of a series of Arctic fronts, instability and moisture will probably be sufficient for snow squalls during this period. The most impactful event may be during the day on Thursday, when organized snow squalls are most favored and surface temperatures could approach freezing, supporting potential for icy conditions to develop as opposed to just slippery. Based on frontal timing they could affect both the morning and evening commute. Ahead of these potential squalls, higher probability (6 hourly PoPs as high as 50- 80%) but less intense types of snow showers are favored Wednesday/Wednesday night in the frontal system's warm sector. Then after the Thursday event, precipitation chances become much more unclear with no clear low pressure system/associated troughs to organize snow. Generally the pattern with colder air aloft will support more lake-effect snow chances. This precipitation will initially be Lake Ontario induced lake-effect when flow is more westerly and then potentially localized snow downwind of Lake Champlain as flow trends north-northwesterly during the weekend.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...Mainly VFR conditions are present this afternoon, with the exception of SLK where light lake-effect snow showers are bringing visibilities and ceilings down into the MVFR range. Brief IFR conditions will be possible. Otherwise, there will be some very light snow possibly impacting sites in Vermont overnight into early Monday associated with a coastal storm. Again, IFR conditions are not expected even if snow falls, but some intermittent MVFR is likely due to a combination of ceilings and visibilities. Probabilities of snow showers and associated IFR conditions ramp up after 12Z at SLK, but have left mention out of the TAF at this time with precipitation chances still rather low (peaking below 50%) and more likely to be light enough for mainly MVFR visibilities. Winds are currently gusty out of the southwest at MSS but are trending lighter, and winds will generally diminish at all sites towards 00Z as weak high pressure builds in. Flow will largely be south-southwesterly as the boundary layer mixes with diurnal heating after 12Z, although winds look mainly 10 knots or less.

Outlook...

Monday Night: VFR. Windy with gusts to 30 kt. Slight chance SHSN. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Chance SHSN. Wednesday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Thursday: Mainly VFR, with areas MVFR possible. Chance SHSN. Thursday Night: VFR. Slight chance SHSN. Friday: VFR. Slight chance SHSN.

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. Use extra caution when navigating the broad waters of Lake Champlain. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...Winter Weather Advisory from 1 PM Monday to 1 PM EST Tuesday for NYZ029-087.