textproduct: Burlington

WHAT HAS CHANGED

As of 155 AM EST Saturday... The remaining Winter Storm Watch areas have been upgraded to a Winter Storm Warning, putting the entire area under a Winter Storm Warning from 1 PM Sunday to 1 AM Tuesday.

KEY MESSAGES

As of 155 AM EST Saturday...

1. Dangerously cold conditions are expected through tonight, with wind chills of -20F to -40F expected. Risk of hypothermia and frostbite is unusually high due to the extreme nature of the cold, especially for vulnerable populations and anyone venturing outdoors without proper cold weather gear.

2. Several inches of moderate to heavy snow are expected for our region late Sunday through Monday. Travel will become hazardous, with the bulk of the snow occurring Sunday evening into Monday morning. Both the morning evening commutes on Monday will be impacted.

3. Continued cold weather is expected behind Monday's storm with daytime temperatures in the 10s and overnight lows in the single digits above and below zero. Upper low pressure lingering overhead will result in periods of isolated to scattered snow showers.

DISCUSSION

As of 155 AM EST Saturday...

.KEY MESSAGE 1: Very Dangerous cold conditions will continue this morning through this afternoon, with wind chills of -20F to -40F areawide. An Extreme Cold Warning remains in effect until 1 PM today. This will be the coldest airmass of the season so far, and given the extreme nature of the cold, the risk of hypothermia and frostbite will be unusually high. This is especially true for vulnerable populations and anyone venturing outdoors without proper cold weather gear.

With an arctic front now to our Southeast, clearing skies with added fresh snow from the prior days lake effect and snow squalls are helping push actual air temperatures well below zero for most valley locations, with negative teens to 20s expected by daybreak across the higher terrain. In addition to the dangerous air temperatures, gusty northwest winds will remain between 15 to 25 MPH pushing wind chills to their lowest values between -20F and -40F by 7 AM with the most extreme conditions in the Adirondacks and northern Greens to Northeast Kingdom. We are urging people to stay indoors if possible today, especially vulnerable populations like the elderly and children. If you must be outdoors, please make sure to wear plenty of warm gear, including gloves or mittens and a hat. Any exposed skin will be susceptible to frostbite in just a few minutes. And don't forget about your pets; bring them inside if at all possible.

The cold will continue well into Saturday evening and Saturday night, but winds will continue to weaken towards light and variable with some sunshine. However, air temperatures will remain below 0 for the entire region with perhaps some 0 to +3F in the wider valleys during the daytime hours today. Although winds will be weakening throughout the day, wind chills will still be -10F to - 20F. There is still some uncertainty with how low ambient air temperatures fall tonight with increasing cloud cover from our next winter storm approaching from the southwest. However, there appears to be a period early tonight where radiative cooling is still likely to take place. As a result a Cold Weather Advisory has been issued Franklin and western Clinton Counties in New York, and Essex County in Vermont from 1 PM today to 7 AM Sunday, where wind chills may remain below -20 this evening and overnight tonight. Outside of the Cold Weather Advisory, wind chills will continue to be -5F to -20F.

KEY MESSAGE 2: The biggest change to the previous forecast is that confidence has increased enough to issue Winter Storm Warnings for the remainder of the forecast area for at least 7 inches of snow from 1 PM Sunday to 1 AM Tuesday. 00Z guidance has shown a stabilized swath of 7-10" across northern New York and northern Vermont and along the International Border with with NBM progs generally favoring 7 inches of more of snow in the aforementioned locations.

Overall, there hasn't been a significant change in the expected weather pattern. An upper trough will dig into the Great Lakes on Sunday, then swinging eastward into the Northeast CONUS on Monday. This will allow a coastal low to deepen as it lifts northeast Sunday into Sunday night, eventually moving south of Cape Cod and out toward the open Atlantic. Amplification of a coastal low will draw in deep layer moisture into all of New England with additional advection induced by the parent mid/upper low over the eastern Great Lakes. There is still some uncertainty regarding the exact liquid equivalent we will receive with a strong retreating 1040mb high to our north. However,trends continue to suggest that this high erode faster with a deeper coastal low, allowing additional moisture to advect into northern New England. Furthermore, there looks to be fairly strong 700-850mb frontogenesis at the onset of the event, particularly in central and southern Vermont, and perhaps up the Champlain Valley which could lead to snowfall rates that exceed 1 inch per hour rates at times. With the core of the system to the south, the axis of dilatation will be oriented southwest to northeast, perpendicular to the expected surface to 850mb layer flow. This convergence aloft could lead to localized mesoscale banding with a deformation band with locally higher amounts where this feature sets up. It is still too early to parse out these mesoscale features, but with large scale systems like this, these features are typical.

All in all, the snowfall forecast has not changed much with only 1- 2" fluctuations across the region. The areal coverage of 12" or more has pushed a bit further north into portions of Chittenden, Lamoille, and Caledonia Counties, with the northern edge of the region into a 7-10" range. The low spot total wise is likely to be in the northern St. Lawrence Valley near Massena, where the best forcing will remain south. However, some ensembles are progging a resurgence of snow potentially Monday afternoon with the passage of an inverted trough with decent 750mb frontogenesis. Time will tell where and if this resurgence occurs. Higher amounts of snow are favored to be across southern Vermont where up to a 1.5 ft of snow is not unrealistic, and the southern spine of the Greens could locally see potentially 20" in places like Killington. Snow Ratios could push 25:1 helping achieve these higher totals with a deep surface to 20kft DGZ and a fully saturated column. Light and high fluff factor dendrites are expected. One could feasibly clear their driveways and cars with a leaf blower. Furthermore, While isolated trees or branches down can't be totally ruled out due to the snow load, the snow just isn't going to be the wet, heavy type that favors more utility-based impacts. Finally, temperatures will remain on the cold side even after the storm passes with highs in the low to mid teens and overnight lows near or just below 0, making shoveling and post storm cleanup potentially hazardous temperature wise.

KEY MESSAGE 3: The forecast scenario depicts varying degrees of strength for an upper low across Quebec and how it transitions towards the Gulf of Maine. Thus, periods of snow showers are possible, but the exact timing of when snow showers may be more pervasive is challenging to completely discern at this time. Given lack of deep moisture, most shower activity should be light. NBM guidance agrees on cold temperatures remaining the theme. Wednesday night into Thursday morning appears the most likely to be cooler, with most everyone below zero. Slowly moderating temperatures will conclude the extended forecast.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Through 12Z Sunday...Prevailing VFR conditions are expected the next 24 hours. North to northwest winds are already slowing down, and will linger around 4 to 8 knots much of the day, though at 10 knots with a few gusts at KMPV through 18z-20z. Winds will subside further after 22-00z. Skies clear until high clouds at or above 20000 ft agl advance from the south into the overnight.

Outlook...

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

CLIMATE

Record low maximum temperatures are possible on Saturday; below are the current records:

KBTV (Burlington area): -4 in 1907 KPBG (Plattsburgh area): 0 in 1976 KSLK (Saranac Lake area): -10 in 1936 KMSS (Massena): -5 in 2004 KMPV (Montpelier): 0 in 2004 SJBV1 (St. Johnsbury): -3 in 1907

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...Extreme Cold Warning until 1 PM EST this afternoon for VTZ001>011-016>021. Winter Storm Warning from 1 PM Sunday to 1 AM EST Tuesday for VTZ001>011-016>021. Cold Weather Advisory from 1 PM this afternoon to 7 AM EST Sunday for VTZ004. NY...Extreme Cold Warning until 1 PM EST this afternoon for NYZ026>031-034-035-087. Winter Storm Warning from 1 PM Sunday to 1 AM EST Tuesday for NYZ026>031-034-035-087. Cold Weather Advisory from 1 PM this afternoon to 7 AM EST Sunday for NYZ027-030-031.