textproduct: Burlington

WHAT HAS CHANGED

As of 200 PM EST Wednesday...An Extreme Cold Watch has been issued for all of northern New York and much of Vermont from 7 pm Friday to 1 pm Saturday. In addition, scattered snow squalls are looking more likely Thursday and Friday, with both evening commutes to be impacted with hazardous travel.

KEY MESSAGES

As of 200 PM EST Wednesday...

1. Scattered snow squalls are expected Thursday afternoon and evening. Gusty winds, heavy snowfall, and rapid snow accumulation will make for hazardous travel, including for the Thursday evening commute. Additional squalls are possible on Friday, as well.

2. Dangerously cold conditions are increasingly likely late this week, with wind chills of -20F to -40F possible. An Extreme Cold Watch is in effect for Friday night and Saturday morning.

3. Widespread snow increasingly likely Sunday night into Monday.

DISCUSSION

As of 200 PM EST Wednesday...

.KEY MESSAGE 1: As we await some light snow for this evening and overnight, our focus for the next 24-48 hours will be the potential for snow squalls.

Low pressure will slide up to our west this evening and cross to our north on Thursday. Light snow associated with warm air advection ahead of this low will spread over the region this evening, bringing mainly light accumulations (less than 1 inch) for the evening commute. This light snow will subside overnight, but expect additional snow showers to develop during the day Thursday as a cold front crosses from west to east. While there's not much frontogenesis associated with this front, steep low level lapse rates from cold air advection will result in SB CAPE values of 50- 100 J/kg, so convective elements are likely. Some guidance indicates mixing as deep as 650mb behind the front, more than ample enough to bring some of the 50+ kt jet at 850 mb down to the surface with these heavier showers. So while showers won't be organized into a line, expect scattered to perhaps numerous squalls Thursday, particularly in the afternoon and into the evening hours. Snowfall rates could exceed 1 in/hr briefly with these squalls, reducing visibility to 1/2 mile or less. This will be especially true downwind of Lake Ontario which will help to enhance moisture and instability. Gusty winds of 30 to 40 mph will only serve to blow any freshly fallen snow and make travel that much more hazardous. Anyone traveling tomorrow, including during the evening commute, should be prepared for highly variable road conditions, with sharply reduced visibility, gusty winds, and snow-covered roads with little warning in squalls. The one saving grace is the incoming airmass isn't bitterly cold, so we don't anticipate a flash freeze with these squalls. Overall snowfall amounts will mainly be 1 to 3 inches, perhaps higher downwind of Lake Ontario.

Unfortunately, we could see another round of squalls on Friday as a secondary, arctic front will move through. Timing would be much the same, mainly in the afternoon and evening, just in time for everyone heading home for the day. Like Thursday, briefly heavy snowfall combined with gusty winds will make for treacherous travel, so please plan ahead if you will be out on the roads.

.KEY MESSAGE 2:Confidence in very cold conditions continues to grow; so much so that we have issued an Extreme Cold Watch for our entire forecast area, effective from 7 pm Friday to 1 pm Saturday.

As the aforementioned arctic cold front crosses our region on Friday, a much colder airmass will spread southward in its wake. 925mb temperatures will approach -30C, with overnight ambient temperatures to drop well below zero by early Saturday morning. The issue on Friday night will be the continued breezy conditions, as strong cold air advection will keep us mixed through much of the overnight hours. Friday's daytime gusts will gradually wane as the strongest winds exit to the south and east. But with lows to be -5F to -20F, even relatively light winds will be enough to result in brutally cold wind chills. As it is, gusts up to 20 mph will be possible through at least the first half of the night, with sustained winds likely still 5-10 mph by daybreak Saturday. Wind chills of -20F to -40F are possible Friday night through Saturday morning, with the coldest conditions to be in the Adirondacks. Although some of our area may not reach Extreme Cold Warning criteria (-30F), it will be dangerously cold for anyone who might be outdoors Friday evening through Saturday morning. If you are unable to avoid being outside, make sure to wear plenty of warm clothing, including hats and mittens or gloves. And don't forget about your pets; bring them inside if able. If not, make sure they have adequate shelter from the cold.

While Saturday night will also be very cold, trends are less certain, as incoming cloud cover would have a larger role to play in just how cold we get. Additional cold weather headlines might be needed.

KEY MESSAGE 3: Widespread Snow Increasing Likely Sunday Night into Monday.

A powerful nor'easter will develop on Sunday and track up the eastern seaboard, with the center of the low tracking well to the southeast. Model consensus right now has it staying a couple hundred miles off the New England coast, taking a close to ideal storm track for southern New England. However, the area of snowfall looks to be uncharacteristically large with this event, extending several hundred miles to the north. The current most likely scenario is that the heaviest snowfall remains to the south, and that the region receives a more glancing blow. Snowfall looks to begin during the day Sunday and continue into the day Monday. In general, the Euro and CAN ensemble members favor a northern snowier track and the GEFS members favor a drier southern track. Current combined GEFS/Euro/CAN probabilities of reaching certain snowfall thresholds using a snow ratio between 15-20:1 as forecast by the NBM are as follows:

Southern Areas 2" 70-90% 6" 50-70% 12" 20-40%

Northern Areas 2" 50-80% 6" 20-40% 12" 0-10%

AVIATION /18Z WEDNESDAY THROUGH SUNDAY/

Through 18Z Thursday...VFR conditions prevail at all terminals, and that will be the case for the next couple hours. Light snow moves into the region from west to east in the late afternoon and evening. It should be heavy and consistent enough to lower visibilities to IFR consistently at SLK and MSS, while it will likely be intervals of IFR conditions at the rest of the terminals. BTV and PBG will likely only see a few brief periods of IFR visibility. These snow showers decline in coverage this evening and visibilities should be VFR for most places for the rest of the night. A few snow showers could linger at MSS. A few rounds of heavier but brief snow showers will move through tomorrow. These will be able to quickly cause IFR at any terminal. Ceilings should be mostly VFR during this period. LLWS develops this evening outside the Champlain Valley (BTV, PBG) and continues for the rest of the night. While it is not expected to reach criteria at BTV and PBG, it will be close. Winds will be gusty and southerly through tonight, becoming southwesterly tomorrow.

Outlook...

Thursday: Mainly VFR, with local MVFR possible. Chance SHSN. Thursday Night: VFR. Slight chance SHSN. Friday: VFR. Chance SHSN. Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight chance SN.

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 Watch from Friday evening through Saturday afternoon for VTZ001>011-016>021. NY...Extreme Cold Watch from Friday evening through Saturday afternoon for NYZ026>031-034-035-087.