textproduct: Burlington

WHAT HAS CHANGED

As of 142 PM EST Tuesday...Slightly slower arrival of cold air on Weds night into Thursday and a small increase in snowfall amounts over northern New York, including the St Lawrence Valley.

KEY MESSAGES

As of 142 PM EST Tuesday...

1. Gusty southerly winds overnight across the northern Adirondacks and Champlain Valley, with much above normal temperatures prevailing through Wednesday.

2. Sharply falling temperatures and rain changing to a widespread light to moderate snowfall late Wednesday into Thursday, will produce hazardous travel conditions.

3. Bitterly cold temperatures coupled with continued breezy winds will lead to near dangerous wind chills Thursday night. Low temperatures and breezy conditions continue into Friday Night.

4. Generally unseasonably cold temperatures will continue by the end of this weekend into next weekend, with several chances for snow showers, which could lead to slick travel at times.

DISCUSSION

As of 142 PM EST Tuesday... .Key Message 1: Gusty southerly winds overnight across the northern Adirondacks and Champlain Valley, with much above normal temperatures prevailing through Wednesday.

A period of gusty south to southwest winds 30 to 45 mph are expected overnight acrs the northern slopes of the Adirondacks and the central/northern Champlain Valley, which could cause a few power outages. Sfc analysis shows 989mb low pres north of Lake Superior, while 1020mb high pres is anchored off the East Coast. As sfc low pres passes to our north overnight the 925mb to 850mb wind fields strengthen with progged 850mb winds of 50 to 60 knots and 925mb values of 40 to 45 knots. Sounding data suggests a strengthening and lowering inversion around 2200 feet, which combined with favorable channeling on south flow wl support gusts 35 to 45 mph northern CPV and parts of the northern slopes near Malone. HREF shows a 80 to 100% probability of wind gusts >40 mph, but only a small area of 20 to 35% probability of gusts >45 mph.

GOES-19 water vapor shows embedded potent s/w energy over northern MI, with cooling cloud tops on the IR satellite imagery moving into the eastern Great Lakes this aftn. This moisture and dynamics wl lift acrs northern NY and extreme northern VT tonight with a period of precip likely. Progged 925mb temps hovering near 0C, support snow levels around 1800 feet acrs the Dacks and northern/central Greens, with rain showers in the valleys. Wind direction and speed wl once again produce a rain shadow in the CPV, but would not be surprised of a few light showers, given the dynamics. Snowfall wl be a dusting to 2 inches with lows in the upper 20s to mid/upper 30s.

.Key Message 2: Sharply falling temperatures and rain changing to a widespread light to moderate snowfall late Wednesday into Thursday will produce hazardous travel conditions.

Deepening mid/upper lvl trof acrs the central Great Lakes, combined with sharpening low lvl thermal gradient wl help in the development of sfc low pres late Weds into Thurs AM. Trends have been for a slightly slower arrival of cold air, while delaying or shifting sfc low pres development to the west. It should be noted there is still a rather large spread in frontal timing and development and track of sfc low pres on Weds night into Thurs, which greatly impacts ptype and snowfall potential.

Given quick movement of system and potential for mid/upper lvl dry slot, an advisory level event is likely for portions of our region, especially northern NY and parts of central/northern VT. NBM for at MSS indicates a 24 hour snowfall range of 0" for the 25th percentile and 7" for the 75th, while the mean is 4". Meanwhile at BTV the 25th is 1" and the 75th percentile is 5", with the mean of 3". Did note the 00z/12z operational ECMWF and 12z GFS is showing an axis of enhanced qpf over northern NY associated with mid lvl deformation and favorable low lvl convergence as sfc low pres tracks over VT, which could produce localized amounts near warning criteria. The progged 925mb temp gradient associated with boundary is pretty impressive, which should result in 10 to 15 degree sfc temp drop in 2 to 3 hours on Thurs morning. This combined with rain changing to snow with a period of accumulating snowfall likely near the Thurs morning commute, wl result in locally hazardous driving conditions likely.

For the CPV did note the Froude is very low 0.10 to 0.50 thru 16z Thurs, supporting snow upstream of the Green Mtns, but wind direction is 250-270 degrees, which does not result in the best convergence or moisture fetch off Lake Champlain to help enhance snowfall locally. Bottom line expecting 2 to 7 inches SLV/Northern Dacks to 1 to 5 inches most of VT, except locally higher in the mtns, where change over occurs sooner. System quickly lifts out of our cwa by 18z Thurs with some lingering mountain snow showers and much cold temps, as progged 850mb temps drop below -20C by 00z Friday. A non- diurnal temp trend continues on Thurs with temps falling below zero summits to single digits and teens valleys.

Key Message 3: Behind a departing longwave trough, strong caa with continued breezy to gusty northwest flow aloft, will drop Thursday night lows into the single digits above and below zero, and wind chills into the negative single digits to negative teens. The coldest locations will be across northern New York where additional snow could enhance any radiative cooling effects with clearing skies. Winds will continue to be on the breezy side through the day Friday and into Friday night with winds becoming southerly and gusting towards 20-25 MPH. Highs Friday will be slow to reach the upper teens to low 20s during Friday afternoon. While winds will continue to gust Friday night, southerly flow will help limit lower temperatures with modest waa. Wind chills Friday night will dip into the single digits to low teens.

Key Message 4: A large-scale upper level gyre will continue to eject numerous shortwaves into the region this weekend through early next week. A brief warmup is possible with southwesterly flow Saturday with highs into the low to mid 30s. However, temperatures will once again come crashing down Saturday night into Sunday as an un-phased shortwave traverses northwest across the St. Lawrence Valley. Temperatures with the onset of precipitation should remain all snow for those who see any showers, mainly across the St. Lawrence Valley. A secondary shortwave will ride along the elongated longwave over the Great Lakes with additional snow shower chances Monday into Monday night. Neither of these systems appear impactful with both unphased to the established moisture corridor off the coast, and marginal forcing. However, a few inches of some fluffy snow is possible across mainly northern New York. Vermont will likely reside in a dry slot between the marginal forcing of the shortwave and the moisture corridor off the coast. Snow lovers in Vermont (outside of the spine of the Greens, where some upslope showers are possible), will be disappointed with this forecast for early next week. Showery weather will continue well into mid to late next week.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 00Z Thursday...Gusty south to southwest winds develop tonight. Scattered rain and mountain snow showers are likely tonight, especially over northern New York with a minor snow accumulation possible. A widespread light to moderate snowfall develops Wednesday night into Thursday.

Winds have become predominantly southerly this evening with increasing gusts expected at all sites. Gusts overnight will reach up to 35 knots at most sites, with channeled flow perhaps increasing gusts towards 35-40 kts at BTV. With these increasing gusts, winds aloft at 2000ft agl will be 35-50 kts leading to widespread LLWS through at least 03Z-15Z Wednesday, though potentially lasting through 22Z-00Z. Winds will remain southerly to southwesterly over the next 24 hours, but will weaken towards 15Z-22Z Wednesday.

Prevailing VFR conditions are expected to continue at all terminals through around 02Z-05Z Wednesday, when rain and snow showers arrive in northern New York and bring with them ceilings around 2500-3000 feet above ground level at SLK and MSS lasting until around 06Z-09Z Wednesday. Scattered rain and snow showers are expected to occur elsewhere as well, but will likely not bring visibilities much lower than 4-6 miles and should do little to lower ceilings outside of the specific sites mentioned.

After the showers and lowered ceilings tonight, VFR conditions are again expected to prevail through around 12Z-14Z Wednesday, when New York sites will again have some lingering MVFR ceilings, and other sites should join them around 18Z-22Z Wednesday. We'll start to see the widespread precipitation arriving around 19Z-00Z, beginning as rain and/or snow depending on location and elevation. Visibility decreases anticipated to follow.

Outlook...

Wednesday Night: Mainly MVFR, with areas IFR possible. Likely SN, Likely RA. Thursday: Mainly VFR, with local IFR possible. Chance SHSN. Thursday Night: VFR. Slight chance SHSN. Friday: VFR. NO SIG WX. Friday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Saturday: Mainly VFR, with areas MVFR possible. Chance SHSN. Saturday Night: Mainly VFR, with local IFR possible. Chance SHSN. Sunday: 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...None.