textproduct: Burlington

WHAT HAS CHANGED

As of 205 AM EST Wednesday...

No significant changes.

KEY MESSAGES

As of 205 AM EST Wednesday...

1. Snow will cause hazardous travel today, first with widespread light snow in the morning, then scattered snow showers and possible embedded snow squalls during the afternoon and evening.

2. A brief warmup is expected for Saturday, with sharply colder temperatures returning Saturday night into early next week.

DISCUSSION

As of 205 AM EST Wednesday...

KEY MESSAGE 1:

Active weather remains on tap today with a typical clipper system tracking to our north. A large area of snow over central New York will race northeastward this morning, beginning about 4 AM in western portions of northern New York and reaching northeastern Vermont by 8 AM, with only about 2 hours of steady snowfall for most locations. This snow will be quite light both in amounts and density; forecast soundings show precipitation developing with deepening cloud layers with a temperature favorable for dendrites coincident with strong vertical motion. Hence, for a upwards of an hour would expect moderate to heavy snowfall rates with visibilities down to a half mile. While there will be variability dependent on some terrain effects given a potent ~40 knot south-southwest low level jet, snow to liquid ratios will be near 20:1; with just 0.05 to 0.1" of liquid you get a fairly quick 1 to 2" of snow. The intensity of the snow, as noted with low visibilities and 0.5-1" per hour snowfall rates, will cause difficult travel

After the warm front and associated isentropic lift exits, we'll have some clearing as wedge of dry air ahead of the clipper's cold front develops. If this was summertime we'd be looking at severe thunderstorm potential this afternoon in the warm sector. As is, southerly flow out ahead of the front does appear to advect in warmer and more moist air. In combination with height falls, lapse rates will steepen and we will see snow showers develop rather quickly. With Lake Ontario mostly open, a lake enhancement to surface moisture and instability seems to be leading to best snow squall ingredients over northern New York where scattered to numerous snow showers will likely fall. Southwest winds look moderately strong; while the boundary layer does not look particularly deep as it can get in more robust snow squall scenarios, forecast soundings in places like Massena and Saranac Lake suggest potential to mix down 35 - 40 MPH gusts. Confidence on these gusts concurrent with snow showers is limited given expected shallow cloud tops and more moist rather than dry low level air. Farther east, while instability is more marginal for snow squalls, it appears that taller, very skinny CAPE will develop such that snow showers could be heavier, especially if they organize into a line such that some Convective Allowing Models are indicating. This snow will also be rather fluffy, with stronger upward motion and somewhat lower altitude snow growth zone compensating for warmer near surface temperatures.

In particular, while frontogenesis also does not appear to be strong, it appears to sharpen across central/southern Vermont in a pre-frontal trough ahead of the cold front during the evening, such that an area of heavy snow develops. This feature is noted in the HRRR/RAP/NAM3, with some important differences in timing, location and intensity. Generally looks like the risk of this heavy snow shower activity increases after 6 PM and greatest likelihood of occurrence is in southern portions of Vermont, although other clusters of heavy snow showers could be ongoing farther north. While this is not an Arctic cold front which tends to overachieve on snow squall activity, any of these snow showers could produce locally difficult travel for the evening commute. Precipitation could linger through at least the first part of the night as the cold front will probably sweep eastward through the region towards midnight. Even behind the front, lingering moisture and upslope southwesterly flow will keep some terrain-driven light snow going and future forecasts may bump up snowfall locally through daybreak Thursday.

Following the cold front, while a broad trough will sit over the region with seasonably cold air in place, a low pressure system will track too far south Thursday afternoon and evening for us to have any significant weather. Then high pressure will build in for Friday and slide to our east Friday night, resulting in a milder night following a cold Thursday night.

KEY MESSAGE 2: Strong southerly flow across the region will usher in warmer air, bringing warmer temperatures for Saturday. As of now, temperatures are expected to climb into the 40s areawide, with some locations in southern Vermont nearing 50. This warm up will be short- lived, as a cold front looks to push across the region Saturday night into Sunday, bringing some sharply colder temperatures and scattered showers. Winter-like weather is expected for early next week, with highs well below freezing and overnight lows in the single digits above and below zero, although more moderate temperatures look to arrive towards mid-week.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thursday...Variable flight conditions are expected this morning as light snowfall continues to overspread the region. Conditions are generally MVFR to IFR within snowfall, with IFR conditions primarily driven by visibilities. This snow will continue to push across the region this morning, before exiting towards 16Z or so. Additional scattered snow showers, with some possible heavier snow showers or even embedded snow squalls, will develop this afternoon. The overall timing and exact location of impacts with these showers is difficult to pinpoint, so several PROB30 groups were utilized to cover this potential. MVFR ceilings will linger at most terminals through much of the day, with some improve back towards VFR possible after 00Z. Winds will become more southerly as the morning progresses, with the strongest winds expected at KBTV and KPBG where gusts of 15 to 25 knots are possible. Some LLWS will continue across the region this morning as snow moves through the region, but will generally only continue for the first few hours of the forecast period.

Outlook...

Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: Mainly VFR, with areas MVFR possible. NO SIG WX. Saturday Night: VFR. Chance SN. Sunday: Mainly VFR, with local MVFR possible. 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...None. NY...None.