textproduct: Burlington

WHAT HAS CHANGED

As of 145 PM EST Saturday...

The warmup for Monday and Tuesday has dampened slightly and chances for light snow Monday night into Tuesday morning have increased.

KEY MESSAGES

As of 145 PM EST Saturday...

1. A brief shot of colder air will follow today's snow showers as a cold front passes this evening.

2. Additional rounds of very light snow could impact the Monday and Tuesday morning commutes, although snowfall rates and relatively mild temperatures will limit accumulations.

3. The weather pattern looks to stay active for mid to late next week with multiple chances for snow, rain, or even a wintry mix.

DISCUSSION

As of 145 PM EST Saturday...

KEY MESSAGE 1: A thermally strong and moisture-starved cold front remains on track to push southward through northern New York and Vermont tonight. Snow showers we have seen today associated with a subtle pre-frontal trough will diminish into the evening as a wedge of drier air between the cold front and this trough scours out some of the marginally deeper moisture in place. We are seeing satellite imagery consistent with this dry punch as some breaks in the clouds are evident this afternoon near the International Border in New York. However, model guidance continues to show enough lingering moisture to squeeze out some terrain-driven snow showers along the cold front tonight, with a somewhat north to south progression of increased coverage of light snow redeveloping. This precipitation will not only be light but largely short-lived as northerly flow behind the boundary should quickly scour out clouds, aside from in the mountains where appreciable accumulation will likely reside exclusively. This shallow front will lead to a period of inverted temperatures; valley temperatures, having tumbled into the single digits above zero in most spots, will be relatively slow to warm compared to the mountains tomorrow. A lobe of seasonably cold 850 millibar temperatures correlating to summit conditions will be quick to depart to the east. As such, have adjusted both winds and temperatures in the high elevations to show these fluctuations tonight into tomorrow. So while warm air advection aloft along with plentiful sunshine will occur through the day with ridging quickly moving in, near surface, terrain-driven north/northeasterly flow will hold temperatures sub-freezing in most locations, save a few lower elevation spots in southern portions of Vermont and northern New York.

KEY MESSAGE 2: Following the light snow today and tonight, two more minor weather systems will roll through the region roughly 24 hours apart. As we have seen many times this winter, even minor snowfall that is poorly timed can cause travel issues, so we'll highlight these two potential light precipitation events here.

On the leading edge of a warmer air mass, some light snow will spread eastward out of southern Ontario Sunday night associated with a decaying wave and inverted trough. As noted by the previous forecaster, this snow will likely shrivel up as precipitation expands into Vermont, especially east of the Green Mountains. The precipitation pattern will probably be related to a continued northward shift of a coastal storm tied to the same upper level wave and the flow between this system and high pressure over the Canadian maritimes, maintaining dry low level air to offset the mid-level moisture flux. As such, little snow is expected for our area, especially in Vermont. Some of the latest reliable model guidance indicates no snowfall at all in Vermont, with only up to an inch in the Adirondack region and little or none elsewhere in New York. For now, with low chances for snowfall, have stuck to a forecast blend showing spotty coatings with trace amounts of snow generally favored. The latest REFS shows earliest onset of snow after 10 PM, with highest chances of accumulations between about 1 AM and 5 AM, again primarily in northern New York. About a 20-30% chance of measurable snowfall still extends into western portions of central Vermont (roughly from southern Chittenden County through Rutland County), although these chances of trended downward. Given this timing and antecedent cold air, some morning commutes may be slick.

In contrast, the next second system for Monday night, has trended more notable for both northern New York and Vermont, but temperatures will be less cold following a milder day on Monday. A small shortwave is progged to track right overhead out ahead of a a weak trough. As such, there should be ample low level moisture and lift to produce widespread, albeit light, snow. The 12Z guidance has been more aggressive the blend of models so have only modestly increased PoPs at this time, but if trends continue PoPs will need to be bumped up above 50% in most if not all of our region. As for potential impacts, precipitation rates would be light enough such that many marginally cold, lower elevation roads may just be wet. In fact, precipitation type may be in isolated pockets a cold rain, with a rain-snow mix currently indicated in the lowest elevations in the northern Champlain Valley and St. Lawrence Valley. However, any predawn wet snowfall, especially where air temperatures dip back below freezing prior to onset of snow, will more easily accumulate. At this time, the greater potential for snow covered roads for morning commute time on Tuesday appears in the Adirondacks. As we move into the timeframe with higher resolution model guidance, the timing and potential for light accumulation will be better fine tuned over the next few forecast cycles.

KEY MESSAGE 3: A frontal boundary will stall somewhere near or south of our forecast area through the latter half of next week, while high pressure tries to nose southward from Canada. A series of low pressure systems will ride along the front, bringing rounds of showers along with them. There remains considerable uncertainty as to where the front will be, and how far south the cold air is able to infiltrate. Meanwhile, warm air will lift up over the cold air, increasing chances for wintry mixed precipitation along/just north of the front, trending towards all snow as one goes north, and more rain as one heads south. Note that the deterministic 12z GFS and CMC both have shifted further south with the frontal boundary for the late Wed-Thu storm system, far enough that much of our area would see little to no precipitation at all, with maybe just Rutland/Windsor Counties getting snow with a bit of rain and/or freezing rain mixed in. However, several of the GEFS/GEPS ensemble members are further north (as is the deterministic 00z ECMWF), bringing widespread snow to much of the area, with some wintry mix possible in southern sections. Another system looks to affect the area toward the weekend, but again, lots of model spread on where the low (or lows) will track and what sort (if any) precipitation will occur across VT and northern NY. So long story short: stay tuned as hopefully trends will become more clear heading forward. There remains the potential for an impactful system at some point next week (especially if we see any wintry mix), but way too much model spread at this point to say anything definitive.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00Z Monday...VFR conditions will be the main flight category for this forecast cycle. The exceptions will be at SLK, MPV, and EFK where some ongoing MVFR CIGs will continue before drier air works in by the 03-05Z time frame. As a weak boundary drops south overnight, a few isolated snow showers could bring some brief MVFR CIG/VIS to these same terminals with VFR likely to remain at other terminals. The biggest questions is MSS where winds have gone calm as skies have cleared. There are some non-zero concerns for fog formation before the weak front moves through given snowmelt from today's warmer temperatures. Otherwise, winds will generally be northwesterly shifting north tonight, then northeast for tomorrow.

Outlook...

Sunday Night: Mainly VFR, with local MVFR possible. Chance SN. Washingtons Birthday: Mainly VFR, with areas MVFR possible. Slight chance SN. Monday Night: Mainly MVFR, with local IFR possible. Chance RA, Chance SN. Tuesday: Mainly MVFR, with local IFR possible. Slight chance RA, Slight chance SN. Tuesday Night: Mainly MVFR, with local IFR possible. NO SIG WX. Wednesday: Mainly VFR, with local IFR possible. Chance SN, Chance RA. Wednesday Night: VFR. Likely SN. Thursday: VFR. Chance SN, Chance RA.

CLIMATE

As of 701 PM EST Saturday... In Burlington, the last day with a temperature breaking 32 degrees was January 22nd. Today's preliminary high temperature was 35 degrees. Therefore the streak has ended at 22 days in a row. Sub-freezing temperature streaks this long are fairly unusual in the Burlington area, last happening January-February 2015.

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. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.