textproduct: Burlington

WHAT HAS CHANGED

As of 237 AM EDT Friday...

No significant changes were made to the current forecast.

KEY MESSAGES

As of 237 AM EDT Friday...

1. A clipper system will bring up to 6 inches of snow to some locations late today into early Saturday.

2. Gusty winds will accompany a clipper system tonight into tomorrow.

3. A strong system will impact the region late Sunday through Monday night.

4. Cool weather returns midweek with some snow showers possible.

DISCUSSION

As of 237 AM EDT Friday...

KEY MESSAGE 1: A clipper type system will move through the region from west to east this late this afternoon into Saturday morning. Snow showers are expected to arrive across northern New York beginning this afternoon, continuing overnight, as showers spread east into Vermont. A Winter Weather Advisory is in effect from 2 PM this afternoon until 1 PM Saturday for the Adirondacks in northern New York, as well as for the southern Greens where up to 6 inches of snow is possible. Higher snow amounts are expected in the Adirondacks with amounts ranging from 3-6", locally higher on mountain summits. Probabilities of exceeding 4" is mainly maximized over the Adirondacks at 50-70%. An initial warm front will bring good waa aloft with a brief surge in 850-700mb frontogenesis supporting brief light to moderate snow. However, given marginal temperatures in the low to mid 30s, even with some wet bulbing, some areas of rain are possible across the St. Lawrence and Champlain Valleys as well as across southern Vermont.

The limiting factor to this system remains low QPF and the surface low track. Total QPF is only forecast to be between 0.1-0.4" as the system does not favor good moisture connections. Moderate 14-16:1 snow ratios should help inflate totals a little with lower QPF, but high snow amounts are unlikely with this system. The low is expected to pass over the northern St. Lawrence Valley and ride along the International Border. These tracks favor shadowing in the Champlain Valley and eastern Greens, with higher amounts favored along the western facing slopes of the Adirondacks and Green Mountains. Locations above 2000ft in the Greens could see locally higher than 6 inches of snow. Outside of summit levels and the Advisory areas, a dusting to locally 3 inches of snow is expected. The timing of the snow this afternoon/evening could impact the Friday evening commute with a quick burst of 1-2" of snow across northern New York and near the Green Mountains. The timing of the heaviest snow will be between 8 PM this evening and Midnight Saturday. The snow will become more showery and confined to the higher terrain and western facing slopes by Saturday afternoon where a few additional inches may be possible as northwest flow supports upslope snow showers. Snow showers will taper off entirely across the region Saturday night.

KEY MESSAGE 2: In addition to the snow component of the clipper type system today into tomorrow, winds will become gusty tonight into tomorrow. As a warm front lifts to the northeast late this evening, winds will become southerly with steepening lapse rates. Furthermore, the surface low will be deepen as it moves through the region, enhancing the isallobaric wind component. This enhancement, coupled with channeled southerly flow and a LLJ of 50-60kts, winds could briefly gust up to 30-40 MPH this evening in the Champlain Valley and in the south-north oriented valleys of eastern Vermont. As the low shifts east, winds will shift to the west by tomorrow morning which should briefly weaken gusts. However, once winds reach the west, downsloping will re-enhance gusts back towards 25-35 MPH east of the Adirondacks and Green Mountains. The surface low will continue to track east, well away from the region Saturday night weakening the pressure gradient and subsequently trending winds towards more calm conditions by Sunday morning.

Have continued to trend towards the NBM90th with gusts this evening and tomorrow, but trends have mostly stabilized with values remaining under wind advisory criteria at this time. All said, tree branches could be broken with these gusty winds, but strong winds are not expected at this time.

KEY MESSAGE 3: Sunday will begin quiet and cool. Surface high pressure will shift offshore, and then a deep layer ridge will expand across the northeastern US. The way precipitation arcs over the ridge axis leaves a narrow axis of moisture within a region of broader dry air within the warm sector of approaching low pressure. This may be a boon, as it could allow for us to simply see some snow that lifts north of the border with little precipitation on the backside due to dry entrainment, and we could then avoid a transition to a broader mixed precipitation event. Still, in case precipitation is slow to exit, indicated slight chance to chance for sleet and freezing rain from the northern Champlain Valley westwards.

After a short interval of drying Sunday night, a plume of moisture will lift north from the Atlantic. Cool, sheltered hollows of eastern Vermont may remain below freezing, and some freezing rain is forecast along the New Hampshire border on Monday morning. Mid- morning to early afternoon, cooler air should begin to mix out and eastern Vermont will transition to all rain, while the Atlantic moisture plume shifts eastwards.

More impactful Sunday night through Monday afternoon will be the arrival of 850mb south winds of 55-65 knots. Strong surface heating to the mid 50s to mid 60s in the warm sector will promote the potential for the mixing of these winds for favorable areas within the northern Champlain Valley and northern slopes of the Adirondacks. The forecast indicates wind gusts in these areas rising to 45 to 50 mph. South winds are typically less impactful as most trees are acclimated to these conditions, but thawing soils may leave things a bit looser at this stage.

For Monday afternoon and evening, there will be a strong cold front moving east. Like 24 hours ago, low resolution global models already depict a line of heavy rain tracking east. Although noting the potential in some of these scenarios that convection may develop well south of our area, and strong unidirectional meridional flow with ample warm advection brings stratiform off that convective activity. There may also just be some shower activity with a range of elevated or MUCAPE depicting about 100-250 J/kg of instability. The front itself will cross near and after sunset with a sharp wind shift and quickly falling temperatures. Depending on how much moisture remains, some snow may mix in with lingering showers. The upper vort is still nearby, and so with the south-southwest flow, perhaps pockets of lake effect may even develop Monday night.

KEY MESSAGE 4: Conditions will become cooler behind the strong front. The weather pattern returns to something a bit more characteristic of this winter season with troughing in the eastern US returning. Weak disturbances could produce some snow showers here and there. We'll have to watch surface temperatures, as the better sun angle means we see temperatures rise into the mid 30s to lower 40s. However, warm air is shallow enough, then we can observe snow showers in spite of temperatures in the mid-upper 30s.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 12Z Saturday...There has been little change over the last 6 hours, with even some snow showers still lingering. Although flow was not blocked, moisture moved little, and now our flow is blocked until 14-15z. So until then, little change is expected, with light and variable winds 5 knots or less. Still expecting some partial clearing before the next system approaches from the southwest. Snow will edge northeast between 21z and 03z. Initially, ceiling and visibility reductions will likely be towards MVFR, and the heavier activity moves in behind this between roughly 23z and 05z based on the latest guidance. Noted some pockets of 2SM visibility. Southeast winds, except northeast at KMSS, will increase towards 8-14 knots sustained with gusts 16-23 knots possible. About 06z, the surface low will track along the international border, and winds will slow as it approaches the area. Terminals will likely be a mix of MVFR and IFR approaching 12z Saturday.

Outlook...

Saturday: Mainly MVFR and IFR, with areas VFR possible. Windy with gusts to 30 kt. Likely SN, Chance SHSN. Saturday Night: VFR. Windy with gusts to 30 kt. NO SIG WX. Sunday: VFR. Chance SN, Chance RA. Sunday Night: Mainly VFR, with local MVFR possible. Strong winds with gusts to 40 kt. Chance RA, Chance FZRA. Monday: Mainly MVFR, with local IFR possible. Strong winds with gusts to 40 kt. Definite RA, Slight chance FZRA. Monday Night: Mainly MVFR, with areas IFR possible. Strong winds with gusts to 40 kt. Definite SHRA, Chance SHSN. Tuesday: Mainly VFR, with local MVFR possible. Windy with gusts to 30 kt. Chance RA, Slight chance SN.

EQUIPMENT

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...Winter Weather Advisory from 2 PM this afternoon to 2 PM EDT Saturday for VTZ019-020. NY...Winter Weather Advisory from 2 PM this afternoon to 2 PM EDT Saturday for NYZ029-030-034.