textproduct: Burlington

WHAT HAS CHANGED

As of 136 AM EST Friday...

A Winter Storm Warnings have been expanded into Orange County, Vermont and portions of northern New York. The timing of the heaviest snow has slowed somewhat, but impacts to the evening commute are still anticipated, especially in southern and central parts of our forecast area.

KEY MESSAGES

As of 136 AM EST Friday...

1. A period of heavy, wet snow tonight will impact travel and could cause isolated to locally scattered power outages before trending to steady light snow by midnight. The timing of snow has slowed some, but very difficult travel this evening is still anticipated.

2. A stretch of relatively quiet and seasonable weather is expected across the region this weekend into next week.

DISCUSSION

As of 136 AM EST Friday...

KEY MESSAGE 1: The overall setup for this event remains unchanged, though delayed a couple hours. Increasing clouds and temperatures in the 30s are expected, perhaps even touching 40 along western foothills of the Greens. A strong warm front will gradually lift northeastwards across Vermont and northern New York this afternoon and evening. NWS Offices across the Ohio River Valley up to the Allegheny range have been issuing convective warnings, and that shows how dynamic a feature we're working with. Analysis of layered forcing shows a warm theta E tongue almost over top of us with maximized omega as strong as 15 to 20 ubar/sec within a moist DGZ. Strong upper divergence is expected as an upper low settles over Lake Ontario and a narrow upper ridge along coastal New England with a favorable coupled jet configuration. A strip of moderate to heavy snow is expected, as a result. The latest HREF progs for 1"/hr snowfall rates gets as high as 80-90 percent over parts of northern New York and central Vermont, and the timing has shifted towards 22z-02z now for the heaviest snow. There are even some 20-30% contours of 2"/hr snowfall rates across eastern facing foothills of the Adirondacks within this time frame of heaviest snow. One of the other things noted is the collapse of the LLJ. 850 southeasterly flow of 30-35 knots will initially result in some downsloping, but high res guidance indicates this feature collapses. Where possible, applied high res guidance that does a good job of shadowing in these cases like Rutland, Lake Placid, Malone, Richmond, and Enosburg. After evening passes, the forecast gradually reduces the level of downsloping by employing coarser blends. Guidance continues to indicate some mix, but by the time heavy snow arrives, there are regions with marginal temperatures, but any wet-bulb temperatures above freezing aloft very quickly fall below 0 C. The interval of any sleet may be very short-lived. Snow still appears like it will be wet at the onset with ratios ranging between 7-11:1, and then gradually increase towards 12-15:1. The wet snow could result in isolated power outages across the region, locally scattered where snowfall amounts exceed 8-10 inches. There fortunately won't be too much in the way of wind with this event, but it should be a breezy terrain- driven northeast wind of 10-20 mph along the St. Lawrence River.

As we approach midnight, forcing collapses as the favorable alignment of atmospheric lift shifts east or decays. So after the interval of heavy snow, we will see a gradual decline to light snow. A backdoor front is still expected to descend out of the north to northeast, and that will slowly shunt snow back to the south or southwest during the day. In terms of totals, there's still a large degree of spread amongst forecast guidance. We could still contend with some dry air infiltrating from the south on the backside of the warm front, and outside heavy snow, marginal surface temperatures will slow accumulations. Seeing convective activity as close as it is certainly indicates the need for caution in forecast totals. Snowfall totals have increased some, especially along the St. Lawrence River, eastern foothills of the Adirondacks, and south- central Vermont. A widespread 3-7" is still the most likely outcome, as indicated by the 50th percentile. Where the favorable alignment of terrain and the initial warm front come together, those are the areas pushed to the 75th percentile and where upgrades to warnings have been done. Regardless of our exact totals, the impacts to the evening commute across the southern half of Vermont into New York, as well as the potential utility impacts, due to heavy, wet snow are still of high confidence. Impacts will overall decrease Saturday with the light snowfall rates and drier snow.

KEY MESSAGE 2: Heading into next week, a relatively quiet stretch of weather is expected. High temperatures will generally be in the 20s to mid 30s as the week progresses, with overnight lows in single digits and teens most nights. A coastal low looks to develop Sunday into Monday, but it looks to track well to the southeast with little to no impacts expected across our forecast area, other than some possible light snow showers across southern Vermont and increased cloud cover. Another system looks to arrive towards the middle of next week, bring more widespread precipitation to the region. At this time, it looks like most of the precipitation should fall as snow, but details will need to be fine-tuned as we get closer.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

Through 06Z Saturday...VFR conditions currently prevail across the region, with a few pockets of MVFR with ceilings generally between 2500 and 4500 ft AGL. These conditions are expected to continue for the next several hours, until precipitation begins to move into the region this afternoon which will bring deteriorating conditions. Snow will overspread the region this afternoon, about 16Z for KSLK and spreading northeastward with snow expected at KEFK around 00Z or so, with periods of heavy snow expected this evening. Visibilities will generally be between 1-2SM within the snow, with even lower conditions possible. Ceilings will lower as the evening progresses, with widespread low MVFR and even IFR ceilings expected. Winds will generally be light and variable throughout the forecast period, with the exception of KMSS where channeled northeasterly winds will allow for sustained winds around 10 knots and gusts around 20 knots.

Outlook...

Saturday: Mainly VFR, with local MVFR possible. Chance SN. Saturday Night: VFR. Slight chance SN. Sunday: VFR. Slight chance SN. Sunday Night: Mainly VFR, with local MVFR possible. Slight chance SN. Monday: Mainly VFR, with areas MVFR possible. Slight chance SN. Monday Night: Mainly MVFR, with local VFR possible. NO SIG WX. Tuesday: Mainly VFR, with areas MVFR possible. NO SIG WX.

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...Winter Storm Warning from 10 AM this morning to 10 AM EST Saturday for VTZ010-018>021. Winter Weather Advisory from 10 AM this morning to 10 AM EST Saturday for VTZ001>009-011-016-017. NY...Winter Storm Warning from 10 AM this morning to 10 AM EST Saturday for NYZ026-028-030-031-034-035. Winter Weather Advisory from 10 AM this morning to 10 AM EST Saturday for NYZ027-029-087.