J.Spin

This afternoon’s update from the BTV NWS should be the last one before the onset of the current system moving into the area. There have been some changes in both the advisories map and the projected accumulations map, with the BTV NWS AFD noting a couple of related forecast changes. The first is regarding a slightly earlier onset time for snow, and the second deals with snow totals, as discussed below: Area Forecast Discussion National Weather Service Burlington VT 416 PM EST Fri Jan 1 2021 NEAR TERM /THROUGH SATURDAY NIGHT/... As of 410 PM EST Friday...The second change in the forecast concerns snow totals, mainly along the Canadian border and across the Northeast Kingdom. Snow totals are now expected in the 4 to 8-inch range across this area, the bulk of which will fall between 7 AM and 1 PM on Saturday. Localized accumulations up to 10 inches are possible across the northern Green Mountains. During this time, a band of heavier snow is possible, producing rates up to 1 inch/hour for a brief period of time. This is attributed to enhanced meteorological forcing paired with higher snow ratios as colder, drier air pushes in from the northwest. By late Saturday afternoon, all precipitation will transition to either snow or rain before coming to an end Saturday evening. Changes in their advisories maps show some Winter Storm Warnings moving into Northern Vermont, and some areas of 8-12” shading in the Northern Greens and Northeast Kingdom. Our point forecast here got a bump to roughly the 6-10” range, and I see some 6-12” forecast numbers for the higher elevations along the spine.

The latest BTV NWS maps for the upcoming storm are below. The notable change in the advisories map is the Winter Storm Warning area in NNH, and on the projected accumulations map they’ve refined it to show some areas in the 6-8” shading. The point forecast here is roughly 3-7” through Saturday, which is right in line with what the map shows.

Well, the great news is that in whatever frozen form it falls, 0.50-0.75” of L.E. would be huge for base building on natural terrain. As long as it’s topped off with a bit of lower density stuff, low-angle terrain would immediately be back in action. Checking on BTV NWS point forecasts, I see projected L.E. of 0.69” here at our site, 0.83” for Bolton, and 0.89” for Mansfield at elevation.

I got a text this afternoon indicating that we’ve been put under a Winter Weather Advisory for this upcoming system, which is substantial enough to have earned the name Winter Storm John. The BTV NWS advisories map is pretty straightforward with wall-to-wall Winter Weather Advisories throughout the north country. Our point forecast here calls for 4-8” of snow with the potential for some sleet mixed in on Saturday. The projected accumulations map looks like it’s on the lower end of that with broad areas in the 3-4” and 4-6” ranges, but the products often get synced up better as the storm gets closer.

Event totals: 0.2” Snow/0.01” L.E. We’ve had flurries/light snow on and off all day, but just an additional 10th of an inch of accumulation through noontime with some of the graupel. I haven’t seen anything accumulate this afternoon with the temperatures a few degrees above freezing – it’s been fluffy flakes that melt fairly easily relative to the graupel. Details from the 12:00 P.M. Waterbury observations: New Snow: 0.1 inches New Liquid: Trace Temperature: 36.5 F Sky: Light Snow (1-2 mm flakes) Snow at the stake: 1.0 inches

Event totals: 0.1” Snow/0.01” L.E. We had some standard flakes yesterday afternoon and last night, and I’ve seen graupel falling today, but a tenth of an inch is all I’ve observed for accumulation from this event (which appears to be the remnants of Winter Storm Ivy merging with a clipper to our north) thus far at our site. Details from the 6:00 A.M. Waterbury observations: New Snow: 0.1 inches New Liquid: 0.01 inches Snow/Water Ratio: 10.0 Snow Density: 10.0% H2O Temperature: 36.1 F Sky: Light Snow/Graupel Snow at the stake: 1.0 inches

Yeah, I saw that relatively strong radar signal as well – it looks like it’s the warm front, but there’s a lot of dry air for the precipitation to overcome. There should be more notable snow starting this evening though: Area Forecast Discussion National Weather Service Burlington VT 1252 PM EST Wed Dec 30 2020 .NEAR TERM /THROUGH THURSDAY/... As of 954 AM EST Wednesday...Some light snow spreading over the area as a warm front moves through. This will be very short- lived with a clear back edge to the snow and minimal daytime accumulations expected. Otherwise, forecast still on track for increasing gusty winds today and more widespread precip this evening into overnight tonight. Previous Discussion... Satellite imagery shows increasing mid and high level clouds moving into the region. There is some snow back across western New York, but feel this may not hold together and move into our region as plenty of dry air remains in place. The better chances will come late in the day and especially tonight as cold front gradually moves toward the region.

Flakes started appearing here in Waterbury around 1:30 P.M. ahead of this next system, but it looks like these are just some early forerunner flakes associated with the warm front that shouldn’t amount to much. The next round of snow comes in this evening, with our point forecast calling for about an inch of accumulation through tomorrow.

And I’d say you’ve got two more wintry systems queued up – one starting tomorrow evening into Thursday, and then a second one Saturday into Sunday. The GFS modeling seems to suggest a more wintry outcome with that second system over the past few cycles.

Nice, even though it’s not quite visible on the radar up there, you’d have to think Jay Peak would be in on something with that sort of flow. It’s always been a bit strange that a place with amazing snowfall like Jay Peak has had such poor webcam representation, but I do see there’s at least a time lapse one available now. It’s on their Photo of the Day page, and it’s a really nice full HD view of the resort going through its daily motions and weather. You can definitely see those snow showers hitting the area as you cycle through the time lapse: https://jaypeakresort.com/resort/photo-day

Well, we’re starting to get some flakes from those streamers here along the spine now, so I guess there’s still a bit of snow to wring out.

On that note, we’re supposed to be clearing out in general, but you can still see a few streams of moisture coming in from the northwest, and they’re passing right over Lake Champlain. With the current temperatures, I’m sure the lake is doing whatever it does to help keep the air with a bit more moisture than it might otherwise have:

The general thought is that while those fetches are clearly too short across Lake Champlain to fire off pure LES, we’ve always figured that having an additional body of water there certainly can’t hurt. There’s no doubt that having that additional moisture present (whenever the lake isn’t frozen) is only going to make a positive contribution by at least helping keep the air heading into the mountains as saturated as possible. It’s a great point to bring up though, because on the map you can see that winds from both those trajectories have to pass over Champlain before hitting the Northern Greens.

That sentiment really doesn’t match the data for last season though – both my site and Alex’s site recorded 140-150” of snowfall, and Phin’s site was over 200”! I think SDD were below average in general, but it’s really hard to call it a crap season with those numbers. We’re currently ahead of average snowfall for this season right now at our site. I’m sure SDD are again below average, but it’s still hard to define it as a crap winter… especially with 4 to 5 months of winter still to go around here.

Event totals: 1.2” Snow/0.05” L.E. We’re partly cloudy at this point, so it looks like the above totals are the final numbers for this system. It looks like the next system is anticipated to come into the area tomorrow afternoon/evening. Details from the 6:00 A.M. Waterbury observations: New Snow: 0.5 inches New Liquid: 0.03 inches Snow/Water Ratio: 16.7 Snow Density: 6.0% H2O Temperature: 20.3 F Sky: Partly Cloudy Snow at the stake: 1.5 inches

Event totals: 0.7” Snow/0.02” L.E. Accumulations are starting to pick up again with the dropping temperatures this evening, so we’ll see what the overnight brings. Details from the 12:00 A.M. Waterbury observations: New Snow: 0.2 inches New Liquid: Trace Temperature: 34.7 F Sky: Light Snow (1 to 3 mm flakes) Snow at the stake: 1.0 inches

Similar to what you’re seeing, it’s just a touch too warm down here at 500’ for the snow to accumulate much, but we actually did get a round of accumulation a little while back when the precipitation was more intense and graupel came down. Temperatures are supposed to drop off substantially tonight, so within the next couple of hours even the valleys should be able to accumulate whatever snow falls after that point.

I haven’t heard of specific shadowing of Great Lakes moisture anywhere along the spine of the Greens, and I know the Southern Greens can catch some nice snowfall with the right flow (I think that snow that backedge reported on the other day might have been from the lakes?) With respect to Adirondack-based shadowing up here in the north, the thoughts about the Northern Greens doing notably better than the Central Greens on northwest flow has always made sense. If you look at the image below, you can see that NW winds just skirt past the Adirondacks to hit the Northern Greens, but the Central and Southern Greens would be shadowed. For reference on the relief map, if you look at the northern part of the Green Mountains, you’ll see two big stripes of green cutting through them. The top one is the Lamoille Valley, and the second one down is the Winooski Valley, which marks the boundary between the Northern and Central Greens. I’ve just always been surprised that we can still catch that Lake Ontario moisture on the 255-260° wind that brings it here into the Northern Greens. That wind has to pass right over the Adirondacks, and even the High Peaks area for the more southern parts of the Northern Greens. It’s as if the more rounded shape of the Adirondacks range lets the moisture get around the peaks easily, but the Greens don’t let much of it pass because they form a long spine and there’s just nowhere for the air to go but up.

The Greens do tend to steal from that plentiful supply of Great Lakes moisture before the Whites can get their share. With that flow off Lake Ontario, I’m still not sure why the Adirondacks don’t try to stop us?

Event totals: 0.5” Snow/0.02” L.E. The snowfall tapered off after 11:00 – 11:30 A.M., and the radar shows that the bulk of the echoes have headed north of this area. Details from the 12:00 P.M. Waterbury observations: New Snow: 0.5 inches New Liquid: 0.02 inches Snow/Water Ratio: 25.0 Snow Density: 4.0% H2O Temperature: 34.3 F Sky: Flurries Snow at the stake: 3.0 inches

I did an 11:00 A.M. check on the boards and found 0.5” of accumulation, so that seems like a decent estimate for the average snowfall rate over the past hour here.

Thanks for the update. First flakes here were around 9:00 A.M., but it didn’t really start to pick up until about 10:00 A.M. The snowfall has generally been light as expected, but perhaps near 0.5”/hr with this latest push of more intense echoes coming in on the radar:

Over the past few minutes I’ve been starting to see some flakes falling here at our site in association with the approach of this next system.

Event totals: 5.9” Snow/0.19” L.E. The snow finally tapered off this afternoon and we even saw a little sun, so it looks like this event is over at our site and the above totals will be the final snow and liquid numbers. Details from the 6:00 P.M. Waterbury observations: New Snow: 0.2 inches New Liquid: Trace Temperature: 25.5 F Sky: Mostly Cloudy Snow at the stake: 3.5 inches

Event totals: 5.7” Snow/0.19” L.E. Details from the 12:00 P.M. Waterbury observations: New Snow: 0.5 inches New Liquid: 0.01 inches Snow/Water Ratio: 50.0 Snow Density: 1.0% H2O Temperature: 30.7 F Sky: Light Snow (2 - 5 mm flakes) Snow at the stake: 4.5 inches