J.Spin

I get these from the Weather Underground BTV radar site – it actually lets you choose from a variety of beam angles, as well as the composite of course: https://www.wunderground.com/radar/us/vt/burlington/cxx I learned from PF that the composite is nice in that it gives you a chance to catch upslope and various other effects that you might not due to mountain shadowing. As you can see, PF uses lots of the different beam angles depending on what he wants to look at. I usually just default to the composite because you know you’re getting the most intense signals from various angles and catching just about everything there is to catch if it’s out there.

Cool, that should be interesting. I also see that there’s been what appears to be a LES band coming off Lake Champlain with this more northerly wind, although the band seems to be fading now.

PF, note that you can see the beginnings of that Waterbury streamer even on your radar grab from this morning. I hadn’t thought much of it at the time, but it’s obvious now. My wife said that it was already snowing in Waterbury when she headed off to work before 7:00 A.M. this morning, and she was just at the Shaw’s in town a little while ago and noted that they got a pretty good shot of snow there. She actually sent me a text early this morning to remark at how hard it was snowing as she went through Stowe, but I was working upstairs and didn’t check my phone until some point in the afternoon. I told her I’d gotten plenty of timely updates from you on the weather forum though!

I’ve got a local update on these mountain streamers. As I was back at the house checking out the radar, I was looking at the streamer down here, and it actually looked like it was shifting to the west (presumably due to a shift in the wind to a more northerly direction). It looked like it was actually shifting enough to bring it near our site, and sure enough, I was looking out the window, and an immediate wall of big flakes came down. It’s funny, having experienced going in and out of the streamer that we’ve got down here during my travels this afternoon, it’s clear that these streamers have a very sharp cutoff like LES bands vs. the typically broader effects we see with upslope. Sometimes we’ll get some very sharp upslope bands, but these have definitely shown quite the cutoff. I’ve got a radar grab below that shows the Waterbury streamer shifting to the west, and it quickly put down a half inch of snow when it got here. The radar image also shows another pulse of moisture coming into the area from the north.

So I got a bit of a surprise this afternoon with respect to this phenomenon. I had to drive my younger son to Harwood to meet with his driving instructor for some practice, which brings me right through town here in Waterbury. We left the house with the small flakes we’ve been getting since yesterday, and just as we reach the fringe of town, it starts pouring big ½” – 1” flakes in probably the 0.5”-1”/hr. range. It was remarkable how quickly it turned on, and then as soon as I hit the southern end of town and started to climb toward Duxbury, it essentially shut off, or was at most just very light snow with the type of flakes we’ve had here at the house. I figured I’d gone through a brief squall or something, but sure enough, as I drove back home, it’s pouring big flakes in the same place – right in town. As soon as I left town heading toward our house, it was back to the light snow/small flakes, and that’s the way it stayed. It was as if the center of town had its own little localized storm going on. I had to check out the radar when I got home, and from what I can see, it’s another streamer, just like the one you’ve been reporting on in Stowe. Looking at the positioning, I wonder if this one is coming off Bolton Mountain the way the one up near you is coming off Mansfield:

Event totals: 0.7” Snow/0.02” L.E. In classic upslope style, the light snow has been ticking along through today as the models suggested. Flakes have been quite small here at our site though, so accumulations continue to be fairly low. Details from the 12:00 P.M. Waterbury observations: New Snow: 0.1 inches New Liquid: Trace Temperature: 25.7 F Sky: Light Snow (1-3 mm flakes) Snow at the stake: Trace

Event totals: 0.6” Snow/0.02” L.E. Details from the 6:00 A.M. Waterbury observations: New Snow: 0.1 inches New Liquid: Trace Temperature: 24.8 F Sky: Flurries Snow at the stake: Trace

That’s pretty neat PF, even for around here in the mountains that’s pretty extreme localization! Here at our site we’ve been getting similar light snow and flurries to what we experienced yesterday, with another tenth of an inch of accumulation overnight.

Event totals: 0.5” Snow/0.02” L.E. The snowfall gradually wound down this afternoon, so that might be it for this event, but I guess there are still potential lobes of mid-level moisture out there that might affect the area over the next 12 to 24 hours and indicated in the BTV NWS AFD: Area Forecast Discussion National Weather Service Burlington VT 621 PM EST Sun Dec 6 2020 .NEAR TERM /THROUGH MONDAY NIGHT/... As of 612 PM EST Sunday...Cyclonic nw upslope flow prevails associated with mid/upper lvl trof acrs the ne conus from departing coastal system. Weak pieces of energy and lobes of slightly better mid lvl moisture continue to rotate thru our cwa for the next 12 to 24 hours. This general pattern will continue to produce on and off light snow showers acrs the favorable upslope regions of the northern dacks and central/northern Greens overnight into Monday. Details from the 6:00 P.M. Waterbury observations: New Snow: 0.1 inches New Liquid: Trace Temperature: 27.9 F Sky: Cloudy Snow at the stake: Trace

I had done a quick look through the models to see what was coming in the next week, and it looks like there are 3 to 4 chances to talk about. There’s this current system that the models suggest would be providing snow for roughly the next 24 hours, and then there’s some mid to late week potential as jc noted. Some model runs have shown that as two pulses, but most seem to show it as one long period of snow. That would run over a couple days though, so it could be a reasonably snowy period, but we’ll have to see how that trends as we move forward. The final chances would be out toward next weekend with a potential synoptic system. As currently modeled, the snow to consider there would be front side and back side snow because we’d be in the warm sector for part of that system. That pace of systems right now seems pretty normal, but only the shortwave period around midweek is really typical bread and butter stuff. Today’s snow is from that northerly flow, although I do see on the radar that it’s beginning to acquire a bit more westerly component, and then the modeling for the next weekend timeframe has the bulk of the snow potential to the west of this area until the storm passes.

Event totals: 0.4” Snow/0.02” L.E. We’ve generally had light snowfall all morning, but the flakes have been quite small and thus accumulation has been relatively slow. Details from the 12:00 P.M. Waterbury observations: New Snow: 0.1 inches New Liquid: Trace Temperature: 28.4 F Sky: Light snow (1 to 2 mm flakes) Snow at the stake: Trace

Checking out the local radar, there’s an obvious moisture stream coming into the area from the north. That’s definitely not our typical bread and butter northwesterly flow around here, but it’s keeping the flakes going even down here in the valley, so it’s certainly supplying a level of moisture. This is presumably the type of snowfall activity that the models have been showing to hang around through as Winter Storm Eartha departs. The models that are catching it well suggest this sort of stuff hangs around for roughly another 24 hours.

That’s really interesting; I didn’t check any of the forecasts over there, but on the precipitation type/moisture outputs from the models, it just looked like a general big swath of blue up and down the state of New Hampshire. Your site did what it’s supposed to do though, just like we’ve been saying based on the data!

Event totals: 0.3” Snow/0.02” L.E. An additional round of accumulation came through overnight. The precipitation was flurries at observations time, and that’s what I’ve seen on and off since then. Details from the 6:00 A.M. Waterbury observations: New Snow: 0.2 inches New Liquid: 0.01 inches Snow/Water Ratio: 20.0 Snow Density: 5.0% H2O Temperature: 26.8 F Sky: Flurries Snow at the stake: Trace

Yeah, I’m sure we’re pretty close to the western edge of the precipitation shield – we’ve had flakes with no accumulation up to this point, but catching your post I went out to check and I see that we’ve just hit 0.1” of accumulation.

We’ve been just cloudy all day and I haven’t seen any snowfall, even off to the east in town when I was there earlier this afternoon. We are starting to get some flakes now though, so the atmosphere must have hit the point where it was moist enough to get them down to the valley despite the dry air off to the west.

I’ve got the latest BTV NWS maps below. It looks like they’ve pushed things east a bit from the previous update, with some of the Winter Storm Warnings from the previous map being switched to Winter Weather Advisories, and the projected accumulations similarly moving eastward.

We’re all pulling for you Phin – we want you to relieve that stress you’ve been putting yourself under to get that first substantial synoptic snow at your NH spot!

Actually, on that note, I see that the BTV NWS has their maps out for this upcoming system. We’re under a Winter Weather Advisory here in Washington County, as it looks like we’re on the western edge of the system with the current guidance. The projected accumulation map shows quite the accumulation gradient from east to west.

I concur; the same output will be there in the morning, and the storm happens whether you look at the models or not. I like to check out the models to get a heads up ahead of the regular forecast for when snow’s potentially coming to ski, but I’m not heavily into the tracking. We’ve literally got paid professionals (that we’re paying with our tax dollars) at the BTV NWS to take care of that for us, and they’re pretty damn good at it. Once they put out their projected accumulations maps, they give you a pretty solid idea of what’s going to happen. I’ve been a bit busy this week to follow this next storm too closely, but it looks like we’ve got the potential for a few inches over here in our neck of the woods. I see the latest run of the GFS has the upslope hanging around for a few frames in the Northern Greens as the storm departs.

Event totals: 0.7” Snow/1.87” L.E. There’s nothing notable on the radar right now, so we’ll have to see if this marks the end of this backside snow. Details from the 12:00 A.M. Waterbury observations: New Snow: 0.2 inches New Liquid: Trace Temperature: 29.3 F Sky: Cloudy Snow at the stake: 0.5 inches

I could see that; they say he’s a bit of a frigid fellow.

It’s good that PF chimed in here with the clarification; the 2 feet of powder from a hint of atmospheric disturbance is generally a mesoscale/mountain/NNE thing. From what I’ve observed over the past several years, much of SNE has to work really hard for their snow. It’s apparent from the weird “we just need to get this system to…” and “if we can keep that system from…” phraseology that is used. One would conclude that if they don’t work hard enough, they simply don’t get the snow. Sometimes there’s this reverse psychology thing that goes on as well, but it would seem like that would only hurt the overall effort?

It was snowing fairly heavily there for a bit, it was that crazy sort of snow with a mixture of different flake sizes and descent rates where it seems like you’re getting snowfall that is from multiple sources/levels in the atmosphere. It didn’t last all that long, but it did put down the quick half inch that we picked up. After a lull for a while, there’s actually a bit more moisture coming into the area on the radar, but the snowfall is fairly light an nothing as potent as that earlier passage.

Event totals: 0.5” Snow/1.87” L.E. Details from the 6:00 P.M. Waterbury observations: New Snow: 0.5 inches New Liquid: 0.03 inches Snow/Water Ratio: 16.7 Snow Density: 6.0% H2O Temperature: 31.5 F Sky: Light Snow (5-15 mm flakes) Snow at the stake: 0.5 inches