J.Spin

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

We’re definitely watching Ginx – after this current event, that’s the next one in the bread and butter lineup. The BTV NWS isn’t concerned about it too much around here at this point, but we’ll see what happens as it gets closer: Area Forecast Discussion National Weather Service Burlington VT 922 AM EST Sun Dec 27 2020 NEAR TERM /THROUGH MONDAY/... As of 922 AM EST Sunday...Southerly flow will increase overnight tonight into Monday ahead our next approaching system. Gusty southerly flow is expected especially in the Champlain Valley with sustained winds 15 to 20 mph with gusts upwards of 30 mph likely, locally higher over the broad lake. Main surface low pressure will pass west of the area and pull off northward into southern Quebec. Temperatures warm tonight into Monday therefore thermal profiles will be supportive mainly of mountain snow and valley rain. Most favored area for steady precipitation will be across western New York with scattered precipitation across Vermont. QPF amounts will generally be a few hundreths to around 0.10" across NY and between a trace and a few hundreths for VT. Snow amounts will generally be confined to a dusting to up to 1" for the Adirondacks.

Exactly; the fact that we’ve already surpassed those snowfall numbers just two days into the forecast period really makes it “iron clad” (as they say), and very hard to argue against exceeding the projection. Sure, snowpack can decrease, but it’s rare to see snowfall numbers decrease once they’re recorded. Yeah, it’s sticking one’s neck out to guarantee that we’re going to exceed those projections with two weeks to go, but sometimes you have to take big risks and ride out your calls.

I know we’re still a full two weeks out from when legitimate verification can be assessed on those projected snowfall numbers, but I honestly expect sites like Mansfield, and even your house, to surpass what the map shows for them.

That is really interesting PF. That observer has got to be measuring/clearing just once a day of course, but even that can’t explain that much compaction. It’s almost as if they’re measuring/clearing even less than once a day and getting more settling than they should. But that can’t explain it for this event – we know when this event started, and we can see everyone’s current depth in the CoCoRaHS data. And, even if you only clear once in a 24-hour period, you can still measure when the snow is at its maximum depth (but I’m guessing this observer doesn’t practice that option). I’ve been doing 6-hour clears and liquid analyses on this event, and you can see the difference is only 0.7” (5.2” collected vs. 4.5” current depth). That should really be about the maximum settling anyone should be seeing at this point. So how does that site settle so much? They’re still getting the liquid, so you’re right, it’s as if collection is done on a surface that is melting from below. Another possibility I guess is that the observer collects in a spot with a bit of wind that is destroying the loft of the dendrites. This morning’s accumulation was definitely fragile at almost 40:1, so with snow like that, wind compaction could be a contributor. What type of results does that site report for dense snow events?

Event totals: 5.2” Snow/0.18” L.E. Details from the 6:00 A.M. Waterbury observations: New Snow: 1.5 inches New Liquid: 0.04 inches Snow/Water Ratio: 37.5 Snow Density: 2.7% H2O Temperature: 23.5 F Sky: Light Snow (2 - 5 mm flakes) Snow at the stake: 4.5 inches

I don’t think we saw any 3”/hr snowfall this evening, but it was pretty close over a shorter period, probably in the 2.5”/hr range. Accumulation on the boards at 10:00 P.M. was 0.8”, and then it was 2.0” at 10:30 P.M., so that would suggest close to 2.5”/hr during that block. You can see on the radar when those 30 db returns coalesced here in the Winooski Valley, that’s the period when the snowfall was most intense:

Event totals: 3.7” Snow/0.14” L.E. Details from the 12:00 A.M. Waterbury observations: New Snow: 2.8 inches New Liquid: 0.11 inches Snow/Water Ratio: 25.5 Snow Density: 3.9% H2O Temperature: 24.1 F Sky: Snow (2 - 15 mm flakes) Snow at the stake: 4.0 inches

Yeah, it’s definitely picked up over the past 20 minutes or so. I was guessing a 0.5”/hr rate around 9:00 P.M., but it’s been ramping up a bit – it looks like 0.4” in the past 30 min, so getting closer to a 1”/hr rate now. You can see a bit of fire hose spray movement on the radar:

I just checked out the radar and I see that pulse pushing in. We’ve had generally just flurries since my 6 PM observations, but we’ll see if this next round kicks the snowfall rate up a bit more. You can often tell if the moisture pulse is getting a bit more serious when the radar switches sensitivity modes.

Event totals: 0.9” Snow/0.03” L.E. Details from the 6:00 P.M. Waterbury observations: New Snow: 0.7 inches New Liquid: 0.03 inches Snow/Water Ratio: 23.3 Snow Density: 4.3% H2O Temperature: 27.9 F Sky: Flurries Snow at the stake: 1.0 inches

While snowfall up here in NNE hasn’t been atrocious, Dryslot’s point is well taken and speaks to the fact that snow preservation has definitely been below average. It’s going to be quite evident in those places like NW Maine that should really be (on average) developing their substantial winter snowpack at this point. Ginx is definitely on track with the map for the SNE/NYC complaining stuff though. I’m pretty sure I’ve heard people down there mentioning how they’re ahead of average on seasonal snowfall? Haven’t some people down there had not one but two substantial synoptic storms at this point?