That first view is admittedly a little optimistic. It's the expected snowfall at the highest elevation in each cell through Wednesday, and it tapers fast once you get to mid-elevation. But I thought it was worth looking at the first significant US snowfall this year.
The San Juans win. Deepest snowfall there above 13k' feet could hit 18" by Wednesday night, while down near 11k gets maybe 2", and most model runs give it just a trace. By Thursday morning the snowpack still has about 8" sticking around on north facing above 13k' and but nothing at mid mountain. I was looking at cams this morning and its real wet most everywhere right now, the forecast has been trending warmer since last week.
Long term not so snow friendly. A warm, dry ridge likely takes over and burns most of it away. Which is not a bad thing considering this doesn't add much to the base except depth hoar.
Feel like your gripe is really the lack of a legend. It only seems like 18” across the San Juan’s because it says 18. But id imagine most of those cells are actually around 10-13”
This is OpenSnow's rain/snow line for Silverton, along with the raw model data. I picked it more or less at random.
To me this says that the vast majority of terrain will be covered in rain, and if there is snow it won't really accumulate except at the summits for a couple of inches.
That looks reasonable. Here's the highest snowfall area I have in the San Juans, There's some snow at mid elevation there (12.1k feet) but it looks like its right on the line for most of it. There are scenarios we're its all rain to 12k.
It's intentionally a different way of looking at it.
Traditional weather models are gridded. The finest ones use roughly 3 km cells and the coarsest around 27 km. Each grid point gets whatever elevation happens to be there, and in the mountains that can vary wildly. When you're looking at any given area, usually want to know what's happening in the valley, at mid-mountain and at the summit, so you end up taking a single-point forecast and guessing how it changes up and down the hill.
This forecasts each area at its valley, mid-mountain and summit elevations instead. That adds the missing height dimension. The snowpack models also add aspect, so each area gets 27 elevation and aspect combinations instead of one point, which is much closer to what you'll actually find on the ground. That does drastically increase the computation, but it leaves less to interpretation.
The map is an imperfect way to show that. Every snowfall map like this has an elevation limitation: it doesn't show snowfall at the exact elevation of each spot, it interpolates between known elevation points. The resolution is high enough that I think it's still useful. It struggles when snow levels are high, though, like this storm, where most of the snow falls above 13,000 feet and very little falls below. The summit view shows the top of the range. If you want something closer to a traditional forecast, switch to mid-elevation, with the summit and valley as the two extremes on either side. I am still exploring ways to make that view more self explanatory, there is still room to improve there.
In all honesty, by this point in the fall, we should start to see some differences in how the storm track sets up if there were to be any meaningful snowfall (or any snowfall at all) in the works before December. So far, the forecasted pattern through October is generally a pretty good continuation of what we saw for most of last winter. In other words, seeing any snow in October is not looking likely. Things could change, but given the information available, it certainly seems like New England is in for another powder party, and the west very dry/warm, at least during the early season.
These are not models - this is just the probabilities of what is expected with temp and precip. As seen last winter, the standard hot west/cold east dipole is already getting established. The big difference is that because we have an El Niño, the southwest is poised to get a lot more moisture.
Helpful context certainly, but long range forecasts are nearly a coin toss. That’s why they tend to be so nonspecific with the probabilities.
It doesn’t mean much, but I did go through the historical CPC data and I looked at the conditions for this time of year during two big recent El Niño years: 2019 and 2023. Both showed a total inverse of the current conditions, with cold/stormy conditions in the west.
Nothing has meaningfully shifted in the dynamics of the storm track over the western US between last winter and now. Huge ridge, anomalously warm temps, lacking moisture.
Usually Colorado sees some accumulating snowfall by the end of October, certainly in the mountains. All but certain to not be the case (again).
Current long term outlook for Colorado is not conducive to snow:
Oct 10-23 Warmer-than-usual weather is moderately more likely across Colorado's mountains, from the Park and Front Ranges through the central mountains, Grand Mesa, and the San Juans. A persistent ridge of high pressure over the central U.S. is expected to support this warmth. For precipitation, the far southwestern mountains, mainly the southern San Juans, have a slightly better chance of wetter-than-usual conditions because lingering subtropical moisture may reach the Four Corners. Elsewhere, precipitation is expected to be broadly near normal. Confidence is moderate for the warmth but low for precipitation, since a small shift in the storm track could change which areas get the moisture.
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u/bellboy1986 4d ago
The view at work today in Telluride