ForecastWeak Wave Tonight, Stronger Storm Monday PM to Tuesday, Another Wave on FridaySome mountain ranges should see double digit snow totals as we start the coldest three months of the year.
- Storm tonight expected to bring 3-6" of snow to some northern mountain ranges, 5" or less most elsewhere.
- Very windy later Sunday, with 60-80mph gusts possible along and east of the Divide.
- Storm on Monday PM to Tuesday could bring double digit totals to some areas. Favored areas are the Park Range, the Flat Tops, west of Vail Pass, the high Elk Mountains, and the northern Front Range near Cameron Pass. Analogs and some models would suggest a good showing for Wolf Creek, but uncertain if the jet will dig far enough south (it's trending that way).
- More snow on Friday/Saturday, and the pattern leans towards the snowier side into December.
Hello and welcome to what is (on average) typically the start of the coldest three month spell that Colorado experiences.
While we were out on vacation, we missed the fact that tonight's weak wave is coming in a little stronger than expected, which should be good for a few inches of snow in the mountains by tomorrow morning, at least Colorado's northern and easternmost ranges.
We have better moisture and dynamics with this storm, but it's a quick hitter. In fact, there looks to be considerably more moisture associated with this storm than the Monday to Tuesday system -- it's just that this one is more progressive.
Though Colorado as a whole should see snow from 6pm today to 6am tomorrow, most areas will really only experience about 6 hours of decent snowfall.
We expect about 3-6" for parts of the Park Range and the along/east of the northern Divide (e.g. Medicine Bow Mountains, Cameron Pass, RMNP, IPW, and parts of the foothills there).
Totals may lessen further south than that -- from Berthoud Pass to Hoosier Pass to Vail Pass (much of Summit County), maybe 2-5".
Parts of the Mosquito Range and eastern Sawatch may get into that range but likelihood of decent snow drops as you look further southwest, where less atmospheric moisture is available. Higher terrain further west along I-70, and south towards Aspen (the Elk Mountains, Grand Mesa, West Elks) only 1-4". In the San Juans, only 0-3", but better further east, with 1-4" for the Sangres.
No significant accumulations are expected east of the foothills, except on the Palmer Divide and perhaps a bit south towards Colorado Springs. That said, some models have been playing around with some interesting surface dynamics, such as the Euro, which is forecasting a small area of 2-5" in the northwest Denver metro area -- this seems quite dubious and not what we would expect from this sort of flow regime.
The sun should come out on Sunday morning, but blustery conditions will prevail across the higher terrain and start blowing some of this new snow around. Winds will intensify into Sunday evening and night, when gusts of up to 80mph are possible along and east of the Divide as a jet max moves over Colorado, ahead of our next system.
Next Storm: Monday to Tuesday
A stronger storm is dropping out of the Pacific Northwest and should be stronger and slower than tonight's system, though the atmosphere is a bit drier.
On a larger scale, snowfall across Colorado will depend on how far south the jet stream sags. Right now the general model consensus is that central and northern Colorado should be well within the jet left exit region (favorable dynamics), but the jet may not drop far enough south for those better dynamics to reach the San Juans and Sangres. Thus, we see that the central and northern mountains are favored for higher snow totals.
Snow will start in northwestern Colorado on Monday afternoon, and the heaviest snow will hit the higher terrain after sunset. This will taper off after 6am on Tuesday as the trough axis moves past us, but pockets of snow will hold on in the mountains into Tuesday afternoon where west-northwesterly orographics are favored.
A cold front will also push down the Front Range on Monday night, with Tuesday's highs expected to be quite cold. This might bring a couple inches of snow to the I-25 corridor on Tuesday morning, with some areas of heavier snow possible for Tuesday morning's commute.
There are five areas most likely to see heaviest snow: The Park Range, the Flat Tops, west of Vail Pass, the high Elk Mountains, and the northern Front Range near Cameron Pass.
There is a potential sixth area: Wolf Creek. Again, this depends on the jet dropping far enough south. Models don't have good agreement about whether it will or not (it's close), so forecasts for Wolf Creek range from a few inches (~5" on the Euro model) to 12"+. We'll lean towards something a bit snowier as the trend does have this system coming in a little deeper.
If we look at analogs for this system, it looks like our forecast is generally in line with how similar systems have performed.
A key difference is near Wolf Creek, which shouldn't be surprising considering what we discussed earlier. Will they go big?
Wednesday and Thursday should be dry, but then things get interesting again.
The most important aspect of the general pattern as we get into December is that a very strong ridge is expected to form over Greenland -- and this is quite a significant signal on the ensembles, meaning it's very likely to occur and likely to be quite strong.
This will help drive troughing over the United States. That troughing may end up predominately over the eastern United States, but it should at least start over the western United States.
We'll likely see a bout of zonal flow (likely southwesterly) starting Friday of next week. Initially, we could be in the jet right entrance region which would drive snowfall from Friday to Saturday.
It's hard to tell where exactly the jet will be after this weekend, but this looks to be slightly favorable for snow in Colorado that following week. We'll see!
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