Two systems will impact the region thru the weekend. The first storm will push in late Thursday into early Friday with generally light showers. A stronger storm will bring widespread mountain snowfall to the northern half of Utah late Saturday into Sunday.
Short Term Forecast
Our first system is moving in today, Thursday. This is a weaker storm but it will serve to cool us down a bit, bring a few showers to the region and "prime" the atmosphere ahead of a stronger system for the weekend. Expect some showers later this evening into the overnight hours. Snow levels will be higher but the peaks could pick up a quick inch or two of snow overnight.
The next storm is much more interesting. This storm pushes in late Saturday, lasting Saturday night into Sunday. There is plenty of moisture, dynamics, and cold air. We should see snow levels crash down to 5000 ft or perhaps even lower by Sunday morning.
How much snow? Latest model projections show the following QPF:
The spine of the Wasatch is in yellow which represents over an inch of liquid. When you convert it to snow it looks something like this:
This is a lower resolution model and I think there is some issue with the mapping of this GFS, but it gives a general idea of high snowfall amounts. I would not expect as much snow in PC area as this model is portraying. Again, I think there are some resolution/mapping issues going on.
Perhaps a better way to look at snowfall amounts is graphically. Here is the latest 12km NAM output:
This is for the Cottonwood Canyons. Notice the first storm tonight brings a couple inches, then an additional 6+ inches thru midday Sunday. This model cuts off, so I'd expect more snow beyond the model range. We can look farther but checking the GEFS plumes:
Every GFS ensemble (dark green lines) brings at least an inch of QPF, with the mean at about 1.4" thru the end of the weekend. Using this, I would say 10-15" of snow is certainly possible for some high elevations by Monday.
The other factor is lake-effect or enhanced snowfall. The GFS and NAM both show this possibility with the NAM currently giving up to a 76% shot at lake effect snow impacting the area south and east of the GSL. This time of year, it doesn't take to much to fire up lake effect. This could add to totals on Sunday -- something to watch.
Overall, this is a healthy Fall snowstorm. We usually get at least one of these storms every October. You may lament the end of Fall in the high country, or the potential weak, faceted layers from storms like this. But more often than not we see these storms and it's just a fact of life in Utah, where winter starts early.
High pressure will, for the most part, re-establish itself next week. We are generally looking at a period of benign weather to close out October. We shall wait and see if that pattern flips again as we move into November.
Evan | OpenSnow
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