Although dry weather will continue through Friday, the ensembles are showing more and more signs of a pattern change that should usher in some precipitation beginning Saturday or Saturday night with more storms to follow.
Members of the European ensemble (ENS) generally bring in the precipitation the earliest, so I'll show the ECMWF HRES forecast (a member of the ENS) valid 1500 UTC 14 November (0800 MST Saturday) to illustrate the change. Although we are currently under the influence of an upper-level ridge, that ridge progresses slowly eastward over the next few days with a digging trough moving into the western United States and bringing precipitation into Utah on Saturday.
The overall pattern is one that we might expect to see a lot of this year with strong flow across the US southwest and overall flow splitting along the west coast. In the forecast above, the trough tracks far enough north to give us some precipitation. That said, the splitty nature of the pattern is one of the reasons for the forecast uncertainty over the next 10 days, with water equivalent and snowfall amounts varying depending on the track and intensity of the three major upper level troughs/storms expected to move through the west through November 21st.
The Utah Snow Ensemble Forecast is probably the most optimistic I've seen so far this season for Alta-Collins. 90% of the members produce at least 1.88 inches of water equivalent and 24 inches of snow through 0000 UTC 21 November. One thing worth noting is there is a good deal of disagreement on the first storm with some members producing scant amounts and others over 15" with a pretty good spread in between. Track will matter a lot for that storm on Saturday and Saturday night.
There are still some members keeping snow levels fairly high at times, but the median wet-bulb 0.5°C height, a rough proxy for snow level, is at or below 8000 feet once the storms start rolling in. We'll have to keep an eye on this. Again much depends on the track and intensity of the troughs.
Assuming we get some snow, avalanche and other hidden hazards (stumps, rocks, tree limbs, etc.) will lurk in the basement within or under the fresh snow. Let's be careful out there.
New Sounding Graphics for weather.utah.edu
I'm working on some new and improved model sounding graphics for weather.utah.edu and dropped in the first update for the HRRR last night. Given the uninteresting weather in the west, I'll use Jay Peak, VT as an example. The idea with these graphics is to provide information not only for deep convection (what most online soundings do) but also for mountain precipitation and precipitation type. Things like the wet-bulb zero height (WBZ), dendritic growth zone (DGZ), profiles of equivalent potential temperature and vapor transport (useful for anticipating orographic precipitation), integrated vapor transport (IVT), and melting and refreezing energy in the sounding are included. Also included are conditional probabilities for ice nucleation and winter precipitation types. Conditional means these are probabilities that apply only if precipitation occurs. They are not probabilities of that precipitation type occurring.
In the graphic above for Jay Peak, there is sufficient melt energy that any precipitation falling at model elevation would be liquid (if it is not hail which we are not considering here).
Later in the forecast, any precipitation falling at model elevation would be snow.
I think these are a significant upgrade. At some point I will provide a more complete overview of the soundings, but I'm up to my ears so to speak with other things. We will be updating the GFS soundings and adding RRFS soundings at some point, the GFS probably sooner than the RRFS.
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