It's déjà vu all over again if you are a meteorologist with another digging trough (or if you prefer "splitting") forecast to move across the western US this weekend.
The last one gave us 8" at Alta-Collins, with another inch yesterday. The current snow depth sitting at 8". I don't think they've bothered firing up the guns yet so the base remains scant even on the Mamba-Corkscrew trails.
The GFS forecasts the 700-mb trough to be right over Salt Lake City at 0600 UTC (0000 MDT) Sunday. As I mentioned the trough is a digger and a splitter, so a the strongest "dynamics" or large-scale rising motion, is to our south over Arizona (the red contour indicates large-scale rising motion of 1.5 cm/s).
Although not a direct hit, the models are generating precipitation over northern Utah as the front moves through (see upper-right panel above) and then a period of cold northwesterly flow on Sunday as the trough moves downstream (see below).
Total water equivalent and snowfall generated by the GFS through 11 PM MDT Sunday at Alta-Collins are 0.99" and 14.3", respectively. A look at the Utah Snow Ensemble shows that 06Z 4 Nov (just an hour later as the ensemble forecasts are only processed every 6 hours), the ENS Mean is about 0.6"/9" and GEFS mean about 0.8"/12".
This reminds me a good deal of the last storm in that it is not all that well put together, but there is some potential if the band with the trough and the post-frontal northwesterlies come through. I'm once again thinking something in the 8-14" range, although if I were a wagering man, I might say the odds of going more than that are bit greater than less than that. This is also indicated by the plume diagrams above which show a lot of clustering between 8 and 12" of snow and then about 10 members that er in the 15-21" range by 06Z 4 Nov.
There is some potential for another storm midweek next week.
Really liking Utah Snow Ensemble, thx for fab effort. Wetbulzero violin charts are a great add, like the brown shading below station elevation. Looks like skiing begins tomorrow if storm verifies ... though the older I get the less interested I am in driving LCC during storms. Thx again for all your great work.
ReplyDeleteJust noticed you are not doing wetbulbzero. You are doing Wet-Bulb 0.5 C. Probably you answered this question, but 0.5 C is the actual rain/snow line, 1000 feet below wetbulbzero
DeleteLCC guidance is still wetbulbzero. Is that right or have you gone wetbulbzero accross all models but haven't re-labeled LCC guidance output.
DeleteAnswers to all your questions at https://wasatchweatherweenies.blogspot.com/2024/09/the-utah-snow-ensemble.html.
DeleteWB0.5 is the level at which we begin to decrease our estimated SLR. We decrease it linearly from that level to 200 m below that level.
If you use the RRFS Snow Ensemble that we've just posted up we do this differently using a more physics based approach. I'll probably post about this at some point, but have simply been to busy of late.
"The way these troughs are behaving is fascinating! The digger-splitter combo definitely keeps things unpredictable. Thanks for the detailed analysis."
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"Thanks for the insight on the storm potential midweek. Hoping this trend of weekly snowfall continues and sets up a solid base for the season!"
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