Friday, February 2, 2024

Storm Update

 Precipitation moved into northern Utah last night producing lowland rain and upland snow.  As of 6 AM, the Alta-Collins automated sensor was up to 6" of moderately high density snow with .66" of water (11% water content).  High density at this stage is good to smooth things out and bury the hard underlying surface.  

Radar at 6:46 AM showed widespread precipitation over the Great Salt Lake and much of northwest Utah.  The Cottonwoods and the central Wasatch were seeing some snowshowers, but were in a bit of a lull.  

That lull should, however, be short lived as the trough moves in from the west.  The HRRR, for example, keeps the central Wasatch on the edge of the action through about 1500 UTC (8 AM).  

But then it swings the trough in with widespread precipitation over all of northern Utah by 1800 UTC (11 AM).

So, snow today, possibly heavy at times, especially with the trough passage.  It is fairly mild out there this morning.  It is 32F at Spruces campground, so the freezing level is around 7000-7500 feet (the snow level would be below this), but temperatures will gradually fall today.  

The HRRR-derived forecast guidance for upper Little Cottonwood summarizes the situation quite well.  The precipitation and snowfall time series on the bottom show the morning lull through about 8 or 9 AM, but then higher precipitation and snowfall rates during the day and into the evening, adding an additional 8" of snow or so to what has already fallen.  The wet-bulb zero (upper right), gradually lowers throughout the day reaching about 6500 feet by 2 PM and 5500 feet by 8 PM.  Thus, snow levels will be lowering to bench levels by late afternoon or evening.  Finally, snow-to-liquid ratios gradually increase, although they hang in there around "average" values (~13:1) for this afternoon.  

I like 6-12" more through 8PM tonight at which point we'll have to see if the post-frontal magic can kick in overnight.  

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