The loop below presents the 700-mb (near crest level) temperatures and winds from 2200 UTC (4 PM MDT) yesterday to 1500 UTC (9 AM MDT) this morning. We've transitioned from warm southwesterly flow with 700 mb-temperatures near +3ºC, leading to a maximum temperature yesterday of 68ºF, to northwesterly flow with 700-mb temperatures near -6ºC.
Those current 700-mb temperatures, when combined with the high precipitation rates we are currently experiencing, are sufficient to bring snow levels down to the valley floor. We are currently seeing heavy snow comprised of large aggregates (i.e., large snowflakes formed by the sticking of snowflakes together) at the University of Utah.
I took that photo about 10 minutes ago and since then the snow is piling up fast. In addition, although the ground is warm, snowfall rates are high enough that snow is sticking on some untreated asphalt and concrete surfaces.
Radar shows not a heck of a lot upstream to our northwest (i.e,. over the northern Great Salt Lake), but the band currently over us is moving very slowly.
That makes this a very tricky forecast. A slow moving band of high intensity can lay down a lot of snow in a hurry, especially on colder surfaces (accumulations today will depend strongly on where you measure). For the University of Utah, I think accumulations of 2-4 inches on colder surfaces are likely today, with snowfall greatest over the next two hours. Ultimately, accumulations will depend on how long the band holds on with lesser amounts if it fizzles and greater amounts if it hangs on.
It looks like tonight could bring a decent lake effect snow event. There is already evidence of some of this on radar at late morning, just behind the cold front.
ReplyDeletewe had ~9" at Snowbird by the time I left at 2pm.
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