About Last Night

A little lake-effect action last night has made a mess of the morning commute. It's been a while since we've had this much valley snowfall, so let's take a look at what happened. 

On the large-scale, there was a weak trough passage that occurred early this morning.  This trough was accompanied by deep instability and moisture, with precipitation enhanced over the Great Salt Lake.  

This transition is clearly seen in upper-air soundings from the Salt Lake City International Airport.  Yesterday afternoon it was well mixed in the lowest levels with a 700-mb (10,000 ft) temperature of -17˚C.  However, the sounding was also fairly dry and it was absolutely stable in the mid levels above 700 mb.  Thus, conditions were not favorable for the development of deep precipitation clouds, although you could find a few snow showers from shallow clouds in the mountains.  

This mornings sounding is only slightly colder at 700 mb (18˚C), but is much colder in the mid levels above 700 mb.  It is also has more moisture.  

I'm not sure if the radar loop below will successfully load in Blogger (I will try to update if this happens).  You may need to hit play twice.  If it loads, you will see some snowshowers moving from the northwest at the start of the event, the initiation of lake-effect snowshowers to expand and enhance those snow showers, and eventually a shift to northerly flow with the lake becoming the primary locus of snowshower initiation.  At the conclusion of the loop, given the northerly flow, lake-effect is confined to the eastern Tooele Valley.  

Sadly, the heaviest action was in the western Salt Lake Valley, Oquirrh Mountains, and eastern Tooele Valley.  In the central Wasatch, I suspect the most snow fell in in the Lone Peak area based on the radar.  As of 7 am this morning, an Alta-Collins reported a total of one inch with a temperature of...wait for it...-2˚F.