Friday, April 27, 2012

Is This Lake Effect?

With rain pelting my window and a cool, moist airmass in place, I slept like a baby last night.  In the mountains the storm delivered largely as advertised, laying down about 6" at the Alta-Collins site overnight, although snow water equivalents (SWE) were a bit higher than expected, totaling just over an inch.  

Some of the SWE fell as rain early in the storm.  In fact, as the front moved in, snow levels looked to be near 11,000 feet.  About .35 inches of SWE fell before temperatures at Alta-Collins fell to below freezing.    

The storm is now much colder with snow showers continuing over the Cottonwoods.  Fairly strong west to west-northwest winds are blowing at crest level, with gusts over the last 3 hours on Mount Baldy in the 60–70 mile per hour range.  Looking at the latest radar loop, I can't help but ask the question, "is this lake effect?"

Precipitation is falling mainly over high topography downstream of the Great Salt Lake.  That is an area where the terrain is higher than the terrain to the north, so perhaps this is just the result of the deeper lift.  On the other hand, maybe lake influences are also important.  

MesoWest data shows a very nice confluence zone over the northern Salt Lake Valley.  The flow over the northern Wasatch front has a bit more of a northerly component than the northwesterly flow over the Great Salt Lake.  Note also the westerly flow near the Saltair Marina just north of the Oquirrh Mountains.  

This could be an instance where both lake and mountain effects are working synergistically to produce the precipitation, as suggested in recent research by Trevor Alcott here at the U.  There seems to be a class of "lake-effect" events where both lake influences (which warms and destabilizes the airmass over and downstream of the lake) and convergence related to blocking by the northern Wasatch Mountains (i.e., the northerly flow evident above which is convergent with the northwesterly flow over and downstream of the lake) are necessary for precipitation generation.   Blocking by the Oquirrh Mountains can further contribute to this "funneling" effect.

So, is this lake effect?  Maybe.  I confess that I'm not sure how to best categorize it, but we'll figure it out eventually.  

No comments:

Post a Comment