Monday, March 5, 2012

Change You Can Believe In

Change you can believe in is coming to the Wasatch, at least with regards to temperature.  Snow?  I'm not sure what to believe yet.

First, let's start with today, which like yesterday should be spectacular and perhaps even a few degrees warmer.  The need to apply and reapply sunblock is evinced by all the blotchy red faces I've seen amongst my adventuresome students today.

Things get interesting tomorrow.  As we discussed on Saturday, the GFS called a strong cold front to move through Utah, while the NAM was out in left field as it has been all year.  As usual, the NAM has finally shifted to a GFS-like solution and both models are now calling for a strong cold front to develop and move into Utah late tomorrow.  The GFS, for example, puts the cold front right on Salt Lake's doorstep by 5 PM MST tomorrow.

For those of you keeping score at home, the 700-mb (crest-level) temperature contrast across the front is massive with -2C at the leading edge of the front and -18C creeping into southwest Idaho.  Strong winds may kick up some dust over southwest and western Utah and Nevada.

An issue for the snowfall forecast is that the upper-level trough doesn't progress directly through Utah, but instead digs southward toward Vegas, taking the cold air and heaviest precipitation with it.

All sorts of things could happen in the Wasatch in such a pattern.  If a good frontal band develops and it pivots over us as the trough digs, we could get several inches of snow.  On the other hand, sometimes the band stalls and fizzles in patterns like this before it gets to us and we're skunked (this is what the NAM calls for).  Finally, on Wednesday, as the trough lifts through Utah, we could get a period of precipitation in the easterly flow (sometimes called wrap-around precipitation), as suggested by the GFS.

The bottom line is that we will see temperature change we can believe in late tomorrow.  For snow, we're just gonna have to see.  This is the type of pattern where I expect the worst and hope for the best. Regardless of what happens with the white stuff, it's going to be a very interesting couple of days meteorologically.

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