Some Early Numbers

As reported by the Utah Avalanche Center at 7am this morning, the biggest winners so far in this storm are those areas typically favored in southwesterly to westerly flow including the northern Wasatch (storm totals ~16"), Upper Big Cottonwood (storm totals ~16-18"), and the Provo Area Mountains (storm totals ~16").  Upper Little Cottonwood lags a bit behind (storm totals ~8-10").

Time series of precipitation from Snowbasin-Middle Bowl and Alta-Collins show some interesting aspects of the early part of the storm.  First, it has come in pieces, with the bulk of accumulation coming from 0000-0900 MST 7 Feb (late Thursday night and Friday morning) and then from about 1600 MST 7 Feb - 0300 MST 8 Feb (Friday afternoon to very early Saturday morning).   Snow water equivalent (see blue line and accumulated precipitation scale at right) was nearly double at Snowbasin compared to Alta-Collins.  However, we had a trough passage early this morning and precipitation rates have picked up at Alta-Collins in the last couple of hours.

Source: MesoWest

Source: MesoWest

The storm total snow water equivalent at Alta-Collins since 0000 MST 7 Feb is about 0.7 inches.  For comparison, the 0000 UTC 7 Feb (1700 MST 6 Feb) initialized 12-km NAM called for about 1.2 inches, so at least so far the 12-km NAM has overforecast the event at Alta-Collins, as we suggested in earlier posts.  We will have to see, however, how things play out today and tomorrow as a series of troughs moves through.  These troughs will cause the crest-level flow to fluctuate back and forth from SW to NW and this, along with shifts in the area of maximum water vapor transport and dynamical forcing, means there will be a lot of variations in storm characteristics.  In the end, however, everyone will get some and we're still on track for the biggest storm of the season so far.  I'll also stick with my forecast from the two previous posts, which called for a storm total by 5 PM Sunday afternoon of 2-3.5 inches of water and 25-40 inches of snow at Alta-Collins.  The high end numbers there might be a bit optimistic at this stage, but I think we'll be able to get to at least 2 inches of SWE/25 inches of snow by then.