Monday, October 5, 2015

Stuck Between Two Regimes

Precipitation over the western United States over the next week is strongly dominated by two regimes.  The first is associated with the deep upper-level trough moving across the southwest U.S. over the next few days that will result in frequent shower and thunderstorm activity.  The second develops later this week as moist southwesterly flow penetrates into the Pacific Northwest.  

The mean precipitation produced over the next 7 days by the North American Ensemble Forecast System (NAEFS) shows these two regimes quite nicely with the largest accumulations over the Southwest and the Northwest.    
NAEFS mean precipitation 0000 UTC 5 October – 0000 UTC 12 October 2015
Northern Utah is just on the fringe of the more monsoonal regime, but misses out on the precipitation over the Northwest.  Thus, our best chance for precipitation in northern Utah is through tomorrow evening as we are brushed by the upper-level trough.  

Because we're stuck between the two regimes, we won't be seeing skiable snow for at least another week.  The NAEFS forecast plume below is for Alta and shows the precipitation through tomorrow afternoon, after which it's pretty much flatlined (i.e., dry).  It's cold enough that the higher elevations may see a dusting or light coat if there's a strong shower, but that's about it.  

No worries.  Best if it holds off for a bit longer.  

1 comment:

  1. The closed low currently to our south looks like a good example of a type of system that is common right around this time of year, and contributes to the October precipitation maximum in parts of eastern Utah (Moab, for example). Some locations have a fairly distinct peak in climatological precipitation from late September until mid October which I thought was curious and unexpected when I first noticed it.