First Part Of December Looks Interesting

Global models forecast the development of a long-wave, cold and intense trough at 500 mb that remains over the West for much of the first part of December. Shown here are the GFS ensemble means at 500 mb - above valid at 12 UTC December 2nd and below valid at 00 UTC December 7th.

By days 6 and 7 as many as 8 of 12 GFS members are forecasting precipitation over the Southwest. Some of the members forecast a wet plume of subtropical air into this region - as per surface and precipitation forecast below, valid at 12 UTC on December 4th. Looks like an interesting start to the last month of 2013.