As expected, the last 24 hours yielded colder temperatures and no
significant precipitation across the ARB. The current IR satellite loop
shows the main baroclinic cloud leaf extending NEward from the California
Bight into southern NV and all of UT. A second organized band of
enhanced IR cloud tops is moving across the Nern half of CA and reflects
the trailing 500-mb cold-core vorticity spoke dropping into the
developing Great Basin trough. However, there is presently no
significant precip beneath the cold cloud tops, based on the 88D
observations. All in all, it’s a rather dull winter day across the ARB.
The 12Z family of models are quite consistent with each other and with
previous runs regarding the western U.S. weather for the next few days.
The 500-mb trough is still progged to cut off over the Great Basin late
tonight and tomorrow, then remain nearly stationary or drift slowly Eward
during the first half of next week. Perhaps a little wrap-around precip
may affect the ARB this evening and tonight, but this shouldn’t amount to
much, given that 700-mb downslope flow will develop and strengthen.
Meanwhile, midtrop ridge building will occur over the eastern Pacific the
next several days. The ridge will likely weaken by midweek with the
approach of minoring-out shortwaves. Any way you slice it, it looks like
cool, mostly dry weather across the ARB through at least the Tuesday...
and probably into our hard-down holiday period starting on Friday.