A large area of high clouds continues to spill southward into NorCal ahead of a weak short-wave trough moving across the PacNW. The clouds are resulting in milder temperatures early this morning with current readings ranging from the upper 20s and 30s in the mountain valleys to the mid 40s to lower 50s across the Central Valley.
Very little change in the overall weather pattern is expected through the end of the week as the Rex Block evolves along the West Coast. This will keep the storm track well to the north. High temperatures will continue to be well above average and overnight lows will be chilly on Valley floors beneath strong surface inversions, while foothill and mountain ridges will remain mild at night.
Extended Discussion (Sunday through Wednesday)
A prominent upper ridge will continue to control the synoptic pattern into early next week supporting warm, dry conditions.
An omega block setup is the culprit which has favored above average 500-mb heights over the western U.S. One aspect of the forecast to keep an eye on is the potential for amplified flow crossing east of the region next Tuesday/Wednesday (November 12/13). Most notably, the 00Z ECMWF ensemble means as well as a few preceding operational runs have shown this scenario unfolding. This would enhance a period dry, northerly flow across Northern California.
However, there is a great deal of uncertainty given not all ensemble systems agree on the evolving pattern. Until then, warm temperatures will remain the norm with daily highs running 10 to 15 degrees above climatology, locally higher. Although optimal radiational cooling under the ridge should keep mornings on the cooler side except around the thermal belts.
By the middle of next week, temperatures run a few degrees cooler than the weekend but remain above average.