Dense Fog in California, December 16 to 20, 2011

The next storm moved into California on December 15th. Rain fell as far south as Madera on the east side of the San Joaquin Valley, but fell along the length of the west side of the Valley with light rain falling as far south as Bakersfield. This case of rain shadowing resulted in Fresno remaining dry while measurable rain fell to the north, west and south of the city. The trace of rain that fell at Meadows Field on December 15th-16th was the only rain for Bakersfield for the month of December, tying for the third driest December on record.

Showers continued over the Kern County deserts into the 17th. A couple of evening showers drifted northwest across the Tehachapi Mountains, bringing light rain as far north as Wheeler Ridge. Another system dropped south along the California coast the next day, moving inland on December 19th. Although this system only brought some clouds to the state, it was the ridge that developed behind the trough that brought extreme cold to the central and southern San Joaquin Valley.

The Tule fog returned to the San Joaquin Valley after the trough pushed east of the state. Fog development occurred for the next several days over the San Joaquin Valley; while the higher elevations, including the Sierra Nevada, nearby foothills, and the desert areas, generally had plenty of sunshine. An inside-slider trough moved over the Great Basin and allowed the upper-level ridge to weaken by the 21st of the month.