Winter Weather in Tulare Cty Foothills, California

Once the early January storm passed through the region, persistent high pressure, along with a fairly strong inversion layer above the area began to set up by the 3rd. This initially created foggy conditions by the evening of the 3rd throughout the central and southern San Joaquin Valley, albeit patchy in nature.

With abundant standing water on the San Joaquin Valley floor, dense fog developed during the night of January 4th-5th. The fog lifted into a stratus layer that blanketed the San Joaquin Valley during the afternoon of the 5th, with the stratus persisting through the night of the 8th-9th.

Locations in the mountains rose to above normal temperatures, while those in the San Joaquin Valley remained consistently below normal, or from the upper 30s to lower 40s, even into the daylight hours during the period from the 4th through the 9th.

An upper-level trough that moved through California, on the 8th-9th, had little impact on the stratus, other than to raise the bases of the clouds. This resulted in the stratus spreading into the Southern Sierra Nevada foothills, creating areas of fog. Temperatures in the foothills fell below freezing during the morning of January 10th, and moisture from the fog froze to create icy road surfaces.