Winter Storm and Winter Weather in California, February 27 to 29, 2012

The first in a series of three upper-level troughs reached the California coast on February 25th. Although this storm did not bring any precipitation to the central California interior, it did cool temperatures back to near normal for all areas except the deserts.

The second trough approached California the following day. This system split as it neared the coast, with the southern part diving southward parallel to the coast before turning onshore during the evening. As this system moved into southern California, it brought snow to the Kern County mountains. Up to 4 inches fell on the Tehachapi Mountains at the pass level, and Interstate 5 over the Grapevine was closed for several hours during the afternoon of February 27th. Trace amounts of snow fell on Grocer Grade in the Temblors and at Glennville in the Southern Sierra Nevada. Bakersfield received 0.12 inch of rain from the storm, nearly doubling its rainfall for February.|The northern part of this storm moved into northern California on the 27th.

Upper-level disturbances rotating around the low moved into the central California interior during the late afternoon, triggering showers that continued into the late evening. One shower strengthened as it moved off the Diablo Range into the western San Joaquin Valley, and dropped hail on Interstate 5 northeast of Coalinga. Snow fell as low as the 3000-foot level in the Southern Sierra Nevada, and Lodgepole received 3 inches of new snow. Further north, Yosemite Valley reported an inch of snow.

The storm moved into the Great Basin during the early morning hours of February 28th. With available ground moisture, a few patches of fog formed in the central and southern San Joaquin Valley. Otherwise, it was dry in the San Joaquin Valley with temperatures near to a few degrees warmer than the previous day (except at the south end of the Valley where clouds cleared and there were several degrees of warming).

The third storm approached the northern California coast during the afternoon of February 28th. A strong upper-level jet dived under the low, and pushed the storm inland during the evening. This storm had better dynamics than its predecessors, and thunderstorms developed along the cold front while it was off shore, continuing as the front moved onto the coast. The storm mainly affected northern California, but it did drop slowly southward during the day on the 29th. Measurable rain finally reached Fresno late in the afternoon of February 29, and Kings and Tulare Counties shortly thereafter. It was locally windy on the west side of the San Joaquin Valley, and over the Kern County mountains and deserts. Nearly a foot of snow fell on the high country of Yosemite National Park, and the Park Service reported that 4 to 6 inches of snow fell of the floor of Yosemite Valley. Further south, up to 9 inches of snow fell in the Southern Sierra Nevada high country in Fresno County, and Lodgepole in Sequoia National Park reported 5 inches of new snow.

The rain that fell at Fresno-Yosemite International Airport on Leap Day, 0.27 inch, accounted for over a third of the total February rainfall at Fresno (0.75 inch), and was close to the total for February at Meadows Field, Bakersfield (0.29 inch). Despite the series of storms at the end of February, the central California interior’s rainfall remained well below normal, both for the month and for the rain season. Average temperatures for February were slightly above normal at both Bakersfield and Fresno.