|February 25 2023
Major West Coast Winter Storm: (2/23/22 - 2/25/23)
By: Zack Taylor, WPC Meteorologist
A significant and impactful winter storm brought widespread precipitation to portions of the West Coast during the last week of February, 2023. This storm was noteworthy for a variety of weather hazards and impacts, particularly for low elevation snow levels that led to measurable snowfall in locations unaccustomed to such accumulations.
The synoptic setup featured an anomalously deep and cold mid-level trough over much of the Western U.S. that eventually formed into a closed low off the Pacific Northwest coast by the 23rd. This low then expanded and moved southward along the California coast, ushering in a surge of Pacific moisture through the 25th. A strong cold front swept through the region on the 21st-22nd, bringing much below normal temperatures and setting the stage for winter precipitation. The combination of upper-level diffluence and the closed low led to widespread precipitation. As the core of the upper low lingered near the California coast, a reinforcing blast of cold air brought snow levels down, especially in and around the Bay Area, where levels dropped below 1000 feet, and in some cases, as low as 200-400 feet. The storm system then moved southward, delivering heavy precipitation to parts of southern California, including significant snowfall in lower elevations unaccustomed to such conditions. By late on the 26th, the center of the upper-level low had moved eastward toward the Desert Southwest, bringing an end to the most significant precipitation in the region.
Snow totals were particularly impressive in California, with isolated storm totals exceeding 50 inches, such as Pinecrest with 59” and Big Bear Lake with 57”. Many other locations in northern California and the Sierra Nevada saw impressive 3 to 4-foot amounts. The powerful storm led to whiteout conditions, closing roads and stranding motorists in mountainous areas. The heavy, wet nature of the snow caused power outages and downed trees. The unusually cold nature of the storm brought snowfall and impacts to areas unaccustomed to such accumulations. The National Weather Service office in Monterey, California reported highway closures in and around the Bay Area, with amounts totaling near a foot (Los Gatos 11” and Calistoga 9”).
As the system moved southward, unusual low snow levels were observed into central and southern California. Even beaches in Santa Cruz, CA experienced a dusting of snow, and the mountains of southern California saw dangerous near-blizzard conditions. In addition to the heavy snow, lower elevations in southern California experienced heavy rainfall and flooding, with many locations receiving over 5” of rainfall during the storm. Isolated total rainfall amounts in excess of 9” were reported in the foothills of southern California, including Altadena and Topanga California.