An upper level low pressure system undercut the persistent ridge over California and approached southern California on December 23. This resulted in a period of increased downslope winds in the Fort Tejon and Tehachapi areas between the morning of December 23 and midday December 24.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HNX wrote it up.
An upper level low pressure system undercut the persistent ridge over California and approached southern California on December 23. This resulted in a period of increased downslope winds in the Fort Tejon and Tehachapi areas between the morning of December 23 and midday December 24. Several stations in these areas measured wind gusts exceeding 45 mph while a few locations measured brief gusts exceeding 60 mph.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at Dec 23, 5:32 AM PST, 5 hours 18 minutes earlier.
Area Forecast Discussion National Weather Service Hanford CA 532 AM PST Wed Dec 23 2020 .UPDATE... Visibility has improved in the Tehachapi area and the Dense Fog Advisory there has been cancelled && .SYNOPSIS... Generally dry and seasonably cool conditions will persist through Christmas Day. The San Joaquin Valley will continue to experience low cloudiness along with mist and fog. A low pressure system will bring a chance of rain and mountain snow Friday night through Saturday. A second system will arrive later on Monday with another round of rain and mountain snow. && .DISCUSSION... The San Joaquin Valley has been experiencing periods of widespread dense fog during the last few days thanks to trapped moisture from previous rainfall. That moisture remains in place, but a brush with shortwave energy dropping through the Great Basin area has helped to lift the fog into a stratus deck with occasional light drizzle and surface visibilities mostly running at least 1 mile or greater. In higher terrain where the loud deck is impacting the land, there have been some very low visibilities overnight, prompting a Dense Fog Advisory in the Tehachapi area through this morning. The stratus deck is typically persistent, but will erode in areas during the day today. Temperatures should top out around normal this afternoon, except Valley locations that remain socked in with clouds will be around 10 degrees cooler. The general pattern will continue into Christmas day under a sharp high pressure ridge in advance of a weak low pressure system approaching from the west. This weak trough is progged to swing inland by Thursday with little impact for central California, except possibly helping to scour out some of the fog/clouds in parts of the Valley. Increased easterly flow and some drier air in Kern County by this afternoon and evening will bump up fire weather concerns there a bit. Models drop a more significant frontal system through our area later Friday and Saturday, bringing rain and mountain snow. Certainty is not yet high on amounts, but snow accumulations around 5-10 inches at the higher elevations are conceivable. This system will be followed by another potentially more potent low pressure system early next week, bringing more rain and mountain snow. && .AVIATION... Low clouds and fog trapped in the San Joaquin Valley will create areas of IFR and local LIFR cigs and vsby during the next 24 hours, along with terrain obscurations in adjacent higher terrain. Elsewhere...VFR conditions are expected above the fog and low cloud deck and in the desert. && .AIR QUALITY ISSUES... On Wednesday December 23 2020... Unhealthy for sensitive groups in Fresno... Kern and Tulare Counties. Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Kings... Madera... Merced and Tulare Counties. No Burning For All in Fresno and Kern Counties. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information an/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... None. && public...JEB aviation....DCH weather.gov/hanford
6 high wind. Local standard time, as filed.
The Southern California Edison station at Cummings Valley measured a peak wind gust of 58 mph.
The Southern California Edison station at Rancho Ridge measured a peak wind gust of 66 mph.
The Pacific Gas and Electric station at Grapevine Road East measured a peak wind gust of 59 mph.
The Pacific Gas and Electric station at Pampa Peak measured a peak wind gust of 62 mph.
The Grapevine Peak RAWS measured a peak wind gust of 59 mph.
The Pacific Gas and Electric station at the Digier Road hilltop 5NE Lebec measured a peak wind gust of 71 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2020Every state in 2020This day in weather historyWarnings in California, December 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 925643, 925644, 925645, 925646, 925647, 925648.