Following the departure of the slow moving low pressure system which brought low elevation snowfall to portions of central California and disrupted holiday travel on December 29 and 30, upslope flow over the Tehachapi Mountains resulted in low clouds banking up producing dense fog in the Tehachapi Valley and to the north of Tejon Pass along interstate 5 which further disrupted holiday travelers…
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
Following the departure of the slow moving low pressure system which brought low elevation snowfall to portions of central California and disrupted holiday travel on December 29 and 30, upslope flow over the Tehachapi Mountains resulted in low clouds banking up producing dense fog in the Tehachapi Valley and to the north of Tejon Pass along interstate 5 which further disrupted holiday travelers during the evening of December 30 until the early afternoon of December 31. In addition, areas of dense fog formed for a few hours in the San Joaquin Valley where skies cleared out, disrupting travel along SR 99 during the morning of December 31 until the fog lifted into a low cloud deck.
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 30, 2:53 PM PST, 3 hours 42 minutes earlier.
Area Forecast Discussion National Weather Service Hanford CA 253 PM PST Thu Dec 30 2021 .SYNOPSIS... Rain and snow over the Kern Tehachapi mountains and desert area will diminish this evening. Cold and dry weather is expected for the weekend. High pressure will then build over the region bringing a return of fog across the San Joaquin Valley for next week. && .DISCUSSION... A trough off the Channel Islands continues to provide showers over Kern County Mountains and desert this afternoon. Precipitation should diminish during the evening as the trough moves SE towards the Baja coast. A winter weather advisory was extended until 6PM due to low elevation snow near pass level. Observation at Sandburg has turn from moderate snow to rain this hour. Hopefully this will allow the opening of Highway 5 over the Grapevine area. The threat of fog will return tonight as the Central CA Interior will be in between weather systems. A drier trough will move through the Great Basin Friday bringing a cold and dry airmass into the area. This will bring breezy north winds across the area with strong gusty winds possible through and below the mountain passes of the Kern CO mountains and desert Friday afternoon and night. Temperature near freezing will be possible ove the weekend. Higher resolution models show some upslope precipitation over the Kern County mountains late Friday and night. Any snowfall near pass level should be light. Ensemble progs have trended weaker with the next storm and keep precipitation accumulations toward North CA leaving central CA dry. Otherwise a ridge over the West Coast will maintain dry conditions with threat of fog in the valley each night and morning. && .AVIATION... MVFR with areas of IFR conditions due to fog are likely across the San Joaquin Valley and lower Sierra Foothills over the next 24 hours. Mountain obscuration with areas of IFR conditions are expected in the Kern CO Mountains until 12z. && .AIR QUALITY ISSUES... None. && .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... Winter Weather Advisory until 6 PM PST this evening for CAZ333>336. && public...MV aviation....DCH weather.gov/hanford
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HANFORD CA
449 PM PST THU DEC 30 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0402 PM DEBRIS FLOW 4 SW LAKE ISABELLA 35.58N 118.52W
12/30/2021 KERN CA LAW ENFORCEMENT
CALIFORNIA HIGHWAY PATROL REPROTED A LARGE
BOULDER ON OLD KERN RIVER CANYON RD.
&&
DSThe national radar mosaic for the moment the first event began.
5 dense fog. Local standard time, as filed.
Visibility below a quarter mile was reported in Tehachapi. California Highway Patrol reported visibility below 1000 feet in the Tehachapi area along SR 58.
Visibility below a quarter mile was reported in Hanford.
Visibility below a quarter mile was reported in Visalia.
California Highway Patrol paced traffic on Interstate 5 south of Fort Tejon to Tejon Pass as a result of visibility below 1000 feet.
Visibility below a quarter mile was reported in Fresno.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, December 2021
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: 990853, 990851, 990852, 990855, 990850.