Clear skies, light winds and a temperature inversion allowed for locally dense fog to form in portions of the San Joaquin Valley during the morning of December 11. The fog completely dissipated by late morning.
Every event with a place to put it; 2 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.
Clear skies, light winds and a temperature inversion allowed for locally dense fog to form in portions of the San Joaquin Valley during the morning of December 11. The fog completely dissipated by late morning.
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 10, 4:47 PM PST, 10 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Hanford CA 447 PM PST Fri Dec 10 2021 .UPDATE... Updated AIR QUALITY ISSUES section. && .SYNOPSIS... Dry and cool conditions will prevail through Saturday. Freezing temperatures are expected across much of the San Joaquin Valley tonight with sub freezing conditions in the Kern Desert. A slow moving storm system may bring significant precipitation from late Sunday night through Tuesday. Active weather may continue through next week. && .DISCUSSION... Very cold conditions are expected to occur this evening with temperatures dropping into the upper 20's in the SJ Valley with temperatures lowering into the lower 20's in the Kern County Desert. This is not surprising given the time of the year and with the dry airmass overhead that allows for significant radiational cooling at night. Dry weather is expected to continue into Sunday as the flow aloft shifts from northwesterly to westerly. Things start to get interesting through the afternoon on Sunday as a strong storm system begins to dip down from the Gulf of Alaska. While dry conditions are expected through most of the afternoon on Sunday, some light flurries may begin to fall in the higher elevations around YNP by late morning. Snowfall intensity will likely pick up by later in the evening on Sunday in Mariposa and Madera counties as the cold front slowly sags south. At the same time, light rain will begin to fall in the valley, mainly in Merced County. Valley rain and mountain snow will continue on Monday, and will increase with intensity and coverage as the front creeps southward towards the CWA. The front should pass through late Monday through early Tuesday, which will lead to periods of moderate to heavy rain in the valley, with high snowfall rates in the mountains. Snow levels generally will remain above 5000 feet through Tuesday morning. After the front exits the region on Tuesday, there could be a window of opportunity for post-frontal convection in the San Joaquin Valley, with small hail being the main threat. Afternoon thunderstorms are highly dependent on surface temperatures though, so we will need clear out by late morning to get a good shot at valley thunderstorms. Rainfall forecast totals through Tuesday are as follows: 1.25" to 2.25" in the valley north of Kern County, with values mostly below 1" of rain in the valley portion of Kern County. Snowfall will be measured by the foot, with elevations above 5,000 feet in the Sierra Nevada seeing 1 to 4 feet of snow totals, with isolated amounts of 6 to 8 feet at elevations above 8000 feet. Snow should remain above pass level in Kern County. Another system appears to be on the heels of the Monday/Tuesday storm, that could impact the district later in the week next week. This system does not appear to have the same moisture tap as this upcoming storm, through. Either way, the pattern is expected to remain active through the next week. && .AVIATION...VFR conditions will prevail across the central CA interior for the next 24 hours. && .AIR QUALITY ISSUES... On Saturday December 11 2021... Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno... Kern... Madera and Tulare Counties. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is high. 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... Hard Freeze Warning from 11 PM this evening to 9 AM PST Saturday for CAZ337-339. Hard Freeze Watch from Saturday evening through Sunday morning for CAZ337-339. Winter Storm Watch from late Sunday night through late Tuesday night for CAZ323-326>331. Freeze Warning from 11 PM this evening to 9 AM PST Saturday for CAZ301>303-305-306-309>312-315-316. && public...Bollenbacher aviation....Bollenbacher weather.gov/hanford
The national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Visibility below a quarter mile was reported in Visalia.
Visibility below a quarter mile was reported in Merced.
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: 988895, 988894.