A shortwave ridge over central California provided for a night of clear skies and light winds. With inversion conditions prevailing over the valley, areas of dense fog formed during the early morning hours of December 8 reducing visibility to as lower a few hundred feet along the center portion of the valley.
Every event with a place to put it; 6 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.
A shortwave ridge over central California provided for a night of clear skies and light winds. With inversion conditions prevailing over the valley, areas of dense fog formed during the early morning hours of December 8 reducing visibility to as lower a few hundred feet along the center portion of the valley. The fog completely dissipated by late morning as an incoming trough mixed out the atmosphere.
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 7, 4:11 PM PST, 9 hours 44 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Hanford CA 411 PM PST Tue Dec 7 2021 Updated Air Quality Issues section .SYNOPSIS... Dry weather will remain in place for the next 24 hours before a more organized system impacts the region Wednesday night and Thursday. Sub-Freezing temperatures are likely in the Kern County deserts and most of the San Joaquin Valley Friday night and Saturday morning. A slow moving and robust storm system may impact the district early next week, bringing significant precipitation with it. && .DISCUSSION... The system that reached the area last night through this morning has exited the area this afternoon after dropping a couple hundredths of an inch of rain for a few areas across the San Joaquin Valley. Shortwave ridging will occur over the area for the next 24 hours, allowing for a brief period of dry weather across Central California. This may allow for patchy fog across the central valley tomorrow morning, but confidence of fog coverage and timing is very low. Otherwise, most of Wednesday should be a dry day with highs around 60 degrees across the valley. A trough of low pressure will dip down and reach the area Wednesday evening and will have much more moisture with it than the system that gave us sprinkles today. High resolution model guidance indicates widespread precipitation will occur across the region starting late Wednesday lasting through Thursday afternoon. Between the ample moisture and upsloping orographics in the Sierra Nevada, a decent bit of snow will fall with this system. Many areas above 7000 feet will be seeing 8-11 inches of snow, with some areas reaching 14 inches of snow. We have issued a Winter Weather Advisory valid at 7 PM Wednesday through 4 PM Thursday for the Sierra Nevada in our CWA. Some snow could fall over the Kern County Mountains/Passes, but certainty on that snowfall is low. Across the valley, one quarter to one half of an inch of rain is predicted to fall, with most of that occuring on Thursday morning. Cool, northwesterly flow should persist Friday, with dry conditions occuring. Model guidance is indicating that we may see sub-freezing temperatures for morning low across a good chunk of the SJ Valley on Saturday and Sunday morning due to the cold airmass overhead. NBM probabilistic guidance is showing around a 75-80% chance for freezing temperatures to occur Saturday morning across the valley. A Hard Freeze may occur in the Kern County Desert Saturday morning as well as temperatures dip into the low to mid 20's. Frigid lows are likely again on Sunday as the airmass there will not modify much. By early next weekly, ensemble guidance is indicating that a strong, slow moving storm system could reach the area. The upper low would be dropping out of the Gulf of Alaska and could bring quite a bit of valley rain and mountain snow to the area, especially on Monday night/Tuesday morning. If things pan out as model guidance is showing right now, there could be a window for convection in the valley Tuesday afternoon as well. We'll see how this unfolds in upcoming model runs though, as this event is still several days away. Stay tuned. && .AVIATION... MVFR to IFR ceilings and visibility in the SJ Valley from 00z Wednesday through 18z Wednesday in haze and mist. Otherwise, VFR conditions will prevail across the central CA interior for the next 24 hours. && .AIR QUALITY ISSUES... On Wednesday, December 8th, 2021, unhealthy in Kern County. Unhealthy for sensitive groups in Fresno, Kings, Madera, and Tulare Counties. Fireplace/wood stove burning status is: no burning unless registered in Kern (Greater Frazier Park Area), Kings, Merced, and Tulare Counties. No burning for all in Fresno, Kern, and Madera 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 and/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 PM Wednesday to 4 PM PST Thursday for CAZ323-326>331. && public...Bollenbacher aviation....Bollenbacher weather.gov/hanford
The national radar mosaic for the moment the first event began.
6 dense fog. Local standard time, as filed.
Visibility below a quarter mile was reported in Fresno. A trained spotter reported visibility of 200 feet in Sanger. Several webcams showed visibility below 1000 feet.
Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Visalia. A trained spotter reported visibility of 250 feet in Lindsay. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Hanford. California Highway Patrol was pacing traffic through the intersection of SR 99 and SR 198. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Lemoore.
Visibility below a quarter mile was reported in Madera.
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: 988304, 988305, 988307, 988306, 988303, 988302.