Although the high pressure center over the Great Basin began to retrograde westward on December 3, areas of dense fog formed during the evening in the San Joaquin Valley Merced and Madera Counties. The fog spread southward overnight and by daybreak much of the valley was covered by a large area of dense fog.
Every event with a place to put it; 8 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.
Although the high pressure center over the Great Basin began to retrograde westward on December 3, areas of dense fog formed during the evening in the San Joaquin Valley Merced and Madera Counties. The fog spread southward overnight and by daybreak much of the valley was covered by a large area of dense fog. The fog lifted into a low cloud deck across most of the valley by afternoon with some locations east of SR 99 and west of interstate 5 clearing out.
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 3, 4:32 PM PST, 4 hours 3 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Hanford CA 432 PM PST Fri Dec 3 2021 .UPDATE... Updated AIR QUALITY ISSUES section. && .SYNOPSIS...Dry conditions will prevail across the area through the weekend, although a cooling trend will take place. A storm moving north of our area will bring a slight chance of precipitation on Monday night. Seasonably cool and dry conditions will prevail on Tuesday and Wednesday. A low pressure system will impact the area late next week bringing precipitation chances and much cooler temperatures. && .DISCUSSION...Some dense fog formed overnight in portions of Merced, Madera and Fresno Counties in the central San Joaquin Valley this morning resulting in several accidents as visibility was reduced to near zero in some locations. The fog finally dissipated giving way to a mostly sunny afternoon with just some high clouds streaming through our area from the east. A rex block pattern over CA has maintained an offshore flow over our area with dry conditions and unseasonably warm temperatures prevailing once again today. SREF is indicating that a change from this nearly persistent pattern will take place this weekend as the low to our south ejects inland and moves through the Desert Southwest region while the Great Basin high shifts offshore and amplifies resulting in a dry northerly flow over central CA which will bring a cooling trend to our area over the weekend with daytime temperatures lowering to near seasonal normals by Sunday. The NBM has been trending further north with an inside slider type system which is progged to drop through the Great Basin and push a cold front through central CA on Monday night. This system will bring a brief period of increased winds to the wind prone areas in Kern County and a slight chance of precipitation to the Sierra Nevada on Monday evening. Latest NBM probabilistic guidance is indicating that Yosemite Valley only has a 14 percent chance, Tuolumne Meadows a 17 percent chance and Shaver Lake a 15 percent chance of measuring 0.01 inches or more of liquid precipitation on Monday evening. High pressure then is progged to strengthen offshore on Tuesday and Wednesday which will result in a dry northwest flow over central CA maintaining dry weather and near normal temperatures. Medium range ensemble means and the NBM are showing a cold upper low pressure system dropping southward into central CA on Thursday which will bring cooler than normal temperatures along with precipitation chances to our area on Thursday and Thursday night with scattered showers continuing into Friday. && .AVIATION...In the San Joaquin Valley, widespread MVFR conditions with areas of IFR visibility due to haze/mist between 09Z and 18Z Saturday. Otherwise, VFR conditions will prevail across the Central CA interior for the next 24 hours. && .AIR QUALITY ISSUES... On Saturday December 4 2021...Unhealthy in Kings County. 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 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... None. && public/aviation/fire...DS pio/idss...Molina weather.gov/hanford
The national radar mosaic for the moment the first event began.
8 dense fog. Local standard time, as filed.
Visibility below a quarter mile was reported in Atwater, Merced and Madera. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Hanford. Several webcams showed visibility below 1000 feet.
Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Visalia and Porterville. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Delano. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Fresno. Several webcams showed visibility below 1000 feet.
Visibility below a quarter mile was reported in Bakersfield.
Visibility below a quarter mile was reported in Lemoore. Several webcams showed visibility below 1000 feet.
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: 988105, 988108, 988111, 988109, 988107, 988106, 988110, 988104.