With high pressure remaining dominant over central California, dense fog reformed over much of the San Joaquin Valley during the early morning of January 10. The fog impacted travel near Hanford for a short time during the morning as traffic was paced by law enforcement on State Routes 198 and 43.
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.
With high pressure remaining dominant over central California, dense fog reformed over much of the San Joaquin Valley during the early morning of January 10. The fog impacted travel near Hanford for a short time during the morning as traffic was paced by law enforcement on State Routes 198 and 43. The fog dissipated by late morning as the ridge axis shifted east some which allowed for the inversion to break earlier in the day.
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 Jan 9, 4:03 PM PST, 9 hours 22 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Hanford CA 403 PM PST Sat Jan 9 2021 Updated Air Quality Issues section .SYNOPSIS... High pressure to build over the forecast area through next week, which will be conducive towards fog and low clouds in the San Joaquin Valley and clear skies elsewhere. Dry conditions are expected into the foreseeable future as afternoon high temperatures warming up in areas outside the San Joaquin Valley next week. && .DISCUSSION... Considerable amount of San Joaquin Valley low clouds have eroded or are in a state of dissipation and this will allow for quite a bit of clearing by this evening. The only area that should stay locked in under the low clouds is Kern County where the cloud cover should preclude dense fog development. A dense fog advisory has been issue for parts of the normally fog favored and clear evening sky areas of the San Joaquin Valley. Remainder of forecast unchanged. && .AVIATION... MVFR with mist and haze through 08z then becoming IFR to LIFR in fog after 10z with fog at terminals. Otherwise, VFR conditions will prevail over the central California interior during the next 24 hours. && .AIR QUALITY ISSUES... On Sunday, January 10th, 2021, 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. && .PREV DISCUSSION... /issued 1224 PM PST Sat Jan 9 2021/ .SYNOPSIS... High pressure to build over the forecast area through next week, which will be conducive towards fog and low clouds in the San Joaquin Valley and clear skies elsewhere. Dry conditions are expected into the foreseeable future as afternoon high temperatures warming up in areas outside the San Joaquin Valley next week. && .DISCUSSION... Water vapor satellite imagery shows very high amplitude ridge over the region with just a few high clouds streaming into the Central California Interior. In the San Joaquin Valley, a very common pattern is in place today with low level morning fog and low clouds as low level moisture remains trapped in the boundary layer. With the low level clouds persisting over the east side of the San Joaquin Valley, the big trick in the forecast is whether the remainder of the clouds erode enough to dissipate by late in the day. If the clouds dissipate, then another widespread fog event will transpire as all of the ingredients will remain in place and the clearing will allow for a quick radiational cooling this evening to below the dew point. If some clouds remain, the clear areas will realize more fog while the cloudy areas have better visibility under a stratus deck. Will need to watch satellite trends and assess the situation later this afternoon. Over the remainder of the forecast area it remains unfortunately for January...clear. Speaking of clear, forecast models for the next 10 days keep a blocking ridge in place off the California coast thus the storm track will remain way to the north and dry weather will prevail. Heights with this ridge are progged to reach in excess of 5850 meters and this will allow for areas which receive sun to get temperatures well above normal for mid January. To the contrary, if low level moisture remains trapped in the SJV cloudy, cool and dank weather may persist through this period. && .AVIATION... MVFR with mist and haze through 08z then becoming IFR to LIFR in fog after 10z with fog at terminals. Otherwise, VFR conditions will prevail over the central California interior during the next 24 hours. && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is high. 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... Dense Fog Advisory from 10 PM PST tonight until 11 AM PST Sunday morning for CAZ180>188. && public...Dudley aviation....Dudley weather.gov/hanford
5 dense fog. Local standard time, as filed.
Hanford reported visibility below a quarter mile. California Highway Patrol reported visibility between 200 and 500 feet between 10th Ave and the Tulare County line and was pacing traffic between 0650 PST and 0826 PST.
Visalia reported visibility below a quarter mile. California Highway Patrol reported visibility between 200 and 500 feet on SR 99 north of Delano on SR 99 between 0344 PST and 0427 PST.
Lemoore reported visibility below a quarter mile.
Merced and Madera reported visibility below a quarter mile.
Reedley reported visibility below a quarter mile.
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, January 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: 928489, 928491, 928488, 928487, 928490.