California, 2021Dense Fog in California, December 3, 2021
December 3, 2021 · NWS HNX · 4 events in 4 counties and zones
Little change in the upper air pattern occurred from the previous day. Clear skies, light winds and inversion conditions in the San Joaquin Valley allowed for areas of dense fog to form in Merced, Madera and Fresno Counties in the central San Joaquin Valley during the early morning hours and the fog resulted in several multi-vehicle accidents including two which had fatalities.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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- Deaths
- 2
- Injuries
- 3
- Property damage
- $400,000
- Crop damage
- None recorded
- Events
- 4
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.
Little change in the upper air pattern occurred from the previous day. Clear skies, light winds and inversion conditions in the San Joaquin Valley allowed for areas of dense fog to form in Merced, Madera and Fresno Counties in the central San Joaquin Valley during the early morning hours and the fog resulted in several multi-vehicle accidents including two which had fatalities. Traffic was paced during the morning commute on SR 99 north of Madera and several school districts had delayed openings. The fog lifted into a low cloud deck by late morning and dissipated during the afternoon.
What forecasters said that 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 Dec 2, 5:41 PM PST, 7 hours 34 minutes earlier.
Area forecast discussion, Dec 2, 5:41 PM PST, 7 hours 34 minutes before
Area Forecast Discussion
National Weather Service Hanford CA
541 PM PST Thu Dec 2 2021
.UPDATE...
Updated AIR QUALITY ISSUES section.
&&
.SYNOPSIS...High pressure and an offshore flow will bring
unseasonably warm temperatures to the area through Friday. Dry
conditions will prevail through the weekend although a cooling
trend will take place over the weekend. A storm moving north of
our area will bring a slight chance of precipitation Monday night
and Tuesday.
&&
.DISCUSSION...Persistent rex block pattern prevailing over CA
with a large high pressure center over the Great Basin and a dry
upper low centered off the Baja coast. This is producing a dry
offshore flow over central CA is providing our area with
unseasonably warm daytime temperatures as well as some high clouds
which are streaming into our area from the east. The pattern is
expected to remain the same on Friday. Some patchy fog formed this
morning for an hour or two in Merced County. Otherwise our area
was fog free this morning. The prevailing dry airmass and offshore
flow along with the lack of low level moisture will inhibit fog
formation tonight and any morning fog on Friday will be very
localized. With the unseasonably warm and dry airmass remain over
the area on Friday, daytime temperatures will be well above
normal once again. Latest NBM probabilistic guidance is indicating
the Bakersfield has a 69 percent chance of reaching 70 Deg F or
higher and Fresno has a 27 percent chance of reaching 70 Deg F or
higher on Friday.
The high is progged to retrograde westward over the weekend as
the low ejects inland into northern baja and then across southern
AZ. This will result in a dry northerly flow over our area and a
gradual cooling trend taking place on Saturday and Sunday with
temperatures lowering to near seasonal normals by Sunday.
The medium range ensemble means are indicating the upper ridge
axis shifting further offshore by Monday as a cold upper low
drops out of the Gulf of AK and into the PAC NW. This system will
drop through the Great Basin on Monday night taking an inside
slider trajectory and push a cold front through central CA. The
main impact from this system will be increased winds across the
wind prone areas Monday night through early Tuesday. This system
will also provide for a slight chance of light precipitation in
the Sierra Nevada and adjacent foothills during this time frame.
Shortwave ridging is progged to return on Wednesday before a very
cold low pressure system drops southward out of western Canada on
Thursday and bring chances of precipitation and potentially much
colder temepratures to our area by the end of next week.
&&
.AVIATION...In the San Joaquin Valley, widespread MVFR conditions
with areas of IFR visibility due to haze/mist between 09Z Friday
and 18Z Friday. Otherwise, VFR conditions will prevail across the
Central CA interior for the next 24 hours.
&&
.AIR QUALITY ISSUES...
On Friday December 3 2021... Unhealthy in Fresno and Kern
Counties. Unhealthy for sensitive groups in Kings... Madera and
Tulare Counties. Fireplace/Wood Stove Burning Status is: No
Burning Unless Registered in 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 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...DS
aviation....Castro
weather.gov/hanford
Dense Fog, Merced-Madera-Mendota
- When
- December 3, 1:15 AM PST to 11:25 AM PST
- Where
- Merced-Madera-Mendota forecast zone
- Deaths
- 0 direct, 1 indirect
- Property damage
- $250,000
- Reported by
- ASOS
- Coordinates
- 37.056, -120.043 (the zone’s center; the record gives no point)
Visibility below a quarter mile was reported in Atwater, Merced and Madera. Several webcams showed visibility below 1000 feet. California Highway Patrol was pacing traffic on SR 99 for several hours during the morning. California Highway Patrol also reported several fog realted multiple car accidents west of Chowchilla where visibility was below 100 feet. One accidents at the intersection of SR 152 and Ave. 9 at 836 PST resulted in one fatality. Several school districts either opened late or delayed or cancelled bus service.
Dense Fog, Caruthers - San Joaquin - Selma
- When
- December 3, 2:00 AM PST to 11:00 AM PST
- Where
- Caruthers - San Joaquin - Selma forecast zone
- Deaths
- 0 direct, 1 indirect
- Injuries
- 0 direct, 3 indirect
- Property damage
- $100,000
- Reported by
- Department of Highways
- Coordinates
- 36.489, -119.224 (the zone’s center; the record gives no point)
Several webcams showed visibility below 1000 feet. California Highway Patrol reported a two vehicle accident involving a semi-trailer and a Chevrolet Astro minivan on SR 145 between Jensen Ave. and North Ave. 3 miles south of Kerman at 658 PST. The driver of the Astro was killed in the accident and the three passengers were injured. Visibility was reported to be below 100 feet at the time of the accident. California Highway Patrol reported also reported another fog related collision at the intersection of SR 145 and North Ave. at 728 PST which involved three vehicles. Several school districts either opened late or delayed or cancelled bus service.
Dense Fog, Fresno - Clovis
- When
- December 3, 7:00 AM PST to 8:00 AM PST
- Where
- Fresno - Clovis forecast zone
- Property damage
- $50,000
- Reported by
- Law Enforcement
- Coordinates
- 36.758, -119.649 (the zone’s center; the record gives no point)
California Highway Patrol reported visibility below 200 feet west of Fresno in fog which resulted in a collision between a semi-trailer and white Ford Pickup at the intersection of North Brawley Ave. and West Belmont Ave. There were no injuries as a result of the collision although both vehicles sustained damage.
Dense Fog, Hanford - Corcoran - Lemoore
- When
- December 3, 7:05 AM PST to 7:45 AM PST
- Where
- Hanford - Corcoran - Lemoore forecast zone
- Reported by
- ASOS
- Coordinates
- 36.351, -119.421 (the zone’s center; the record gives no point)
Visibility below a quarter mile was reported in Hanford.
- Dense Fog
- Fog reducing visibility to a quarter mile or less, filed where it caused accidents or disruption.
After NWS Directive 10-1605, the rules offices file Storm Data by.
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: 988099, 988101, 988102, 988100.