California, 2018

Dense Fog in California, December 19, 2018

December 19, 2018 · NWS HNX · 4 events in 3 counties and zones

High pressure prevailed over California on December 19. While stratus kept fog from forming in Merced County and in the south end of the valley, dense fog prevailed over portions of the central and south San Joaquin Valley for much of the morning, but had dissipated at most locations by around 900 am PST.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
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.

What happened

The episode as NWS HNX wrote it up.

High pressure prevailed over California on December 19. While stratus kept fog from forming in Merced County and in the south end of the valley, dense fog prevailed over portions of the central and south San Joaquin Valley for much of the morning, but had dissipated at most locations by around 900 am PST.

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 18, 1:16 PM PST, 10 hours 59 minutes earlier.

Area forecast discussion, Dec 18, 1:16 PM PST, 10 hours 59 minutes before
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Event by event

4 dense fog. Local standard time, as filed.

Dense Fog, Se S.J. Valley

When
December 19, 12:15 AM PST to 2:35 AM PST
Where
Se S.J. Valley forecast zone
Reported by
AWOS

Visibility below a quarter mile was reported in Visalia.

Dense Fog, E Central S.J. Valley

When
December 19, 5:21 AM PST to 8:35 AM PST
Where
E Central S.J. Valley forecast zone
Reported by
ASOS

Visibility below a quarter mile was reported in Fresno and Madera.

Dense Fog, Se S.J. Valley

When
December 19, 6:50 AM PST to 8:54 AM PST
Where
Se S.J. Valley forecast zone
Reported by
AWOS

Visibility below a quarter mile was reported in Visalia. A few school districts opened late or delayed bus service.

Dense Fog, Sw S.J. Valley

When
December 19, 7:20 AM PST to 8:35 AM PST
Where
Sw S.J. Valley forecast zone
Reported by
ASOS

Visibility below a quarter mile was reported in Hanford. A few school districts opened late or delayed bus service.

What these are

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.

The same day elsewhere

More

Every storm in California in 2018Every state in 2018This day in weather historyWarnings in California, December 2018

Sources

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 2026-10-01. Each event’s entry at NCEI: 790144, 790142, 790145, 790143.