Plenty of low level moisture and stable conditions under high pressure allowed dense fog to form each night and morning from January 11 to 16, 2015. In the days prior to this, there had been patchy fog, but it became more widespread throughout the San Joaquin Valley after a weak weather disturbance brought rain across Kern county on the January 10-11.
The dense fog formed in Kings and Tulare counties in the evening of January 11, then spread into Fresno, Madera, and Merced counties as well as south into Kern county by early morning on January 12. Visibilities dropped to less than 500 feet in many areas. The fog lifted in most areas by noon on January 12. Dense fog also developed on parts of the Kern county desert areas near Edwards AFB and Ridgecrest.
The fog quickly redeveloped in the early evening of January 12 and continue through the morning of January 13 with widespread visibilities below 1/4 mile and many areas reporting visibility below 800 feet. The fog cleared between 10 AM and noon.
The worst of the fog occurred on January 14, with dense fog developing around midnight, but not clearing until nearly 2 pm. There were numerous school bus delays due to the dense fog and California Highway Patrol was pacing traffic on area highways. A major traffic accident occurred in Visalia involving three vehicles and resulting in major injuries to two people.
The dense fog redeveloped on the evening of January 14 and continue through noon on January 15. It then quickly redeveloped early evening on the 15th, but lifted above 1/4 mile by 3 am on the 16th as a weak disturbance moving by to the north helped to lift the fog into a stratus deck.

Dense Fog in E CENTRAL S.J. VALLEY, CALIFORNIA
From 12-JAN-15 02:45:00 to 12-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in E CENTRAL S.J. VALLEY, CALIFORNIA
From 15-JAN-15 16:00:00 to 16-JAN-15 03:04:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in SW S.J. VALLEY, CALIFORNIA
From 11-JAN-15 22:00:00 to 12-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in SE S.J. VALLEY, CALIFORNIA
From 11-JAN-15 19:15:00 to 12-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Visibility less than 100 feet in Bakersfield.

Dense Fog in SW S.J. VALLEY, CALIFORNIA
From 15-JAN-15 16:00:00 to 16-JAN-15 03:04:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in INDIAN WELLS VLY, CALIFORNIA
From 11-JAN-15 21:45:00 to 12-JAN-15 09:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Public

Visibility less than 300 feet on US395 in Ridgecrest.

Dense Fog in SE KERN CTY DESERT, CALIFORNIA
From 12-JAN-15 06:52:00 to 12-JAN-15 09:09:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Visibility 1/8 mile at Edward AFB.

Dense Fog in W CENTRAL S.J. VALLEY, CALIFORNIA
From 12-JAN-15 18:45:00 to 13-JAN-15 10:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in E CENTRAL S.J. VALLEY, CALIFORNIA
From 14-JAN-15 00:00:00 to 14-JAN-15 12:15:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. Fresno Airport visibility less than 1/16 mile resulting in flight delays.

Dense Fog in E CENTRAL S.J. VALLEY, CALIFORNIA
From 12-JAN-15 18:45:00 to 13-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet.

Dense Fog in SW S.J. VALLEY, CALIFORNIA
From 13-JAN-15 23:30:00 to 14-JAN-15 13:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. CHP pacing on State Route 43.

Dense Fog in SW S.J. VALLEY, CALIFORNIA
From 12-JAN-15 18:43:00 to 13-JAN-15 10:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet.

Dense Fog in W CENTRAL S.J. VALLEY, CALIFORNIA
From 14-JAN-15 00:00:00 to 14-JAN-15 12:15:00 (PST-8)
Crop damage: 0.00K
Reported by: Law Enforcement

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. CHP pacing on State Route 41.

Dense Fog in SE S.J. VALLEY, CALIFORNIA
From 13-JAN-15 23:30:00 to 14-JAN-15 13:30:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet.

Dense Fog in SE S.J. VALLEY, CALIFORNIA
From 12-JAN-15 18:12:00 to 13-JAN-15 10:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 800 feet.

Dense Fog in E CENTRAL S.J. VALLEY, CALIFORNIA
From 14-JAN-15 18:15:00 to 15-JAN-15 11:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. CHP pacing traffic on much of Highway 99.

Dense Fog in W CENTRAL S.J. VALLEY, CALIFORNIA
From 14-JAN-15 20:00:00 to 15-JAN-15 11:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. CHP pacing on Interstate 5 in Merced and Fresno counties.

Dense Fog in SW S.J. VALLEY, CALIFORNIA
From 14-JAN-15 19:50:00 to 15-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet. Visibility at KNLC reported near zero.

Dense Fog in INDIAN WELLS VLY, CALIFORNIA
From 12-JAN-15 18:20:00 to 13-JAN-15 08:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Trained Spotter

Patchy fog with visibility near 100 feet in Ridgecrest.

Dense Fog in W CENTRAL S.J. VALLEY, CALIFORNIA
From 12-JAN-15 06:00:00 to 12-JAN-15 12:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Dense Fog in SE S.J. VALLEY, CALIFORNIA
From 14-JAN-15 19:50:00 to 15-JAN-15 12:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Mesonet

Widespread visibility less than 1/4 mile with areas of visibility less than 500 feet.