Dense Fog in California, December 7 to 8, 2001

Name: Dense Fog in California, December 7 to 8, 2001
Start: 2001-12-07T23:00
End: 2001-12-08T12:00
Location: California

December 7 to 8, 2001 · NWS HNX · 4 events in 4 counties and zones

Rather persistent fog formed around midnight in the Central and South San Joaquin Valley leading to widespread visibilities less than 1/4mile and locally as low as 200 feet.

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.

Rather persistent fog formed around midnight in the Central and South San Joaquin Valley leading to widespread visibilities less than 1/4mile and locally as low as 200 feet.

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 7, 8:15 PM PST, 2 hours 45 minutes earlier.

Area forecast discussion, Dec 7, 8:15 PM PST, 2 hours 45 minutes before

INTERIOR CENTRAL CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
815 PM PST FRI DEC 7 2001 ... PEARL HARBOR DAY

ONE NEAR TERM CONCERN FOR DENSE FOG FORMATION. DAY-SHIFT FELT THAT
STRONG OFFSHORE FLOW WOULD PROVIDE SUFFICIENT DRYING INFLUENCE TO
MINIMIZE THE INCREASE IN BREADTH AND WIDTH OF DENSE FOG TONIGHT.
HOWEVER TEMPS AND DEW POINTS INTO THE EVENING DO NOT APPEAR TO
PROVIDE ENOUGH DRYING TO PRE-EMPT FOG FORMATION. WITH ONLY MINIMAL
HIGH CLOUD COVER EXPECT RADIATIVE COOLING TO CLOSE TEMP/DEW POINT
SPREADS BEFORE MIDNIGHT IN MUCH OF THE VALLEY. HAVE ISSUED NON-
PRECIPITATION ADVISORY FOR DENSE FOG IN CAZ089>092 - CENTRAL AND
SOUTH SAN JOAQUIN VALLEY. AREA-OF-EXCEPTION WILL BE SOUTHEASTMOST
PORTION OF SJ VALLEY WHERE OFFSHORE FLOW IS PROVIDING DOWNSLOPE
DRYING/WARMING ONTO SOUTH VALLEY FLOOR. OTHER AREA OF CONCERN IS
GUSTY SOUTHEAST WIND IN THE TEHACHAPI MOUNTAINS IN RESPONSE TO STRONG
OFFSHORE PRESSURE GRADIENTS OVER SOUTH STATE. HOWEVER WIND LOOKS TO
REMAIN BELOW ADVISORY LEVELS FOR THE SOUTH KERN MOUNTAIN ZONE.

RIDGING ON SATURDAY OVER THE INTERIOR CENTRAL CALIFORNIA FORECAST
AREA TO GIVE WAY TO TROF PASSAGE EARLY SUNDAY. MODELS CONSISTENT IN
TIMING AND RELATIVE DEPTH OF THE TROF. MODELS ARE NOW DEPICTING THE
MAIN CENTER ABOUT 1-2 DEGS LONGTITUDE FARTHER EAST THAN RUNS 48
HOURS AGO. MODELS DO REMAIN CONSISTENT ON RATHER WEAK MOISTURE
FIELDS SO IT LOOKS TO BE A LOW QUANTITATIVE PRECIP EVENT. HOWEVER
PRELIMINARY OPINION IS THAT POPS ARE TOO LOW FOR SUNDAY IN THE
FORECAST. WILL FOCUS UPDATING ZONES TO REFLECT THE NPW FOR FOG
TONIGHT AND LET THE SUBSEQUENT SHIFT EVALUATE MOISTURE FIELD
FURTHER FOR ANY ADJUSTMENTS IN POPS.

BREEZY NORTHWEST-TO-NORTH WIND OVER THE HIGHER TERRAIN AND KERN
DESERTS LATE SUNDAY AND MONDAY IN THE WAKE OF THE TROF PASSAGE BUT
SURFACE GRADIENTS LIKELY TO MINIMIZE STRONG BREEZES ON THE VALLEY
FLOOR. NO OTHER CHANGES IN CURRENT FORECAST PACKAGE WITH RELATIVELY
HIGH HEIGHTS IN A DRY NORTHWEST FLOW TUESDAY UNTIL FRIDAY WHEN
THE NEXT SHORT-WAVE COMES OVER THE RIDGE AND DIVES OVER THE AREA.

HNX...DENSE FOG ADVISORY FOR CAZ89>92 CENTRAL AND SOUTHERN SAN
JOAQUIN VALLEY UNTIL 10 AM PST SATURDAY.

GUDGEL

Event by event

4 dense fog. Local standard time, as filed.

Dense Fog, Sw Sj Valley

When: December 7, 11:00 PM PST to December 8, 12:00 PM PST
Where: Sw Sj Valley forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

Dense Fog, Se Sj Valley

When: December 8, 2:15 AM PST to 12:00 PM PST
Where: Se Sj Valley forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

Dense Fog, W Central Sj Valley

When: December 8, 5:00 AM PST to 9:00 AM PST
Where: W Central Sj Valley forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

Dense Fog, E Central Sj Valley

When: December 8, 5:00 AM PST to 8:00 AM PST
Where: E Central Sj Valley forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

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

Every storm in California in 2001 Every state in 2001 This day in weather history Warnings in California, December 2001

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 2026-09-24. Each event’s entry at NCEI: 5276276, 5276277, 5276274, 5276275.