Dense Fog in California, December 7 to 11, 2014

Name: Dense Fog in California, December 7 to 11, 2014
Start: 2014-12-07T21:35
End: 2014-12-11T01:00
Location: California

December 7 to 11, 2014 · NWS HNX · 13 events in 4 counties and zones

Stable conditions under a ridge of high pressure resulted in areas of dense fog developing in the San Joaquin Valley each night from December 7 through 11. On the evening of December 7, the dense fog began in the center of the valley from Merced to Hanford, then spread throughout the valley after midnight with widespread visibility less and 1/4 mile except at Fresno and Bakersfield.

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 13

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.

Stable conditions under a ridge of high pressure resulted in areas of dense fog developing in the San Joaquin Valley each night from December 7 through 11.

On the evening of December 7, the dense fog began in the center of the valley from Merced to Hanford, then spread throughout the valley after midnight with widespread visibility less and 1/4 mile except at Fresno and Bakersfield. Visibility lowered to less than 200 feet at times, resulting in the California Highway Patrol pacing traffic on area highways. The fog cleared by mid-morning on December 8.

Dense fog redeveloped quickly after sunset on December 8, and became widespread during the evening, including the Fresno and Bakersfield areas. Parts of Kings and Kern counties had near zero visibility. There were many school bus delays due to the fog. The dense fog lasted until around noon.

The was a repeat of the dense fog on the evening of December 9 lasting until mid-morning on December 10. As a storm system approached the area bringing clouds across the region on afternoon of December 10, dense fog was limited only to the south end of the San Joaquin Valley, where visibility in Kern County fell to less than 1/4 mile for a only few hours, lifting around 2 am.

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, 6:31 PM PST, 3 hours 4 minutes earlier.

Area forecast discussion, Dec 7, 6:31 PM PST, 3 hours 4 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
631 PM PST SUN DEC 7 2014

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL TODAY BEFORE ANOTHER WEAK WEATHER SYSTEM
SKIRTS ACROSS THE NORTHERN PORTION OF THE STATE ON MONDAY. A MUCH
STRONGER STORM IS EXPECTED BY LATE IN THE WEEK BRINGING A THREAT OF
PRECIPITATION TO MUCH OF THE AREA.

&&

.DISCUSSION...
QUICK UPDATE TO THE GRIDDED FORECAST TO INCREASE FOG COVERAGE
TONIGHT. SOME OF THE VALLEY STATIONS ARE ALREADY AT 2-3SM VISBY AS
OF 6PM. XOVER TEMPS LOOK VERY ATTAINABLE TONIGHT. SUCCESSIVE HRRR
RUNS ARE INCREASINGLY PESSIMISTIC WITH VISBY VALUES TOWARD THE AM
COMMUTE TIME. DESPITE HIGH CLOUDS THINKING FOG IS FAIRLY LIKELY TO
FORM. DENSEST FOG LIKELY ALONG THE BOTTOM OF THE VALLEY FROM
ROUGHLY CORCORAN TO LEMOORE TO MERCED. COULD SEE SOME IMPACT TO
I5/99 CORRIDORS BUT MORE LIKELY...AS USUALLY...WILL BE ALL THE
ROADS CRISS-CROSSING THE CENTRAL VALLEY.

SEE MAP ON OUR FACEBOOK PAGE OR TWITTER FEED.

&&

.PREV DISCUSSION... /ISSUED 243 PM PST SUN DEC 7 2014/

DISCUSSION...
A WEAK FRONTAL BAND AND A COUPLE OF UPPER DISTURBANCES BRINGING
LOTS OF MID AND HIGH CLOUDS ACROSS CENTRAL CALIFORNIA. LITTLE
MEASURABLE PRECIPITATION EXPECTED. LIMITED AND PATCHY FOG
EXPECTED AS CLOUD COVER SHOULD MITIGATE FOG FORMATION. FOG MAY BE
A BIT MORE PREVALENT TUESDAY NIGHT WITH A SHORT WAVE RIDGE AND
CLEARER CONDITIONS.

MEDIUM RANGE MODELS ARE INDICATING A STRONG STORM SYSTEM WILL
AFFECT CALIFORNIA AT THE END OF THE WORKWEEK. FORECAST CONFIDENCE
IS MEDIUM AT THE MOMENT. DUE TO TIMING DIFFERENCES IN THE
OPERATIONAL MODELS. GFS IS ABOUT A DAY MORE PROGRESSIVE THAN THE
ECWF. THE ENSEMBLE MEANS OF BOTH MODELS FAVOR THE SLOWER SOLUTION
OF THE EC. THUS WILL SLOW THE ONSET OF PRECIPITATION TO LATE
THURSDAY INTO CENTRAL CALIFORNIA. MODELS ALSO DEVELOP STRONG N-S
SURFACE PRESSURE GRADIENTS ACROSS CENTRAL AND NORTH CALIFORNIA
AHEAD OF THE FRONT. HIGH WIND POTENTIAL WILL BE PROBABLE AHEAD OF
THE STORM ESPECIALLY ALONG THE WEST SIDE OF THE SAN JOAQUIN VALLEY
AND TEHACHAPIS ALONG THE GRAPEVINE AREA. BOTH OP MODELS PROG S
FLOW AROUND 50KT ALONG THE CENTRAL COAST. WIDESPREAD PRECIPITATION
WILL BE LIKELY WITH CURRENT MODELS ESTIMATING 1-2 FEET OF NEW
SNOW OVER THE SOUTHERN SIERRA NEVADA. RAINFALL AMOUNTS OVER THE
BURN SCARS NEAR YOSEMITE ARE FORECAST TO BE AROUND AN INCH...AND
ROCK AND DEBRIS FLOWS ARE POSSIBLE.

THE STORM IS FORECAST TO MOVE EAST OF CALIFORNIA SATURDAY NIGHT INTO
NEXT SUNDAY FOR A RETURN OF DRY WEATHER AND MORE CHANCES FOR NIGHT
AND MORNING SAN JOAQUIN VALLEY FOG.

&&

.AVIATION...
IN THE SAN JOAQUIN VALLEY...PATCHES OF MVFR VISIBILITIES IN MIST AND
LOCAL IFR CONDITIONS IN FOG FROM 08Z THRU 18Z MONDAY. OTHERWISE
EXPECT VFR CONDITIONS TO PREVAIL OVER THE CENTRAL CALIFORNIA
INTERIOR OVER THE NEXT 24 HOURS.

&&

.AIR QUALITY ISSUES...
ON MONDAY DECEMBER 8 2014... FIREPLACE/WOOD STOVE BURNING STATUS
IS: NO BURNING UNLESS REGISTERED IN KERN AND KINGS COUNTIES.
FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG

&&

.CERTAINTY...

THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS MEDIUM.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM.

THIS INFORMATION IS PROVIDED AS PART OF A TRIAL PROJECT CONDUCTED
BY THE NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD.
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT
WWW.WEATHER.GOV/HNX/CERTAINTY.PHP /ALL LOWER CASE/ FOR ADDITIONAL
INFORMATION AND/OR TO PROVIDE FEEDBACK.

&&

.CLIMATE...
             RECORDS
SITE DATE    HI_MAX:YEAR LO_MAX:YEAR HI_MIN:YEAR LO_MIN:YEAR

KFAT 12-07       69:1937     42:1965     52:1950     25:1978
KFAT 12-08       77:2006     42:1965     50:1897     25:1978
KFAT 12-09       70:1950     38:1972     53:1902     23:1972

KBFL 12-07       76:1907     41:1965     53:1950     24:1912
KBFL 12-08       83:1915     43:1965     52:1949     24:1903
KBFL 12-09       74:1979     36:1972     52:1955     24:1923
&&

.HNX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

PUBLIC...INIGUEZ
AVN/FW...DUDLEY
PREV DISCUSSION...MV
SYNOPSIS...BSO

WEATHER.GOV/HANFORD

Hazardous weather outlook, Dec 7, 10:56 AM PST, 10 hours 39 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
1056 AM PST SUN DEC 7 2014

CAZ089-091-095-081900-
WEST CENTRAL SAN JOAQUIN VALLEY-SOUTHWESTERN SAN JOAQUIN VALLEY-
KERN COUNTY MOUNTAINS-
1056 AM PST SUN DEC 7 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WEST SIDE OF THE SAN
JOAQUIN VALLEY AND ADJACENT MOUNTAIN AREAS AS WELL AS THE
GRAPEVINE VICINITY.

...STRONG WINDS POSSIBLE THURSDAY THROUGH FRIDAY...

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER EXPECTED.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

* WINDS: SOUTH TO SOUTHWEST WINDS GUSTING IN EXCESS OF 60 MPH
  POSSIBLE.

* TIMING: THURSDAY AFTERNOON THROUGH FRIDAY MORNING.

* LOCATIONS INCLUDE: GRAPEVINE, TEJON RANCH BUSINESS PARK,
  COTTONWOOD PASS ALONG HIGHWAYS 41 AND 46, COALINGA, AVENAL, LOS
  BANOS, PACHECO PASS ALONG HIGHWAY 152. INTERSTATE 5 FROM
  GRAPEVINE TO THE STANISLAUS COUNTY LINE.

* IMPACTS: DANGEROUS TRAVEL FOR HIGH PROFILE VEHICLES. POTENTIAL
  FOR DOWNED TREES AND POWER LINES. ROOFING DAMAGE DUE TO LOST
  SHINGLES. OTHER OBJECTS THAT COULD BECOME AIRBORNE.

* FOLLOW TWITTER @NWSHANFORD, FACEBOOK AT US NATIONAL WEATHER
  SERVICE HANFORD CA, OR TUNE TO NOAA WEATHER RADIO...OR YOUR
  FAVORITE NEWS SOURCE...FOR FURTHER INFORMATION.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION IS NOT ANTICIPATED.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT OR
UNUSUAL CONDITIONS TO THE NATIONAL WEATHER SERVICE.

DUDLEY

Event by event

13 dense fog. Local standard time, as filed.

Dense Fog, E Central S.J. Valley

When: December 7, 9:35 PM PST to December 8, 9:30 AM PST
Where: E Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, W Central S.J. Valley

When: December 8, 2:00 AM PST to 9:30 AM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Sw S.J. Valley

When: December 8, 2:00 AM PST to 9:30 AM PST
Where: Sw S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Se S.J. Valley

When: December 8, 7:00 AM PST to 9:30 AM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, E Central S.J. Valley

When: December 8, 5:45 PM PST to December 9, 1:00 PM PST
Where: E Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Sw S.J. Valley

When: December 8, 5:45 PM PST to December 9, 11:00 AM PST
Where: Sw S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Se S.J. Valley

When: December 8, 7:15 PM PST to December 9, 11:00 AM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, W Central S.J. Valley

When: December 8, 9:22 PM PST to December 9, 11:00 AM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Se S.J. Valley

When: December 9, 3:55 PM PST to December 10, 9:30 AM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Sw S.J. Valley

When: December 9, 5:56 PM PST to December 10, 9:30 AM PST
Where: Sw S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, E Central S.J. Valley

When: December 9, 10:00 PM PST to December 10, 9:30 AM PST
Where: E Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, W Central S.J. Valley

When: December 10, 2:00 AM PST to 9:30 AM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Se S.J. Valley

When: December 10, 11:20 PM PST to December 11, 1:00 AM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

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 2014 Every state in 2014 This day in weather history Warnings in California, December 2014

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: 550697, 550696, 550698, 550699, 550701, 550702, 550703, 550700, 550707, 550706, 550705, 550704, 550708.