Dense Fog and Winter Weather in California, December 11 to 14, 2012

Name: Dense Fog and Winter Weather in California, December 11 to 14, 2012
Start: 2012-12-11T00:00
End: 2012-12-14T11:00
Location: California

December 11 to 14, 2012 · NWS HNX · 15 events in 9 counties and zones

The toll

Deaths: 0
Injuries: 0
Property damage: $79,000
Crop damage: None recorded
Events: 15

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.

A weak storm system moved through northern California during the night of December 4th, and moved south the next day bringing a few showers to Merced and Mariposa Counties by noon. Ahead of the storm, patchy dense fog developed in northern Kings County during the early morning hours of the 5th. This was a warm storm, and low temperatures on December 5th were again above normal. The low at the Fresno-Yosemite International Airport on the 5th was 52 degrees, tying the record high minimum temperature for the date. The low at Fresno the next day was even warmed, bottoming out at 55 degrees. This broke the old record high minimum temperature for the 6th by 3 degrees. For the seven days from November 30th through December 6th, Fresno broke or tied the record high minimum temperature on six days.

In the wake of the storm of December 5th-6th, an upper-level ridge formed over the eastern Pacific. The circulation around the ridge set up a northwest flow aloft over California, bringing cooler temperatures. Cooler was a relative term, however, as temperatures were still above normal.

The upper-level ridge also brought a stable environment to the central California interior. This triggered the development of night and morning fog over parts of the central and southern San Joaquin Valley on December 9th through the 11th. December 11th also saw the approach of the next Pacific storm system, which reached the central California interior that night. This storm brought up to 15 inches of new snow to the higher elevations of the Southern Sierra Nevada, and 3 inches of snow as far south as Frazier Park. Snow levels fell into the upper foothills in the cold airmass behind the front, dropping to around 3500 feet during the afternoon of the 12th.

The storm moved east of the region during the morning of December 13th, leaving only a few showers over the Kern County deserts. Behind the departing trough, another east-Pacific upper- level ridge built into the state, bringing more fog to the central and southern San Joaquin Valley.

The airmass was drier the next morning, and in the absence of fog, radiational cooling allowed lows in the central and southern San Joaquin Valley to drop into the upper 20s to around 30.

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 10, 2:45 PM PST, 9 hours 15 minutes earlier.

Area forecast discussion, Dec 10, 2:45 PM PST, 9 hours 15 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
245 PM PST MON DEC 10 2012

.SYNOPSIS...
ANOTHER ROUND OF PATCHY VALLEY FOG IS LIKELY TONIGHT AND INTO
TUESDAY...MAINLY DURING THE LATE NIGHT THROUGH MID MORNING HOURS.
COOLER AND WETTER CONDITIONS ARE EXPECTED WEDNESDAY AND THURSDAY DUE
TO AN APPROACHING FRONTAL SYSTEM.

&&

.DISCUSSION...
A COMPLEX WEATHER SITUATION WILL DEVELOP OVER THE COMING WEEK. THE
IMMEDIATE CONCERNS ARE THE POTENTIAL FOR FOG AND PATCHY FROST TONIGHT
IN THE CENTRAL AND SOUTHERN SAN JOAQUIN VALLEY. FOG THIS MORNING WAS
NOT AS WIDESPREAD AS THE LAST COUPLE OF MORNINGS...BUT PATCHY DENSE
FOG DEVELOPED FROM NEAR REEDLEY SOUTH TO THE HIGHWAY 198 CORRIDOR
AND INTO PORTERVILLE AND CORCORAN. THIS DENSE FOG LINGERED INTO
MIDDAY NEAR HANFORD AND VISALIA BEFORE DISSIPATING. UPPER-LEVEL
SHORT-WAVE RIDGING IS FORECAST TO CONTINUE ONE MORE NIGHT OVER THE
CENTRAL CALIFORNIA SO HAVE KEPT SAN JOAQUIN VALLEY FOG IN THE
FORECAST FOR TONIGHT. WHERE THE SKIES WERE CLEAR...LOW TEMPERATURES
DROPPED BELOW FREEZING...WITH A FEW SPOTS ON THE WEST SIDE OF THE
SAN JOAQUIN VALLEY NEAR COALINGA AND N.A.S. LEMOORE FALLING INTO THE
28-30 DEGREE RANGE. WITH SIMILAR CONDITIONS EXPECTED TONIGHT...HAVE
ADDED PATCHY FROST TO THE VALLEY FORECAST...ESPECIALLY ON THE WEST
SIDE.

THE NEXT CONCERN IS THE STORM SET TO ARRIVE FOR THE MIDDLE OF THE
WEEK. PRECIPITATION WILL MOVE INTO THE NORTHERN PART OF THE HANFORD
WARNING/FORECAST AREA AFTER MIDNIGHT TUESDAY NIGHT...WITH THE
HEAVIEST PRECIPITATION EXPECTED WEDNESDAY AFTERNOON AND EVENING. THE
MODELS CONTINUE TO FORECAST A SHARP DROP IN 850-MB TEMPERATURES OVER
THE CENTRAL CALIFORNIA INTERIOR DURING THE DAY WEDNESDAY AS THE COLD
AIRMASS MOVES INTO THE REGION BEHIND THE COLD FRONT. THE SNOW LEVEL
IS FORECAST TO FALL TO AROUND 3500 FEET NEAR YOSEMITE WEDNESDAY
AFTERNOON WITH ACCUMULATING SNOW ON THE YOSEMITE VALLEY FLOOR. TOTAL
NEW SNOW ACCUMULATIONS FOR YOSEMITE VALLEY FOR WEDNESDAY AFTERNOON
THROUGH THURSDAY ARE FORECAST TO BE 3-5 INCHES...WITH 6-8 INCHES
OVER THE HIGHER ELEVATIONS. A WINTER WEATHER ADVISORY HAS BEEN ISSUED
FOR THE SIERRA NEVADA...FROM YOSEMITE TO KINGS CANYON...FOR
WEDNESDAY AND THURSDAY.

SNOW WILL FALL INTO THE HIGHER SIERRA NEVADA FOOTHILLS WEDNESDAY
AFTERNOON THROUGH THURSDAY...WITH 1-2 INCHES OF SNOW ABOVE 3500 FEET.

TO THE SOUTH...THE SNOW LEVEL IN THE TEHACHAPI MOUNTAINS IS FORECAST
TO FALL BELOW 4000 FEET WEDNESDAY NIGHT. AS THIS IS BELOW THE LEVEL
OF THE MAJOR PASSES THROUGH THE KERN COUNTY MOUNTAINS...ACCUMULATING
SNOW WILL BE POSSIBLE ON THE GRAPEVINE AND TEHACHAPI PASS.

THE TROUGH IS FORECAST TO LINGER OVER CALIFORNIA THURSDAY...THEN
MOVE EAST FRIDAY MORNING. THE NEXT TROUGH IS FORECAST TO REACH
CALIFORNIA SATURDAY ALTHOUGH THERE ARE SIGNIFICANT MODEL DIFFERENCES
BETWEEN THE GFS AND ECMWF CONCERNING TIMING AND STRENGTH WITH THE GFS
KEEPING THE EMBEDDED LOW WELL OFFSHORE. BECAUSE OF THESE
UNCERTAINTIES...HAVE KEPT MAINLY SLIGHT CHANCE POPS OVER THE HANFORD
WARNING/FORECAST AREA OVER THE WEEKEND WITH CHANCE POPS CONFINED TO
THE HIGHER ELEVATIONS OF THE SOUTHERN SIERRA NEVADA.

&&

.AVIATION...
IN THE SAN JOAQUIN VALLEY...AREAS OF FOG REDEVELOPING
DURING THE EVENING WITH AREAS IFR TO LIFR CONDITIONS 06Z-18Z...THAN
MVFR VISIBILITIES IN HAZE THEREAFTER. OTHERWISE VFR CONDITIONS
ELSEWHERE ACROSS THE CENTRAL CALIFORNIA INTERIOR THROUGH 00Z
WEDNESDAY.

&&

.AIR QUALITY ISSUES...
ON MONDAY DECEMBER 10 2012...FIREPLACE/WOOD STOVE BURNING IS
PROHIBITED IN KERN COUNTY.
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.

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 12-10       74:1939     38:1972     58:1937     26:1951
KFAT 12-11       69:1933     39:1932     56:1937     25:1972
KFAT 12-12       69:1969     40:1932     55:1929     18:1932

KBFL 12-10       85:1912     41:1972     53:1937     24:1923
KBFL 12-11       81:1912     35:1932     58:1937     24:1923
KBFL 12-12       75:1913     43:1932     53:1893     20:1901

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 AM WEDNESDAY TO 4 PM PST THURSDAY
FOR THE SOUTHERN SIERRA NEVADA FROM YOSEMITE NATIONAL PARK TO
KINGS CANYON /CAZ096/.

&&

PUBLIC...SANGER
AVN/FW...MV
SYNOPSIS...BSO

WEATHER.GOV/HANFORD

Hazardous weather outlook, Dec 10, 8:59 PM PST, 3 hours 1 minute before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
859 PM PST MON DEC 10 2012

CAZ089>099-120500-
WEST CENTRAL SAN JOAQUIN VALLEY-EAST CENTRAL SAN JOAQUIN VALLEY-
SOUTHWESTERN SAN JOAQUIN VALLEY-SOUTHEASTERN SAN JOAQUIN VALLEY-
MARIPOSA MADERA AND FRESNO COUNTY FOOTHILLS-
TULARE COUNTY FOOTHILLS-KERN COUNTY MOUNTAINS-
SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON-
TULARE COUNTY MOUNTAINS-INDIAN WELLS VALLEY-
SOUTHEASTERN KERN COUNTY DESERT-
859 PM PST MON DEC 10 2012

...VALLEY FOG AND WINTER WEATHER...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF INTERIOR CENTRAL
CALIFORNIA.

.DAY ONE...TONIGHT

PATCHY DENSE FOG IS POSSIBLE IN THE SAN JOAQUIN VALLEY TONIGHT.
OTHERWISE NO HAZARDOUS WEATHER IS EXPECTED. REFER TO THE LATEST
SPECIAL WEATHER STATEMENT...OR /SFOSPSHNX/ FOR MORE INFORMATION.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

PATCHY DENSE FOG IS POSSIBLE IN THE SAN JOAQUIN VALLEY THROUGH
LATE TUESDAY MORNING. ON WEDNESDAY AND THURSDAY...RAIN AND
MOUNTAIN SNOW ARE POSSIBLE THROUGHOUT THE CENTRAL CALIFORNIA
INTERIOR DUE TO A RELATIVELY COLD WINTER STORM. IN
ADDITION...ISOLATED THUNDERSTORMS ARE POSSIBLE IN PARTS OF THE
CENTRAL SAN JOAQUIN VALLEY DURING WEDNESDAY AFTERNOON. REFER TO THE
LATEST SPECIAL WEATHER STATEMENT...OR /SFOSPSHNX/ FOR MORE
INFORMATION.

A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE SOUTHERN SIERRA
NEVADA FROM YOSEMITE TO KINGS CANYON FROM 6 AM PST WEDNESDAY
MORNING UNTIL 4 PM PST THURSDAY AFTERNOON. REFER TO THE LATEST
WINTER WEATHER STATEMENT...OR /SFOWSWHNX/ FOR MORE DETAILS.

.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.

WP

In the hours before

Special weather statement, Dec 10, 9:25 PM PST, 2 hours 35 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
925 PM PST MON DEC 10 2012

CAZ089>092-111330-
WEST CENTRAL SAN JOAQUIN VALLEY-EAST CENTRAL SAN JOAQUIN VALLEY-
SOUTHWESTERN SAN JOAQUIN VALLEY-SOUTHEASTERN SAN JOAQUIN VALLEY-
925 PM PST MON DEC 10 2012

...PATCHY FROST AND AREAS OF FOG TONIGHT...
...RAIN WEDNESDAY AND THURSDAY...

AREAS OF FOG WILL REDEVELOP OVER THE CENTRAL AND SOUTHERN SAN
JOAQUIN VALLEY TONIGHT AND PERSIST INTO TUESDAY MORNING. THE FOG
WILL BE LOCALLY DENSE AT TIMES...WITH VISIBILITIES OF 500 FEET OR
LESS IN THE THICKEST FOG. MAJOR ROADS THAT MAY BE IMPACTED WILL
INCLUDE HIGHWAYS 41...43...99...180 AND 198.

PATCHY FROST WILL BE POSSIBLE IN OUTLYING AREAS WHERE FOG DOES NOT
FORM. TEMPERATURES WILL FALL JUST BELOW 32 DEGREES IN THE COLDEST
LOCATIONS DURING THE EARLY MORNING HOURS...WITH DURATIONS OF 3 TO 5
HOURS. THE COLDEST SPOTS MAY BRIEFLY DROP TO AROUND 28 DEGREES
TOWARD DAYBREAK.

A PACIFIC STORM WILL MOVE INTO CENTRAL CALIFORNIA LATE TUESDAY
NIGHT. RAIN WILL BEGIN BY DAYBREAK WEDNESDAY...WITH THE HEAVIEST
RAINFALL EXPECTED WEDNESDAY AFTERNOON AND EVENING. RAIN WILL
DIMINISH WEDNESDAY NIGHT...BUT SHOWERS WILL LINGER INTO THURSDAY.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR FAVORITE NEWS SOURCE FOR
UPDATES ON THIS DEVELOPING SITUATION.

CAZ093-094-097-111330-
MARIPOSA MADERA AND FRESNO COUNTY FOOTHILLS-
TULARE COUNTY FOOTHILLS-TULARE COUNTY MOUNTAINS-
925 PM PST MON DEC 10 2012

...SNOW OVER THE SIERRA NEVADA FOOTHILLS AND THE TULARE COUNTY
MOUNTAINS WEDNESDAY AND THURSDAY...

A PACIFIC STORM WILL MOVE INTO CENTRAL CALIFORNIA LATE TUESDAY
NIGHT. RAIN AND HIGHER ELEVATION SNOW WILL BEGIN BY DAYBREAK
WEDNESDAY...CHANGING INTO MAINLY SNOW BY WEDNESDAY AFTERNOON AS THE
SNOW LEVEL LOWERS INTO THE SIERRA FOOTHILLS TO AROUND 3500 FEET.
THE HEAVIEST SNOWFALL IS EXPECTED WEDNESDAY AFTERNOON AND
EVENING...WITH ONE OR TWO INCHES OF SNOW POSSIBLE ABOVE 3500 FEET
AND SIX TO EIGHT INCHES OVER THE HIGHER ELEVATIONS. THE SNOW
WILL DIMINISH WEDNESDAY NIGHT...BUT SNOW SHOWERS WILL LINGER INTO
THURSDAY.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR FAVORITE NEWS SOURCE FOR
UPDATES ON THIS DEVELOPING SITUATION.

CAZ095-111330-
KERN COUNTY MOUNTAINS-
925 PM PST MON DEC 10 2012

...SNOW POSSIBLE ON THE PASSES WEDNESDAY NIGHT AND THURSDAY...

A PACIFIC STORM WILL MOVE INTO CENTRAL CALIFORNIA LATE TUESDAY
NIGHT. RAIN AND HIGHER ELEVATION SNOW WILL BEGIN BY DAYBREAK
WEDNESDAY...CHANGING INTO MAINLY SNOW BY WEDNESDAY EVENING AS THE
SNOW LEVEL LOWERS TO AROUND 3500 FEET. THE HEAVIEST SNOWFALL IS
EXPECTED WEDNESDAY EVENING...WITH ONE OR TWO INCHES OF SNOW POSSIBLE
AT THE PASS LEVEL THROUGH THURSDAY AND THREE TO FIVE INCHES OVER
THE HIGHER ELEVATIONS.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR FAVORITE NEWS SOURCE FOR
UPDATES ON THIS DEVELOPING SITUATION.

WEATHER.GOV/HANFORD

Event by event

6 dense fog, 5 winter weather, 4 frost/freeze. Local standard time, as filed.

Dense Fog, W Central S.J. Valley

When: December 11, 12:00 AM PST to 8:00 PM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, E Central S.J. Valley

When: December 11, 12:00 AM PST to 8:00 PM PST
Where: E Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Sw S.J. Valley

When: December 11, 12:00 AM PST to 8:00 PM PST
Where: Sw S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, Se S.J. Valley

When: December 11, 12:00 AM PST to 8:00 PM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

Winter Weather, S Sierra Mtns

When: December 12, 4:00 PM PST to December 13, 4:00 AM PST
Where: S Sierra Mtns forecast zone
Property damage: $2,000
Reported by: Park/Forest Service

Winter Weather, Tulare Cty Mtns

When: December 12, 4:00 PM PST to December 13, 4:00 AM PST
Where: Tulare Cty Mtns forecast zone
Property damage: $2,000
Reported by: Park/Forest Service

Winter Weather, Kern Cty Mtns

When: December 12, 4:00 PM PST to December 13, 4:00 AM PST
Where: Kern Cty Mtns forecast zone
Property damage: $25,000
Reported by: Park/Forest Service

Winter Weather, S Sierra Foothills

When: December 12, 4:00 PM PST to December 13, 4:00 AM PST
Where: S Sierra Foothills forecast zone
Property damage: $25,000
Reported by: Park/Forest Service

Winter Weather, Tulare Cty Foothills

When: December 12, 4:00 PM PST to December 13, 4:00 AM PST
Where: Tulare Cty Foothills forecast zone
Property damage: $25,000
Reported by: Park/Forest Service

Frost/Freeze, W Central S.J. Valley

When: December 14, 3:00 AM PST to 8:00 AM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Frost/Freeze, E Central S.J. Valley

When: December 14, 3:00 AM PST to 8:00 AM PST
Where: E Central S.J. Valley forecast zone
Reported by: Mesonet

Frost/Freeze, Sw S.J. Valley

When: December 14, 3:00 AM PST to 8:00 AM PST
Where: Sw S.J. Valley forecast zone
Reported by: Mesonet

Frost/Freeze, Se S.J. Valley

When: December 14, 3:00 AM PST to 8:00 AM PST
Where: Se S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, W Central S.J. Valley

When: December 14, 4:00 AM PST to 11:00 AM PST
Where: W Central S.J. Valley forecast zone
Reported by: Mesonet

Dense Fog, E Central S.J. Valley

When: December 14, 4:00 AM PST to 11:00 AM PST
Where: E Central 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.
Winter Weather: Snow, sleet or freezing rain below warning levels that still caused disruption, damage or casualties.
Frost/Freeze: Frost or temperatures at or below freezing during the growing season, usually filed for crop damage.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2012 Every state in 2012 This day in weather history Warnings in California, December 2012

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: 427347, 427348, 427349, 427350, 427342, 427343, 427344, 427345, 427346, 427353, 427354, 427355, 427356, 427351, 427352.