A strong low pressure trough approached the California coast during the night of December 9th-10th. High clouds ahead of the trough helped moderate overnight lows, preventing a third night of a widespread freeze.
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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.
The episode as NWS HNX wrote it up.
A strong low pressure trough approached the California coast during the night of December 9th-10th. High clouds ahead of the trough helped moderate overnight lows, preventing a third night of a widespread freeze. Then rain came to the San Joaquin Valley with snow in the mountains. The greatest snow accumulations were above the 7000 feet elevation on Dec 11th through the 13th, due to a series of low pressure systems associated with the general trough pattern. Snowfall amounts from the 12th through the morning of the 13th averaged around 3 feet above 7000 feet with locally higher amounts to nearly 5 feet. Temperatures warmed on the 11th as a subtropical feed that moved over the area, bringing plenty of moisture. The warm, moist airmass also triggered isolated thunderstorms over the central and southern San Joaquin Valley. There was heavy rain in the mountains up to around the 7000-foot elevation on the 11th and 12th, prior to changing to snow during the night of the 12th. The snow continued through the day on the 13th, with snow levels dropping to around 5000 feet as cooler air filtered into the region.
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, 8:30 PM PST, 2 hours 28 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 830 PM PST THU DEC 10 2009 .SYNOPSIS... A SERIES OF DISTURBANCES WILL MOVE THROUGH CENTRAL CALIFORNIA OVER THE NEXT FEW DAYS PRODUCING PERIODS OF MODERATE RAIN AND HEAVY SNOWFALL IN THE HIGHER ELEVATIONS. && .DISCUSSION... LOW PRESSURE SYSTEM CONTAINING A BAND OF SUBTROPICAL MOISTURE IS CURRENTLY PUSHING THROUGH CENTRAL CA WITH KHNX 88D INDICATING THE BULK OF IT/S PRECIPITATION IS AFFECTING FRESNO COUNTY SOUTHWARD WHERE SEVERAL LOCATIONS HAVE ALREADY MEASURED BETWEEN A TENTH AND THREE TENTHS OF AN INCH OF LIQUID PRECIPITATION. BASED OFF OF CURRENT TEMPERATURES...SNOW LEVELS HAVE BEEN RUNNING BETWEEN 5000 AND 5500 FEET...BUT EXPECT RISING SNOW LEVELS OVERNIGHT AS THIS SYSTEM IS ASSOCIATED WITH A WARM FRONTAL BAND. THE SYSTEM IS CURRENTLY CENTERED NEAR 36N/132W AND IS MOVING RAPIDLY NORTHEAST. 00Z WRF IS INDICATING THIS SYSTEM WILL BE EAST OF OUR CWFA BY DAYBREAK FRIDAY. CURRENT MENTION OF CATEGORICAL POPS FOR MOST OF OUR AREA FOR TONIGHT AND A WINTER WEATHER ADVISORY FOR THE SOUTHERN SIERRA NEVADA MOUNTAINS LOOKS GOOD. TEMPERATURES FOR TONIGHT LOOK TO BE ON THE TRICKY SIDE BASED ON THAT WE MAY SEE SOME RISES THROUGH THE EVENING HOURS AT SOME LOCATIONS THEN SEE A COOL DOWN NEAR SUNRISE AS SKIES CLEAR OUT BEHIND THE DEPARTING LOW. AM NOT PLANNING TO UPDATE THIS EVENING ALTHOUGH WILL PASS THE IDEA OF SOME SIGNIFICANT BREAKS IN THE ACTION TO THE UPCOMING MIDNIGHT CREW. 00Z WRF INDICATING THE NEXT PAC S/W SYSTEM WILL REACH OUR AREA LATE FRIDAY WHICH WILL BRING A ROUND OF MAINLY LIGHT PRECIPITATION TO OUR AREA FRIDAY NIGHT. SNOW LEVELS WILL RANGE FROM AROUND 5000 FEET OVER YOSEMITE PARK TO AROUND 6000S FEET OVER KERN COUNTY. THIS SYSTEM WILL BE FOLLOWED BY MOISTURE FROM AN INTENSE LOW PRESSURE SYSTEM WHICH IS PROGGED TO CROSS NORCAL ON SATURDAY NIGHT. THIS THIRD SYSTEM HAS THE POTENTIAL TO PRODUCE MODERATE TO LOCALLY HEAVY PRECIPITATION ACROSS MUCH OF OUR AREA FROM LATE SATURDAY THROUGH SUNDAY MORNING WHEN OUR AREA WILL BE UNDER THE FAVORED LFQ OF A CYCLONICALLY CURVED 120KT 250MB JET MAXIMUM. A WINTER STORM WATCH HAS BEEN POSTED FOR THE SOUTHERN SIERRA NEVADA AND TEHACHAPI MOUNTAINS TO COVER BOTH OF THESE UPCOMING EVENTS AND IT WILL LIKELY NEED TO BE UPGRADED TO A WINTER STORM WARNING ONCE THEIR TIMING BECOMES PINNED DOWN. THE PRECIPITATION WILL BECOME MORE SHOWERY ON SUNDAY AS A COOLER AND UNSTABLE AIRMASS PUSHES INTO CENTRAL CA UNDER CYCLONIC FLOW ALOFT. MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT WITH ENDING THE PRECIPITATION SUNDAY NIGHT THEN DRYING OUT OUR AREA NEXT WEEK WITH AN UPPER RIDGE BUILDING INTO CENTRAL CA. WHILE THIS WILL RESULT IN PLEASANT CONDITIONS OVER THE MOUNTAINS AND KERN DESERTS...THE SAN JOAQUIN VALLEY WILL LIKELY HAVE OVERNIGHT AND MORNING FOG EACH DAY WHICH MAY PERSIST IN SOME AREAS SINCE THE SUN ANGLE IS LOW IN MID DECEMBER. && .AVIATION... IN THE SAN JOAQUIN VALLEY...OCCASIONAL IFR VIS IN RA THRU 18Z...THEN MAINLY VFR WITH SCT -SHRA THRU 06Z SAT. OVER THE SIERRA AND TEHACHAPIS...FREQUENT MTN OBSCURATION IN CLDS/PRECIP THRU 06Z SAT. ELSEWHERE...VFR OR MVFR IN CLOUDS/SHOWERS. && .AIR QUALITY ISSUES... NONE. && .HNX WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL NOON PST FRIDAY FOR CAZ096-097. WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SUNDAY MORNING FOR CAZ095>097. && PUBLIC...DS AVN/FW...BINGHAM SYNOPSIS...PJ WEATHER.GOV/HANFORD
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 405 PM PST THU DEC 10 2009 CAZ096-097-120015- SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON- TULARE COUNTY MOUNTAINS- 405 PM PST THU DEC 10 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE HIGHER ELEVATIONS OF THE SOUTHERN SIERRA NEVADA. .DAY ONE...TONIGHT A WINTER WEATHER ADVISORY IS IN EFFECT FROM 8 PM THIS EVENING TO NOON PST FRIDAY. A WINTER STORM WATCH IS NOW IN EFFECT FROM FRIDAY EVENING THROUGH SUNDAY MORNING. SEE THE LATEST SFOWSWHNX OR WWUS46 KHNX FOR DETAILS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THE WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL NOON PST FRIDAY. THE WINTER WEATHER WATCH REMAINS IN EFFECT THROUGH SUNDAY MORNING. SEE THE LATEST SFOWSWHNX OR WWUS46 KHNX FOR DETAILS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT OR UNUSUAL CONDITIONS TO THE NATIONAL WEATHER SERVICE. WEATHER.GOV/HANFORD CAZ095-120015- KERN COUNTY MOUNTAINS- 405 PM PST THU DEC 10 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE KERN COUNTY MOUNTAINS. .DAY ONE...TONIGHT A WINTER STORM WATCH NOW IN EFFECT FROM FRIDAY EVENING THROUGH SUNDAY MORNING. SEE THE LATEST SFOWSWHNX OR WWUS46 KHNX FOR DETAILS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THE WINTER STORM WATCH REMAINS IN EFFECT FROM FRIDAY EVENING THROUGH SUNDAY MORNING. SEE THE LATEST SFOWSWHNX OR WWUS46 KHNX FOR DETAILS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT OR UNUSUAL CONDITIONS TO THE NATIONAL WEATHER SERVICE. WP WEATHER.GOV/HANFORD
The national radar mosaic for the moment the first event began.
2 flood, 2 winter storm, 1 heavy rain. Local standard time, as filed.
The California Highway Patrol reported 2 vehicles were stuck in flood waters and the intersection of Southgate Drive and South M Street.
California Highway Patrol reported water up to 1 and a half feet deep at the intersection of CA-99 and Jenson Avenue.
Caltrans reported a rockslide caused by heavy rain on CA-178 in the Kern Canyon east of Bakersfield. Rainfall at the time was estimated by radar around one inch.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2009Every state in 2009This day in weather historyWarnings in California, December 2009
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: 209064, 209065, 209066, 209068, 209069.