1 tornado, as filed by the National Weather Service.
Every event with a place to put it. Tap one for its entry below.
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 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 Los Angeles, CA wrote its last area forecast discussion before the first event at Dec 20, 9:20 PM PST, 3 hours 20 minutes earlier.
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
920 PM PST THU DEC 20 2001
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS MOVING INTO SLO/SBA
COUNTIES THIS EVENING...WITH SHOWERS BECOMING A BIT MORE WIDESPREAD
OVER VTU/L.A. COUNTIES. ALSO...RECENT SPOTTER REPORT OF THUNDER...GUSTY
WINDS AND SMALL HAIL IN GLENDALE. THE AIRMASS IS QUITE UNSTABLE WITH
MSAS LIS CLOSE TO -2 OVER THE CENTRAL COAST...AND NEAR 1 OVER L.A.
COUNTY...AND 500 MB TEMPS WERE -25 DEG C. UPPER LOW SPINNING JUST NW
OF THE SFO BAY AREA THIS EVENING WAS MOVING SLOWLY TO THE SE...AND
ASSOCIATED 1003 MB SURFACE LOW IN THIS AREA IS FORECAST TO MOVE SE
AND WEAKEN OVERNIGHT. FOR THE DISTRICT...AREA OF SHOWERS AND
THUNDERSTORMS AS SEEN ON SATELLITE AND RADAR WILL PUSH THROUGH THE
DISTRICT OVERNIGHT. MESO-ETA CROSS SECTIONS SHOW THE BULK OF THE
SYSTEM TO MOVE THRU BY LATE TONIGHT. SNOW LEVELS THIS EVENING ARE
AROUND 4000 TO 4500 FEET...AND ARE EXPECTED TO LOWER A BIT MORE
OVERNIGHT...WITH ACCUMULATING SNOW LIKELY ABOVE 5000 FEET. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR THE MOUNTAINS...PLEASE SEE LAXWSWLAX
FOR INFORMATION ON THIS.
THE UPPER TROF WILL MOVE INTO THE GREAT BASIN FRI...WITH THE FLOW OVER
THE DISTRICT TURNING NORTHWESTERLY. MOST OF THE SHOWERS OVER THE
DISTRICT WILL END IN THE MORNING...WITH LINGERING SNOW SHOWERS IN THE
MOUNTAINS...ESPECIALLY ON THE NORTH SLOPES. A WEAK UPPER RIDGE IS
FORECAST TO BUILD INTO SOCAL FRI NITE AND SAT. AN UPPER TROF WILL MOVE
INTO THE PAC NW SAT NITE...THEN MOVE SOUTHEAST THRU THE GREAT BASIN
AS AN INSIDE SLIDER SUN. THE AVN FORECASTS ANOTHER WEAK RIDGE TO
BUILD INTO SOCAL MON...WITH A WEAK UPPER TROF TO MOVE INTO MAINLY
CENTRAL CA TO NORTHERN PARTS OF THE DISTRICT CHRISTMAS DAY. DRY
WEATHER IS EXPECTED OVER THE REGION FROM LATER FRI THRU CHRISTMAS
DAY...ALTHOUGH PARTLY CLOUDY SKIES AT TIMES CAN BE EXPECTED. SOME
OFFSHORE FLOW IS EXPECTED DURING THE NIGHT AND MORNING SUN NITE INTO
CHRISTMAS DAY AS WELL. DAYTIME TEMPS SHOULD BE COOLER THAN NORMAL THRU
SAT...THEN NEAR OR SLIGHTLY ABOVE NORMAL SUN THRU CHRISTMAS DAY.
A LARGE NW SWELL WAS MOVING INTO THE OUTER COASTAL WATERS THIS EVENING
AND IS EXPECTED TO MOVE INTO THE INNER WATERS OVERNIGHT. HEAVY SURF
ADVISORY IS IN EFFECT ALONG ALL WEST AND NORTHWEST FACING COASTAL
AREAS THROUGH FRIDAY. PLEASE SEE THE PRODUCT LAXMWSLAX FOR THE LATEST
INFORMATION ON THIS.
WILL UPDATE THE ZONES BY 945 PM MAINLY TO FRESHEN UP THE FIRST
PERIOD...AND MENTION SMALL HAIL WITH THUNDERSTORMS FOR ALL VALLEY AND
COASTAL ZONES. REMAINDER OF ZONES LOOKS GOOD.
LAX 8500. SIRARD.
.LOX...WINTER WEATHER ADVISORY (SEE LAXWSWLAX).
HEAVY SURF ADVISORY (SEE LAXMWSLAX)
SMALL CRAFT ADVISORY (SEE LAXCWFLAX).The Santa Ana Mts radar (KSOX), 31 km away, was scanning. The volume nearest the first event began at 08:41 UTC.
1 tornado. Local standard time, as filed.
In the community of Walnut, a weak tornado touched down in the early morning hours. Several homes sustained minor roof damage and about 30 trees were knocked down. No injuries were reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2001Every state in 2001This day in weather historyThe tornado archive for California, 2001Warnings in California, December 2001
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: 5273933.