Winter Storm in California, May 20 to 21, 2002

Name: Winter Storm in California, May 20 to 21, 2002
Start: 2002-05-20T06:00
End: 2002-05-21T03:00
Location: California

May 20 to 21, 2002 · NWS HNX · 2 events in 2 counties and zones

In a little less than 24 hours, significant snow fell in the Southern Sierra Nevada Mountains of Central California. Larger snow amounts included Volcanic Knob receiving 24" of new snow, Quaking Aspen and Pascoes 21", and Huntington Lake and Chilkoot Meadows 20".

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 2

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.

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 May 20, 3:50 AM PST, 2 hours 10 minutes earlier.

Area forecast discussion, May 20, 3:50 AM PST, 2 hours 10 minutes before

INTERIOR CENTRAL CALIFORNIA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
450 AM PDT MON MAY 20 2002

...CORRECTED WARNING AND ADVISORY SECTION...

WATER VAPOR IMAGES SHOW A LARGE CUTOFF UPPER LEVEL LOW CENTER OFF
THE NORTH CALIFORNIA COAST. COLDER MORE UNSTABLE AIR OVER
NORTHWESTERN CA. A FEW SHOWERS AND THUNDERSTORMS AFFECTED THE
CENTRAL SAN JOAQUIN VALLEY AND YOSEMITE OVERNIGHT. THE THREAT OF
SHOWERS AND THUNDERSTORMS WILL BE HIGH TODAY AS THE UPPER LOW MOVES
EAST ACROSS CALIFORNIA. THE COLDER AIR ALOFT WILL FURTHER
DESTABILIZE THE ATMOSPHERE AND THE SAN JOAQUIN VALLEY WILL BE UNDER
THE FAVORABLE LEFT FRONT QUAD OF A STRONG 130 KNOT JET. HODOGRAPH
SHOWS STRONG STRAIGHT LINE SHEAR FAVORABLE FOR RIGHT SPLITTING
CELLS. LOW WETBULB ZERO TEMPERATURE INDICATES STORMS MAY BE
ACCOMPANIED WITH SMALL HAIL. SOUTHWEST MID LEVEL WIND AT 40-50 MPH
WILL PROVIDE FAVORABLE OROGRAPHIC LIFT OVER THE SIERRA. WILL POST A
WINTER STORM WARNING FOR THE SIERRA NORTH OF KINGS CANYON FOR
POSSIBLE SNOW ACCUMULATIONS OF 6-12 INCHES...AND A WINTER WEATHER
ADVISORY FOR THE TULARE COUNTY MOUNTAINS FOR SNOW ACCUMULATIONS OF
3-8 INCHES. ALSO WILL HOIST A WIND ADVISORY FOR KERN COUNTY
MOUNTAINS AND DESERTS FOR THIS AFTERNOON AND EVENING WITH UPPER JET
MOVING OVER THE TEHACHAPI MNTS AND MODELS PROG LOCAL PRESSURE
GRADIENTS TO INCREASE 10-12MB. BEST DYNAMICS WILL BE ACROSS THE
CENTRAL SAN JOAQUIN VALLEY AND SIERRA AND WILL CARRY
LIKELY-CATEGORICAL POPS AND CHANCE IN THE SOUTHERN SAN JOAQUIN AND
KERN COUNTY MOUNTAINS. WIND FLOW TURNS NORTHWEST AS THROUGH AXIS
MOVES THROUGH AROUND 06Z MONDAY NIGHT. EXPECT LOTS OF LOW LEVEL
CLOUDINESS TUESDAY MORNING WITH SOME LINGERING SHOWERS ALONG THE
MOUNTAINS WITH NW LOW LEVEL FLOW MAY BANKING MOISTURE ALONG
FOOTHILLS AND SOUTH SIDE OF THE VALLEY. 500MB HEIGHTS RISE BY 50M
AND TEMPERATURES SHOULD RECOVER WEDNESDAY. A HIGH PRESSURE RIDGE
BUILDS OVER THE AREA FOR THE EXTENDED PERIOD AND WARM DRY WEATHER
SHOULD RETURN CA.

.HNX...WINTER STORM WARNING TODAY AND TONIGHT FOR THE SOUTHERN
       SIERRA NEVADA ABOVE 4500 FEET FROM YOSEMITE TO KINGS CANYON
    ...WINTER WEATHER ADVISORY TODAY AND TONIGHT FOR THE TULARE
       COUNTY MOUNTAINS ABOVE 5500 FEET
    ...WIND ADVISORY FOR KERN COUNTY MOUNTAINS AND DESERTS THIS
       AFTERNOON THROUGH 9:00 PM...

MV

In the hours before

Special weather statement, May 20, 3:15 AM PST, 2 hours 45 minutes before

CAZ089>099-201700-
CONVECTIVE OUTLOOK
NATIONAL WEATHER SERVICE HANFORD CA
415 AM PDT MON MAY 20 2002

AN UNSEASONABLY COLD LOW PRESSURE SYSTEM WILL MOVE ACROSS CENTRAL
CALIFORNIA THIS AFTERNOON AND EVENING. ENOUGH MOISTURE AND
INSTABILITY WILL BE PRESENT TO TRIGGER SHOWERS AND THUNDERSTORMS
ACROSS MUCH OF THE CENTRAL INTERIOR...ESPECIALLY THIS AFTERNOON AND
EVENING. SOME OF THE THUNDERSTORMS THAT DEVELOP WILL CONTAIN
HAIL...AND PRODUCE LOCALLY GUSTY WINDS AND BRIEF HEAVY RAIN.

PERSONS WITH OUTDOOR PLANS SHOULD CLOSELY MONITOR LOCAL CONDITIONS.
BE PREPARED TO SEEK SHELTER IF THREATENING WEATHER APPROACHES.

SPOTTER ACTIVATION MAY BE REQUIRED.

JSN

Event by event

2 winter storm. Local standard time, as filed.

Winter Storm, S Sierra Mtns

When: May 20, 6:00 AM PST to May 21, 3:00 AM PST
Where: S Sierra Mtns forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm, Tulare Cty Mtns

When: May 20, 6:00 AM PST to May 21, 3:00 AM PST
Where: Tulare Cty Mtns forecast zone
Reported by: AWOS,ASOS,MESONET,ETC

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.

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

The same day elsewhere

Every storm in California in 2002 Every state in 2002 This day in weather history Warnings in California, May 2002

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: 5291622, 5291623.