Heavy Snow in California, May 20, 2002

Name: Heavy Snow in California, May 20, 2002
Start: 2002-05-20T11:30
End: 2002-05-20T14:30
Location: California

May 20, 2002 · NWS REV · 1 event in 1 county or zone

The Mammoth Ranger Station reported 3-4 inches of new snow in 3 hours.

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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 REV wrote it up.

The Mammoth Ranger Station reported 3-4 inches of new snow in 3 hours.

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 Reno, NV wrote its last area forecast discussion before the first event at May 20, 8:00 AM PST, 3 hours 30 minutes earlier.

Area forecast discussion, May 20, 8:00 AM PST, 3 hours 30 minutes before

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
900 AM PDT MON MAY 20 2002

ACTIVE WEATHER DAY LOOKS TO BE ON TAP WITH VERY COLD UPPER LOW OFF
CALIFORNIA COAST. COLD AIR FROM THIS LOW HAS ALREADY MOVED INLAND
OVERNIGHT BEHIND FIRST COLD FRONT. ABOUT 2 INCHES OF NEW SNOW
REPORTED IN WESTERN LASSEN COUNTY AND 2-4 INCHES IN TAHOE AREA THIS
MORNING...WITH SNOW JUST STARTING IN MAMMOTH LAKES AREA. SNOWFALL
HAS TAPERED OFF TEMPORARILY BUT WILL INCREASE AGAIN BY AROUND MIDDAY
AS SECONDARY COLD FRONT NOW OVER CENTRAL CALIFORNIA MOVES INTO
SIERRA. THIS NEXT SURFACE FEATURE BEING ENHANCED AND DRIVEN EASTWARD
BY APPROACHING JET MAX NOW HEADING NORTHEAST FROM BASE OF OFFSHORE
LOW. NEW AVN MODEL APPEARS TO HAVE THIS FEATURE ANALYZED BEST. JET
MAX INDUCES CONSIDERABLE VERTICAL MOTION OVER SIERRA THIS AFTERNOON.
SYNOPTIC LIFTING A BIT LESS IN WESTERN NEVADA AS IS TYPICAL...BUT
CONSIDERING INSTABLILITY OF TODAYS AIR MASS OVER THE REGION ONLY
MINOR SURFACE HEATING OR DYNAMIC LIFTING SHOULD GENERATE PLENTY OF
SHOWERS AND THUNDERSTORMS. BEST CHANCE FOR THUNDERSTORMS THIS
AFTERNOON LOOKS TO BE IN EASTERN AND SOUTHERN ZONES AND GIVEN
SITUATION THERE APPEARS TO BE SOME THREAT OF SEVERE WEATHER. MODEL
GUIDANCE...ESPECIALLY AVN...HAS DONE AN OUTSTANDING JOB WITH THIS
SYSTEM THUS FAR. CURRENT ZONES IN GOOD SHAPE. LAMONI

.REV...WINTER STORM WARNING TODAY AND TONIGHT CAZ071>073 NVZ002.

In the hours before

Special weather statement, May 20, 9:00 AM PST, 2 hours 30 minutes before

CAZ070>073-NVZ001>005-202300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RENO NV
1000 AM PDT MON MAY 20 2002

...THUNDERSTORMS POSSIBLE ACROSS THE SIERRA NEVADA...NORTHEAST
CALIFORNIA AND WESTERN NEVADA TODAY...

THUNDERSTORMS ARE POSSIBLE ACROSS THE REGION TODAY AS A COLD LOW
PRESSURE SYSTEM ALONG THE CALIFORNIA COAST MOVES INLAND.  THE BEST
CHANCE FOR THUNDERSTORMS WILL BE THIS AFTERNOON IN MONO COUNTY
CALIFORNIA AND IN MINERAL...LYON...CHURCHILL AND PERSHING COUNTIES
IN WESTERN NEVADA.

LIGHTNING IS A DANGER WITH ALL THUNDERSTORMS SO REMEMBER TO TAKE
SHELTER IN A BUILDING OR VEHICLE IF YOU HEAR THUNDER. THUNDERSTORMS
MAY ALSO BRING HAIL...HEAVY RAIN AND GUSTY WINDS.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT
HTTP://WWW.WRH.NOAA.GOV/RENO

SKYWARN SPOTTERS ARE REQUESTED TO REPORT ANY SEVERE WEATHER FROM
TODAYS THUNDERSTORMS TO THE NATIONAL WEATHER SERVICE IN RENO.

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 heavy snow. Local standard time, as filed.

Heavy Snow, Mono

When: May 20, 11:30 AM PST to 2:30 PM PST
Where: Mono forecast zone
Reported by: PARK/FOREST SERVICE
Coordinates: 37.939, -118.887 (the zone’s center; the record gives no point)

What these are

Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.

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: 5299746.