Flash Flood in Wyoming, August 21, 2002

Name: Flash Flood in Wyoming, August 21, 2002
Start: 2002-08-21T16:15
End: 2002-08-21T19:15
Location: Wyoming

August 21, 2002 · NWS RIW · 1 event in 1 county or zone

The water was reported 6 feet deep along Trabing Road. 5 inches of rain in this area.

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 RIW wrote it up.

The water was reported 6 feet deep along Trabing Road. Also, estimates of 3.5 inches of rain in this area.

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 Riverton, WY wrote its last area forecast discussion before the first event at Aug 21, 12:59 AM MST, 15 hours 16 minutes earlier.

Area forecast discussion, Aug 21, 12:59 AM MST, 15 hours 16 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
159 AM MDT WED AUG 21 2002

SATELLITE IS SHOWING UPPER CUT OFF LOW CURRENTLY SPINNING OVER THE
PACIFIC NORTHWEST. ALSO MOISTURE CONTINUES TO FLOW INTO THE AREA FROM
THE SOUTH.

MODELS IN GENERAL AGREEMENT SHOWING DIVERGENCE AT 300 MB AND 700 MB
CONVERGENCE. IN ADDITION...RESIDUAL BOUNDARIES LEFT OVER FROM CURRENT
CONVECTION WILL ALLOW FOR SCATTERED T-STORMS TODAY THROUGH TONIGHT.
700 MB WIND FIELD SHOWS SOUTHWEST WINDS OVER SOUTHWEST WY WITH
NORTHEAST WINDS OVER SHERIDAN AND JOHNSON COUNTIES...THUS FORMING
SOME KIND OF BOUNDARY EXTENDING FROM TETON COUNTY DOWN ALONG THE
WIND RIVER MOUNTAINS. EXPECT TO SEE CONVECTION TO FIRE ALONG THIS
BOUNDARY AND MOVE NORTHEAST. MODELS ALSO INDICATE THE FORMATION OF A
MCS OVER NORTHEAST WY TONIGHT.

CURRENT FORECAST HAS 40 POPS IN MOST PLACES TODAY...THIS LOOKS TO BE
GOOD AND WILL NOT CHANGE. WILL CONTINUE THE CHANCE OF MAINLY LATE
DAY SHOWERS/T-STORMS THU AND FRI...BUT WITH A LESSER CHANCE IN THE
SOUTH WHERE LESS MOISTURE AND INSTABILITY.

IN THE EXTENDED...WILL ADD CHANCE POPS TO SATURDAY AND SUNDAY...
ESPECIALLY IN THE NORTH...AS THE MODELS NOW SHOW A WETTER SOLUTION.
CHANCE POPS MONDAY AND TUESDAY LOOK GOOD.

.RIW...NONE.

MLC

The radar

The Riverton/Lander radar (KRIW), 187 km away, was scanning. The volume nearest the first event began at 23:13 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Johnson

When: August 21, 4:15 PM MST to 7:15 PM MST
Where: Johnson County, 10 mi SE of Buffalo
Reported by: LAW ENFORCEMENT
Coordinates: 44.039, -106.585 (the zone’s center; the record gives no point)

What these are

Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

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

The same day elsewhere

Every storm in Wyoming in 2002 Every state in 2002 This day in weather history Warnings in Wyoming, August 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: 5314323.