Idaho, 2002

Flash Flood and Hail in Idaho, June 21, 2002

June 21, 2002 · NWS BOI · 2 events in 2 counties and zones

Slow-moving thunderstorms intensified over the West Central Mountains dropping 1 inch diameter hail at the Landmark campgrounds, ten miles east of Warm Lake. Radar precipitation estimates of 3 to 4 inches of rain in 90 minutes were recorded near the Boise-Valley County line.

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

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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 BOI wrote it up.

Slow-moving thunderstorms intensified over the West Central Mountains dropping 1 inch diameter hail at the Landmark campgrounds, ten miles east of Warm Lake. Radar precipitation estimates of 3 to 4 inches of rain in 90 minutes were recorded near the Boise-Valley County line. Mudslides occurred on Highway 17, closing the road for several hours overnight. Mudslides also occurred at Kirkum campground near Lowman.

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 Boise, ID wrote its last area forecast discussion before the first event at Jun 21, 1:32 PM MST, 2 hours 28 minutes earlier.

Area forecast discussion, Jun 21, 1:32 PM MST, 2 hours 28 minutes before
SOUTHWEST IDAHO/SOUTHEAST OREGON AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE IDAHO
230 PM MDT FRIDAY JUNE 21 2002

AN ACTIVE CONVECTIVE EVENING SETTING UP OVER THE FORECAST AREA AS
PARAMETERS COME TOGETHER NICELY JUST AT THE RIGHT TIME OF DAY
STRONG SHORT WAVE ROTATING UP FROM SOUTHERN NEVADA WILL PROVIDE THE
DYNAMIC LIFT TO ORGANIZE STORMS. AIR MASS ALREADY VERY BUOYANT WITH
LIS DOWN TO -2 AND PWS QUITE HIGH AT NEAR ONE INCH.  FEEL PRIMARY
THREAT AT THIS TIME REMAINS LOCAL FLASH FLOODING FROM TRAINING
STORMS IN SLOW MOVING SOUTHERLY FLOW.  HAVE ALREADY ISSUED FLASH
FLOOD WATCH FOR EXTREME SW IDAHO COUNTIES AND MAY EXPAND TO FURTHER
ZONES IF CONDITIONS WARRANT BY 4PM.  SHEAR VALUES NOT ALL THAT
IMPRESSIVE IN KBOI CWFA AT THIS TIME BUT THEY ARE PRESENT FARTHER
NORTH OVER CENTRAL IDAHO MTNS AND KMSO FORECAST AREA.  RADAR
ESTIMATES ALREADY PICKING UP ON A FEW ONE INCH+ AMOUNTS OVER SW
IDAHO WITH STRONGER CELLS YET TO COME FROM NORTH CENTRAL NEVADA.
WILL INCLUDE BEEFED UP WORDING TO SEVERAL ZONES FOR LOCAL HEAVY RAIN
AND GUSTY WINDS ON EVENING PACKAGE. ACTIVITY MAY LAST FOR SEVERAL
HOURS THIS EVENING AND POSSIBLY AS LATE AS MIDNIGHT.  ACTION WINDS
DOWN OVERNIGHT BUT UNSTABLE AIR MASS CONTINUES FOR SATURDAY WITH
MORE SHOWERS AND THUNDERSTORMS OVER THE AREA INTO THE EARLY EVENING
HOURS.  WILL OPT TO DECREASE POPS GRADUALLY THROUGH THE PERIOD WITH
HIGHEST VALUES TONIGHT TAPERING OFF WEST TO EAST ON SATURDAY.  TEMPS
STAY VERY WARM WARM THROUGH THE WEEKEND WITH VERY LITTLE CHANGE DAY
TO DAY THROUGH MONDAY.

EXTENDED...LATEST MRF AND OTHERS SHOW LARGE UPPER RIDGE MOVING OVER
THE AREA NEXT WEEK AND INTENSIFYING BY MIDWEEK.  THIS SCENARIO WILL
PRODUCE A HOT DRY EXTENDED PERIOD OF WEATHER STARTING TUESDAY AND
LASTING INTO NEXT WEEKEND.  WITH HIGH HEIGHT CENTER APPROACHING 600,
SURFACE TEMPS WILL FLIRT WITH 100F ACROSS THE SNAKE PLAIN.

.BOI...FLASH FLOOD WATCH IN EFFECT FOR ID ZONES 15 AND 29 UNTIL
       MIDNIGHT.

G.SKARI

The radar

The Boise radar (KCBX), 143 km away, was scanning. The volume nearest the first event began at 22:59 UTC.

Open the radar archive at this moment

Event by event

1 hail, 1 flash flood. Local standard time, as filed.

Hail, Valley

When
June 21, 4:00 PM MST to 4:30 PM MST
Where
Valley County, 10 mi E of Warm Lake
Measured
1 in hail
Reported by
GENERAL PUBLIC
Coordinates
44.650, -115.467

Flash Flood, Boise

When
June 21, 4:15 PM MST to 8:00 PM MST
Where
Boise County, 3 mi E of Banks
Reported by
LAW ENFORCEMENT
Coordinates
43.989, -115.730 (the zone’s center; the record gives no point)

What these are

Hail
Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
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

More

Every storm in Idaho in 2002Every state in 2002This day in weather historyWarnings in Idaho, June 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: 5304942, 5304943.