Idaho, 2002

Flash Flooding in Idaho, July 19, 2002

July 19, 2002 · NWS BOI · 2 events in 2 counties and zones

A large, almost stationary thunderstorm cell produced very heavy rainfall over the southeast corner of Valley County and the northeast corner of Boise County. A two hundred foot section of Fire Rd 579 was washed out by flash flood waters near the Boise-Valley County line.

Where it happened

Every event with a place to put it; 2 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.

A large, almost stationary thunderstorm cell produced very heavy rainfall over the southeast corner of Valley County and the northeast corner of Boise County. A two hundred foot section of Fire Rd 579 was washed out by flash flood waters near the Boise-Valley County line.

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 Jul 19, 1:30 PM MST, 4 hours 30 minutes earlier.

Area forecast discussion, Jul 19, 1:30 PM MST, 4 hours 30 minutes before
SOUTHWEST IDAHO/SOUTHEAST OREGON AREA FORECAST DISCUSSION NATIONAL
WEATHER SERVICE BOISE IDAHO
230 PM MDT FRI JUL 19 2002

POTENTIAL FOR FLASH FLOODING OVER SE OREGON AND MOUNTAINS OF
SOUTHWEST IDAHO TONIGHT AS UPPER LOW CENTER DRIFTS OVER THE AREA.
INDIVIDUAL STORMS WILL HAVE VERY HIGH RAINFALL EFFICIENCY WITH PWAT
VALUES OVER AN INCH AND VERY SLOW MOVEMENT.  CENTER OF THE COLD POOL
PROGGED OVER SOUTHWEST IDAHO AT 00Z THEN FORECAST TO LIFT SLOWLY
NORTHEAST OVER THE CENTRAL MOUNTAINS OF IDAHO DURING THE NIGHTTIME
HOURS. THIS APPEARS TO BE A FLASH FLOOD SYNOPTIC SIGNATURE BASED ON
CASE STUDIES AND WILL OPT FOR ENHANCED WORDING ON EVENING FORECAST.
SYSTEM EXITS FROM THE AREA EARLY SATURDAY LEAVING RESIDUAL MOISTURE
OVER THE CENTRAL MOUNTAINS FOR PARTLY CLOUDY SKIES AND MORNING
SHOWERS.  EVERYWHERE ELSE BEGINS CLEARING AS DRIER AIR ADVECTS IN
FROM THE WEST.  CLEAR SKIES AND COMFORTABLE TEMPS FOR SUNDAY AND
MONDAY AS HIGH PRESSURE BUILDS OVER THE REGION.

EXTENDED...GOING WITH A CHANCE OF SHOWERS/THUNDERSTORMS TUESDAY AND
WEDNESDAY WITH A WEAK WAVE RIDING NORTHEAST THROUGH NORTHERN
CALIFORNIA AND SOUTHERN OREGON.  OTHERWISE, DRY AND SEASONAL
CONDITIONS FOR THURSDAY AND FRIDAY.

.BOI...FLASH FLOOD WATCH IN EFFECT TONIGHT FOR IDAHO ZONES 11 13 29
       AND OREGON ZONES 61 AND 63.

G.SKARI

The radar

The Boise radar (KCBX), 69 km away, was scanning. The volume nearest the first event began at 00:59 UTC.

Open the radar archive at this moment

Event by event

2 flash flood. Local standard time, as filed.

Flash Flood, Boise

When
July 19, 6:00 PM MST to 7:00 PM MST
Where
Boise County, Northeast Portion
Reported by
PARK/FOREST SERVICE
Coordinates
43.989, -115.730 (the zone’s center; the record gives no point)

Flash Flood, Valley

When
July 19, 6:00 PM MST to 7:00 PM MST
Where
Valley County, Southeast Portion
Reported by
PARK/FOREST SERVICE
Coordinates
44.767, -115.566 (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

More

Every storm in Idaho in 2002Every state in 2002This day in weather historyWarnings in Idaho, July 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: 5309838, 5309839.