Idaho, 2001

Flash Flood in Idaho, September 13 to 14, 2001

September 13 to 14, 2001 · NWS BOI · 1 event in 1 county or zone

m. on the afternoon of the 13th.

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
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 BOI wrote it up.

A powerful thunderstorm dropped a half inch of rain in 15 minutes and nearly an inch in the hour between 3:00 and 4:00 p.m. on the afternoon of the 13th. This caused flash flooding in the steep terrain alongside the Payette River. The flash flooding triggered mudslides along a stretch of Highway 17 from 2 miles East of Banks to 8 miles East of Banks. Highway 17 was closed for 20 hours. A second area of mudslides located 2 miles North of Banks closed Highway 55 overnight . Some vehicles were trapped between mudslides but no one was injured. Cost of clearing the slides was estimated at $500K.

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 Sep 13, 3:15 PM MST, 45 minutes earlier.

Area forecast discussion, Sep 13, 3:15 PM MST, 45 minutes before
SOUTHWEST IDAHO/SOUTHEAST OREGON AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE IDAHO
415 PM MDT THU SEP 13 2001

18Z RAOB SHOWED MODIFIED CAPE TO 1600 WHILE SCAN LOCAL CAPES SHOWS
UP TO 2200 J/KG. LI -6.  SATELLITE IN RSO SINCE 1PM SHOWING
OVERSHOOTING TOPS IN VIS/IR WITH LOCAL REPORTS OF DIME HAIL NR
ARROWROCK DAM AND OUTFLOW BOUNDARY THRU UPPER TREASURE VALLEY EARLY
AFTN AND IN LOWER T.V. AT 415 PM.  HEAVY RAIN REPORTS ALL OVER LAST
NIGHT AND TODAY WITH ONE HOUR TOTALS TO 0.4 AND STORM TOTALS TO 0.8
AT HIGH ELEVATION RAWS.

SHORTWAVE TROF WITH COMMAHEAD OVER TREASURE VALLEY TO CONTINUE
MOVING NORTH AS UPPER LOW IN SOUTH CENTRAL OREGON, WITH LESS
IMPRESSIVE RW/TRW, SHIFTS NE THROUGH THE CWFA.  SOME CLOUDS
LINGERING TONIGHT BUT JUST ISOLATED BY MIDNIGHT.  LOTS OF MOISTURE
FROM BRIEF HEAVY RAIN FOR SOME CLOUDS FRIDAY.  SOME CLEARING FRIDAY
NIGHT FOR COOLER NIGHT.  WEAK SHORTWAVE SATURDAY AFTERNOON FOR SLIM
CHANCE POPS.  SUNDAY DRY.  YESTERDAYS 12Z AVN AND ABOUT 3 RUNS AGO
MRF COMING TOGETHER WITH A CHANCE OF RAIN MONDAY.  DRYING AND WARMER
TUESDAY THROUGH THURSDAY.

.BOI...NONE.

The radar

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

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Boise

When
September 13, 4:00 PM MST to September 14, 8:00 AM MST
Where
Boise County, Banks
Reported by
LAW ENFORCEMENT
Coordinates
43.989, -115.730 (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 2001Every state in 2001This day in weather historyWarnings in Idaho, September 2001

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: 5269247.