Name: Flash Flood in Montana, August 29, 2002
Start: 2002-08-29T20:00
End: 2002-08-29T21:00
Location: Montana

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 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 Great Falls, MT wrote its last area forecast discussion before the first event at Aug 29, 7:30 PM MST, 30 minutes earlier.

Area forecast discussion, Aug 29, 7:30 PM MST, 30 minutes before

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
830 PM MDT THU AUG 29 2002

UPDATE FOR ZONES PLANNED.

.SHORT TERM...WILL DROP TEMPERATURES A FEW DEGREES AND FRESHEN
WORDING ON SHOWERS AND THUNDERSTORMS. SHORT WAVE ENERGY OVER WRN MT
CONTINUES TO SLOWLY DRIFT NE TONIGHT. CLOUDINESS AND SHOWERS WILL
CONTINUE INTO THE MORNING HOURS AND IS COVERED WELL IN PREVIOUS
PACKAGED. WILL ADD PATCHY FOG FOR SW ZONES DUE TO AMOUNT OF RAIN
WITH SOME CLEARING OF SKIES. CAMP

.EXTENDED...UPPER LEVEL TROF TO MOVE OVER MAINLY NORTHERN ZONES ON
MONDAY WITH A DRY AND SUNNY FORECAST FOR TUESDAY. SOUTHWEST FLOW
RETURNS ON WEDNESDAY WITH ANOTHER UPPER LEVEL TROF TO MOVE OVER THE
AREA ON THURSDAY. MOISTURE AT THIS TIME NOT IMPRESSIVE SO WILL ONLY
GO FOR ISOLATED THUNDERSTORMS WEDNESDAY NIGHT AND THURSDAY. CAMP

.CCF NUMBERS
GTF BB 052/080 052/075 048 08412
    BBUBB 077/046 071/048 077/048 074/044 071 32211001222
CTB BB 048/078 047/073 046 08312
    BEUBB 075/042 068/044 074/044 071/041 068 21121001112
HLN BB 054/083 054/081 052 08413
    BBUBB 082/051 075/053 081/053 078/045 077 32211001222
BZN BB 048/078 046/075 045 08623
    BBUBB 077/043 073/045 079/047 079/043 070 32211001222
WEY BB 035/067 036/066 037 08623
    BBUBB 070/035 069/037 075/039 075/035 068 32211001222
DLN BB 045/078 046/075 045 08623
    BBUBB 077/044 072/046 078/048 075/044 070 32211001222
HVR BB 054/083 053/078 050 08412
    BEUBB 080/046 074/048 080/050 080/043 075 21221001112
LWT BB 052/080 052/076 048 08413
    BEUBB 077/044 071/046 077/048 077/043 073 32211001222

.TFX...NONE.

In the hours before

Local storm report, Aug 29, 3:01 PM MST, 4 hours 59 minutes before

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
401 PM MDT THU AUG 29 2002

TIME(MDT)  .....EVENT  LOCATION..... ST   ...EVENT/REMARKS...........
           .....COUNTY LOCATION.....

0350 PM    HOBSON                    MT   0.25 INCH HAIL
08/29/02   JUDITH  BASIN

NNNN

The radar

The Great Falls radar (KTFX), 85 km away, was scanning. The volume nearest the first event began at 02:58 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Lewis and Clark

When: August 29, 8:00 PM MST to 9:00 PM MST
Where: Lewis and Clark County, Canyon Ferry
Reported by: TRAINED SPOTTER
Coordinates: 47.122, -112.390 (the zone’s center; the record gives no point)

Heavy rains over the burn areas from the forest fires of 2000 near Canyon Ferry caused a mud slide at 2000 MST. A debris flow 8 inches deep and 60 feet wide came down the side of the mountain. At the base of the mountain, water ran through a marina and campground. Severe damage did occur to the buildings in the marina.

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 Montana in 2002 Every state in 2002 This day in weather history Warnings in Montana, 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: 5317934.