Montana, 2002

Flash Flooding and Hail in Montana, August 20 to 21, 2002

August 20 to 21, 2002 · NWS GGW · 7 events in 2 counties and zones

An area of thunderstorms developed over southern Valley County during the late evening of August 20. The storms remained stationary between Glasgow, Fort Peck and the Pines Recreation Area on Fort Peck Lake until 4 am on the 21st.

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
$50,000
Crop damage
$25,000
Events
7

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 GGW wrote it up.

An area of thunderstorms developed over southern Valley County during the late evening of August 20. The storms remained stationary between Glasgow, Fort Peck and the Pines Recreation Area on Fort Peck Lake until 4 am on the 21st. The hail began to fall from these storms around midnight and continued until 3 am. Up to golf ball sized hail fell in this area with rainfall reports up to 5 inches. Flooding was reported in the town of Fort Peck and along Willow Creek south of Glasgow and west of Fort Peck. Between 4 am and 5 am, the storms moved east into McCone County. Up to baseball sized hail and flooding was report along Highway 528 in northern McCone County. The storms weakened as they crossed Highway 13 north of Vida around 545 am.

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 Glasgow, MT wrote its last area forecast discussion before the first event at Aug 20, 7:45 PM MST, 3 hours 25 minutes earlier.

Area forecast discussion, Aug 20, 7:45 PM MST, 3 hours 25 minutes before
NORTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
845 PM MDT TUE AUG 20 2002

.SHORT TERM...
WILL INCREASE POPS TO SEVERAL WESTERN COUNTIES FOR TONIGHT.

THUNDERSTORM CLUSTER ROLLING EAST THROUGH CENTRAL MT BEING WATCHED THIS
EVENING. THIS AREA IS NOT MOVING ALL THAT FAST (ABOUT 20-25 MPH)...AND
AM NOT CONFIDENT THAT IT WILL MAKE MUCH HEADWAY EAST INTO NE MT
OVERNIGHT. WILL BUMP UP POPS OVER SOME OF THE WESTERN ZONES
(PHILLIPS/GARFIELD AND PETROLEUM) TO 40 PERCENT...BUT LEAVE 20 PERCENTS
FOR THE REMAINDER OF THE CWA. JAMBA

.LONG TERM...
MED RANGE MODELS IN SOME DISAGREEMENT ON SOLUTION THROUGH EXTENDED
PERIOD BUT GENERAL TREND IS TO DEVELOP OMEGA BLOCK TYPE PATTERN
WITH UPPER LOW OVER PACIFIC NORTHWEST AND RIDGE OVER CENTRAL CANADA.
WILL KEEP CHANCE POPS WITH PROXIMITY OF UPPER LOW AND DIFFLUENT
FLOW. EBERT

KGGW TBB 057/080 055/082 058/081 90243111
     BBBB 051/081 050/084 051/081 052/083 9011333333
KGDV TBB 057/082 058/084 058/084 90243111
     BBBB 052/082 050/083 050/082 051/084 9012333333

.GGW...NONE.

The radar

The Glasgow radar (KGGW), 25 km away, was scanning. The volume nearest the first event began at 06:08 UTC.

Open the radar archive at this moment

Event by event

5 hail, 2 flash flood. Local standard time, as filed.

Hail, Valley

When
August 20, 11:10 PM MST
Where
Valley County, 15 mi S of Glasgow
Measured
0.75 in hail
Reported by
TRAINED SPOTTER
Coordinates
47.983, -106.633

Hail, Valley

When
August 21, 12:00 AM MST
Where
Valley County, 15 mi NW of Glasgow
Measured
1.75 in hail
Reported by
TRAINED SPOTTER
Coordinates
48.350, -106.867

Hail, Valley

When
August 21, 12:20 AM MST to 1:20 AM MST
Where
Valley County, 2 mi SW of Ft Peck
Measured
1 in hail
Reported by
TRAINED SPOTTER
Coordinates
48.000, -106.483

Flash Flood, Valley

When
August 21, 1:30 AM MST to 11:00 AM MST
Where
Valley County, South Portion
Property damage
$20,000
Reported by
NWS STORM SURVEY
Coordinates
48.365, -106.667 (the zone’s center; the record gives no point)

Hail, McCone

When
August 21, 4:00 AM MST
Where
McCone County, 20 mi N of Vida
Measured
1 in hail
Reported by
AIRPLANE PILOT
Coordinates
48.117, -105.500

Hail, McCone

When
August 21, 4:20 AM MST to 4:30 AM MST
Where
McCone County, 15 mi N of Vida
Measured
2.75 in hail
Property damage
$10,000
Reported by
NEWSPAPER
Coordinates
48.050, -105.500

Flash Flood, McCone

When
August 21, 6:00 AM MST to 6:30 AM MST
Where
McCone County, Northwest Portion
Property damage
$20,000
Crop damage
$25,000
Reported by
NEWSPAPER
Coordinates
47.645, -105.795 (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 Montana in 2002Every state in 2002This day in weather historyWarnings 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: 5317205, 5317206, 5317207, 5317210, 5317208, 5317209, 5317204.