Name: Debris Flow in Montana, September 19, 2004
Start: 2004-09-19T15:00
End: 2004-09-19T15:00
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

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The toll

Deaths: 0
Injuries: 2
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 MSO wrote it up.

A Canadian couple were injured and hospitalized when their 2003 Porsche Carrera GT was struk by falling rocks the size of basketballs on Glacier National Park's Going to the Sun road. The rock slide was caused by excessive rains over the area.

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 Missoula, MT wrote its last area forecast discussion before the first event at Sep 19, 12:36 PM MST, 2 hours 24 minutes earlier.

Area forecast discussion, Sep 19, 12:36 PM MST, 2 hours 24 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
136 PM MDT SUN SEP 19 2004

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...UPPER LEVEL TROUGH AXIS
REMAINS TO THE WEST OF THE WATCH AREA AND WILL SLOWLY MOVE OVERHEAD
TONIGHT AND TOMORROW MORNING. MODELS IN GOOD AGREEMENT. EXPECT
SHOWERS TO FORM THIS AFTERNOON OVER THE NORTHERN ZONES UNDER A
CLOSED UPPER LOW. UPPER LEVEL TEMPERATURES WILL DROP AS WELL AND
THIS SHOULD LOWER THE SNOW LEVEL TO AROUND 6000 FEET IN MOST
AREAS. WILL HAVE TO WATCH POSSIBILITY OF PATCHY FOG ONCE AGAIN FOR
THE MORNING. EXPECT SHOWERS TO  DECREASE FROM NORTH TO SOUTH BY
MONDAY NIGHT AS TROUGH MOVES EAST.

LONG TERM...TUESDAY THROUGH SUNDAY...AN EXITING LOW PRESSURE TROUGH
WILL GIVE WAY TO A POSITIVELY TILTED RIDGE TUESDAY. THIS FLAT RIDGE
WILL HAVE SOME PACIFIC MOISTURE MOVE THROUGH IT...RESULTING IN MOSTLY
CLOUDY SKIES...BUT LOW POPS ACROSS THE NORTH WEDNESDAY AND THURSDAY.
FINALLY...MODELS AGREE IN THE BUILDING OF A STRONG RIDGE OVER THE
NORTHERN ROCKIES BY FRIDAY AND SATURDAY. WILL TEMPER THE AGGRESSIVE
WARMING ADVERTISED BY MOS GUIDANCE...BECAUSE STRONG SURFACE-BASED
INVERSION WILL BE DIFFICULT TO FULLY MIX OUT OF THE VALLEY.
HOWEVER...SOME WARMING IS STILL EXPECTED THURSDAY THROUGH SATURDAY.
VALLEY FOG IS A POSSIBILITY ACROSS THE NORTH THURSDAY AND FRIDAY.
&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

SHORT TERM/KREYENHAGEN
LONG TERM/MSJ

The radar

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

Open the radar archive at this moment

Event by event

1 debris flow. Local standard time, as filed.

Debris Flow, West Glacier Region

When: September 19, 3:00 PM MST
Where: West Glacier Region forecast zone
Injuries: 2 direct, 0 indirect
Reported by: NEWSPAPER
Coordinates: 47.971, -114.069 (the zone’s center; the record gives no point)

What these are

Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Montana in 2004 Every state in 2004 This day in weather history Warnings in Montana, September 2004

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: 5421664.