Flash Flood in Montana, August 23, 2003

Name: Flash Flood in Montana, August 23, 2003
Start: 2003-08-23T20:45
End: 2003-08-23T21:00
Location: Montana

August 23, 2003 · NWS MSO · 1 event in 1 county or zone

Strong thunderstorms produced heavy rain and flash flooding near the East Fork Bitterroot River at mile marker 4. Mudslides blocked the East Fork road.

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.

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Wind
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Winter weather
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Cold
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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 MSO wrote it up.

Strong thunderstorms produced heavy rain and flash flooding near the East Fork Bitterroot River at mile marker 4. Mudslides blocked the East Fork road.

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 Aug 23, 8:14 PM MST, 31 minutes earlier.

Area forecast discussion, Aug 23, 8:14 PM MST, 31 minutes before

WESTERN MONTANA AND NORTH CENTRAL IDAHO FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
914 PM MDT SAT AUG 23 2003

.SHORT TERM...UPDATES TO ZFP AND SFP PLANNED. CONFLUENT UPPER FLOW
BETWEEN THE POLAR AND SUBTROPICAL JET CONTINUES TONIGHT. A NORTHERN
STREAM SHORTWAVE MOVING THROUGH SOUTHERN BC THIS EVENING IS
SPREADING A COUPLE OF BANDS OF MID/HIGH LEVEL MOISTURE ACROSS WA AND
NORTHEAST OREGON. THIS MOISTURE IS NOW SPREADING INTO NORTHWEST
MONTANA. A FEW SHOWERS HAVE DEVELOPED OVER THE HIGHER TERRAIN IN
NORTHEAST OREGON IN A REGION OF MID LEVEL CONVERGENCE. THESE SHOWERS
SHOULD DISSIPATE BEFORE REACHING NORTH CENTRAL IDAHO. CANT RULE OUT
ADDITIONAL VERY LIGHT SHOWERS DEVELOPING OVER NORTHWEST MONTANA BUT
OTX WSR-88D JUST SHOWS SOME MID LEVEL RETURNS. DESPITE THE INCREASE
IN CLOUD COVER THIS EVENING GOOD RADIATIONAL COOLING IS STILL
EXPECTED...ESPECIALLY CENTRAL AND SOUTHERN AREAS. DUE TO LAST NIGHTS
RAINFALL OVER PORTIONS OF THE AREA WILL INTRODUCE AREAS OF VALLEY FOG
TO THE FORECAST OVER NORTH CENTRAL IDAHO AND PATCHY VALLEY FOG IN
WEST CENTRAL MONTANA. WILL ALSO LOWER MINIMUM TEMPERATURES MANY
LOCATIONS.

SUNDAY STILL LOOKS MAINLY DRY AND WARMER. MODELS ARE NOW INDICATING
THE REMNANTS OF A WEAK UPPER LOW NOW OFF THE NORTHERN CALIFORNIA
COAST WILL SHEAR THROUGH SOUTHWEST MONTANA LATE IN THE DAY. MAY HAVE
TO INTRODUCE ISOLATED CONVECTION OVER THE HIGHER TERRAIN FROM LEHMI
COUNTY OVER THE BUTTE FOR LATE AFTERNOON AND EVENING IN THE NEXT
FORECAST PACKAGE.

FIRE WEATHER CONCERNS...RIDGETOP WINDS WILL REMAIN A PROBLEM
THROUGH THE SHORT TERM. THE SHORTWAVE MOVING THROUGH THE REGION
TONIGHT WILL CAUSE AN INCREASE IN RIDGETOP WINDS OVERNIGHT. RIDGETOP
AND VALLEY WINDS SHOULD BE SIMILAR ON SUNDAY AS TODAY...BUT SLIGHTLY
WEAKER UP NORTH. BY MONDAY THE FLOW WILL BEGIN TO BACK MORE TO THE
SOUTHWEST ON THE RIDGETOPS...WITH WEAKER VALLEY WINDS EXPECTED. AN
INCREASE IN WINDS ARE EXPECTED TUESDAY AS A TROUGH APPROACHES FROM
THE WEST. THERE WILL BE A WARMING DRYING TREND THE NEXT FEW DAYS...
WITH POORER MID SLOPE HUMIDITY RECOVERIES AT NIGHT. PETRESCU

.LONG TERM...SOUTHWEST FLOW TUESDAY NIGHT AS UPPER LEVEL TROUGH
CONTINUES TO MOVE EAST ACROSS CANADA. WEDNESDAY A RIDGE BUILDS ALONG
THE WEST COAST FOR NORTHWEST TO ZONAL FLOW THROUGH SATURDAY.
SLIGHTLY ABOVE NORMAL TEMPERATURES AND NO PRECIPITATION EXPECTED
IN THE EXTENDED.  KOCH

.MSO...NONE.

...7-DAY SPOT TEMPS AND POPS...
LIB BUU 046/081 046/082 045/083 40000000
     UUUU 047/084 050/086 049/087 050/088 3600000000
FCA BBU 044/077 045/078 039/079 40000000
     UUUU 041/080 046/082 045/083 046/084 3600000000
POL BUU 052/079 055/080 048/080 40000000
     UUUU 050/081 053/083 052/084 053/085 3600000000
MSO BUB 046/079 048/081 045/084 40000000
     UUUU 047/083 050/085 049/087 050/088 3600000000
HMM BUB 047/080 048/082 047/085 40000000
     UUUU 049/083 052/086 051/088 052/089 3600000000
BTM BUB 043/079 046/079 040/081 40011000
     UBBB 042/080 044/083 044/084 045/085 3600000000
ORO BUU 054/084 055/085 052/089 40000000
     UUUU 054/088 056/090 054/092 056/092 3600000000
GRV BUU 046/077 049/079 045/085 40000000
     UUUU 047/085 050/087 049/089 050/089 3600000000
SMN BUB 047/083 048/084 048/085 40000000
     UUBB 050/083 053/085 052/088 053/089 3600000000

Hazardous weather outlook, Aug 23, 5:00 AM MST, 15 hours 45 minutes before

MTZ001>007-043-IDZ005>010-241200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MISSOULA MT
600 AM MDT SAT AUG 23 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MONTANA AND NORTH
CENTRAL IDAHO

.DAY ONE... TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

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, Ravalli

When: August 23, 8:45 PM MST to 9:00 PM MST
Where: Ravalli County, 4 mi E of Sula
Reported by: LAW ENFORCEMENT
Coordinates: 46.082, -114.121 (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

Every storm in Montana in 2003 Every state in 2003 This day in weather history Warnings in Montana, August 2003

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: 5332926.