A persistent closed low pressure system brought heavy rain to much of North Central Montana. Rainfall of 2 to 5 inches was common over the plains and valleys while rain amounts over 10 inches were reported in the mountains.
Every event with a place to put it. Tap one for its entry below.
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.
The episode as NWS TFX wrote it up.
A persistent closed low pressure system brought heavy rain to much of North Central Montana. Rainfall of 2 to 5 inches was common over the plains and valleys while rain amounts over 10 inches were reported in the mountains. The heavy rains caused many rivers and streams to overflow their banks for several days.
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 May 23, 5:05 AM MST, 3 hours 55 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 605 AM MDT FRI MAY 23 2008 ...UPDATE TO AVIATION... .DISCUSSION... TODAY THROUGH SUNDAY...A CLOSED LOW PRESSURE CENTER WILL BE OVER NEVADA AND UTAH TODAY AND SOUTHEAST FLOW ALOFT WILL CONTINUE OVER THE ZONES...AND STRONG DIFFLUENCE ALOFT CONTINUES THROUGH SATURDAY MORNING. SURFACE HIGH PRESSURE OVER CANADA WILL CONTINUE TO KEEP A TIGHT GRADIENT OVER THE NORTH AND CENTRAL ZONES AND KEEP BRISK EAST FLOW IN THE FORECAST. COLDER AIR ALOFT IS BEGINNING TO MOVE OVER THE ZONES FROM THE SOUTH AND HELPING TO CAUSE WEAK INSTABILITY. SEVERAL LIGHTNING STRIKES YESTERDAY AND A REPEAT IS POSSIBLE TODAY. UPSLOPE FLOW WEAKENS TONIGHT BUT STRENGTHENS AGAIN AGAIN SATURDAY ACROSS THE NORTH AND CENTRAL ZONES...AND IS STRONGEST SATURDAY AFTERNOON. POPS WILL REMAIN HIGH IN THIS AREA ALTHOUGH THEY WILL BEGIN TO TREND DOWNWARDS OVER SOUTHWEST MONTANA WHERE THE LOWER LEVELS WILL BEGIN TO DRY. WILL SEE ENOUGH INSTABILITY SATURDAY AND SUNDAY AFTERNOONS TO MENTIONS SLIGHT CHANCE OF THUNDERSTORMS. THE WINTER STORM WARNING WILL CONTINUE OVER THE ROCKIES...AND WILL ALSO LET THE HEAVY SNOW WARNING TO THE EAST CONTINUE THIS MORNING...MOST HEAVY SNOW SHOULD BE ENDING BUT ADDITIONAL ACCUMULATIONS WILL CONTINUE INTO THE MORNING. ZELZER SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A BROAD AREA OF UPPER LEVEL LOW PRESSURE WILL LINGER OVER SOUTHWESTERN CANADA SOUTH INTO THE GREAT BASIN SUNDAY NIGHT INTO MONDAY. DEEP MOISTURE WITH WEAK ENERGY MOVING AROUND THIS LOW WILL COMBINE WITH EASTERLY UPSLOPE SURFACE WINDS TO KEEP A GOOD CHANCE OF PRECIPITATION OVER NORTH CENTRAL AND SOUTHWEST MONTANA DURING THIS TIME. THE SNOW LEVEL WILL GRADUALLY RISE DURING THIS TIME...LIMITING SNOWFALL TO MAINLY THE HIGHER MOUNTAIN PEAKS. A SHORTWAVE TROUGH WILL THEN EJECT FROM THE BROAD UPPER LOW AND MOVE OVER SOUTHWEST AND CENTRAL MONTANA MONDAY NIGHT AND TUESDAY FOR A CONTINUED CHANCE OF SHOWERS THERE. HOWEVER...SHOWERS WILL GRADUALLY DECREASE ACROSS NORTH CENTRAL MONTANA DURING THIS TIME. A FEW THUNDERSTORMS WILL ALSO BE POSSIBLE IN FAR SOUTHWEST MONTANA MONDAY THROUGH TUESDAY DUE TO A WEAKLY UNSTABLE AIRMASS THERE. THE BROAD UPPER LOW WILL GRADUALLY SHIFT WEST TO THE PACIFIC COAST TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS THE UPPER LEVEL RIDGE OVER THE CENTRAL CONUS BUILDS BACK TOWARDS THE ROCKY MOUNTAINS. THIS WILL PUT THE AREA UNDER AN UNSETTLED SOUTHWESTERLY FLOW ALOFT...WHICH WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA. CLOUDS AND PRECIPITATION ASSOCIATED WITH THE UPPER LOW WILL KEEP TEMPERATURES BELOW SEASONAL AVERAGES THROUGH TUESDAY...BUT TEMPERATURES WILL GRADUALLY WARM TO ABOVE NORMAL BY WEDNESDAY. COULSTON THURSDAY THROUGH FRIDAY...MODELS ARE IN FAIR AGREEMENT WITH SLIGHT DIFFERENCES IN TIMING AND AMPLITUDE OF FEATURES. A WEAK UPPER LEVEL RIDGE OVER THE DAKOTA BORDER IS FLATTENED AND NUDGED EAST AS A SERIES OF SHORTWAVE TROUGHS ARE EJECTED FROM AN UPPER LEVEL LOW THAT LINGERS THROUGH THIS PERIOD OFF THE WEST COAST. THIS SHOULD RESULT IN A FAIRLY MOIST AND UNSTABLE SOUTHWESTERLY FLOW ALOFT OVER THE FORECAST AREA. MOSTLY CLOUDY SKIES ARE EXPECTED WITH ISOLATED TO SCATTERED SHOWERS. A FEW AFTERNOON AND EVENING THUNDERSTORMS ARE POSSIBLE THURSDAY AS THAT IS WHEN THE BEST ENERGY IS APPARENT. TEMPERATURES SHOULD BE NEAR TO A LITTLE ABOVE SEASONAL AVERAGES. EK && .AVIATION... UPDATED 1205Z. AN UPPER LEVEL LOW PRESSURE AREA WILL REMAIN OVER THE GREAT BASIN THROUGH AT LEAST 12Z SATURDAY...CONTINUING THE MOIST EASTERLY FLOW ALOFT OVER NORTH CENTRAL AND SOUTHWEST MONTANA. CONDITIONS TODAY WILL BE VFR ACROSS SOUTHWEST MONTANA (KBZN TERMINAL) WITH OCCASIONAL RAIN AND MOUNTAIN SNOW SHOWERS CAUSING MVFR CONDITIONS AND MOUNTAIN OBSCURATION. THE AIRMASS THERE WILL BECOME SLIGHTLY UNSTABLE THIS AFTERNOON AND EVENING FOR A CHANCE OF THUNDERSTORMS AS WELL. MORE WIDESPREAD MVFR TO OCCASIONAL IFR CONDITIONS AND MOUNTAIN OBSCURATION IN RAIN AND MOUNTAIN SNOW WILL CONTINUE ACROSS CENTRAL AND NORTH CENTRAL MONTANA. CONDITIONS WILL IMPROVE SOMEWHAT LATE THIS MORNING THROUGH THIS AFTERNOON ACROSS THE ENTIRE AREA AS SLIGHTLY DRIER AIR MOVES INTO THE AREA. HOWEVER...A DISTURBANCE WITH INCREASED MOISTURE WILL MOVE INTO THE AREA AFTER 00Z...BRINGING MORE WIDESPREAD PRECIPITATION AND MVFR CONDITIONS TO THE AREA ONCE AGAIN. BREEZY EASTERLY SURFACE WINDS ACROSS NORTH CENTRAL MONTANA TODAY WILL DECREASE SOMEWHAT OVERNIGHT. COULSTON && .HYDROLOGY... RECENT SNOWMELT COMBINED WITH A PERIOD OF SIGNIFICANT RAIN OVER THE NEXT FEW DAYS WILL CAUSE MINOR TO MODERATE FLOODING IN AREAS OF SOUTHWEST MONTANA...THIS INCLUDES THE GALLATIN...BIG HOLE AND JEFFERSON RIVERS. ANOTHER AREA OF CONCERN IS THE ROCKY MOUNTAIN FRONT WHERE CONTINUED RAIN IS EXPECTED AT LOWER ELEVATIONS. FLOOD WATCHES WILL BE CONTINUED FOR THIS REGION AS WELL. && .PRELIMINARY POINT TEMPS/POPS... GTF 53 45 55 44 / 100 80 80 60 CTB 50 42 51 41 / 100 80 80 60 HLN 53 46 58 46 / 80 70 60 60 BZN 54 41 58 42 / 70 60 60 50 WEY 46 32 45 34 / 70 60 60 50 DLN 52 39 57 41 / 60 60 50 40 HVR 56 47 55 46 / 100 80 80 50 LWT 50 42 51 41 / 100 80 80 40 && .TFX WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR MTZ008>010-012>015- 044>046-048>055. HEAVY SNOW WARNING UNTIL NOON MDT TODAY FOR MTZ008-015-055. WINTER STORM WARNING UNTIL 6 PM MDT THIS AFTERNOON FOR MTZ009- 014-048. FLOOD WARNINGS UNTIL FURTHER NOTICE FOR MTZ008-015-055. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREAT FALLS MT 356 AM MDT FRI MAY 23 2008 MTZ008>010-012>015-044>046-048>055-241115- BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-CASCADE- CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-TOOLE- LIBERTY-EASTERN PONDERA-SOUTHERN ROCKY MOUNTAIN FRONT- EASTERN TETON-JUDITH BASIN-FERGUS-JEFFERSON-BROADWATER-MEAGHER- GALLATIN- 356 AM MDT FRI MAY 23 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT MINOR FLOODING IS FORECASTED FOR PORTIONS OF BEAVERHEAD...MADISON...AND GALLATIN COUNTIES. A FLOOD WATCH REMAINS IN EFFECT FOR MUCH OF NORTH CENTRAL AND SOUTHWEST MONTANA. CONTINUED PRECIPITATION MAY CAUSE SOME RIVERS TO EXCEED FLOOD STAGE. A HEAVY SNOW WARNING REMAINS IN EFFECT UNTIL NOON TODAY ABOVE 7000 FEET IN BEAVERHEAD...CASCADE...JUDITH BASIN...MADISON...MEAGHER... AND GALLATIN COUNTIES. A WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT TODAY FOR THE NORTHERN ROCKIES. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY A FLOOD WATCH REMAINS IN EFFECT THROUGH SUNDAY AFTERNOON. MINOR FLOODING IS FORECASTED FOR PORTIONS OF BEAVERHEAD...MADISON...AND GALLATIN COUNTIES. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ011-047-241115- HILL-BLAINE- 356 AM MDT FRI MAY 23 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
The national radar mosaic for the moment the first event began.
7 flood, 1 heavy rain. Local standard time, as filed.
Reports of 6 to 8 inches of water over Red Hill Road near Half Moon Canyon in Big Snowy Mountains.
Saint Mary Visitor Center parking lot was flooded and Saint Mary bridge was closed. Rising Sun Campground was flooded. A few landslides and debris flows have been reported with flooding reported on Belly River and Dry Creek near Trout Lake.
Storm total of 6.95 inches of rain led to flooding in and around Half Moon Pass area of eastern Fergus County.
Dupuyer Creek over bankfull causing some lowland flooding.
Numerous small creeks running at or just above bankful including Bridger, Bozeman, Middle, Sourdough and Beasley Creeks. One paved private road was washed out in this region.
Water over several area roadways near creeks...including Wolf Creek area and Elk Creek area near Augusta.
Storm total rainfall was 5.20 inches. Deep Creek was out of its banks and approached a home.
The Marias River south of Shelby came out of its banks and flooded nearby areas...including the golf course and adjacent low lands. Debris flow of logs...caused some river jamming.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2008Every state in 2008This day in weather historyWarnings in Montana, May 2008
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: 108813, 108820, 108822, 108823, 108828, 108834, 108840, 108838.