1 thunderstorm wind, as filed by the National Weather Service.
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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 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 12, 2:00 PM MST, 1 hour 23 minutes earlier.
SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 300 PM MDT SAT MAY 12 2001 ACCAS SHOWING UP OUTSIDE WITH PLENTY OF IT UPSTREAM IN SOUTHWEST FLOW ALOFT. STILL THINK WITH LATE AFTERNOON HEATING...AN ISOLATED THUNDERSTORM NOT OUT OF THE QUESTION OVER THE WEST PART OF CWA. BEEN NOTICING A GOOD FETCH OF MOISTURE FEEDING INTO THE NORTHWEST CORNER OF THE STATE ALSO. WILL GO WITH ISOLATED SHOWERS AND EVENING THUNDERSTORMS FOR THIS EVENING OVER WEST AND SOUTHWEST AND CARRY SLIGHT CHANCE FOR CTB/GTF/LWT. UPPER RIDGE CONTINUES TO BUDGE EAST OVERNIGHT AS PACIFIC COOL FRONT ENTERS WESTERN MT BY MIDNIGHT AND MAKES PASSAGE THROUGH GTF BY 12Z. H5 HEIGHT FALLS OF 30-40M THROUGHOUT SUNDAY FOR SOME COOLING. FRONT HANGS UP OVER SOUTHWEST SUNDAY AFTERNOON WITH SOME MOISTURE CONVERGENCE OVER THAT AREA. SOUTHWEST FLOW ALSO CONTINUES ALOFT WITH A PIECE OF VORTICITY ENTERING SOUTHWEST LATE AFTERNOON. ETA SHOWING SOME MODERATE CAPE... WILL GO WITH ISOLATED SHOWERS AND AFTERNOON THUNDERSTORMS. SCATTERED SHOWERS CONTINUING INTO MONDAY MORNING OVER MOUNTAINS BEFORE FLAT RIDGE COMES OVERHEAD. SURFACE PRESSURE GRADIENT TIGHTENS UP A TAD FOR FAIRLY STRONG DOWNSLOPE EAST OF DIVIDE MONDAY./SCHMIDT EXTENDED DISCUSSION...EXTENDED PORTION CONTINUES TO LOOK DRY WITH ZONAL FLOW FOR MOST OF THE PERIOD...AND CWA ON ANTI-CYCLONIC SIDE OF JET STREAM. THE FLOW BUCKLES SLIGHTLY ON WEDNESDAY AS COLD FRONT MOVES THROUGH THE CWA...BUT THE MOISTURE WITH THIS FEATURE DRIES UP AS IT CROSSES THE MOUNTAINS...AND THERE IS LITTLE MID/UPPER LEVEL SUPPORT. AVN RUN FROM 12Z HAS PUSHED THE UPPER LOW AND ASSOCIATED ENERGY ON WEDNESDAY MUCH FURTHER NORTH THAN WAS DEPICTED IN THE 00Z RUN. ON THURSDAY ZONAL FLOW RETURNS...WITH TEMPERATURES ONLY SLIGHTLY COOLER. ANOTHER WEAK PACIFIC FRONT INTO CENTRAL MONTANA ON SATURDAY FOR A CHANCE OF SHOWERS. KP CCF NUMBERS GTF EE 050/081 046/077 044 11222 CTB BE 049/077 043/074 042 11211 HLN BB 049/081 046/078 044 11222 BZN EB 045/081 042/078 040 11222 WEY EB 032/074 030/071 030 11222 DLN EB 045/079 041/076 044 11222 HVR EE 051/083 046/079 044 11111 LWT EB 050/081 046/077 044 11222
The Pocatello radar (KSFX), 215 km away, was scanning. The volume nearest the first event began at 22:18 UTC.
1 thunderstorm wind. Local standard time, as filed.
Actual report location is Brenner RAWS site at Grant 8 SW...Estimated 52 kt gust reported by spotter at Grant and measured 50 kt gust reported at Dillon Airport ASOS with both reports coming in at 1626 MST.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2001Every state in 2001This day in weather historyWarnings in Montana, May 2001
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: 5249955.