Heavy rain and snowmelt caused several roads to be washed out as the Judith River and many small streams and creeks flooded. Flood declaration made for Judith Basin county on 5/23/11.
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.
Heavy rain and snowmelt caused several roads to be washed out as the Judith River and many small streams and creeks flooded. Flood declaration made for Judith Basin county on 5/23/11.
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 19, 10:40 AM MST, 22 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1140 AM MDT THU MAY 19 2011 .UPDATE... ALL SEEMS TO BE ON TRACK FOR A FAIRLY GOOD AREA OF RAIN TO AFFECT THE EASTERN PORTIONS OF OUR REGION FRIDAY THROUGH THE WEEKEND. WITH FAIRLY QUIET WEATHER/SCATTERED SHOWERS OVER THE WESTERN PORTIONS. TEMPERATURES TODAY LOOK ON TRACK...BUT DO EXPECT A WIND SHIFT TO THE NORTH OVER NORTH CENTRAL MONTANA. AGAIN...THE MAIN CONCERN WILL BE THE FLOODING POTENTIAL OVER THE NEXT FEW DAYS. CURRENT MODELS DELAY THE HEAVIER PRECIP MOVING INTO THE REGION UNTIL LATER TONIGHT...SO THE START TIME FOR THE FLOOD WATCHES MIGHT START A BIT LATER...BUT OVERALL NO BIG CHANGES. BRUSDA && .AVIATION... UPDATED 1800Z. LOW PRESSURE CENTERED OVER EASTERN UT WILL DRIFT TO THE NORTH AND NORTHEAST TONIGHT INTO WY BY FRIDAY MORNING. MOST AREAS WILL REMAIN PRECIPITATION FREE THROUGH THIS EVENING BEFORE MOISTURE SPREADS INTO THE REGION FROM THE SE AHEAD OF THE LOW PRESSURE SYSTEM. SCT-BROKEN LOWER CLOUDS WILL OCCASIONALLY PRODUCE MVFR CEILINGS AT NORTH CENTRAL MT TERMINALS WITH LOWEST CEILINGS AT THE KCTB TERMINAL. SHOWERS ALONG WITH MVFR CEILINGS WILL BECOME MORE PERSISTENT AND WIDESPREAD AT THE BOZEMAN AND LEWISTOWN TERMINALS BY EARLY FRIDAY MORNING WITH SIMILAR CONDITIONS DEVELOPING AT HELENA AND GREAT FALLS BY NOON FRIDAY. HOENISCH && .HYDROLOGY... THE SMALL STREAM FLOOD ADVISORY FOR FERGUS...JUDITH BASIN AND CASCADE COUNTIES HAS BEEN REPLACED WITH A FLOOD WATCH. THE FLOOD WATCH ALSO INCLUDES MEAGHER...GALLATIN...CHOUTEAU...HILL AND BLAINE COUNTIES. RAIN WILL MOVE INTO THE FORECAST AREA OVERNIGHT WITH PERIODS OF RAIN CONTINUING THROUGH SATURDAY NIGHT. SNOW LEVELS ARE RELATIVELY HIGH WITH THIS STORM SYSTEM SO RAIN FALLING ON THE EXISTING SNOW PACK WILL ACCELERATE SNOWMELT CAUSING RIVERS AND STREAMS COMING OUT OF THE MOUNTAINS TO SWELL...AND INCREASING THE LIKELIHOOD OF FLOODING. && .PREV DISCUSSION... /ISSUED 600 AM MDT THU MAY 19 2011/ TODAY THROUGH SATURDAY...MODELS HAVE COME INTO BETTER AGREEMENT AND APPEAR TO BE HONING IN ON A SOLUTION FOR THE ANTICIPATED RAIN EVENT OVER THE NEXT FEW DAYS. AT THIS TIME IT APPEARS THAT RAIN...POSSIBLY HEAVY AT TIMES...WILL MOVE FROM SOUTHEAST AND SOUTH CENTRAL MONTANA INTO EASTERN AND SOUTHERN PORTIONS OF MY FORECAST AREA OVERNIGHT. PERIODS OF RAIN WILL CONTINUE TO AFFECT MUCH OF THE FORECAST AREA THROUGH SATURDAY NIGHT. THE HEAVIEST PRECIPITATION AMOUNTS ARE EXPECTED TO BE OVER AND ADJACENT TO THE CENTRAL MONTANA ISLAND RANGES AS WELL AS THE GALLATIN AND BRIDGER RANGES IN GALLATIN COUNTY. SNOW LEVELS ARE EXPECTED TO BE FAIRLY HIGH SO I AM EXPECTING RAINFALL ON EXISTING SNOWPACK TO ACCELERATE SNOWMELT FROM THE MOUNTAINS AND INCREASE THE LIKELIHOOD OF FLOODING OF CREEKS AND STREAMS COMING OUT OF THE MOUNTAINS. PLEASE SEE HYDROLOGY SECTION BELOW FOR ADDITIONAL INFORMATION. SNOWFALL IN THE MOUNTAINS SHOULD BE ABOVE 8000 FEET AND MODEL GUIDANCE SUGGESTS THAT ACCUMULATION AMOUNTS WILL REMAIN BELOW WARNING CRITERIA. HOWEVER...THE ANTICIPATED HEAVY NATURE OF THE PRECIPITATION COULD CAUSE SNOW LEVELS TO DROP LOWER THAN EXPECTED AND ACCUMULATIONS TO BE HIGHER. THIS POSSIBILITY WILL BE MONITORED THROUGH THE EVENT AND WINTER HIGHLIGHTS WILL BE ISSUED IF NEEDED. MPJ SATURDAY NIGHT THROUGH WEDNESDAY...UNSETTLED WEATHER WILL PERSIST OVER THE REGION THROUGH MOST OF THE LONG TERM FORECAST AS A MOIST SOUTHERLY FLOW HOLDS OVER THE REGION. MODELS ARE CONSISTENT WITH SLOWLY BRINGING A SYSTEM THROUGH THE REGION OVER THE WEEKEND AND INTO NEXT WEEK. MODELS REMAIN IN FAIR AGREEMENT WITH BRINGING A DECENT AMOUNT OF PRECIPITATION TO PORTIONS OF CENTRAL MONTANA BUT THERE REMAIN DIFFERENCES IN EXACTLY HOW MUCH AND WHERE. PRECIP WILL BE SHOWERY IN NATURE SO QPF AMOUNTS STILL REMAIN SUBJECT TO CHANGE AND THUS CONFIDENCE IS NOT OVERLY HIGH IN EXACT VALUES. THE BIGGEST THING IS MODEL AGREEMENT THAT PORTIONS OF CENTRAL MONTANA SHOULD RECEIVE THE BULK OF ANY PRECIPITATION. BY THE END OF THE PERIOD THE MODELS CONTINUE TO BE MESSY WITH SHOWERY PRECIP SCATTERED ACROSS THE REGION. ANOTHER PACIFIC LOW LOOKS TO PASS SOUTH OF MONTANA PULLING MOST OF THE EXPECTED WEEKEND MOISTURE AWAY WITH IT. SCATTERED PERIODS OF INSTABILITY WILL ALLOW FOR AFTERNOON CONVECTIVE ACTIVITY A COUPLE DAYS SO KEPT THUNDER IN THE FORECAST. TEMPERATURES WILL BE AROUND SEASONAL AVERAGES THROUGHOUT THE PERIOD. && .PRELIMINARY POINT TEMPS/POPS... GTF 64 47 57 47 / 20 30 80 80 CTB 63 44 61 45 / 20 20 50 60 HLN 66 47 58 46 / 20 30 70 70 BZN 62 42 56 41 / 30 70 80 70 WEY 49 34 47 32 / 40 60 70 50 DLN 61 40 57 38 / 30 40 60 50 HVR 68 48 65 48 / 20 20 60 80 LWT 57 43 51 44 / 30 90 100 90 && .TFX WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH FROM THIS EVENING THROUGH LATE SATURDAY NIGHT FERGUS...GALLATIN...JUDITH BASIN...MEAGHER. FLOOD WATCH FROM FRIDAY MORNING THROUGH LATE SATURDAY NIGHT BLAINE...CASCADE...CHOUTEAU...HILL. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREAT FALLS MT 427 AM MDT THU MAY 19 2011 MTZ050-051-054-055-201200- JUDITH BASIN-FERGUS-MEAGHER-GALLATIN- 427 AM MDT THU MAY 19 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT A FLOOD WATCH HAS BEEN ISSUED FOR THIS EVENING THROUGH LATE SATURDAY NIGHT. RAIN WILL MOVE INTO THE REGION TONIGHT WITH PERIODS OF RAIN CONTINUING THROUGH SATURDAY NIGHT. SNOW LEVELS WILL REMAIN HIGH DURING THIS EVENT SO RAINFALL ON EXISTING MOUNTAIN SNOWPACK WILL ACCELERATE SNOWMELT AND INCREASE THE LIKELIHOOD OF FLOODING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THE FLOOD WATCH REMAINS IN EFFECT THROUGH LATE SATURDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS REQUIRED ALONG ALL CREEKS...SMALL STREAMS AND RIVERS. REPORTS OF FLOODING WOULD BE GREATLY APPRECIATED. MTZ011>013-047-201200- HILL-CASCADE-CHOUTEAU-BLAINE- 427 AM MDT THU MAY 19 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA AND NORTH CENTRAL MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER TODAY AND TONIGHT IS LOW. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A FLOOD WATCH HAS BEEN ISSUED FOR FRIDAY MORNING THROUGH LATE SATURDAY NIGHT. RAIN WILL MOVE INTO THE REGION EARLY FRIDAY MORNING WITH PERIODS OF RAIN CONTINUING THROUGH SATURDAY NIGHT. SNOW LEVELS WILL REMAIN HIGH DURING THIS EVENT SO RAINFALL ON EXISTING MOUNTAIN SNOWPACK WILL ACCELERATE SNOWMELT AND INCREASE THE LIKELIHOOD OF FLOODING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS REQUIRED ALONG ALL CREEKS...SMALL STREAMS AND RIVERS. REPORTS OF FLOODING WOULD BE GREATLY APPRECIATED. MTZ008>010-014-015-044>046-048-049-052-053-201200- BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER- CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-TOOLE-LIBERTY- EASTERN PONDERA-SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON- JEFFERSON-BROADWATER- 427 AM MDT THU MAY 19 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER TODAY AND TONIGHT IS LOW. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A STORM SYSTEM WILL BRING PERIODS OF RAIN AND HIGH MOUNTAIN SNOW TO THE REGION FRIDAY AND SATURDAY. THE ANTICIPATED PRECIPITATION COULD CAUSE ADDITIONAL RISES ON CREEKS...STREAMS AND RIVERS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION COULD BE REQUIRED ALONG ALL CREEKS...SMALL STREAMS AND RIVERS FRIDAY THROUGH SUNDAY. REPORTS OF HEAVY PRECIPITATION AND ANY FLOODING WOULD BE GREATLY APPRECIATED.
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Several roads were washed out including the Utica area and areas south of Stanford and Hobson.
KRTV reports U.S. 487 washed out near Utica in addition to many landowner's private bridges.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2011Every state in 2011This day in weather historyWarnings in Montana, May 2011
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: 369900, 370420.