Rising rivers, rapid snowmelt and continuous rain prompted the declaration on 5/24/11.
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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 episode as NWS TFX wrote it up.
Rising rivers, rapid snowmelt and continuous rain prompted the declaration on 5/24/11.
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 23, 10:00 PM MST, 2 hours earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1100 PM MDT MON MAY 23 2011 UPDATED AVIATION SECTION .DISCUSSION... CURRENT FORECAST IS ON TRACK...BUT DID RAISE POPS ACROSS MUCH OF NORTH CENTRAL MONTANA. WITH A VERY MOIST AIRMASS IN PLACE...WIDESPREAD SHOWERS ARE DEVELOPING OVER THE REGION ALONG WITH ISOLATED THUNDERSTORMS. THIS SHOWER ACTIVITY SHOULD INCREASE IN COVERAGE AREA AFTER MIDNIGHT...WITH A WIDESPREAD RAINFALL EXPECTED ACROSS MUCH OF THE REGION FOR TUESDAY. OVERNIGHT LOWS WILL NOT DROP MUCH FROM CURRENT TEMPS...THUS THEY WILL NOT RISE MUCH DURING THE DAY ON TUESDAY. ALL ELSE IS ON TRACK. BRUSDA && .AVIATION... UPDATED 0500Z. SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE OVERNIGHT AS AN UPPER LEVEL DISTURBANCE APPROACHES WESTERN MONTANA. SHOWERS WILL BECOME WIDESPREAD AFTER 12Z. VFR CONDITIONS PREVAIL WITH MVFR CONDITIONS IN THE VICINITY OF SHOWERS. MVFR/IFR CONDITIONS WILL BECOME MORE WIDESPREAD AFTER 12Z DUE TO LOWERING CEILINGS AND RAIN. MOUNTAINS WILL BECOME OBSCURED AFTER 12Z. && .HYDROLOGY... FLOODING CONTINUES OVER PORTIONS OF CENTRAL MONTANA...WITH SOME VERY MINOR IMPROVEMENTS REPORTED THIS EVENING...BUT MOST RIVERS/STREAMS REMAIN ABOVE FLOOD STAGE...THUS THE FLOOD WARNING WILL CONTINUE. AN AREA OF HEAVY RAIN DEVELOPED WEST OF CUT BANK THIS EVENING...THUS A SMALL STREAM FLOOD ADVISORY HAS BEEN ISSUED FOR THIS REGION FOR TONIGHT. THE FLOOD WATCH REMAINS IN EFFECT FOR THE REMAINDER OF THE REGION. WIDESPREAD RAINFALL AMOUNTS OF A 0.50 INCHES UP TO 1.50 INCHES ARE POSSIBLE OVER THE REGION ON TUESDAY. THUS THE THREAT FOR FLOODING WILL CONTINUE. ADDITIONALLY...MANY MAJOR RIVERS ARE RISING AND ADDITIONAL FLOOD HIGHLIGHTS COULD BE ISSUED LATER THIS WEEK FOR ADDITIONAL MAJOR RIVERS ACROSS THE REGION. && .PREV DISCUSSION... /ISSUED 545 PM MDT MON MAY 23 2011/ PACIFIC NORTHWEST COAST WILL CONTINUE TO BRING A MOIST UNSTABLE FLOW INTO MONTANA TONIGHT. WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS WILL AFFECT MY FORECAST AREA OVERNIGHT WITH SOME LOCALLY HEAVY SHOWERS LIKELY. MODELS SHOW THAT THE CORE OF THE UPPER LOW WILL BE KICKED EASTWARD ON TUESDAY WITH DYNAMICS MOVING ACROSS SOUTHERN MONTANA THROUGH THE DAY. AT THE SURFACE AN INVERTED TROUGH WILL STRETCH ACROSS WYOMING AND MONTANA INTO BRITISH COLUMBIA WITH RAINS PERSISTING ACROSS THIS REGION THROUGH THE DAY AND INTO TUESDAY NIGHT. BY WEDNESDAY THE DYNAMICS ASSOCIATED WITH THE REMNANT LOW WEAKEN AS ANOTHER LOW FORMS OVER THE EASTERN PACIFIC AND RIDGING BUILDS INTO MONTANA. HOWEVER...I STILL EXPECT SCATTERED SHOWERS AND A FEW THUNDERSTORMS TO LINGER OVER THE REGION ON WEDNESDAY. TEMPERATURES ARE EXPECTED TO BE COOLER ON TUESDAY AS PRECIPITATION IS EXPECTED TO PREVAIL ACROSS THE REGION...BUT REBOUND AGAIN ON WEDNESDAY AS THE RIDGE AND PARTIAL CLEARING MOVE OVER CENTRAL MONTANA. MPJ WED NIGHT-THURSDAY...WEAK SHORTWAVE RIDGE ACROSS AREA WED NIGHT WITH SOME LINGERING SHOWERS POSSIBLE FROM OVER-RUNNING SW FLOW AHEAD OF DEEP UPPER LEVEL TROUGH OFF THE PAC NW COAST. SHORTWAVE WILL MOVE INTO THE AREA EARLY THURSDAY BRINGING WITH IT AMPLE MOISTURE. DECENT MID LEVEL LAPSE RATES AND WEAK SFC INSTABILITY MAY ALLOW FOR SOME THUNDERSTORMS. TEMP PROFILES SHOW THAT THE PRECIP SHOULD BE ALL LIQUID BELOW 8000 FEET...MAYBE EVEN HIGHER. RAINFALL AMOUNTS OF .25 TO .5 INCHES WILL BE POSSIBLE ACROSS THE ENTIRE AREA WITH ISOLATED HIGHER AMOUNTS POSSIBLE IN THUNDERSTORMS. FLOODING CONCERNS OR ISSUES WILL PERSIST AND WILL LIKELY WORSEN IN SOME LOCATIONS DUE TO THIS PRECIP. FRIDAY-MONDAY...WEAK SHORTWAVE RIDGE IN PLACE EARLY FRIDAY AS SYSTEM PUSHES EAST. MAYBE SOME LINGERING PRECIP ACROSS THE NORTHEAST PORTIONS OF THE FORECAST AREA...MAINLY HILL AND BLAINE COUNTIES. MOST OF THE AREA WILL BE DRY FRIDAY AS THE NEXT SYSTEM HEADS TOWARDS THE REGION. MOIST SW FLOW DEVELOPS ONCE AGAIN BY EARLY SATURDAY AND THE NEXT TROUGH WORKS INTO THE REGION. DECENT DIVERGENCE WITH SOME JET DYNAMICS WILL CREATE DECENT LIFT ACROSS THE REGION ALLOWING FOR PRECIP ACROSS THE STATE. MODEL AGREEMENT NOT AS GOOD WITH THE WEEKEND STORM AS IT WAS WITH THURSDAYS EVENT. WITH MANY SOLUTIONS STILL POSSIBLE...LOWER THAN AVERAGE CONFIDENCE AT THIS TIME. SOME SOLUTIONS ARE SHOWING THE BULK OF THE PRECIP ON SATURDAY OVER SOUTHWEST MONTANA. OTHER MODEL SOLUTIONS ARE SHOWING THE ENTIRE STATE WITH PRECIP THROUGH THE WEEKEND AND INTO MONDAY. THIS PERIOD WILL NEED TO BE WATCHED CLOSELY AS EXTENDED PERIODS OF PRECIP THROUGH THE ENTIRE WEEKEND MAY CAUSE SERIOUS FLOODING CONCERNS. && .PRELIMINARY POINT TEMPS/POPS... GTF 53 54 45 65 / 80 80 70 30 CTB 49 52 42 62 / 90 80 60 40 HLN 50 55 44 68 / 60 80 60 30 BZN 49 59 42 66 / 60 80 60 30 WEY 42 48 33 55 / 60 70 50 30 DLN 44 56 39 67 / 60 80 40 20 HVR 55 63 46 65 / 80 60 40 30 LWT 48 56 43 57 / 100 80 60 50 && .TFX WATCHES/WARNINGS/ADVISORIES... FLOOD WARNINGS THROUGH AT LEAST TUESDAY MORNING FOR CASCADE...FERGUS...JUDITH BASIN...CHOUTEAU...BLAINE AND MEAGHER COUNTIES. FLOOD WATCH THROUGH TUESDAY AFTERNOON BEAVERHEAD...BROADWATER... CENTRAL AND SOUTHERN LEWIS AND CLARK...EASTERN GLACIER...EASTERN PONDERA...EASTERN TETON...GALLATIN...HILL...JEFFERSON... LIBERTY...MADISON...NORTHERN ROCKY MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT...TOOLE. FLOOD WATCH FOR THE BIG HOLE RIVER AT MELROSE FOR TUESDAY EVENING THROUGH FRIDAY AFTERNOON. SMALL STREAM FLOOD ADVISORY UNTIL TUESDAY MORNING FOR PORTIONS OF GLACIER COUNTY. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE GREAT FALLS MT 1140 PM MDT MON MAY 23 2011 MTZ008>015-044>055-241200- BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL- CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON- TOOLE-LIBERTY-EASTERN PONDERA-BLAINE- SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS- JEFFERSON-BROADWATER-MEAGHER-GALLATIN- 1140 PM MDT MON MAY 23 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT A FLOOD WARNING IS IN EFFECT FOR BLAINE...CASCADE...CHOUTEAU... FERGUS...JUDITH BASIN...AND MEAGHER COUNTIES. A FLOOD WATCH IS IN EFFECT FOR THE REMAINDER OF NORTH CENTRAL... CENTRAL...AND SOUTHWEST MONTANA NOT MENTIONED ABOVE. A SMALL STREAM FLOOD ADVISORY IS IN EFFECT FOR GLACIER AND HILL COUNTIES. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THE FLOOD WARNING IS IN EFFECT THROUGH AT LEAST THURSDAY MORNING. THE FLOOD WATCH IS IN EFFECT THROUGH AT LEAST TUESDAY AFTERNOON. THE SMALL STREAM FLOOD ADVISORY IS IN EFFECT UNTIL TUESDAY MORNING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS REQUESTED ALONG ALL CREEKS AND RIVERS. REPORTS OF FLOODING WOULD BE GREATLY APPRECIATED.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Rising rivers, rapid snowmelt and continuous rain prompted the declaration on 5/24/11.
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: 372194.