Heavy rains in Petroleum and Garfield counties swelled creeks and resulted in higher levels on the Musselshell River to above Flood Stage.
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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 GGW wrote it up.
Heavy rains in Petroleum and Garfield counties swelled creeks and resulted in higher levels on the Musselshell River to above Flood Stage.
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 Glasgow, MT wrote its last area forecast discussion before the first event at May 9, 8:22 PM MST, 6 hours 2 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GLASGOW MT 922 PM MDT MON MAY 9 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH WEDNESDAY... UPDATED FORECAST TONIGHT TO INCLUDE GREATER COVERAGE OF THUNDER TONIGHT AND TO RAISE AN AREAL FLOOD WATCH FOR THE SOUTHERN AND EASTERN AREAS THROUGH TUESDAY NIGHT. HAVE HAD IN EXCESS OF ONE INCH OF RAIN ALREADY IN THE LAST 24 HOURS ACROSS GARFIELD COUNTY AND PARTS OF WIBAUX COUNTY...WITH A MORE GENERAL ONE HALF TO ONE INCH ELSEWHERE SOUTHEAST OF A LINE FROM PLENTYWOOD TO GLASGOW TO CONTENT. LATEST SPC MESO ANALYSIS CONTINUES TO SHOW AREA OF WEAK MUCAPES OVER THE SOUTHEAST AREAS WITH HIGHER VALUES SUSTAINING VIGOROUS CONVECTION OVER WRN SOUTH DAKOTA. THIS CONVECTION WILL LIKELY CONTINUE TO FEED NORTH AND THEN NORTHWESTWARD AROUND DEVELOPING MID LEVEL LOW PRESSURE MOVING OVER SOUTHEASTERN MT LATE TONIGHT. STRONG Q-VECTOR CONVERGENCE AND FRONTOGENETICAL FORCING DEVELOPS OVER THE SOUTHEAST HALF OF NORTHEAST MT TUESDAY AND CONTINUES INTO TUESDAY NIGHT. SO THE FLOOD WATCH SERVES TWO PURPOSES. ONE TO HIGHLIGHT POTENTIAL HIGHER RAINFALL RATES LEADING TO QUICK RISES OF WATER TONIGHT...AND THEN MORE GENERAL MODERATE TO HEAVY RAIN FOR TUESDAY. WITH ANOTHER 1 TO 3 INCHES OF RAIN AND LOCALLY HIGHER AMOUNTS EXPECTED OVER THE NEXT 24 TO 36 HOURS AND GIVEN MOIST GROUND CONDITIONS...FEEL FLOODING IS QUITE POSSIBLE. MOYER ...PREVIOUS DISCUSSION... A VERY WET STORM SYSTEM CENTERED OVER THE GREAT BASIN CONTINUES TO PUSH AMPLE MOISTURE AND DISTURBANCES INTO NORTHEAST MONTANA THIS AFTERNOON. THIS EVENING AND OVERNIGHT THE PRECIPITATION WILL PICK UP IN INTENSITY AS A 700MB LOW DEEPENS OVER NORTHEAST WYOMING. AS THIS OCCURS A WELL DEVELOPED TROWAL FEATURE WILL SET UP OVER NORTHEAST MONTANA ON THE BACK SIDE OF THE LOW. THIS MORE INTENSE PRECIPITATION WILL LINGER INTO TUESDAY BEFORE FINALLY TAPERING OFF TUESDAY NIGHT INTO WEDNESDAY. STORM TOTAL PRECIPITATION AMOUNTS CONTINUE TO LOOK TO BE IN THE 1-3 INCH RANGE. WITH THE DEVELOPING LOW...GUSTY WINDS WILL CONTINUE. THUS THE LAKE WIND ADVISORY LOOKS ON TRACK. AS THE PRECIP BEGINS TO WIND DOWN TUESDAY NIGHT THE THREAT FOR THE SNOW LEVEL TO LOWER TO THE SURFACE REMAINS GIVEN AMPLE DYNAMIC COOLING. AGREE WITH THE PREVIOUS FORECASTER THAT A COLD RAIN LOOKS MOST LIKELY BUT GIVEN THE IMPACTS OF HEAVY WET SNOW THIS TIME OF YEAR CONTINUED MENTION OF LIGHT SNOW ACCUMULATIONS TUESDAY NIGHT INTO WEDNESDAY MORNING. WITH THE EXITING SYSTEM WEDNESDAY DRIER AIR WILL WRAP INTO THE WESTERN ZONES OUT OF CANADA. TEMPERATURES WILL ALSO WARM THERE AS THE SKIES BREAK OUT. SOME LINGERING CHANCES FOR PRECIPITATION REMAIN OVER THE EASTERN ZONES. THESE POPS ARE REALLY DEPENDENT ON THE SEED IN WHICH THE STORM EXITS. GILCHRIST .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY... THE GOES WATER VAPOR IMAGERY SHOWS A HIGH PRESSURE RIDGE NUDGING UP AGAINST THE CANADIAN WEST COAST TODAY THAT WILL WORK ITS WAY EAST TO BE OVER THE ROCKY MOUNTAINS AND MONTANA PLAINS WEDNESDAY NIGHT. THIS RIDGE WILL BLOCK THE UPPER TROUGH FOLLOWING THE RIDGE WHERE IT WILL HANG UP ALONG THE PACNW COAST AT LEAST THROUGH FRIDAY NIGHT. FROM THAT POINT THERE ARE DIFFERENCES IN THE EXTENDED SOLUTIONS. WITH THE EC ON SATURDAY...WHICH HPC IS CALLING AN OUTLIER...THE UPPER TROUGH TO THE EAST RETROGRADES A BIT AND SENDS A WAVE INTO OUR BACK DOOR FROM THE NORTHEAST. THEN AROUND SUNDAY THE PACNW TROUGH AND THE BACKDOOR TROUGH MERGE TO CONTINUE THE UNSETTLED WEATHER FOR THE WEEKEND AND EARLY NEXT WEEK. THE GFS MAINTAINS THE BLOCK AND RIDGE OVER EASTERN MONTANA THROUGH THE WEEKEND. WHEN THE BLOCK BREAKS DOWN THE WEST COAST TROUGH WILL THEN BEGIN TO MOVE EAST BRINGING ON A WET PERIOD NEXT WEEK. FEW CHANGES WERE NEEDED. SCT PREVIOUS DISCUSSION... MAJORITY OF THE EXTENDED PERIOD WILL BE UNDER THE INFLUENCE OF UPPER RIDGE AS QUASI OMEGA BLOCK PATTERN DEVELOPS. UPPER LOW OFF THE NEW ENGLAND COAST PERSIST THROUGH THE WEEK BLOCKING PROGRESSION OF SYSTEMS COMING OUT OF THE PACIFIC. SPLIT UPPER TROF MOVING FROM THE GREAT BASIN INTO THE NORTHERN AND CENTRAL PLAINS DURING THE SHORT TERM REFORMS INTO AN ELONGATED LOW OVER THE MIDWEST...WHILE ANOTHER UPPER LOW DROPS SOUTH ALONG THE PACIFIC COAST. BLOCK BEGINS TO BREAK DOWN OVER THE WEEKEND AS THE ATLANTIC COAST LOW WEAKENS ALLOWING THE MIDWEST AND PACIFIC TROFS TO SHIFT EASTWARD. OVERALL EXPECT DRY AND WARMER WEATHER FOR NORTHEAST MONTANA WITH RIDGE AXIS JUST TO THE WEST OF THE REGION. SOME POSSIBILITY OF THE NORTHERN PORTION OF THE MIDWEST LOW RETROGRADING BRINGING CLOUDS AND SHOWERS INTO THE REGION. THIS SOLUTION STILL AN OUTLIER SO FOR NOW WILL KEEP FORECAST DRY INTO THE WEEKEND. MORE REASONABLE CHANCE OF SHOWERS WILL BE AT THE END OF THE FORECAST PERIOD WHEN RIDGE AXIS SHIFTS EAST AS THE BLOCK BREAKS DOWN. EBERT && .AVIATION... EXPECT MVFR TO IFR CEILINGS AND VISIBILITIES. A LARGE SCALE UPPER TROUGH/STORM SYSTEM CENTERED OVER THE GREAT BASIN WILL CONTINUE TO EJECT A SIGNIFICANT AMOUNT OF PACIFIC MOISTURE NORTH INTO MONTANA TONIGHT AND TUESDAY. THIS WILL RESULT IN LENGTHY PERIODS OF MODERATE...AND INTERMITTENTLY HEAVY...RAIN. A FEW EMBEDDED THUNDERSTORMS ARE ALSO POSSIBLE AT THE KSDY AND KGDV TAF SITES. IN ADDITION... A STRONG CLOSED SURFACE LOW IN NEBRASKA WILL TRACK NORTH INTO NORTH DAKOTA ON TUESDAY. THIS LOW WILL GENERATE STRONG NORTHERLY SURFACE WINDS THAT WILL INCREASE FROM 20-30KT TODAY TO 25-35KTS TUESDAY. SCT && .HYDROLOGY... SIGNIFICANT RAINFALL CONTINUES TO FALL ACROSS NORTHEAST MONTANA... WITH MORE ON THE WAY. AT THIS TIME THE HEAVIEST RAINFALL CONTINUES TO LOOK EAST OF A SCOBEY TO GLASGOW TO WINNETT LINE. RISES CAN BE EXPECTED ON THE MILK...YELLOWSTONE...POPLAR... MUSSELSHELL...AND POPLAR RIVERS...AS WELL AS ON BIG MUDDY CREEK. SMALLER CREEKS WILL ALSO SEE RISES...SUCH AS BEAVER CREEK IN WIBAUX COUNTY. PERSONS ARE STILL ADVISED TO KEEP A WATCHFUL EYE FOR CHANGING RIVER AND STREAM CONDITIONS THROUGH MIDWEEK. GILCHRIST && .GLASGOW WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH THROUGH TUESDAY EVENING FOR GARFIELD...MCCONE... DAWSON...PRAIRIE...WIBAUX. LAKE WIND ADVISORY UNTIL 9 PM MDT TUESDAY FOR FORT PECK LAKE. FLOOD WATCH THROUGH LATE TUESDAY NIGHT FOR SHERIDAN...WESTERN ROOSEVELT...RICHLAND...EASTERN ROOSEVELT. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE GLASGOW MT 940 PM MDT MON MAY 9 2011 MTZ016>018-021-059>061-110345- CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY- DANIELS-PETROLEUM-NORTHERN PHILLIPS-SOUTHWEST PHILLIPS- NORTHERN VALLEY- 940 PM MDT MON MAY 9 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TONIGHT PERIODS OF MODERATE TO HEAVY RAIN ARE LIKELY TONIGHT. WITH WINDS OF 20 TO 35 MPH...A LAKE WIND ADVISORY FOR FORT PECK LAKE HAS BEEN ISSUED FOR THE PERIOD. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY PERIODS OF MODERATE TO HEAVY RAIN WILL CONTINUE TUESDAY BUT TAPER OFF FROM WEST TO EAST TUESDAY NIGHT. ONE TO POSSIBLY AS MUCH AS THREE INCHES OF RAIN IS POSSIBLE BY TUESDAY NIGHT. THIS WILL LIKELY RESULT IN SOME PONDING OF WATER IN LOW LYING AND POOR DRAINAGE AREAS. NORTH WINDS WILL ALSO INCREASE ON TUESDAY AND COMBINED WITH THE RAIN WILL POSE A SIGNIFICANT HAZARD TO YOUNG LIVESTOCK. RANCHERS ARE ADVISED TO TAKE NECESSARY PRECAUTIONS TO PROTECT NEWBORN CALVES. RIVER RISES ARE ALSO EXPECTED AS THE RAINFALL RUNS OFF. SIGNIFICANT RISES ON AREA RIVERS AND STREAMS ARE POSSIBLE THROUGH THE WEEK. A LAKE WIND ADVISORY FOR FORT PECK LAKE CONTINUES THROUGH TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ019-020-022>027-062-110345- SHERIDAN-WESTERN ROOSEVELT-GARFIELD-MCCONE-RICHLAND-DAWSON- PRAIRIE-WIBAUX-EASTERN ROOSEVELT- 940 PM MDT MON MAY 9 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TONIGHT SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH MUCH OF THE NIGHT. RAINFALL RATES IN EXCESS OF ONE HALF INCH PER HOUR ARE POSSIBLE. A FLOOD WATCH IS IN EFFECT FOR THE AREA. FOR FURTHER DETAILS GO TO OUR WEBSITE AT WWW.WEATHER.GOV/GLASGOW. WITH WINDS OF 20 TO 35 MPH...A LAKE WIND ADVISORY FOR FORT PECK LAKE HAS BEEN ISSUED FOR THE PERIOD. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY PERIODS OF MODERATE TO HEAVY RAIN WILL CONTINUE TUESDAY BUT TAPER OFF FROM SOUTHWEST TO NORTHEAST TUESDAY NIGHT. ONE TO THREE INCHES OF RAIN WITH LOCAL AMOUNTS IN EXCESS OF 4 INCHES ARE POSSIBLE BY TUESDAY NIGHT. THIS WILL LIKELY RESULT IN OVERLAND FLOODING AND EXTENSIVE PONDING OF WATER IN LOW LYING AND POOR DRAINAGE AREAS. A FLOOD WATCH CONTINUES IN EFFECT THROUGH TUESDAY NIGHT. IT IS POSSIBLE THAT SNOW WILL MIX WITH THE RAIN OR THE RAIN WILL CHANGE TO ALL SNOW NEAR THE NORTH DAKOTA BORDER TUESDAY NIGHT. IF A COMPLETE CHANGEOVER OCCURS...ACCUMULATING SNOW IS LIKELY. NORTH WINDS WILL ALSO INCREASE ON TUESDAY AND COMBINED WITH THE RAIN WILL POSE A SIGNIFICANT HAZARD TO YOUNG LIVESTOCK. RANCHERS ARE ADVISED TO TAKE NECESSARY PRECAUTIONS TO PROTECT NEWBORN CALVES. RIVER RISES ARE ALSO EXPECTED AS THE RAINFALL RUNS OFF. SIGNIFICANT RISES ON AREA RIVERS AND STREAMS ARE POSSIBLE THROUGH THE WEEK. A LAKE WIND ADVISORY FOR FORT PECK LAKE CONTINUES THROUGH TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MOYER
The national radar mosaic for the moment the first event began.
4 flood. Local standard time, as filed.
USGS river gauge at Mosby recorded a crest of 9.18 feet (1.18 feet over flood stage). Chain Buttes RAWS reported heavy rain of 1.61 inches in a short period of time. Dry Blood Creek RAWS reported 1.13 inches in a short period of time.
South Sawmill Raws measured 1.95 inches of rain in a short period of time. Creeks that fed into the Musselshell River in western Garfield County were out of their banks.
High river levels continued on the Musselshell River and its tributaries. The gauge at Mosby crested at 1843 MST on May 11th at 13.98 feet. This is almost 6 feet above Flood Stage.
High river levels continued on the Musselshell River and its tributaries. The gauge at Mosby crested at 1843 MST on May 11th at 13.98 feet. This is almost 6 feet above Flood Stage.
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: 309003, 309004, 309645, 309646.