Areas of heavy rain produced flooding on small streams in most of northeast Montana. The rainfall across the area during the month of May totaled 300 to 600 percent of normal.
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 GGW wrote it up.
Areas of heavy rain produced flooding on small streams in most of northeast Montana. The rainfall across the area during the month of May totaled 300 to 600 percent of normal.
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 18, 3:00 AM MST, 2 hours 18 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 400 AM MDT WED MAY 18 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH FRIDAY... RAIN ALONG THE THETA-E RIDGE IN EASTERN MONTANA HAS DIMINISHED SOMEWHAT EARLY THIS MORNING...BUT FAIRLY NARROW BAND OF RAIN IS EXPECTED TO REDEVELOP TODAY AS A SHORTWAVE SLIDES NORTH. THIS RAIN WILL BE IN A SIMILAR PLACE AS YESTERDAY...AND WITH UP TO A HALF INCH ACCUMULATION EXPECTED COULD SEE SOME STREAMS PUSHED OUT OF THEIR BANKS. SIGNIFICANT RAIN SHOULD END TONIGHT WITH THE WAVE LIFTING INTO CANADA. THE BRIEF LULL SHOULD LAST THROUGH THURSDAY AS THE UPPER LOW TIGHTENS OVER THE CENTRAL ROCKIES...WRAPPING THE MOISTURE INTO WYOMING INSTEAD OF ALLOWING IT TO STREAM NORTH INTO MONTANA. RAIN SHIELD ASSOCIATED WITH THIS SYSTEM WILL BEGIN TO SPREAD INTO MONTANA THURSDAY NIGHT...AND SHOULD OVERSPREAD MOST OF NORTHEAST MONTANA BY FRIDAY MORNING AS THE UPPER LOW DRIFTS NORTHWARD. MORE WIDESPREAD AND POTENTIALLY SIGNIFICANT RAINFALL...AS PRECIPITITABLE WATER APPROACHES ONE INCH...WILL CONTINUE THROUGH FRIDAY. WITH THE CLOUDS AND RAIN TEMPERATURES THROUGH THE PERIOD WILL CONTINUE ON THE COOL SIDE FOR MID MAY. WINDS ARE ALSO EXPECTED TO INCREASE FROM THE EAST THURSDAY...AND MORE SO ON FRIDAY...AS THE LOW PRESSURE DEVELOPS TO THE SOUTH. EBERT .LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY... THE BLOCKING RIDGE OVER THE MISSISSIPPI RIVER VALLEY WILL STILL BE A PLAYER IN KEEPING THE LONG-WAVE TROUGH OVER THE WESTERN STATES AT THE BEGINNING OF THE EXTENDED PERIOD FRIDAY NIGHT. THE CLOSED LOW STORM SYSTEM LOCATED OVER THE NORTHERN HIGH PLAINS WILL CONTINUE TO CHANNEL MOISTURE INTO NORTHEAST MONTANA THROUGH SUNDAY. THE BLOCKING RIDGE FINALLY BEGINS TO BREAK DOWN AND MOVE FARTHER EAST ALLOWING THE CLOSED LOW TO MOVE EAST OF NEMONT. THIS WILL ALLOW A WEAK RIDGE TO MOVE INTO MONTANA SUNDAY NIGHT AND MONDAY MORNING LOWERING THE CHANCE FOR PRECIPITATION. MONDAY AND BEYOND...THE NEXT UPPER TROUGH BEGINS PUSHING INTO THE PACNW SENDING A FRONT OUT OVER THE DIVIDE MONDAY. PACIFIC MOISTURE PICKED UP BY THE BASE OF THE TROUGH WILL BE EJECTED NORTH ACROSS THE BOUNDARY. A THERMAL RIDGE STRETCHED OUT AHEAD OF THE FRONT WILL CAUSE ENOUGH INSTABILITY FOR THUNDERSTORMS BY AFTERNOON AND INTO THE EVENING...MAINLY IN OUR SOUTHWESTERN ZONES. THE GFS AND EC DIFFER IN THAT THE EC DRAWS THE BOUNDARY MORE TO THE WEST...THUS IS DRY FOR US. THE GFS IS QUITE WET ALONG OUR WESTERN ZONES...WHICH THEN SHIFTS EAST OVER NEMONT THROUGH WEDNESDAY. WITH THE UNCERTAINTY...WILL HAVE TO STAY IN THE MIDDLE FOR NOW WITH AT LEAST CLIMO. OVERALL LONG TERM TEMPERATURES DO NOT DEVIATE MUCH FROM THE NORM...SO EXPECT MOSTLY SEASONAL HIGHS AND LOWS. SCT && .AVIATION... A LARGE SCALE UPPER LEVEL TROUGH PARKED OVER THE WESTERN STATES WILL SEND A CONTINUOUS TRAIN OF RAIN INTO NORTHEAST MONTANA TODAY. THIS WILL RESULT IN MVFR TO VFR CEILINGS WITH POSSIBLY BRIEF IFR SPELLS FROM HEAVY RAIN SHOWERS. BY LATE AFTERNOON OR EARLY EVENING THE RAIN WILL END AND THE CEILINGS WILL LIFT. EASTERLY WIND OF LESS THAN 10 KTS THIS MORNING WILL INCREASE TO 15-20KTS TODAY. WINDS DIMINISH TONIGHT WHICH COULD ALLOW SOME MIST OF FOG TO FORM AFFECTING VISIBILITIES AND CEILINGS. SCT && .HYDROLOGY... WET WEATHER WILL CONTINUE THROUGH THE WEEKEND AS A LARGE SCALE UPPER LOW ROTATES THROUGH THE REGION. ANOTHER BAND OF RAIN IS EXPECTED TO LIFT ACROSS NORTHEAST MONTANA TODAY. RAINFALL OF A QUARTER TO HALF AN INCH IS POSSIBLE ALONG A LINE THROUGH GLASGOW AND GLENDIVE. THE RAIN IS EXPECTED TO TAPER OFF TONIGHT. THE ADDITIONAL RAIN TODAY MAY SEND ALREADY SWOLLEN STREAMS AND CREEKS OUT OF THEIR BANKS AND A FLOOD WARNING IS IN EFFECT FOR MUCH OF THE REGION. SNOW MELT OUT OF THE LITTLE SNOWY MOUNTAINS IS ADDING TO HIGH WATER LEVELS ON CREEKS IN PETROLEUM COUNTY AND A FLOOD ADVISORY IS IN EFFECT FOR FLATWILLOW CREEK. AS THE LOW PRESSURE STORM SYSTEM MOVES INTO THE CENTRAL PLAINS LATE IN THE WEEK...WIDESPREAD RAIN WILL RETURN TO THE REGION. RAINFALL AMOUNTS OF UP TO ONE INCH ARE POSSIBLE ON FRIDAY AND AGAIN ON SATURDAY. FLOODING POTENTIAL REMAINS HIGH WITH THIS ADDITIONAL EXCESSIVE RAINFALL. && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 325 AM MDT WED MAY 18 2011 MTZ016>027-059>062-190930- CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY- DANIELS-SHERIDAN-WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE- RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN PHILLIPS- SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT- 325 AM MDT WED MAY 18 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT WET WEATHER WILL CONTINUE THROUGH THE WEEKEND AS A LARGE SCALE UPPER LOW ROTATES THROUGH THE REGION. ANOTHER BAND OF RAIN IS EXPECTED TO LIFT ACROSS NORTHEAST MONTANA TODAY. RAINFALL OF A QUARTER TO HALF AN INCH IS POSSIBLE ALONG A LINE THROUGH GLASGOW AND GLENDIVE. THE RAIN IS EXPECTED TO TAPER OFF TONIGHT. THE ADDITIONAL RAIN TODAY MAY SEND ALREADY SWOLLEN STREAMS AND CREEKS OUT OF THEIR BANKS AND A FLOOD WARNING IS IN EFFECT FOR MUCH OF THE REGION. SNOW MELT OUT OF THE LITTLE SNOWY MOUNTAINS IS ADDING TO HIGH WATER LEVELS ON CREEKS IN PETROLEUM COUNTY AND A FLOOD ADVISORY IS IN EFFECT FOR FLATWILLOW CREEK. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY AS THE LOW PRESSURE STORM SYSTEM MOVES INTO THE CENTRAL PLAINS LATE IN THE WEEK...WIDESPREAD RAIN WILL RETURN TO THE REGION. RAINFALL AMOUNTS OF UP TO ONE INCH ARE POSSIBLE ON FRIDAY AND AGAIN ON SATURDAY. FLOODING POTENTIAL REMAINS HIGH WITH THIS ADDITIONAL EXCESSIVE RAINFALL. .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.
10 flood. Local standard time, as filed.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
Small streams rose out their banks due to heavy rains and above normal wet spring.
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: 321340, 321339, 321341, 321342, 321343, 321344, 321345, 321346, 321347, 321348.