A moist and very unstable air mass combined with a trough of low pressure at the surface to produce rotating severe thunderstorms.
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.
A moist and very unstable air mass combined with a trough of low pressure at the surface to produce rotating severe thunderstorms.
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 Jul 8, 9:07 AM MST, 2 hours 46 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 1007 AM MDT FRI JUL 8 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY... UPDATE...STRONG CONVECTION HAS YET TO DEVELOP THIS MORNING...THANKS TO AMPLE CLOUD COVER COVERING MOST OF NEMONT. HOWEVER SHOWER ACTIVITY IS ONGOING THUS UPDATED TO TREND UP POPS ACROSS MUCH OF THE AREA. ALTHOUGH WINDS CURRENTLY REMAIN RELATIVELY LIGHT OVER FORT PECK LAKE...STILL EXPECT AN INCREASE THIS AFTERNOON BEHIND THE FRONT SO WILL LEAVE IT AS IS. GILCHRIST PREVIOUS DISCUSSION...THE MAJOR STORM SYSTEM MOVES EAST OF THE CANADIAN ROCKIES AND OUT OVER THE PRAIRIE PROVINCES TODAY WHERE THE LOW CENTERS STACK UP. THIS CYCLONIC STORM SYSTEM SENT A WAVE ACROSS THE NORTHEAST MONTANA EARLY THIS MORNING THAT IS ASSOCIATED WITH A SURFACE TROUGH EXTENDING FROM THE STORM CENTER IN ALBERTA. THIS WAVE PRODUCED THUNDERSTORMS AND RAIN SHOWERS ALL NIGHT THAT WILL CONTINUE TODAY. BEHIND THE WAVE CONDITIONS WILL BEGIN TO CLEAR FROM THE WEST. MOST SHOWERS AND THUNDERSTORMS TODAY WILL BE IN THE EASTERN ZONES BEFORE MOVING INTO NORTH DAKOTA AND SASKATCHEWAN. MODELS ARE SHOWING MODERATE TO HEAVY RAIN IS POSSIBLE IN THOSE ZONES...ESPECIALLY IN THE NORTHEAST. THE STORMS WILL FIND A MORE UNSTABLE ENVIRONMENT THERE AND SOME STORMS COULD BECOME SEVERE WITH LARGE HAIL...DAMAGING WINDS AND HEAVY RAIN BEFORE EXITING THE AREA. TONIGHT...THE STORM CENTER MOVES PARTLY INTO SASKATCHEWAN AND THE ASSOCIATED WAVE WILL HAVE MOVED OUT OF THE LOCAL AREA. HOWEVER A SECONDARY COLD FRONT SWINGS ACROSS THE AREA INITIATING A FEW THUNDERSTORMS MAINLY SOUTH OF THE CWA. BUT SOME OF THE EVENING THUNDERSTORMS COULD NUDGE NORTH INTO OUR AREA. SATURDAY THROUGH SUNDAY...THE STORM CENTER MOVES FULLY INTO SASKATCHEWAN SATURDAY. THE CYCLONIC FLOW...SURFACE AND ALOFT...WILL BE REINFORCING. SO SATURDAY AFTERNOON COULD END UP WINDY AS DRIER AIR IS PULLED ACROSS THE CWA FROM THE WEST. ON SUNDAY THE CANADIAN STORM MOVES FARTHER EAST INTO MANITOBA. THIS WILL ALLOW AN UPPER LEVEL RIDGE TO BEGIN BUILDING UP OVER THE NORTHERN ROCKIES. THE CANADIAN STORM SYSTEM WILL PUSH THE WARM AIR BOUNDARY SOUTH OF NEMONT. SO TEMPERATURES WILL TREND COOLER THAN LATELY TO A MORE SEASONAL LEVEL FOR THE WEEKEND. SCT .LONG TERM...SUNDAY NIGHT THROUGH FRIDAY... AN UPPER RIDGE OVER MONTANA WILL KEEP SUNDAY NIGHT DRY. THE RIDGE AXIS SHIFTS EAST INTO THE DAKOTAS ON MONDAY. THIS WILL TURN THE FLOW ALOFT OVER EASTERN MONTANA BACK TO THE SOUTHWEST AS ANOTHER UPPER TROUGH/LOW MOVES INTO THE WEST COAST. THIS UPPER LOW WILL REMAIN STATIONARY IN THE PACIFIC NORTHWEST FOR SEVERAL DAYS WITH SOUTHWEST FLOW ALOFT OVER MONTANA. A LEE SIDE TROUGH POSSIBLY A SURFACE LOW WILL DEVELOP OVER CENTRAL MONTANA ON MONDAY AND REMAIN IN PLACE FOR A FEW DAYS. PERIODIC SHORTWAVES IN THE SW FLOW ALOFT WILL COMBINE WITH THE UNSTABLE AIR OVER CENTRAL AND EASTERN MONTANA TO PROVIDE CHANCES FOR THUNDERSTORMS STARTING ON MONDAY AND CONTINUING THE REMAINDER OF THE WEEK. FORRESTER && .AVIATION... VFR CONDITIONS WILL PREVAIL MOST OF THE TIME WITH MID AND HIGH CLOUDS TODAY. SHOWERS AND THUNDERSTORMS WILL PROVIDE BRIEF PERIODS OF MVFR VISIBILITIES AND CEILINGS. A COLD FRONT WILL SHIFT WINDS TO THE WEST BY AFTERNOON AT KGGW AND THE OTHER TAF SITES THIS AFTERNOON WITH SPEEDS OF 15 TO 20 KNOTS. LOOK FOR CLEAR SKIES TONIGHT WITH WEST TO NORTHWEST WINDS 5 TO 10 KNOTS. && .GLASGOW WATCHES/WARNINGS/ADVISORIES... LAKE WIND ADVISORY UNTIL 9 PM MDT THIS EVENING FOR FORT PECK LAKE. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 325 AM MDT FRI JUL 8 2011 MTZ024>027-090900- RICHLAND-DAWSON-PRAIRIE-WIBAUX- 325 AM MDT FRI JUL 8 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A COLD FRONT MOVING OVER THE AREA TODAY WILL BRING THUNDERSTORMS AND RAIN SHOWERS...SOMETIMES HEAVY. SOME THUNDERSTORMS MAY BECOME SEVERE IN THE AFTERNOON WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE. THE YELLOWSTONE RIVER WILL CONTINUE TO RUN HIGH FOR THE NEXT FEW DAYS. THE RIVER LEVEL AT GLENDIVE WILL RUN STEADY AT 1 TO 2 FEET BELOW FLOOD STAGE THROUGH THE WEEKEND. RANCHERS AND WATER USERS MAY WANT TO TAKE PRECAUTIONS IF THE HIGHER RIVER LEVELS AFFECT THEIR OPERATIONS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ018>020-062-090900- DANIELS-SHERIDAN-WESTERN ROOSEVELT-EASTERN ROOSEVELT- 325 AM MDT FRI JUL 8 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A COLD FRONT MOVING OVER THE AREA TODAY WILL BRING THUNDERSTORMS AND RAIN SHOWERS...SOME WITH HEAVY RAIN. SOME THUNDERSTORMS MAY BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ016-017-021>023-059>061-090900- CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY- PETROLEUM-GARFIELD-MCCONE-NORTHERN PHILLIPS-SOUTHWEST PHILLIPS- NORTHERN VALLEY- 325 AM MDT FRI JUL 8 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A COLD FRONT MOVING OVER THE AREA THIS MORNING WILL BRING THUNDERSTORMS AND RAIN SHOWERS...SOME WITH HEAVY RAIN. A FEW STORMS MAY BECOME SEVERE THIS MORNING WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE. A LAKE WIND ADVISORY FOR FORT PECK LAKE HAS BEEN ISSUED TODAY FOR NORTHWESTERLY WIND OF 15 TO 25 MPH THROUGH MID EVENING. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY WESTERLY WIND BEHIND THE COLD FRONT WILL INCREASE SATURDAY TO 15 TO 25 MPH. THIS MAY REQUIRED A WIND ADVISORY FOR FORT PECK LAKE. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
The Glasgow radar (KGGW), 153 km away, was scanning. The volume nearest the first event began at 18:53 UTC.
2 hail, 1 funnel cloud. Local standard time, as filed.
Hail fell for about 7 minutes. Hail stones varied from dime-sized to quarter-sized.
General cloud rotation and a brief funnel cloud were observed.
A variety of hail stone sizes were reported with golf ball-sized being the largest. Some leaves were stripped from trees.
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, July 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: 334561, 334558, 334562.