An unstable atmosphere, favorable winds, and plentiful surface moisture combined to allow severe thunderstorms to develop along and near an advancing frontal system through eastern Montana.
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.
An unstable atmosphere, favorable winds, and plentiful surface moisture combined to allow severe thunderstorms to develop along and near an advancing frontal system through eastern Montana.
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 Jun 21, 8:40 AM MST, 3 hours 40 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 940 AM MDT SUN JUN 21 2015 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY... UPDATE... FORECAST REMAINS ON TRACK WITH ATTENTION TURNING TO RADAR OVER THE NEXT FEW HOURS. EXPECT CONVECTIVE INITIATION AS SHORTWAVE TROUGH APPROACHES AT UPPER LEVELS WHILE LEE SURFACE TROUGH SLIDES EAST WITH LOW PRESSURE TRACKING INTO NORTHEAST WYOMING. SSEO SEEMS TO SUPPORT GREATEST RISK NEAR NORTH DAKOTA BORDER...CONSISTENT WITH BUFKIT FORECAST SOUNDING CONVECTIVE PARAMETERS. IN PARTICULAR THERE IS QUITE A BIT OF 0-6 KM DIRECTIONAL SHEAR...SO WILL HAVE TO SEE IF SUPERCELLULAR STRUCTURES DEVELOP WHICH COULD LEAD TO A LARGE HAIL THREAT IN PARTICULAR LATE THIS AFTERNOON OR EVENING. CONVECTION SHOULD EXIT TO THE SOUTHEAST AFTER 00Z. MALIAWCO PREVIOUS DISCUSSION... UPPER FLOW EXPECTED TO TURN SLIGHTLY SOUTHWEST TODAY IN ADVANCE OF TWO SHORTWAVES MOVING THROUGH THE REGION. WITH DEVELOPMENT OF LEE TROF AND LOW LEVEL SOUTHEASTERLIES ACROSS THE HIGH PLAINS PULLING MOISTURE NORTHWARD...CONDITIONS SETTING UP FOR SEVERE WEATHER POTENTIAL OVER EASTERN MONTANA THIS AFTERNOON AND EVENING. THE LEE TROF ADVANCES EASTWARD...DEVELOPING INTO AN INVERTED FRONT BISECTING EASTERN MONTANA WITH LOW PRESSURE CENTER FORMING IN NORTHEAST WYOMING BY THIS AFTERNOON. UPPER FORCING PROVIDED BY SHORTWAVE TROF SWINGING ALONG THE CANADIAN BORDER...ALONG WITH GOOD SHEAR AND INSTABILITY COULD RESULT IN STORMS PRODUCING LARGE HAIL AND STRONG WIND GUSTS TO THE EAST OF THE BOUNDARY. WITH PRECIPITABLE WATER NEAR 1 INCH...HEAVY RAIN IS ALSO A POSSIBILITY. A SECOND AREA OF STORMS IS EXPECTED TO DEVELOP ACROSS SOUTHERN MONTANA THIS EVENING AS ANOTHER SHORTWAVE PUSHES THROUGH IDAHO. WHILE THESE STORMS ARE NOT EXPECTED TO BE AS STRONG...HEAVY RAIN WILL CONTINUE AS A THREAT. UPPER TROF MOVES EAST BY MONDAY WITH HIGH PRESSURE MOVING INTO EASTERN MONTANA. COOLER WEATHER EXPECTED WITH NORTHWEST FLOW BEHIND THE UPPER TROF...AND A LITTLE LINGERING INSTABILITY COULD PRODUCE A FEW SHOWERS OR THUNDERSTORMS ACROSS THE NORTH. TUESDAY SEES THE RIDGE PUSHING EAST WITH ANOTHER TROF MOVING THROUGH THE PACIFIC NORTHWEST. THUNDERSTORMS AGAIN EXPECTED ALTHOUGH CONDITIONS NOT AS FAVORABLE FOR SEVERE STORMS. EBERT .LONG TERM...TUESDAY NIGHT THROUGH SUNDAY... THE EXTENDED FORECAST BEGINS WITH GOOD MODEL AGREEMENT SHOWING NEARLY ZONAL FLOW ACROSS THE REGION WHICH WILL GRADUALLY BECOME NW BY WEDNESDAY EVENING. MODEL AGREEMENT FALLS APART BY THURSDAY EVENING WITH THE EC BUILDING IN A MUCH STRONGER HIGH PRESSURE RIDGE OVER THE WESTERN CONUS WHILE THE GFS HOLD ONTO A NORTHERN STREAM LOW PRESSURE TROUGH WHICH PUSHES RIGHT THROUGH NE MONTANA THROUGH MOST OF NEXT WEEKEND. IN A WAY...BOTH MODELS SHOW A WESTERN CONUS SUMMER-TIME DRY HIGH PRESSURE RIDGE...BUT DIFFERING VERSIONS OF THAT FLOW REGIME WHEN IT COMES TO THE PERIPHERY OF THE RIDGE ARE STILL HIGHLY QUESTIONABLE. GENERALLY SPEAKING...THE EC IS A MUCH DRIER SOLUTION WHILE THE GFS KEEPS DIRECTING PERIODS OF SHOWERS AND THUNDERSTORMS THROUGH NE MONTANA THROUGH SATURDAY NIGHT. BEYOND SATURDAY NIGHT...BOTH MODELS ALLOW THE HIGH PRESSURE CENTER TO MOVE OVER THE NORTHERN ROCKIES. AT THAT TIME...EVEN WITH SOME MODEL DIFFERENCES...THIS SHOWS BETTER MODEL AGREEMENT FOR A HOT AND DRY FORECAST FOR NEXT SUNDAY AND BEYOND. BMICKELSON && .AVIATION... EXPECT DRY VFR CONDITIONS THROUGH THIS MORNING. AS CUMULUS CLOUDS QUICKLY BUILD THROUGH THE MID-DAY HOURS...CHANCES FOR SHOWERS AND THUNDERSTORMS WILL INCREASE DURING THE AFTERNOON HOURS. VCTS WILL BE POSSIBLE EARLY THIS AFTERNOON FOR KGGW AND KOLF WHILE VCTS WILL BE POSSIBLE LATER THIS AFTERNOON AND EVENING FOR KSDY AND KGDV. LIGHT SE WINDS WILL INCREASE TODAY TO 10 TO 15 MPH FROM THE SOUTH BY MID-DAY...THEN ABRUPTLY SHIFT OUT OF THE NORTHWEST BEHIND A COOL FRONT SUNDAY NIGHT. BRIEF PERIODS OF DAMAGING WINDS AND LARGE HAIL ARE POSSIBLE NEAR THE STRONGEST STORMS. EXPECT AMENDMENTS FROM 18Z TO 03Z. BMICKELSON && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 310 AM MDT SUN JUN 21 2015 MTZ016>027-059>062-220915- 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- 310 AM MDT SUN JUN 21 2015 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A COLD FRONT MOVING ACROSS THE REGION TODAY WILL BRING THE POTENTIAL FOR THUNDERSTORMS THIS AFTERNOON AND EVENING. SOME OF THE STORMS MAY BECOME SEVERE...AND PRODUCE LARGE HAIL AND/OR DAMAGING WIND GUSTS. THE GREATEST THREAT FOR STRONG STORMS IS EXPECT TO BE ALONG AND EAST OF A LINE FROM PLENTYWOOD THROUGH CIRCLE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY 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.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE GLASGOW MT 104 PM MDT SUN JUN 21 2015 MTZ019-211945- SHERIDAN- 104 PM MDT SUN JUN 21 2015 THE NATIONAL WEATHER SERVICE IN GLASGOW HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR... NORTHERN SHERIDAN COUNTY IN NORTHEAST MONTANA... UNTIL 145 PM MDT. AT 1253 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 7 MILES SOUTHEAST OF ARCHER...MOVING EAST AT 30 MPH. HAIL UP TO THE SIZE OF NICKELS IS EXPECTED WITH THIS STORM...ALONG WITH BRIEF HEAVY RAIN. LOCATIONS IN THE ADVISORY INCLUDE... PLENTYWOOD... LAT...LON 4862 10473 4880 10477 4890 10404 4866 10404 TIME...MOT...LOC 1904Z 261DEG 26KT 4872 10461 TFJ WEATHER.GOV/GLASGOW
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE GLASGOW MT 110 PM MDT SUN JUN 21 2015 MTZ019-020-062-212000- SHERIDAN-ROOSEVELT- 110 PM MDT SUN JUN 21 2015 THE NATIONAL WEATHER SERVICE IN GLASGOW HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR... CENTRAL ROOSEVELT COUNTY IN NORTHEAST MONTANA... SOUTHERN SHERIDAN COUNTY IN NORTHEAST MONTANA... UNTIL 200 PM MDT. AT 1259 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A COUPLE OF STRONG THUNDERSTORMS...ONE WAS 12 MILES NORTH OF POPLAR...MOVING EAST AT 30 MPH. HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH BRIEF HEAVY RAIN. LOCATIONS IN THE ADVISORY INCLUDE... RURAL AREAS OF CENTRAL ROOSEVELT COUNTY... RURAL AREAS OF SOUTHERN SHERIDAN COUNTY... LAT...LON 4855 10460 4822 10447 4816 10537 4836 10534 TIME...MOT...LOC 1909Z 248DEG 27KT 4831 10516 TFJ WEATHER.GOV/GLASGOW
The Glasgow radar (KGGW), 166 km away, was scanning. The volume nearest the first event began at 19:20 UTC.
5 hail. Local standard time, as filed.
Trained spotter reported quarter-sized hail and 0.60 inches of precipitation in only 25 minutes.
Trained spotter reported quarter-sized hail.
Trained spotter reported tennis ball sized hail.
Trained spotter reported nickel-sized hail and on-going heavy rain.
Trained spotter reported half dollar sized hail and heavy rain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2015Every state in 2015This day in weather historyWarnings in Montana, June 2015
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: 586635, 586636, 586639, 586644, 586640.