Discrete storms developed initially ahead of a strong shortwave in moderate instability and shear. The initial storms produced large hail and several funnel clouds along with three short-lived tornadoes, one in Morton County, one in Stark, and one in Dunn County.
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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 BIS wrote it up.
Discrete storms developed initially ahead of a strong shortwave in moderate instability and shear. The initial storms produced large hail and several funnel clouds along with three short-lived tornadoes, one in Morton County, one in Stark, and one in Dunn County. There was no damage with the three tornadoes and so they were all rated EF0. Additional storm growth then occurred, forming into a small mesoscale convective system with large hail and strong wind gusts as the main threats. The largest hail was half-dollar size, and fell in both Hettinger and Dunn Counties. The strongest wind gusts of 75 mph occurred in Morton and Rolette counties.
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 Bismarck, ND wrote its last area forecast discussion before the first event at May 31, 10:47 AM MST, 1 hour 56 minutes earlier.
Area Forecast Discussion National Weather Service Bismarck ND 1247 PM CDT Thu May 31 2018 .UPDATE... Issued at 1229 PM CDT Thu May 31 2018 Made a few adjustments for pops based on latest radar, otherwise no changes to the going forecast. CAMS are still pointing to convective initiation around 19-21 UTC along the Montana border. Will be launching a special 20Z sounding this afternoon. UPDATE Issued at 1033 AM CDT Thu May 31 2018 Have cancelled the dense fog advisory. Latest satellite shows fog quickly diminishing across the area. Made some minor updates to pops based on latest radar and consensus of short range model forecast reflectivity. UPDATE Issued at 853 AM CDT Thu May 31 2018 Dropped a couple counties along the fringes of the dense fog advisory, but extended the majority of the advisory area through 11 AM. Can cancel early if visibilities start to improve early. Otherwise no significant changes to the going forecast. UPDATE Issued at 633 AM CDT Thu May 31 2018 Little change with this update other than for observed trends through 11 UTC. Overall thinking regarding the convective scenario for this afternoon and evening remains unchanged. UPDATE Issued at 406 AM CDT Thu May 31 2018 Quick update to expand the Dense Fog Advisory across central North Dakota. && .SHORT TERM...(Today and tonight) Issued at 406 AM CDT Thu May 31 2018 Dense fog this morning, and severe convective potential this afternoon into tonight highlight the short term forecast. Per webcam, GOESEast Nighttime Microphysics RGB, and surface observations through 0830 UTC, issued a Dense Fog Advisory from the Turtle Mountains into portions of south central North Dakota through 14 UTC. An expansion of the Advisory is likely per CAM visibility forecast trends through early this morning. Will continue to monitor observations. Scattered thunderstorms are expected to continue across northwest North Dakota this morning with the low level baroclinic zone. SPC has expanded the slight risk to include most of western and north central North Dakota, with a marginal risk across most of the remainder of western and central North Dakota for today. The most likely scenario is for potential initiation, perhaps as early as 19-20 UTC, along a stalling cold front from near Beach through Watford City, and New Town as low level convergence increases. The CAMs through the 06 UTC HRRR favor this initiation scenario. In particular, the 00 UTC HREF updraft helicity signal is strongest across these areas, with a 50-60 percent neighborhood probability of updraft helicity of greater than 150 m2/s2. Strong deep layer shear increasing to 40-45 kts with deep veering profiles are most perpendicular to the surface boundary across the southwest, and have a more parallel component closer to Watford City and New Town. Thus, the longevity of discrete supercells would be greatest across the southwest, with a possible quicker upscale transition to a clustered to linear mode further north. One or two line segments are certainly possible by early to mid evening across central North Dakota supported by a strong low and mid level jet. Regarding threats, given the shear and instability balance, large hail to two inches in diameter would seem to be an average high- end ceiling for hail. Damaging winds in excess of 70 mph are possible, although this is a bit more uncertain. Regarding the tornado threat, the area of most concern would be near the Watford City and New Town areas where LCLs are lower, with enhanced low level helicity via easterly surface winds. Further southwest, while a strong wind field supports strong low level shear/helicity, LCLs are higher as dewpoints may mix out into the lower to mid 50s with high temperatures in the mid to upper 80s. While precipitable water values near 1.50-1.75 inches, expected storm motions should limit the flash flood threat outside of urban areas. A special 19 or 20 UTC sounding will be launched today at NWS Bismarck. Additional thunderstorms may move across western and central North Dakota tonight from Montana, again aided by the strong low and mid level jet, steep mid level lapse rates, and moisture transport. .LONG TERM...(Friday through Wednesday) Issued at 343 AM CDT Thu May 31 2018 Severe convective potential on Friday highlights the extended forecast. The consistent signal continues for a potential significant severe weather event, especially across central North Dakota, on Friday. SPC has upgraded portions of the south central to an Enhanced Risk in their Day 2 Outlook. A surface low across southwest North Dakota Friday morning with a stationary front along I-94 will lift northeast through the day, with a cold front arriving between US Highway 83 and 85 by mid to late afternoon, with a warm front from north central through southeast North Dakota. Forcing is expected to be strong, especially with the arrival of the significant mid level wave by Friday evening. However, some sources of uncertainty do remain. First, potential elevated convection through Friday morning across the north central may limit how much instability will build and the eventual severe weather risk for these areas. Second is how quickly convection will remain discrete ahead of the cold front versus grow upscale, as the orientation of the strong deep layer shear vectors may bisect the cold front at a 30-45 degree angle. That said, with MLCAPE around 2000-2500 j/kg, and the strength of deep layer shear, all hazards are possible. Certainly very large hail to tennis balls or larger are possible with any discrete supercell. However, the hail threat could rather quickly transition to a more predominant wind threat with gusts over 70 mph possible with a squall line/QLCS development. The tornadic threat certainly exists with the possible narrow discrete mode window, however, the QLCS tornado threat will have to be monitored. Storm motion is expected to limit the flash flood threat to those prone urban areas (low lying underpasses etc.). A dry, but, windy post-cold front Saturday is expected with possible northwest wind gusts of 30-35kts. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1229 PM CDT Thu May 31 2018 Thunderstorms and low VFR/possibly MVFR ceilings are the aviation hazard for the 18Z TAF period. Thunderstorms in the west will continue developing through the afternoon and push eastward through the evening hours. Some storms in the west and in north central areas may become severe with damaging winds and large hail. A few tornadoes may be possible. Areas with thunderstorms should expect gusty and erratic winds, along with low VFR/MVFR ceilings. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && UPDATE...TWH SHORT TERM...PA LONG TERM...PA AVIATION...TWH
Hazardous Weather Outlook National Weather Service Bismarck ND 1235 PM CDT Thu May 31 2018 NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-011745- Divide-Burke-Renville-Bottineau-Rolette-Williams-Mountrail-Ward- McHenry-Pierce-McKenzie-Dunn-Mercer-Oliver-McLean-Sheridan-Wells- Foster-Golden Valley-Billings-Stark-Morton-Burleigh-Kidder- Stutsman-Slope-Hettinger-Grant-Bowman-Adams-Sioux-Emmons-Logan- La Moure-McIntosh-Dickey- 1235 PM CDT Thu May 31 2018 /1135 AM MDT Thu May 31 2018/ This Hazardous Weather Outlook is for portions of north central North Dakota, northwest North Dakota, south central North Dakota, southeast North Dakota, and southwest North Dakota. .DAY ONE...This Afternoon and Tonight severe thunderstorms are expected to develop across western North Dakota this afternoon, potentially between 1 and 3 PM MDT, from Bowman through Watford City, Killdeer, and New Town. These storms may form into one or two lines as they enter central North Dakota this evening. The primary threats are large hail to around two inches in diameter, damaging wind gusts in excess of 70 mph, possibly a few tornadoes, and dangerous lightning. The greatest threat is this afternoon across western North Dakota. Additional thunderstorms, possibly strong to severe, may move across western and central North Dakota late tonight from Montana. .DAYS TWO THROUGH SEVEN...Friday through Wednesday For Friday, a potentially significant severe weather event is forecast, especially across central North Dakota. Severe thunderstorms may develop between US Highway 83 and 85 by early Friday afternoon, and quickly form into a squall line as they progress east through the remainder of the afternoon and into the evening. Threats are still a bit uncertain, and depend on how fast individual storms form into a line. However, there is the potential for very large hail in the afternoon. The threat may quickly change to predominately wind with a squall line with potential gusts over 70 mph. A few tornadoes are also possible. .SPOTTER INFORMATION STATEMENT... Spotters activation is likely today through Friday across most of western and central North Dakota. TWH
Special Weather Statement National Weather Service Bismarck ND 108 PM MDT THU MAY 31 2018 NDZ018-033-311945- Stark ND-Dunn ND- 108 PM MDT THU MAY 31 2018 ...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHEASTERN DUNN AND NORTH CENTRAL STARK COUNTIES UNTIL 145 PM MDT... At 107 PM MDT, strong thunderstorms were located along a line extending from near Manning to 5 miles northwest of Gladstone. Movement was northeast at 30 mph. Penny size hail and wind gusts to 50 mph will be possible with these storms. Locations impacted include... Halliday, Dunn Center, Manning, Marshall and Hirschville. Very heavy rainfall is also occurring with these storms, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4754 10230 4703 10217 4688 10272 4725 10278 TIME...MOT...LOC 1907Z 232DEG 26KT 4722 10270 4692 10265 HAMILTON
The Bismarck radar (KBIS), 146 km away, was scanning. The volume nearest the first event began at 19:40 UTC.
10 hail, 6 thunderstorm wind, 3 tornado, 1 funnel cloud. Local standard time, as filed.
The tornado occurred over rural locations northwest of Hirschville. No damage occurred, therefore the tornado was rated EF0.
Windows were broken by the hail.
A COOP Observer estimated a thunderstorm wind gust of 60 mph.
One semi-trailer was blown over and a spruce tree was uprooted. Some tin from a pole barn style building also blew off.
The tornado occurred over rural locations south of Richardton. No damage occurred, therefore the tornado was rated EF0.
A wind break was torn down and a roof was damaged.
Law enforcement estimated a thunderstorm wind gust of 60 mph.
The tornado occurred over rural locations north of Glen Ullin. No damage occurred, therefore the tornado was rated EF0.
A deputy sheriff located in Carson observed the funnel cloud and estimated it to be about three miles east of Carson.
The public estimated a thunderstorm wind gust of 60 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in North Dakota in 2018Every state in 2018This day in weather historyThe tornado archive for North Dakota, 2018Warnings in North Dakota, May 2018
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: 754756, 754394, 754753, 754395, 754396, 754772, 754419, 754397, 754399, 754400, 754401, 754765, 754403, 754404, 754405, 754406, 754407, 754408, 754754, 754409.