Ahead of a larger scale bowing segment in eastern South Dakota, an isolated thunderstorm developed across southwest Minnesota on the nose of a strong low-level jet. The storm pulsed briefly stronger and produced hail across areas near and in the city of Marshall.
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The episode as NWS FSD wrote it up.
Ahead of a larger scale bowing segment in eastern South Dakota, an isolated thunderstorm developed across southwest Minnesota on the nose of a strong low-level jet. The storm pulsed briefly stronger and produced hail across areas near and in the city of Marshall.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Sep 18, 2:23 AM CST, 1 hour 51 minutes earlier.
Area Forecast Discussion National Weather Service Sioux Falls SD 323 AM CDT Tue Sep 18 2018 .SHORT TERM...(Today and Tonight) Issued at 321 AM CDT Tue Sep 18 2018 This morning will bring increasing thunderstorm coverage as a distinct shortwave moves along the elevated boundary draped across the region. Moisture for these storms is primarily located in the 800 to 900 hPa layer, and storms are expected to build to the south over time as the weak low-level jet provides additional moisture advection. Precipitable water values are unseasonably high in the incoming air mass, so heavy rain will be possible under storms; thankfully, this cluster of cells looks to remain fairly progressive. The primarily threat from these storms will be abundant lightning, brief heavy rainfall, and localized hail. During the afternoon and early evening, another subtle upper-level wave has the potential to fire off additional storms as the stationary frontal boundary remains over the region. Overall, short- range models favor locations south of I-90 for this activity, so have increased PoPs around the Sioux City vicinity. Late this evening into the overnight hours, cooler air from the north is forecast to push the boundary slightly farther to the south, especially over southwest MN and northwest IA. This will bring the northern terminus of the low-level jet into the tri-state area, and increase the threat for training thunderstorms causing heavy rain and localized flash flooding issues. The ultimate location of where this boundary sets up is still uncertain, given little consensus among CAMs; however, today would be a good time to make sure the sump pump is working well, especially if you live along and east of I-29. Flash flood watches may still be needed during this Tuesday night into Wednesday morning timeframe, but have again held off due to a lack of confidence on where this band of heaviest rainfall will end up. For now, will continue to monitor trends to determine where the ingredients best line up. .LONG TERM...(Wednesday through Monday) Issued at 321 AM CDT Tue Sep 18 2018 Wednesday into Wednesday night, thunderstorms continue to be a threat as dynamics increase ahead of an incoming longwave trough. Wednesday evening in particular looks to be a favorable time for additional heavy rain, given the intensifying surface low pressure system. On Thursday, the strong upper trough still looks to push through the Northern Plains. This will bring a drier Canadian airmass into the region by the afternoon. Friday through the weekend looks dry and cooler with seasonal autumn conditions. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1036 PM CDT Mon Sep 17 2018 Still a fairly low confidence forecast with a few different rounds of showers and thunderstorms possible, along with varying cloud decks. As of late evening, a few showers were beginning to develop along the I-90 corridor in SW MN, along with a IFR/LIFR cloud deck running from near BKX to MJQ. The fringes of this cloud deck may back into KFSD within the next few hours although confidence is low. The second challenge will be timing the various thunderstorm chances of over the next 24 hours. Will include a couple hours mention of TSRA at both KHON and KFSD late tonight and early Tuesday given a slightly better consistency in the high resolution models. Beyond mid-morning though, model consistency and forecast confidence preclude anymore than VCSH and VCTS mention at this time. Overall, plan for an unsettled day Tuesday into Tuesday night with likely periods of ceiling and potentially visibility restrictions. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...VandenBoogart LONG TERM...VandenBoogart AVIATION...Kalin
Hazardous Weather Outlook National Weather Service Sioux Falls SD 427 AM CDT Tue Sep 18 2018 IAZ001>003-012>014-020>022-032-MNZ071-072-080-081-089-090-097-098- SDZ039-040-054>056-060>062-065>067-069>071-190930- Lyon IA-Osceola-Dickinson-Sioux-O'Brien-Clay IA-Plymouth-Cherokee- Buena Vista-Ida-Lincoln MN-Lyon MN-Murray-Cottonwood-Nobles- Jackson-Pipestone-Rock-Kingsbury-Brookings-Miner-Lake-Moody- Hanson-McCook-Minnehaha-Hutchinson-Turner-Lincoln SD-Yankton- Clay SD-Union- 427 AM CDT Tue Sep 18 2018 This Hazardous Weather Outlook is for portions of northwest Iowa, west central Iowa, southwest Minnesota, east central South Dakota, and southeast South Dakota. .DAY ONE...Today and Tonight Thunderstorms will be possible throughout the day, with a marginal chance for isolated strong storms producing gusty winds and hail to the size of quarters. Multiple rounds of slow moving thunderstorms this evening and overnight will likely bring 1-2 inches of rainfall, with locally higher amounts. Heavy rain with flash flooding will be possible under the most persistent storms. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Wednesday into Thursday morning will bring continued chances for thunderstorms with heavy rain. Wednesday evening currently looks like the period with the highest threat for heavy rain. Dry weather moves in Thursday afternoon through the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated. IAZ031-NEZ013-014-SDZ038-050-052-053-057>059-063-064-068-190930- Woodbury-Dixon-Dakota-Beadle-Gregory-Jerauld-Sanborn-Brule-Aurora- Davison-Charles Mix-Douglas-Bon Homme- 427 AM CDT Tue Sep 18 2018 This Hazardous Weather Outlook is for portions of west central Iowa, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota, and southeast South Dakota. .DAY ONE...Today and Tonight Thunderstorms will be possible throughout today and tonight, with a marginal chance for isolated strong storms producing gusty winds and hail to the size of quarters. Heavy rain is possible under the strongest storms. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Wednesday into Thursday morning will bring continued chances for thunderstorms with heavy rain. Wednesday evening currently looks like the period with the highest threat for heavy rain. Dry weather moves in Thursday afternoon through the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated.
The Sioux Falls radar (KFSD), 122 km away, was scanning. The volume nearest the first event began at 10:13 UTC.
3 hail. Local standard time, as filed.
Penny to nickel size hail fell, but spotter was not under the stronger part of the storm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2018Every state in 2018This day in weather historyWarnings in Minnesota, September 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: 784802, 784803, 784804.