Strong non-thunderstorm winds across portions of northwest Iowa produced isolated damage during the early morning hours of April 19th.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 FSD wrote it up.
Strong non-thunderstorm winds across portions of northwest Iowa produced isolated damage during the early morning hours of April 19th.
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 Apr 18, 10:12 PM CST, 4 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1112 PM CDT Tue Apr 18 2023 .SHORT TERM...(This Evening through Wednesday Night) Issued at 351 PM CDT Tue Apr 18 2023 Key Messages: 1. Red Flag Warning for high fire weather concerns today, expiring during the evening hours. 2. Chance for scattered thunderstorms this evening, with low chances for severe weather overnight across the area. 3. Temperature roller coaster continues, with a couple chances for precipitation prior to the weekend. --------------------------------------------------------------------- Early afternoon water vapor imagery shows the ridge axis sliding overhead, with southwesterly flow moving in as the trough digs off to our west. At the surface, an area of low pressure is approaching the region from the west with a warm front moving in out ahead of it, resulting in warm and dry air overspreading the region. Winds have been overachieving and have brought drier air down as well, so did have to issue a Red Flag Warning for portions of the area along and west of I-29. Focus for the evening hours switches to chances for showers and thunderstorms, though we'll likely have to wait until the later evening hours before we see such activity. There is a small window shortly after sunset where some of the high resolutions convection allowing models (CAMs) do produce some showers as the low-level jet (LLJ) starts to intensify, though most have been backing down on that activity with subsequent model runs. The better chances for showers and thunderstorms will come from the west, where storms are expected to fire near the WY/SD/NE border as the mid-level wave As these storms move eastwards, the surface inversion strengthens which forces the storms to become elevated, with the HREF showing 1000-1500 J/kg of MUCAPE available for the storms as they move into the region. Given 40 to 50 knots of 0-6 km shear, though probably closer to 30-40 knots given the environment for the storms won't include the lowest 2 km of the profile, some organized storms are possible. Looking at the CAMs, they all generally show a broken-line of showers and thunderstorms moving in from west to east starting shortly before midnight for areas near Chamberlain, and given the strong inversion in place am not inclined to think strong wind gusts could reach the surface. Given the 1000-1500 J/kg of MUCAPE, there is a threat for quarter to half-dollar sized hail, so that will need to be monitored, and is appropriately covered by a marginal threat by the storm prediction center (SPC). A cold front will be pushing through the area from west to east throughout the day, resulting in a couple things to keep an eye on. First, remaining showers and thunderstorms will at first be dwindling down throughout the morning hours on Wednesday, though areas east of I-29 will likely see redevelopment/continuation of showers throughout the day as the lower atmosphere remains saturated. Second, for the morning hours, dry and breezy winds behind the front tomorrow west of I-29 will lead to a period of enhanced fire danger, with relative humidity values below 25% combined with wind gusts 30 to 35 mph. As the fire threat dwindles by the mid/late morning hours as the winds decrease combined with the strange time-window for fire weather concerns, not issuing any further headlines at this time. The 500mb low stalls out over the ND/MT/Canada border, with the cold front expected to fall across our eastern county warning area. This is where the next round of showers and thunderstorms are expected for the evening and overnight hours, with our second chance for severe weather. Given the severe threat is driven by the proximity to the front, there remains uncertainty amongst the high res CAM's along with global models, but it looks like 1000-2000 J/kg of CAPE/MUCAPE with 50 knots of shear will be available. Strong winds, large hail, even a tornado will be possible with the strongest storms, though again we'll need to see if this activity occurs in our area or just to our east in central Iowa. .LONG TERM...(Thursday through Tuesday) Issued at 351 PM CDT Tue Apr 18 2023 By Thursday morning, as the main wave catches up to the cold front, cyclogenesis leads to a strengthening low pressure system just off to our east. This, along with our slowly meandering 500 mb low just to our north, will continue chances for showers throughout the day. Unfortunately given the close proximity to the low, breezy northwesterly winds can be expected with wind gusts 30 to 40 mph throughout the day. We'll likely see a break in the precipitation late Thursday into early Friday, but with wrap-around moisture reaching back down into the area we'll likely see a round of light snow throughout the day as temperatures dip down into the upper 30s for the morning hours. Accumulations should remain under an inch, mostly under half an inch for areas south of I-29, with temperatures warming again throughout the day. Winds look to remain breezy/windy with gusts 30 to 40 mph expected, likely resulting in reductions in visibility while snow is falling. Overnight into Saturday the trough axis finally moves off to our east, though looks to stall somewhere over the Great Lakes region through the weekend. This will keep a surface high pressure parked to the north of the area, keeping winds from the northwest resulting in cooler temperatures for the weekend and into next week. 40s can again be expected for Saturday, warming up slightly into the 40s and 50s for Sunday, with the Climate Prediction Center showing the region is favored to continue our below normal temperatures to finish off the month of April. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday Night) Issued at 1103 PM CDT Tue Apr 18 2023 Increasing convective chances and development of MVFR-IFR ceilings and/or localized visibility restrictions are the primary aviation concerns. Clusters of thunderstorms moving through eastern Nebraska and central South Dakota late this evening are converging on the forecast area early in this TAF period, with additional scattered development also likely out ahead of this activity. While timing is uncertain at any specific location, have attempted to highlight what currently appears to be the most favored window for each TAF site. Stronger storms could produce hail, but damaging winds appear less likely due to a stout surface-based inversion. This initial activity likely to push northeast of the forecast area by daybreak, but additional shower/thunderstorm development is possible by late afternoon/evening near/east of I-29. At this time, confidence in details of this development is low, but did include a mention for KSUX late in the period, as northwest IA looks be the more favored area for elevated storm development. Increasing low level moisture beneath the inversion may result in development of fog and/or low stratus later tonight, especially east of a boundary that is sliding across the forecast area. These conditions are favored east of the James River Valley by daybreak, remaining most persistent near/east of I-29 through the end of this TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...APT LONG TERM...APT AVIATION...JH
Hazardous Weather Outlook National Weather Service Sioux Falls SD 504 AM CDT Tue Apr 18 2023 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-191015- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook- Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton- Union- 504 AM CDT Tue Apr 18 2023 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Scattered thunderstorms are expected to develop across the area tonight. Stronger storms could produce hail to the size of quarters, with a lesser threat of winds gusts to 60 mph. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. There will be another chance for isolated thunderstorms Wednesday evening - mainly over northwestern Iowa. Stronger storms could produce large hail and strong wind gusts. Minor flooding will continue on portions of the West Fork Des Moines River and Big Sioux River through the week ahead, while minor to moderate flooding will continue along portions of the James River. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
2 high wind, 1 strong wind. Local standard time, as filed.
The Automated Surface Observing System (ASOS) at Sioux City (KSUX) measured a wind gust to 66 mph.
Sustained winds were between 40 and 50 mph at the Automated Surface Observing System (ASOS) at Spencer (KSPW) with a peak wind gust of 68 mph.
Mesonet station FW1255 6 miles west-northwest of Fostoria measured a wind gust to 57 mph and mesonet station FW7399 2 miles west-southwest of Terril measured a wind gust to 55 mph. The county emergency manager reported a roof peeled off a mobile home in Spirit Lake, shingle damage in Superior, and damage to a hay shed and shingles 4 miles east-southeast of Orleans.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2023Every state in 2023This day in weather historyWarnings in Iowa, April 2023
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: 1097722, 1097719, 1097715.