Conditions averaged slightly drier at 70 to 100 percent of normal during August with temperatures which were generally 2 to 3 degrees above normal.
Every event with a place to put it; 4 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.
Conditions averaged slightly drier at 70 to 100 percent of normal during August with temperatures which were generally 2 to 3 degrees above normal.
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 Aug 7, 9:43 PM CST, 2 hours 17 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1043 PM CDT Mon Aug 7 2023 .SHORT TERM...(This Evening through Tuesday) Issued at 307 PM CDT Mon Aug 7 2023 Key Messages: 1.) Low to moderate chances exist for precipitation tonight and Tuesday night in the Missouri Valley. 2.) Gradual warming trend expected through the week with highs at or slightly above normal by Thursday. 3.) Conditional severe weather risk continues to exist for late Tuesday afternoon and evening LATE THIS AFTERNOON AND TONIGHT: Cumulus have develop across much of the area as convective temperatures in the upper 70s to lower 80s have been reached. More moisture exists in northwestern Iowa and southwestern Minnesota where dew points remain in the lower to mid 60s. Deeper cumulus have developed there with a few sprinkles evident on radar. As heating continues a few of these showers may develop enough to produce a few hundredths of an inch of rain and even a little lightning through 00Z. Once temperatures cool, showers will quickly end east of I-29 and cumulus rapidly dissipates after dark. To the west, an area of weakening showers is moving into south central South Dakota associated with a weak upper wave moving into Nebraska. Instability and moisture are very limited with this feature. As a result these showers will weaken as the approach the Missouri River. However, continued forcing for ascent and MUCAPEs of 200-500 J/kg will keep a low probability (20-30%) of precipitation in the Missouri Valley through the night and into Tuesday morning. Rainfall will be less than a tenth of an inch. As noted in the previous discussion, mixing this afternoon has decreased dew points over much of southeastern SD and southwestern Minnesota and should also begin to bring drier air into northwestern Iowa. While temperatures along and north of I-90 are expected to fall into the 50s overnight, the drier air both at the surface and aloft make fog less likely tonight in most areas. The one possible exception in around Hwy 71 in northwestern Iowa where enough moisture may linger and, with radiational cooling, result in patchy fog around rivers and lakes. TUESDAY: Any chance for showers will end by mid morning in the Missouri Valley. Then partly to mostly sunny skies are expected with the most sun expected north of I-90. With light winds and sun, highs will rise into the 80s with the possible exception near KSUX if clouds are able linger into early afternoon. .LONG TERM...(Tuesday Night through Monday) Issued at 307 PM CDT Mon Aug 7 2023 TUESDAY NIGHT AND WEDNESDAY: Ensembles continue to have strong agreement on the next wave moving into the plains Tuesday afternoon through Wednesday. This wave is expected to move from southern Wyoming/northern CO on Tuesday afternoon into Kansas by Wednesday. Models show neither strong warm advection with a low level jet nor dPVA across SD. There is more instability in place with MUCAPEs of 500-1500 J/kg near the Missouri River. So even the weak forcing for ascent may result in storms developing in south central South Dakota Tuesday evening and move along the NE/SD border Tuesday night. While less likely, there is low (20%) probability a storm could develop as far north as I-90. Areas north of I-90 look to remain dry. The overall result is that the probability of rainfall anywhere outside of the Missouri Valley is less than 50%. With the better instability and moisture south of I-80, rainfall amounts are likely to be less than a quarter inch in the Missouri Valley. Any rainfall should end Wednesday morning although a low probability for a late afternoon thunderstorm exists near Hwy 20 due to instability of 1000-1500 J/kg. But lack of any boundary to focus lift is expected to limit development during the afternoon. Similar to Tuesday, the warmest temperatures on Wednesday will be north of I-90 and west of I29 where low to mid 80s are expected. Due to clouds, highs are likely to remain the mid to upper 70s in northwestern Iowa. THURSDAY AND THURSDAY NIGHT: As quickly as Wednesday's wave exits, the next wave will move from the Pacific northwest into the Plains on Thursday night. Southerly winds in the lowest 2 km will bring moisture back into the eastern Dakotas by Thursday afternoon as both the GEFS and ECE show 925 specific humidity above the 10th percentile by 00Z Friday. With temperatures warming into the mid 80s, MLCAPE exceeding 2000 J/kg is likely by late afternoon. 700 mb temperatures, while warming will only be +7 to +10 across the area, will result in MLCIN around -50 J/kg and is likely to limit convective development until late afternoon or evening. The deterministic 06Z and 12Z GFS remains an outlier with the wave moving a long the ND/SD border. Many GEFS and ECE members as well as the deterministic EC show the wave moving into SD with a 50-60 kt upper level jet. As a result, shear will be increasing during the afternoon and evening with the approaching jet. Ensembles vary on the strength of the jet with 500 mb winds varying from 30 kts to 50 kts in the ensemble. So deep layer shear may be anywhere from 30 kts to greater than 40 kts. So there are questions on how organized storms will be and with the cap in place exactly where and when storms will develop. The overall ensemble consensus is that storms would develop in northeastern SD/southeastern ND or west central MN during the late afternoon and evening. Uncertainty then increases as to whether storms can develop farther south into east central/southeastern SD and move east. Thus PoPs in much of southeastern SD into NW Iowa are less than 50%. There is also uncertainty if any storms that form in northeastern SD/west central MN will initially move east into east central MN or turn southeast toward southwestern Minnesota. Confidence is increasing in the latter solution and have increased the probability of rain to greater than 60% in southwestern Minnesota. Any storms that do form are expected to move east late Thursday night. Overall confidence remains low whether there will be severe storms but there are enough ingredients in place to remain aware of the potential for severe storms Thursday night. FRIDAY THROUGH MONDAY...After near normal temperatures on Friday, ensemble solutions show a gradual cooling trend through Monday. Ensembles continue to show the best chance for any thunderstorms on Saturday night through Sunday night. But a large amount of spread exists for the weekend so forecast details are likely to change as the weekend approaches. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday Night) Issued at 1043 PM CDT Mon Aug 7 2023 Showers have dissipated across the region as of 3Z, with the main potential for additional development being along the Missouri River Valley. Models indicate showers/storms develop between 5-8Z along the central NE/SD border, and travel eastwards before dissipating during the morning hours. Given the scattered nature, have left mention out of the KSUX TAF. With light and variable winds expected for majority of the overnight period, will likely see the return of patchy fog again for areas that didn't dry out well today, namely portions of NW Iowa. After a VFR cumulus field likely develops again throughout the day, additional chances for scattered showers and thunderstorms develop Tuesday evening especially for areas south of I-90. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...Schumacher LONG TERM...Schumacher AVIATION...APT
Hazardous Weather Outlook National Weather Service Sioux Falls SD 655 PM CDT Mon Aug 7 2023 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-090000- 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- 655 PM CDT Mon Aug 7 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...Tonight. Patchy fog may again develop across northwest Iowa overnight, especially in low-lying areas. Isolated showers and thunderstorms remain possible into early Tuesday morning. The greatest risk for this activity will be near the Missouri River Valley. Severe storms are not expected. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Additional risks for rain arrive by Tuesday afternoon through Wednesday, however the risk for severe storms is low at this time. Thunderstorms may also be possible Thursday afternoon and evening. While the location is uncertain, a strong storm or two may be possible. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
4 drought. Local standard time, as filed.
Moderate (D1) drought conditions worsened to severe (D2) in early August.
Moderate (D1) drought conditions worsened to severe (D2) in early August.
Moderate (D1) drought conditions worsened to severe (D2) in early August.
Moderate (D1) drought conditions worsened to severe (D2) in early August.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2023Every state in 2023This day in weather historyWarnings in Minnesota, August 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: 1129792, 1129793, 1129794, 1129795.