Areas ahead of a weak frontal boundary exhibited pooling of moisture with dew point readings into the upper 70s to lower 80s. As temperatures reached the lower to mid 90s, dangerous heat conditions developed during the afternoon hours with heat index values from 100 to 111 degrees.
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The episode as NWS FSD wrote it up.
Areas ahead of a weak frontal boundary exhibited pooling of moisture with dew point readings into the upper 70s to lower 80s. As temperatures reached the lower to mid 90s, dangerous heat conditions developed during the afternoon hours with heat index values from 100 to 111 degrees.
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 5, 11:27 AM CST, 33 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 1227 PM CDT Mon Aug 5 2024 .KEY MESSAGES... - Scattered showers and thunderstorms today with the better chances north of I-90. By later this afternoon an isolated strong to severe storm will be possible in parts of northwest IA and southwest MN. - Heat indices around 100 near the Missouri River into parts of northwest IA this afternoon. - Below normal but comfortable temperatures Tuesday through Sunday. Friday and Saturday may prove to be the coolest days. - The next better chance for showers and storms will be Tuesday night into Wednesday. Severe weather looks isolated. && .DISCUSSION... Issued at 307 AM CDT Mon Aug 5 2024 Scattered showers and thunderstorms remain possible across the area this morning, with the better chances north of I-90 into southwest MN. The severe weather threat will remain very limited through the morning as the elevated instability likely remains at or below about 1500 J/kg. By late afternoon into the evening a warm front will be in place across parts of northwest IA and southwest MN. This could serve as a focus for a few thunderstorms and if they can overcome the capping inversion isolated severe storms will be possible, including one or two tornadoes. Surface based CAPE will likely be close to 1500 J/kg and the 0-3 km shear has decent directional turning and is running about 25 knots or so. Something to keep an eye on as the confidence in development is low. Otherwise will see a fairly large spread in temperatures across the area with highs likely in the 70s along highway 14 and into the 90s along the Missouri River into northwest IA. The combination of heat and humidity will bring heat indices close to 100 mainly near and south of a Vermillion SD to Spencer IA line. North of the warm front there may be a little wrap around showers and thunderstorm activity but not expecting severe or heavy rain with this. As the wave passes tonight cooler air settles in behind, bringing temperatures below normal for Tuesday. Morning lows will likely be in the upper 50s to lower 60s while highs top out in the 70s. Tuesday should prove to be a fairly pleasant day, but will need to watch for the potential for a little drizzle, especially west of I- 29. Low level moisture deepens to 5-6 kft with weak lift which may promote some light drizzle development. The other concern with this will be if this deeper moisture lingers long enough into the afternoon to have an effect on temperatures. Models soundings do hint at some self destructive sunshine through the afternoon as the stratus wears off, some weak instability develops at the top of the mixed layer which could mean a brief period of sunshine before clouds once again expand. The next wave of interest will move into the are Tuesday night through Wednesday. Model soundings indicate plenty of moisture to support showers and thunderstorms, especially west of I-29, while areas near and east may have a bit of dry air from about 900 mb to 700 mb to overcome. Overall the severe threat is not real high but some potential for about 1000-1500 J/kg of elevated CAPE with 20-30 knots of deeper shear. Temperatures will be difficult to determine as cloud cover could limit heating. Looks like areas in south central SD down the Missouri River will see the better chance for some sunshine and warmer temperatures. Right now thinking most areas will see highs in the 70s, with a few 80s in the warmer areas. Once this wave passes on Wednesday night drier and cooler air will settle more firmly into the area and keep precipitation chances mostly confined to near the Missouri River and points west and south. A northern stream wave will dive south Thursday night and may be a time when chances for showers increases a bit but confidence not overly high. The temperatures dip a bit more behind this wave and from the looks of it highs Friday and Saturday may struggle to get above 70 in southwest MN. In fact the GEFS is indicating that there will be about a 50% chance for temperatures to remain at or below 70 degrees in southwest MN. Still a ways out so will need to see more consistency but will keep an eye on this cooler weather. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1225 PM CDT Mon Aug 5 2024 A surface low will slide from west to east across the Tri-State area this afternoon, bringing a risk for showers and thunderstorms along Highway 14 and then across the Buffalo Ridge later this afternoon. As the surface low passes, low-lvl stratus will begin to advect southeast with a high probabilities of MVFR to IFR conditions developing overnight and into Tuesday morning. I can't rule out some minor visibility restrictions or even drizzle tomorrow morning, but confidence too low to include ATTM. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...08 AVIATION...Dux
Hazardous Weather Outlook National Weather Service Sioux Falls SD 319 AM CDT Mon Aug 5 2024 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-060830- 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- 319 AM CDT Mon Aug 5 2024 This Hazardous Weather Outlook is for portions of 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 Isolated strong to severe storms will be possible in parts of southwest Minnesota and northwest Iowa today. Confidence is low but the main threats will be quarter sized hail and wind gusts to 60 mph. Heat indices will climb to near 100 degrees near the Missouri River into parts of northwest Iowa this afternoon. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Scattered showers and thunderstorms are possible on Tuesday night into Wednesday but any severe threat should remain isolated. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
2 heat. Local standard time, as filed.
Afternoon heat index values reached 101 degrees at a personal weather station near Hardwick.
Afternoon heat index values reached 102 degrees at a personal weather station near Round Lake.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2024Every state in 2024This day in weather historyWarnings in Minnesota, August 2024
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: 1214760, 1214762.