textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers and thunderstorms this afternoon are capable of lightning, brief heavy rain, small hail, and gusty winds up to 30-40 mph. These storms will persist for the rest of the afternoon hours before dissipating this evening.

- Isolated severe storms are possible mainly west of I-29 on Monday. Large hail up to golf ball size and damaging winds to 65 mph will be the main hazards should a storm develop. Another chance for storms is possible Monday night though this potential is more uncertain.

- There is a moderate chance (40-90%) of highs exceeding 90F Tuesday and Wednesday, with the highest probabilities coming on Tuesday. Be prepared to enact any heat related safety measures.

- Severe storm chances look to make a return to the region on Tuesday and Wednesday. Details remain uncertain so continue to keep up to date with the latest forecast for the most up to date information.

DISCUSSION

Issued at 247 PM CDT Sun Jun 7 2026

A weak upper level low has pushed into the area this afternoon. This low is encountering a less stable environment characterized by instability values around 1000 J/kg of MLCAPE. Deep layer shear will be quite weak on the order of 10-15 knots. Thus, severe storms are not expected. Lightning, brief heavy rain, small hail, and gusty winds up to 30-40 mph are the main hazards. Should see storm chances diminish this evening as the boundary layer stabilizes. A second round of showers and some storms remains possible late this evening an night. These storms will be from a weakening MCS and could clip locations near and north of highway-14. Should these storms make it into the forecast area, they will be elevated and not severe given weak vertical shear in the area.

The previously mentioned weak upper level wave will push northeast of the forecast area on Monday. This will promote subsidence on its back side. The morning hours look to be dry while high temperatures warm to the upper 80s to low 90s by the afternoon. A cold front will be pushing into the area from the west. This front looks to push into locations west of the James River tomorrow. This front looks to serve as a potential trigger for thunderstorms. Questions remain about this potential though due to capping. Mid level lapse rates look to exceed 8.0 C/km aloft while forcing for ascent remains weak to . This will result in a cap right over the front. Latest REFS shows an ensemble average about about a -60J/kg cap right over the front. Individual members of the REFS show a variable cap with some members showing a stronger cap and others showing little to no cap. Latest HRRR, RRFS, and some of the newer MPAS models do show convection developing along the front. Thus, confidence is higher in convection developing than not at this time. Storms look to fire along the front west of I-29. If the front can progress eastwards enough, locations west of I-29 but along and east of the James River may be where most of the storms develop. As of now, these storms look to be isolated in coverage in an environment characterized by 2,000+ J/kg and effective shear values up to 35-40 knots. This looks to support multi-cells to potentially supercells capable of large hail up to golf ball size and damaging winds to 65 mph. Hodographs are generally straight which would support splitting storms. Larger hail can be achieved in a left split storm. Some disagreement remains about an MCS that looks to develop across western Nebraska. Tough to say how this MCS may track as the latest hi-res guidance is split on whether this MCS pushes into the forecast area or stays south along I-80. Will keep an eye on this potential.

Severe storm chances persist through the middle of the week, beginning on Tuesday. A stronger upper level wave will begin to eject into the Northern Plains on Tuesday, sending shortwave troughs out ahead of it. Before storm chances occur, Tuesday will be a hot day with high temperatures soaring to the 90s to up to about 100F.The ensembles continue to support this as they show a 40-90% chance for high temperatures to exceed 90F. Dew points will remain moist in the 60s to even 70s will result decently humid conditions. A Heat Advisory may be needed for Tuesday as heat indices rise to near to just above 100F. A second cold front will be working its way through the Northern Plains on Tuesday, serving as the trigger for convection. The best forcing for ascent looks to be to the north and west of the forecast area with the previously mentioned shortwaves. This seems to be somewhat supported by the RRFS, MPAS-RN model, and the NAM12km as they show the bulk of the convection in this area. Despite this, the cold front will be draped across a large portion of the Northern and Central Plains. So convection may still develop in or near the forecast area. Tough to say at this time but the environment supports severe storms should they develop.

Wednesday will also see another chance for strong to severe storms. The main wave and associated exit region of an upper level jet will push into the Northern Plains. Despite these favorable features being in place, questions remain regarding how quickly the previously mentioned cold front will progress. If the front were to progress at a faster rate of speed, then severe storm chances could be lowered if the front is able to push east of the forecast area before convection develops. If the fronts speed is slower, then convection could develop on the front in the forecast area. Latest medium range guidance and ML guidance is in agreement in the front pushing through the area more quickly. While these trends are looking better, can't say for sure that they will continue. If the front were to slow down and allow convection to develop in the area, then a line of storm could develop before racing east of the area. Will keep an eye on the front's trends over the coming days. Aside from storm chances, Wednesday will be another hot, although slightly cooler day with highs warming to the mid 80s to 90s, warmest along and east of the James River. Similar probabilities remain in the ensembles of a 40-80% chance for highs to exceed 90F. Slightly lower dew points look to keep heat indices a little lower, down to the 90s. That said, both Tuesday and Wednesday will see moderate to major heat risk.

The rest of the week and weekend looks to see a return to near to slightly above seasonable temperatures with highs lowering to the 70s and 80s. Broad troughing over the northern CONUS could keep rain chances (20-30%) in the forecast for this period of time. Latest AI guidance suggests that any chance for severe storms will remain at 15% or less into early next week.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1238 PM CDT Sun Jun 7 2026

A few showers and isolated thunderstorms have developed early this afternoon. Expect these showers to become more scattered through the afternoon hours along and east of I-29. Lightning is possible with the showers as well. Have included -TSRA in both KFSD and KSUX's TAFs for this afternoon. These showers and storms will dissipate this evening. A second round of showers and some storms are possible late tonight along and north of highway-14. Confidence is too low to include in KHON's TAF at this time. Will keep an eye on these trends.

Ceilings have fallen to MVFR levels within the showers and storms but then break up to more scattered coverage rather than a full ceiling in locations that are not seeing rain. Another round of more widespread MVFR ceilings is possible tonight into tomorrow morning. This second round of low ceilings looks to be widespread enough to affect all TAF sites. Could see the ceilings drop to lower categories but confidence is not high enough to include mention of IFR or LIFR ceilings. Trends will again be monitored for the rest of today. A cold front will be moving into locations west of the James River tomorrow morning, turning winds to out of the northwest in its wake to end the period.

FSD WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None. IA...None. NE...None.