textproduct: Sioux Falls

KEY MESSAGES

- Continued unsettled conditions remain in the region through the week. No widespread severe weather risks, but conditional and highly localized risks will be possible.

- Focus areas for the majority of the severe weather risks ahead will be west of I- 29 and especially along or west of the James River valley.

- Temperatures remain in the 80s through the week and rise towards the upper 80s by the end of the weekend.

DISCUSSION

Issued at 112 PM CDT Mon Jun 1 2026

THIS AFTERNOON/EVENING: Rather stable conditions across the region early this afternoon, outside of a lone elevated storm over north central Iowa. Satellite shows a weak mid-lvl wave crossing central Nebraska and lifting towards the Tri-State area. Soundings closer to home show a very stable layer that should prevent any surface based convection to develop as temperatures rise towards the 80s. What this wave may do is briefly slow the rise in temperatures, but bring a chance for a few high based sprinkles. A second area we'll be monitoring today is right along the eastward edge of the CWA where a bit less inhibition is in place. With a very weak shear profile, any storm that develops is not expected to be strong to severe.

TONIGHT: Most of the focus during the overnight hours will be across the Nebraska Panhandle, Black Hills region, and western Kansas. As yet another wave ejects out of the central Rockies, we should see renewed convection develop and quickly try to congeal into one or more clusters as they cross western Nebraska and South Dakota. Latest CAMS continue to hint at these storms trying to slowly lift northeast but should weaken as they reach a more stable atmosphere. That said, Could continue to see a limited wind risk into south central South Dakota and along portions of the Missouri River valley by 3am. Further north, the abundance of low-lvl moisture combined with light winds could lead to patchy fog developing.

TUESDAY: We'll have to keep a close eye on the progression of the convection in Nebraska as guidance does show signs of a developing MCV that may track east and slowly north during the day. At this point, destabilization of the boundary layer will need to be watched as we could see pockets of 2000 J/KG MLCAPE develop in a narrow corridor ahead of this wave. Isolated to scattered storms could develop based on the weakening of convective inhibition somewhere between the James river and I-29. Effective shear remains very weak. but there may still be appreciable 0-1km helicity to lead to a few rotating storms/funnels. However the widespread severe risk remains low and more focused on marginal hail, but could see future outlooks extended further east. Better focus for convection will be across far western SD along a frontal boundary edging into the state. As yet another wave ejects into the Plains scattered convection along this boundary should develop and begin to track east northeast. One thing to note today is that mid-lvl heights may be rising across central SD in the evening, with 700 mb temperatures also rising. The more meridional 700:500 flow should prevent a strong eastward shift after dark.

WEDNESDAY/THURSDAY: Uncertainty grows with the Wednesday and Thursday forecast as we remain stuck in this general mid-lvl southwesterly flow pattern. The aforementioned front will attempt to slide eastward on Wednesday, though a much more e complicated forecast in regards to the environment ahead of the front. Yet another weak mid-lvl area of vorticity tracks through the Tri-State area, increasing the risks for mid-lvl clouds but also a few showers and isolated thunderstorms by the afternoon. The area with the greatest risks for strong convection will be along that frontal boundary in central South Dakota by mid-late afternoon. Additional showers and thunderstorms may be possible into the overnight hours further east as the LLJ intensifies. Latest NBM guidance suggests 8- 95% PoPs in this timeframe, but my confidence in overall coverage is not as high as that chance suggests. A bit of a repeat performance on Thursday, with the greatest severe risks again focused west of the James River and into Southwestern South Dakota by the afternoon.

FRIDAY-SUNDAY: MId-lvl troughing moves through the Dakotas on Friday, potentially pushing strong convective risks further east into MN/IA. Confidence is very low in this time period given all of the various uncertainty associated with the forecast in the days before. Confidence rises for next weekend with drier weather and near to slightly above normal temperatures likely.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1205 PM CDT Mon Jun 1 2026

Localized MVFR ceilings continue to mix-out early this afternoon. We'll be watching mid-upr clouds moving northeast out of Nebraska this afternoon and evening. While a very low chance, a few sprinkles may develop.

Any convection that forms in Nebraska will lift northeast after midnight, spreading an overcast mid-upr cloud deck through the MO River valley. The wave associated with this convection could bring enhanced cloud cover and scattered showers and thunderstorms into the Tri-State area by mid-day. Very low confidence on this development.

FSD WATCHES/WARNINGS/ADVISORIES

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