textproduct: Sioux Falls

KEY MESSAGES

- Isolated to scattered showers and thunderstorms are expected this afternoon. While severe weather is not expected, lightning and occasionally strong wind gust up to 40-45 mph are possible.

- After warmer temperatures through Thursday, conditions will cool towards more seasonal temperatures over the weekend with low to moderate precipitation chances (30-70%) concentrated along and west of the James River Valley.

- Low chances (<=30%) for rain will persist through the first half of next week. However, severe storm chances continue to look low over the next week.

DISCUSSION

Issued at 157 PM CDT Wed May 27 2026

Beginning to see some CU develop early this afternoon. This CU field looks to mature just a little bit more to produce weak thundershowers across the area over the next few hours. With weak instability in place (~500 J/kg) and deep layer shear values on the order of 10-15 knots, severe weather is not expected. With dry low levels and high LCLs, DCAPE values will be high, near 1,000 J/kg. Thus, gusty winds are possible with any weak storm that forms. The strongest gusts could reach up to 40-45 mph. Lightning is also possible as well which could impact outdoor events. The good news is that these weak storms will be diurnally driven so they will quickly dissipate by sundown. Low temperatures will remain on the warm side, only falling down to the low to mid 60s.

The omega block pattern will persist through Thursday, with broad, weak southeast flow persisting across the area. This will keep high temperatures in the upper 80s to low 90s. Dew points will remain in the 50s which will result in lower humidity values across the area. There could be a few showers though moisture quality is a bit uncertain. Thus, have left the forecast dry for Thursday afternoon and evening. Winds will strengthen out of the south east with gusts up to about 30 mph. With dry conditions in place, there could be locally elevated fire danger in locations that received little to no rain recently. Otherwise, low temperatures will remain warm, only falling down to the upper 50s to low 60s.

Friday looks to be another dry day for the majority of the area. High temperatures will begin to cool this day with highs warming to the 80s to up to about 90F. Breezy southerly winds will persist though the strongest winds will take place west of I-29 and especially west of the James River as the surface pressure gradient will be tighter in this area. Gusts up to 20-35 mph is expected with isolated gusts potentially reaching up to about 40 mph. A closed low that is spinning over the western CONUS will begin to push eastwards. This trough will not make it fully to the forecast area but begin to brush up against the area Friday evening. This could result in some showery activity along and west of the James River though chances for rain are low (<=30%) at this time.

Chances for rain will only increase for Saturday and Sunday as the trough edges closer to the area. The highest chances for rain will come Saturday night as a warm air advection (WAA) strengthens aloft in tandem with weak shortwaves rotating around the base of the upper trough. The ensembles show a 40-70% chance for rainfall amounts to exceed a tenth of an inch for this period of time, highest along and west of the James River. Chances for rain will decrease for the day on Sunday, down to a 30-50% chance for exceeding the same amount of rain. Some instability looks to be in place, signaling the potential for thunderstorms though shear values remain weak, precluding severe storm chances. With rain chances hanging around for the weekend, high temperatures will be a bit cooler, only warming to the 80s.

The omega block pattern looks to persist through the first half of next week. High temperatures will remain on the warm side in the 80s. While forcing for ascent will be weak, the ensembles continue to show a <=30% chance for rainfall amounts to exceed a tenth of an inch, signaling low end chances for rain during this period of time. With the ridge axis centered over or near the forecast area, wind shear looks to remain weak. While thunderstorms will be possible, severe weather chances look to remain low at this time.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1223 PM CDT Wed May 27 2026

VFR conditions are expected for the TAF period. Light and variable winds begin the period but will turn weakly westerly over the next few hours. A few weak showers are beginning to push into KHON but lightning is not expected with these weak showers. However, additional showers and thunderstorms are expected to develop later this afternoon. Confidence is highest in storm occurring around KFSD and thus have added a PROB30 group to KFSD's TAF. These showers and storms will dissipate this evening, leaving quiet conditions for the rest of the evening and overnight hours. Winds will turn to out of the southeast to end the TAF period tomorrow morning.

FSD WATCHES/WARNINGS/ADVISORIES

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