textproduct: Sioux Falls

KEY MESSAGES

- Near to slightly below normal temperatures prevail through Saturday. A couple spotty shower and storm chances are possible during this time.

- An extended period of heat and humidity is expected starting Sunday into next week. Heat indices up to the low 100s could lead to Major to Extreme Heat Risk. Begin planning now to reduce risk of heat illness and impacts.

- An active pattern aloft leads to isolated chances for stronger storms Saturday night and again into early and mid next week. However, some uncertainty remains.

UPDATE

Issued at 344 AM CDT Fri Jun 26 2026

Increased pops a bit for the early morning hours, although precipitation continues to struggle north of I-90 with dry sub cloud layer. Any lingering showers/sprinkles come to an end through late morning. Thunder risk remains low. Highs today warm into the upper 70s to lower 80s with decreasing afternoon clouds. Wind gusts around 30 mph this afternoon for south central SD.

Slightly warmer but more humid and breezy on Saturday, with guidance still showing stratus over the area - which may temper highs slightly. Breezy, with gusts 35 mph. Very strong capping remains in place Saturday afternoon through Saturday night/early Sunday, which should prohibit widespread storms. However, if a storm can break the cap or move into our area, there is ample instability and shear in addition to steep mid level lapse rates. An isolated strong to severe storm is possible if storms overcome the cap, with wind gusts to 60 mph and hail to ping pong ball size Saturday evening into early Sunday.

Confidence remains high with the building heat and humidity Sunday into mid next week, with the hottest days still progged to be Sunday and Monday. Ensemble probabilities of temperatures above 90 degrees remain moderate to very high (above 50% to near 100%) both Sunday and Monday. Very warm (possibly record warm) overnight lows provide little relief and drive Heat Risk into the Major and even Extreme categories. Plan ahead now to limit heat exposure, especially those with outdoor plans and vulnerable populations/those more susceptible to heat illness.

DISCUSSION

Issued at 215 PM CDT Thu Jun 25 2026

CURRENTS & TONIGHT: Beautiful conditions continue! Taking a look across the area, fall-like conditions continue this afternoon with many sites reporting temperatures in the low to upper 70s with lighter winds as of 1 pm. We're also starting to see some scattered showers progress into the Missouri River Valley mainly in response to weak shortwave and weakening LLJ. While severe weather is not expected, could see this festering activity continue through the early evening mainly across the same areas before things gradually dissipate with the loss of diurnal heating. Otherwise, could see additional showers develop overnight into Friday morning as another wave interacts with a strengthening nocturnal LLJ. Lastly, more seasonable temperatures are expected overnight as lows fall into the mid to upper 50s for the night.

THE WEEKEND: Looking into the weekend, we'll continue to see a few lingering showers in our far northwestern zones to start the day on Friday. As the LLJ weakens, this activity should gradually diminish by mid-morning. Quieter conditions will return for the rest of Friday into the first half of Saturday as highs continue to sit in the low to mid 80s. Otherwise, cloud cover will gradually build during the day on Saturday as warm air advection (WAA) strengthens. With southwesterly flow in place aloft, increases in isentropic lift with an approaching wave could lead to a few pockets of drizzle to light shower developing in the lower cloud deck. However, severe weather is not expected mainly due to strong cap according to soundings. Looking into Sunday, the focus will shift to the building heat as southerly surface winds and increasing mid-level WAA leads to a push towards highs mainly in the low to upper 90s. This combined with dew points closer to upper 60s to low 70s will lead to heat indices in the 90s to low 100s for parts of the area with the warmest conditions across northwestern IA. While a heat headline could be needed, decided to forgo it at this time mainly due to uncertainty with spacial extent. Nonetheless, with muggy conditions expected through Sunday evening make sure to stay hydrated and to limit any strenuous activities!

NEXT WEEK: Heading into the extended period, the focus will continue to be on the heat as upper-level ridging continues to build over the eastern CONUS. With southerly surface winds in place and multiple pushes of warmer air aloft, expect temperatures to continue to hover in the low to upper 90s from Monday onwards with heat indices (Hi) in the 90s to low 100s degree marks at times. While conditions won't quite make it into excessive heat territory, we could see many areas touch heat advisory criteria (HI>100) at times each day so this will be something to watch moving forward. Either way, the conditions will lead to moderate to major heat risk for most areas from Monday through Wednesday so make sure to drink plenty of water and to take plenty of breaks when working outdoors! Otherwise, we'll also have to keep any eye to the skies through midweek as south-southwesterly flow aloft help ushers in multiple pieces of energy into the area through weak perturbation. With plenty of heat in the forecast, all that's needed is a strong enough trigger to break through the cap to get something strong to severe. Nonetheless, its still uncertain if this can happen given the warmer temperatures +20 to +28 degrees C at 800 mb through midweek. With all this in mind, make sure to monitor your local forecast as things will be subject to change moving forward.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 625 AM CDT Fri Jun 26 2026

Seeing some brief and localized MVFR conditions this morning with heavier showers. Otherwise, VFR conditions expected through the period as showers and sprinkles diminish late this morning. Some ensemble guidance hints at MVFR stratus moving into the southern MO River Valley, including KSUX, by the end of the period; however, with low confidence have omitted at this time.

Winds through the day become southeasterly with gusts around 20 to 25 knots through much of the period, including into the overnight hours - mainly west of the James River.

FSD WATCHES/WARNINGS/ADVISORIES

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