textproduct: Sioux Falls

KEY MESSAGES

- Isolated strong to severe storms are possible late tonight into Sunday morning. Confidence in coverage is diminishing as the capping inversion appears to be strengthening.

- A Heat Advisory has been issued for some areas Sunday into Monday, and further adjustments to headlines are possible in the coming days.

- Summer heat and humidity is expected Sunday into next week. Daily heat indices of 95 to 105 degrees will lead to Major to locally Extreme Heat Risk at times. Begin planning now to reduce the risk of heat illness and impacts.

- An active pattern through the week leads to periodic moderate chances for showers and storms. Uncertainty in the timing of rain also brings lower confidence in daytime high temperatures.

DISCUSSION

Issued at 1248 PM CDT Sat Jun 27 2026

The first concern will be the potential for thunderstorms tonight. The current run of models is really pushing for a strong capping inversion, which strengthens through the night. This suggests that tapping into the deeper instability may be impossi.ble. Above this capping inversion some moisture and weak (500 J/kg) instability may allow for some ACCAS showers and thunderstorms late tonight into Sunday morning, but any severe threat would be very limited. Will need to see some fairly large changes in the upcoming data and model runs for the severe threat to become more prevalent. If a storm can tap into the lower, deeper instability (2500-3000 J/kg) a very isolated threat for hail to the size of golf balls is possible.

Very warm air and a continued strengthening capping inversion barrels north on Sunday, which should shut down convective chances through about Monday night. Later Sunday night into Monday morning some patchy elevated showers or storms will be possible but for now confidence is too low and will keep chances at 20 percent or less.

Concerns for heat ramp up Sunday but one big question mark remains, stratus. The latest run of the nam has some fairly deep and widespread stratus that would really bite into the afternoon heat indices. For now confidence is not high enough to drop the heat advisory but will need to monitor the trends of this stratus as well as the trends of the dew points. The nearest 70+ dew point in south central NE and surface winds are expected to remain southeast into Sunday morning.

Monday may prove to be the hotter more humid day with less chance for stratus. Expanded the heat advisory into parts of southwest MN to cover the potential for more widespread heat indices above 100. Monday does look to be windy which will help take the edge off of the heat a touch.

Otherwise, Tuesday through Saturday will have southwest flow aloft with the stronger upper level ridging just to the east of the area. This will allow periodic waves to move through the area with off and on threats for showers and thunderstorms. More than likely this upper level pattern will keep the extreme heat at bay most of the days, but still see highs from the upper 80s to mid 90s. But with these threats for showers and thunderstorms will come "unexpected" outflow boundaries and stratus at times so there will be some variability in which days are hottest and which are less hot.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 628 PM CDT Sat Jun 27 2026

2500 to 3500 ft stratus will sink to more widespread IFR and MVFR ceilings overnight into Sunday morning. Aside from stratus and a gusty southeast wind, scattered showers and thunderstorms are likely to spread eastward near and north of the I-90 corridor overnight. A few strong to severe storms with large hail and damaging wind gusts are more likely near and north of the Highway 14 corridor (near Huron) after 06z. Model forecast soundings have fairly high confidence in winds weakening and stratus lifting and eroding around mid day Sunday.

CLIMATE

Issued at 410 AM CDT Sat Jun 27 2026

Summer heat builds into the area from Sunday through much of next week. This will lead to a potential for a few temperature records to be tied, or possibly broken:

Current Record Highs:

Monday (06/29): KFSD(101|2002) KSUX(100|2022)

Current Record Warm Lows:

Monday (06/29): KFSD(77|2020) KSUX(80|1931) KHON(75|2020)

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory from 1 PM Sunday to 9 PM CDT Monday for SDZ062- 066-067-069>071. Heat Advisory from 1 PM to 9 PM CDT Sunday for SDZ060-061-065- 068. MN...Heat Advisory from 1 PM to 9 PM CDT Monday for MNZ072-080-081- 089-090-098. IA...Heat Advisory from 1 PM Sunday to 9 PM CDT Monday for IAZ001>003-012>014-020>022-031-032. NE...Heat Advisory from 1 PM Sunday to 9 PM CDT Monday for NEZ013- 014.