textproduct: Sioux Falls

KEY MESSAGES

- Warm and humid conditions continue for Tuesday. Please ensure you are hydrated and take breaks out of the heat!

- Scattered severe storms capable of half dollar size hail and 60-65 mph winds will again be possible from late Tuesday afternoon into early Wednesday.

- Temperatures will rise towards the middle 90s to 100 degree mark by next weekend.

UPDATE

Issued at 929 PM CDT Mon Jul 6 2026

Satellite water vapor imagery shows an upper low spinning over Manitoba and Ontario, as well as a cold front draped from there through Minnesota, eastern North Dakota, central South Dakota, and into western Nebraska. A line of strong to severe thunderstorms have formed along the front and are progressing southeast through Minnesota as of 9 pm CDT. Evidence of the front is found in the form of a fine line in the radar scan moving through northeast South Dakota, but at this time, storms have failed to sustain themselves or become severe in this area. Model soundings indicate there may remain just enough of a cap on the environment to prevent surface based storms from firing. CAMs guidance has also shown a decrease in potential storm activity in the past couple of runs. While sufficient instability remains, confidence on timing and location of strong to severe storm development for this evening and tonight is low. Should storms develop, they will most likely be elevated in nature, and bring a threat of 60 mph wind gusts with them. The severe threat should be east of the region in the early morning hours of Tuesday.

Tuesday will be another hot and humid day, with highs in the upper 80s to low 90s. Ensemble guidance indicates there is a 50% or less probability of reaching 90 degrees F for areas east of a rough line from Huron, to Dell Rapids, to Anthon Iowa. West of there the probabilities increase to 90-95%. This is slightly cooler than the current NBM temperatures. In fact, today's NBM highs were 3 to 5 degrees warmer than reality, with the warm bias looking to continue for Tuesday. So, while there will still be very warm temperatures in the forecast, have nudged overall highs down by a couple degrees using a blend of the NBM and CONSShort. Heat index values will be near to surface temperatures, and no heat headlines are needed at this time. However, caution while working and playing outside are still needed.

Tuesday afternoon southerly winds will be on the breezy side, gusting to 25 mph for areas west of I-29. With the winds will come increasing dew points into the upper 60s to low 70s. This moisture will pool along the now stalled surface front until a shallow mid- level wave moves in from the west. At the same time the LLJ increases and storms begin to fire along the boundary in the late afternoon to early evening Tuesday. A moderately unstable environment will be in place with 1500-2500 J/kg of MUCAPE, steep mid-level lapse rates from 7 to 8 deg C/km, and 0-6km Bulk Shear of 30-40 kts. However, The best dynamics do not align well, leading to considerable uncertainty in the severity of storms. Model soundings indicate strong caps in place Tuesday, slowly eroding through the afternoon. However, some also indicate enough of a cap may linger to hamper surface based convection. Should stronger storms develop, the area along and north of Highway 14 has the best alignment of convective parameters, and therefore the greatest risk of severe weather. This is outlined will in the SPC Day 2 Slight Risk (level 2 of 5). Main risks for stronger updrafts will include hail to the size of a half dollar and wind gusts to 60-65 mph. While the risk is low, an area of enhanced stretching potential along and north of Highway 14 could also see a tornado or two with convective initiation. As the evening continues, storms are expected to grow upscale into a line with bowing segments, at which point risks will transition to a wind threat. Greatest severe risk timing from roughly 6 pm through midnight.

DISCUSSION

Issued at 230 PM CDT Mon Jul 6 2026

CURRENTS & TONIGHT: Taking a look across the area, we're continuing to watch a broken line of scattered showers with isolated thunderstorms progress across western and central SD this afternoon mainly in response to the approaching cold front. With a small cap in place aloft according to soundings, the general expectation is for this activity to gradually weaken upon approach. However, as diurnal heating persist and eventually erodes the rest of the cap; short-range guidance continues to show additional convection developing with the cold front this evening initially across northeastern SD and potentially southcentral SD. Both areas of convection will likely meet in our area during the late evening to early overnight hours mainly along and north of I-90 with the main hazards being up to quarter-sized hail and strong wind gusts up to 60 mph. Otherwise, should see this activity gradually weaken past the I-90 corridor as instability wanes with the loss of diurnal heating. Lastly, expected another warm night with lows mainly in the upper 60s to low 70s.

TUESDAY-THURSDAY: Looking into Tuesday, quieter conditions will return for the first half of the day as quasi-zonal flow continues aloft. With similar conditions to today in place, expect another dose of the summer heat as highs to peak in the upper 80s to upper 90s for most areas with heat indices in the low to upper 90s. With this in mind, make sure to stay hydrated and to take frequent breaks when working outdoors. Otherwise, the main focus continues to be the severe weather potential from late Tuesday into Wednesday. Looking aloft, we're still on track for scattered showers and thunderstorms to track from central SD through areas along and north of I-90 with the surface front during the evening to overnight hours. However, the main question continues to be how does this developing activity evolve during this time and will it be severe. With the better forcing continuing to sit closer to the ND/SD border, we'll continue to hedge our bets on the better severe risk being north of us.

However, still can't completely rule a few isolated gusts up to 60 mph north of I-90 if strong cold pools can develop with a few weakening thunderstorms. Otherwise, gradual weakening should continue through Wednesday morning as this activity progresses southeastwards with the surface front into a more stable environment. Slight cooler conditions will be possible by Wednesday as cooler air funnels in behind the previously mentioned boundary leading to highs mainly in the 80s to low 90s. Additional showers and thunderstorms could develop along/ahead of the boundary by Wednesday afternoon mainly across northwestern IA and the lower Missouri River Valley. While an isolated severe risk can't be ruled out mainly across the Highway-20 corridor and portion of northwestern IA, the location will be highly dependent on where the surface boundary ends up setting up during the afternoon. Lastly, mostly quiet conditions should return by Thursday as highs slightly decrease into the low to upper 80s for the day.

THE WEEKEND: Heading into the extended period, an active period will continue aloft as quasi-zonal flow continues into the weekend. Multiple waves will progress through the plains leading to at least some smaller chances (<30%) through Saturday. With the ridging expected to strengthen over the western CONUS during the upcoming weekend, we could see the return of oppressive temperatures mainly in the 90s to low 100s as early as Sunday. With heat indices potentially reflecting similar values, make sure to stay hydrated and to monitor your local forecast!

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1220 AM CDT Tue Jul 7 2026

VFR conditions are expected to prevail this period. Winds are light and variable. After sunrise winds will become southeast to south and increase. Areas west of I-29 will see afternoon gusts ranging from 20 to 30 kts, with the strongest gusts in south central South Dakota. East of I-29 wind gusts remain around 15 kts or less. Breezy winds continue into the overnight as a cold front moves through the region, turning winds behind it to the north.

Isolated to scattered thunderstorms are possible early this period, mainly along and north of Highway 14 from roughly the James River Valley and east into Minnesota. Risk for severe storms is low, though small hail and gusts to 50 mph are possible. Storms rapidly dissipate in the early morning hours of Tuesday. Another round of showers and thunderstorms are possible near the end of the period late Tuesday afternoon into the evening along the previously mentioned cold front. Some storms could be strong to severe producing hail to the size of a half dollar and wind gusts up to 65 mph.

FSD WATCHES/WARNINGS/ADVISORIES

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