textproduct: Sioux Falls

KEY MESSAGES

- A Heat Advisory remains in effect until 9PM for areas along and west of the James River.

- Light rain showers will persist for the rest of the afternoon hours. Another round of showers and storms is possible late tonight into tomorrow morning. The bulk of the showers look to stay just northeast of the area, but some could make it into parts of southwest Minnesota.

- Chances for strong to severe storms returns to the area Monday afternoon and evening near and south of highway-20. Large hail up to the size of golf balls and damaging winds to 70 mph are the main hazards.

DISCUSSION

Issued at 229 PM CDT Sun Jul 19 2026

A few light showers persist across the area this afternoon. These showers are also accompanied by a mid level cloud deck which has kept temperatures a bit cooler than previously expected. However, sunshine remains across parts of south central South Dakota. Thus, temperatures have warmed to the upper 70s, 80s, and a few locations pushing into the 90s. With dew points remaining in the 60s to low 70s, heat indices have warmed to the 80s and 90s with a few locations hitting 100F. With some diurnal warming left to go, should still see the heat indices nudge a little higher, allowing for the Heat Advisory to remain in effect until 9PM this evening. Another round of showers and thunderstorms remains possible late tonight into tomorrow morning (11PM to 6AM). These storms will develop along a cold front in North Dakota and move southeastwards through the evening hours. These storms may grow into a line as they push southeastwards. However, there remains some uncertainty in whether these storms will push into southwest Minnesota or stay just outside the forecast area. These storms look to be focused on the nose of the low level jet where convergence and the strongest warm air advection (WAA) will lie. The bulk of the hi-res guidance and the ensembles also support the storms remaining in this location. Still have left light chance to chance PoPs across southwest Minnesota in case lingering showers and storms pass through the area.

The thermal ridge will push directly over the forecast area on Monday, pushing 850 mb temperatures up to +25C to about +30C. Mixing these temperatures down to the surface will result in widespread high temperatures up to the 90s to low 100s, hottest along the Missouri River Valley. With dew points remaining in the 60s to low 70s, heat indices will warm up to 100F to 105F south of I-90. As such, have issued another Heat Advisory for this area. The Advisory is in effect from noon to 8 pm. The previously mentioned cold front will be pushing through the area throughout the day. While this front will cool temperatures, the main cold advective push from the front will come in the late afternoon and evening timeframe, thus allowing for hot and humid conditions to continue. This front will serve as the focal point for additional showers and storms between 4PM and 10PM. The front will push through rather quickly, limiting the severe weather threat to near and south of highway-20. Storms look to remain more discrete as the develop and quickly race out of the area along the boundary. The moisture pooling along the boundary will push CAPE values up to 2,000 to 2,500 J/kg. Hodographs show deep layer shear values on the order of about 45 knots. Hodographs are generally straight with slight backing aloft. This should allow for large hail up to the size of golf balls. DCAPE will also be high around 1,500 J/kg, resulting in the potential for damaging winds to 70 mph. Since these storms are discrete and look to only impact a small area, should only see isolated impacts from severe storms. Once the front pushes through, temperatures will fall to the 60s to low 70s overnight.

Tuesday will be a cooler day with the post frontal airmass in place. High temperatures will be seasonable in the 80s with dew points falling to the 50s. While this would usually make for a pleasant Summer day, smoke will filter in behind the front which could affect sensitive individuals. Fortunately, it looks like the highest concentration of smoke will come Monday night into Tuesday morning and be slowly decreased thereafter. These seasonable conditions will persist for the rest of the work week as northwest flow persists aloft. Next chances for rain look to come on Thursday and Friday as a shortwave trough pushes through the area. The ensembles support this as they show a 40-60% chance for rainfall amounts exceeding a tenth of an inch for this period of time. Instability looks to be quite limited, so severe storms are not expected at this time. Upper level ridging looks to potentially make a comeback next weekend, leading to a return of above average temperatures. This potential remains uncertain so will keep an eye on how the pattern evolves over the next week.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1236 PM CDT Sun Jul 19 2026

VFR conditions begin the TAF period. Light rain showers are currently ongoing between KHON and KFSD. They are moving southeastwards but are weakening with southeastward extent. A stray lightning strike is possible but confidence is not high enough to include in a TAF at this time. These showers will dissipate, leaving VFR level mid level clouds for the remainder of the afternoon hours. Additional showers and storms are possible tonight into tomorrow morning. Latest guidance is showing these showers pushing mainly north and east of the area though locations across southwest Minnesota may still see chances for showers and storms through the night. The low level jet (LLJ) will strengthen tonight, leading to low level wind shear (LLWS) across locations along and northwest of a KAGZ to KFSD to KTKC line. A cold front will be pushing through the area, turning winds northwesterly towards the end of the period.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory from noon to 8 PM CDT Monday for SDZ050-063>071. Heat Advisory until 9 PM CDT this evening for SDZ038-050-052- 053-057>060-063>065-068-069. MN...None. IA...Heat Advisory from noon to 8 PM CDT Monday for IAZ001>003- 012>014-020>022-031-032. NE...Heat Advisory from noon to 8 PM CDT Monday for NEZ013-014.