textproduct: Sioux Falls

KEY MESSAGES

- Isolated to scattered thunderstorm risks grow this evening, but focus morseo overnight. Ping-pong ball size hail and 60 mph winds will be possible.

- Quiet and warm conditions continue through the middle of the week.

- Rain chances increase by Friday and continue on and off through next weekend though recent trends have been drier. Severe weather risks remain low as temperature lower back toward seasonal normals.

DISCUSSION

Issued at 1246 PM CDT Mon May 25 2026

THIS AFTERNOON/EVENING: Temperatures continue to rise through the 80s this morning, on their way to the 90s in a handful of areas. Aloft, mid-lvl moisture AOA 600 mb continues to pivot east across the MO river valley into NW Iowa. Further development can't be ruled out, but profiles suggest no more than sprinkles as this area of clouds move east. Some slight modification of high temperatures over NW Iowa may be possible due to these clouds. Dew points have risen into the 60s in portions of the area.

Later this afternoon we'll begin to watch CU field expected to develop over central and western Nebraska where increased surface convergence along a weak boundary may spark a few thunderstorms. Further northeast, despite the increase in mid- lvl lapse rates and resultant MLCAPE near 2000-2500 J/KG, soundings continue to show convective inhibition hanging around near 750mb into the early evening along the northeastern extent of this boundary which may extend into southwest Minnesota by 00z. CAMS indicate scattered Nebraska convection may tend to drift northward into south central South Dakota this evening as low-lvl lapse rates are steeper and inhibition is less. The development further northeast into eastern South Dakota and southwest Minnesota along the boundary is MUCH less certain and may be isolated if it does form. The consequence of mixing deeper in south central South Dakota may result in lower hail potential, but more gusty outflow with high inverted V soundings as storms move northeast.

The gradual ramp-up in the LLJ after 00Z, but especially near or after 03Z may result in additional isolated to scattered convection into the early overnight hours further north towards I-90. Should the boundary layer be cut-off any parcel lifted off the 850mb surface would still have 2000+ J/KG MUCAPE, however effective shear may be marginal for any persistent rotating structures.

The increase in weak dPVA through northern Nebraska into central SODAK may result in a bit of an uptick in convective risk through daybreak. While sharply veering by daybreak, the LLJ convergence favors areas along and east of I-29. MUCAPE lowers through the night, but there may still be sufficient instability for isolated hailers into daybreak. The lack of meaningful shear will keep organized storms to a shorter duration. Hazards this evening and overnight include ping-pong ball size hail and brief 60+ mph gusts through mid-late evening before boundary layer stabilization occurs.

TUESDAY: Some elevated convection may linger in SW Minnesota through mid-morning but rapid dissipation is likely as forcing moves off to the east. A very warm is expected Tuesday with temperatures rising into the upper 80s to 90s. Drier air mixing eastward off the Western Plains should lower dewpoints slightly, keeping heat index values near their air temp.

WEDNESDAY-THURSDAY: An elongated NW to SE oriented mid-lvl ridge builds from central Canada into the southeastern United States. We'll reside under this ridge axis through Thursday which will keep winds aloft very weak, and temperatures in the middle 80s.

FRIDAY-SUNDAY: The brief Omega block will weaken as we move into next weekend with a stronger wave rotating southward into the Central and Eastern Great Lakes by Friday and Saturday. Meanwhile, meridional low-lvl return flow will be focused more towards the western Dakotas and Nebraska, keeping shower and thunderstorm chances focused over the western CWA into Saturday. Perhaps the best risk for any rain locally will move in Saturday into Sunday should the cooler Great Lakes airmass reach this far to the west. There is quite a bit of spread in ensemble guidance for next weekend, with the GEFS/GFS showing considerably more precipitation risks that the ECMWF/ECE. The official forecast has lowered PoPs for next weekend towards the 10-30% range, with minimal shear really prohibiting any severe risks. NBM mean temperatures still in the lower 80s may be a touch warm, but do fall right in the middle of a reasonable 25/75th spread from the mid 70s to the mid 80s.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1211 PM CDT Mon May 25 2026

VFR conditions continue through the afternoon and early evening as mid-lvl AC deck moves through the Tri-State area. This high based activity could lead to virga or a sprinkle, but probabilities of a wetting rain are very low.

We'll have a slightly increased risk for convection along a weak boundary stretching from western Nebraska into southwestern Minnesota later this evening and overnight. Probabilities at any one location remain low, and will indicate with PROB30 at FSD. Localized hail and brief gusty winds in convection will be possible.

Storm risks move east after daybreak Tuesday, leaving VFR conditions into the morning hours with a southerly wind remaining in place.

FSD WATCHES/WARNINGS/ADVISORIES

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