textproduct: Sioux Falls

KEY MESSAGES

- A few spotty sprinkles to very light showers are expected this afternoon with minimal accumulations.

- Chances (40-70%) for rain increase late this evening and night before persisting through the majority of the day on Friday. Rainfall totals for Friday look to be light, between a few hundredths to a few tenths.

- Chances (40-60%) for rain will persist through the weekend. Saturday has a conditional chance for strong to severe storms across south central South Dakota. Total rainfall amounts (including Friday's rainfall) may reach or exceed a half an inch through the weekend. Locations across south central South Dakota are most favored to see the bulk of this beneficial rainfall at this time.

- Low chances (<=30-40%) for rain will persist through the bulk of next week. However, severe storm chances continue to look low (5%) through next week.

DISCUSSION

Issued at 222 PM CDT Thu May 28 2026

High level cirrus continues to blanket the area early this afternoon. There is enough heating to result in some spotty showers for the rest of the afternoon and early evening timeframe though. Some rumbles of thunder and perhaps a few gusts up to 30-40 mph could accompany the showers. Like yesterday, these showers will be diurnally driven and will cease as the boundary layer stabilizes by sunset. However, rain chances will not be done yet as a diffuse upper level low currently over the central Plains will slowly push into the area this evening and night. This will bring more stratiform precipitation to the area with the potential for a rumble or two of thunder mainly for locations along and north of the Missouri River and west of I-29. The clouds and rain will keep low temperatures on the warm side, only falling to the upper 50s and 60s.

Friday is looking to be cooler than previously thought as this same system will take its time meandering through the forecast area. A few convective showers to weak thunderstorms are possible on its front edge where slightly less cloud cover and slightly higher instability will be present. But with the rain in the area, high temperatures will only warm to the 70s to low 80s, making for a warm but dreary day. On top of the rain, southeast winds will be strengthening in response to as the surface pressure gradient tightens across the area. Gusts up to 15-35 mph is expected, with the strongest winds occurring along and west of the James River. Latest guidance is suggesting that saturation in the dendritic growth zone (DGZ) could become offset from the better low level saturation. This looks to potentially lead to some drizzle in locations that are not saturated aloft. Chances (40-60%) for rain will persist through the overnight hours. Low temperatures will fall to the 50s overnight. Rainfall through this period of time looks to be light ranging from a few hundredths to a few tenths.

The next chance for isolated strong to severe storms will come on Saturday as an upper level trough grazes the western fringes of the area. Broad southeast flow will advect higher moisture into central Nebraska and central/western South Dakota. Deep layer shear will remain weak at about 20 knots. Instability however looks to potentially (40-80% chance) exceed 1,000 J/kg across parts of south central South Dakota. Warm air advection (WAA) in conjunction with shortwave troughs rotating through the base of the upper level trough will provide forcing for ascent. Some questions remain as to whether the instability can overcome the weaker deep layer shear and where the warm sector sets up. For now, think a conditional risk for strong to severe storms is on the table. Rain chances look to continue through the night and on Sunday as well. Severe weather chances are questionable on Sunday as well since the main upper level trough's vort max will be advected well northwest of the area. Steeper mid level lapse rates may also result in a large cap aloft. For now, the ensembles show a broad 40-60% chance for rainfall totals to exceed a tenth of an inch on Sunday. Will keep an eye on this potential over the next few days. Total rainfall amounts look to reach up to and possibly exceeding a half an inch by the end of the weekend. The highest totals look to fall across central and south central South Dakota. The amount and location of heaviest rain can still change over the coming days depending on how showers and storms shake out. Aside from rain chances, the weekend will see breezy southeasterly winds with high temperatures warming to the upper 70s to low 80s.

The omega block pattern looks to persist into early next week. Medium range guidance depicts the omega block beginning to break down by the middle of next week. For the Northern Plains, it looks like zonal flow will take over. This pattern change will still keep rain chances in the forecast as broad southerly flow will advect sufficient moisture into the area. The ensembles show 30-40% chance or less for rainfall exceeding a tenth of an inch through the bulk of next week. Questions remain regarding whether or not vertical shear will be strong enough to support strong to severe storms. This uncertainty is nicely shown in the latest machine learning (ML) guidance as all of the ML models show a 5% chance or less for severe storms. Aside from rain and storm chances, high temperatures look to remain warm in the 80s.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1224 PM CDT Thu May 28 2026

VFR conditions are expected for the TAF period. High level cirrus currently covers most of the area this afternoon. Expect the cirrus to become thicker in time. Low level cumulus clouds are developing early this afternoon as well. Expect spotty rain showers to develop from the CU field. An isolated lightning strike is possible with the showers but confidence is too low to include mention of lightning in a TAF at this time. Rain chances look to increase this evening and night mainly west of I-29. Rain chances will be expanding across the area towards the end of the TAF period. Have left any mention of rain out of KFSD and KSUX's TAFs at this time though as the rain should make it to the terminals just after the end of the period. Ceilings and visibilities will remain VFR while rain is falling.

FSD WATCHES/WARNINGS/ADVISORIES

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