textproduct: Sioux Falls

KEY MESSAGES

- Patchy frost expected this morning, greatest risk for portions of southeast South Dakota and southwest Minnesota. Frost Advisory remains in effect until 8 am CDT.

- Conditions remain more favorable for widespread frost by early Saturday morning. Additional headlines will likely be needed tonight-early Saturday.

- After above normal temperatures over the weekend, more seasonable conditions return by midweek as mostly dry conditions persist.

UPDATE

Issued at 324 AM CDT Fri May 1 2026

No major changes to the forecast this morning. Scattered showers east of I-29 continue to meander southeast, and should diminish around daybreak. Still keeping an eye on cloud cover and temperatures early this morning. Where skies have cleared and winds are calm, temperatures have fallen into the lower and mid 30s. Cirrus in the west and mid clouds with the showers in the east are keeping some locations in the upper 30s and lower 40s. Spencer, IA this morning dropped to 33 degrees when skies cleared and winds were calm, but warmed back in to the upper 30s when clouds and rain moved overhead. Based on these trends, frost may be less widespread than previously expected; however, no plans to change the on-going headline which is set to expire at 8 AM. Most of the area should stay dry today with the better shower chances to the east. Highs in the 50s.

Surface high pressure and light winds should allow for efficient radational cooling, with widespread frost likely with temperatures in the lower and mid 30s into Saturday morning. With frost headlines on-going, do not plan to issue any headlines overnight. If trends continue, a headline is highly likely for tonight into early Saturday morning.

DISCUSSION

Issued at 154 PM CDT Thu Apr 30 2026

CURRENTS & TONIGHT: A mild day continues! Taking a look across the area, we continue to see a growing cumulus ("Cu") field develop on visible satellite imagery mainly due to about 100 J/kg or less of instability above the mixed layer. As our next wave approaches from the northwest, could see a few diurnally-driven showers develop across the area mainly north of I-90. While accumulations will be minimal, can't rule out a few pockets of moderate showers mainly across southwestern MN. Otherwise, the main concern continues to be the frost potential tonight. While there could be some lingering clouds overnight, decided that the combination of temperatures near to below freezing along with lighter surface winds tonight would be enough to get scattered areas of frost to develop especially south of I-90. With this in mind, decided to issue a Frost Advisory for most areas from 1 am to 8 am on Friday. Make sure to cover/bring in any susceptible plants!

THE WEEKEND: Looking into the weekend, could see some additional spits to very light showers across southcentral SD to start the day on Friday as another quick shortwave swings through. However, any accumulations would be minimal (if any). With lighter winds expected by Friday night with an approaching surface high, we could see our first widespread freeze with lows expected to be just near to just below freezing. With this in mind, make to cover/bring in any susceptible plants from the colder conditions. By Saturday, more northwesterly flow will set up aloft as rising heights over the western CONUS begin to flatten. Temperatures will trend warmer as increasing warm air advection (WAA) and southwesterly surface winds leads to highs in the mid 60s to low 70s. Looking aloft, another dry cold front will swing through the area from Saturday night into Sunday. Otherwise, the above normal conditions will continue into Sunday as highs approach the upper 60s to low 70s for the day. All in all, this weekend looks to be beautiful to say the least especially with the light winds in place.

NEXT WEEK: Heading into the extended period, the warmest conditions of the week will likely occur on Monday ahead of our next cold front with highs mainly in the upper 60s to upper 70s. Otherwise, more seasonable conditions will return through midweek with highs mainly in the upper 50s to mid 60s. Lastly, mostly dry conditions will continue through the end of the week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 614 AM CDT Fri May 1 2026

Observations and satellite this morning have shown some very patchy fog, which could lead to brief categorical reductions through mid morning. Otherwise, VFR conditions continue through the period with diurnally driven cumulus this afternoon and into the evening. Mid and high clouds continue through the period. Northerly winds today with afternoon/evening gusts around 20 knots. Winds become light and variable late tonight.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Frost Advisory until 8 AM CDT this morning for SDZ038>040-050- 052>071. MN...Frost Advisory until 8 AM CDT this morning for MNZ071-072-080- 081-089-090-097-098. IA...Frost Advisory until 8 AM CDT this morning for IAZ001>003- 012>014-020>022-031-032. NE...Frost Advisory until 8 AM CDT this morning for NEZ013-014.