textproduct: Sioux Falls

KEY MESSAGES

- Frost and freeze conditions are expected tonight into early Wednesday morning across the area - take precautions to protect sensitive vegetation. Frost/Freeze headlines go into effect late tonight.

- Scattered showers will return Wednesday afternoon mainly west of the James River Valley with light accumulations expected.

- Cooler conditions continue this week. Another round of showers and isolated thunderstorms is expected from Thursday afternoon through Friday. Severe weather not expected. However, some ensembles guidance suggests up to a 10 to 30 percent chance for a half an inch of rain during this time.

UPDATE

Issued at 842 PM CDT Tue May 19 2026

The forecast remains on track with the main the focus being on the frost/freeze potential tonight. With a surface high continuing to progress through the northern plains, we're already starting to see lighter winds take hold across the area this evening. This combined with rapidly cooling temperatures and a smaller dew point depression overnight will likely lead to frost/freeze conditions especially in our northwestern zones. With this in mind, we're still on track for scattered areas of frost with patchy areas of widespread freeze mainly along the Highway-14 corridor so make sure to cover/bring in any sensitive vegetation! Otherwise, a chilly start is ahead as most areas will wake up to temperatures in the low to mid 30s to start Wednesday. However, these conditions won't stay for long as southerly/southeasterly winds help temperatures improve to the 60s for the day. Lastly, can't completely rule out a few scattered showers mainly west of the James River Valley by Wednesday afternoon. Nonetheless, any accumulations would be light at best.

DISCUSSION

Issued at 1245 PM CDT Tue May 19 2026

Cool high pressure settles into the area tonight and will bring a very good chance for temperatures tall to or below 35 for most of the area with temperatures at or below freezing possible north of I- 90. Thus a freeze warning is in place for highway 14 and nearby locations in SD with a frost advisory for the remainder of the area.

Isolated pockets of fog will be possible early Wednesday morning but at this time it does not appear as though it will become more widespread.

A weak wave will move through the area on Wednesday which could bring a few sprinkles but overall should mainly be an increase in mid level clouds. Otherwise slightly more mild temperatures are expected as southerly flow develops and brings highs back into the 60s for most locations.

Another weak wave moves across NE on Thursday and could bring some light showers to the Missouri River corridor into northwest IA. Precipitation amounts will be light as moisture with the system is very limited.

A bit stronger and more negatively tilted system will swing through on Friday bringing the next best chance for rainfall. Instability very minor with CAPE values generally 500 J/kg or less. The model soundings do indicate the potential for some efficient rainfall however so maybe some half inch or so amounts will be possible. The latest ensemble output indicating about a 10 to 30 percent chance for more than a half an inch and the latest Nam is indicating a couple of areas with more than a half an inch. Long story short, only minor impacts expected with no severe weather.

As this system moves northeast and out of the area a few lingering showers will be possible on Saturday, but warmer temperatures will begin to work into the region. Sunday through the middle of next week will see troughiness to the west and ridging to the east, leaving the area in warmer southerly flow. While there is very little agreement, there should be a couple of weaker waves that could bring showers and thunderstorms to the area, but for now confidence is too low to include in the forecast. Otherwise highs should be in the 80s with lows mainly in the 50s Monday through Wednesday.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1200 AM CDT Wed May 20 2026

VFR conditions will continue this TAF period. Mostly clear conditions will likely persist throughout the first half of the day before clouds cover increases for the south with our next wave. Besides a few scattered showers mainly west of the James River Valley, most areas should remain dry. Otherwise, light and variable winds will become more southerly with the breeziest conditions west of I-29.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Frost Advisory until 8 AM CDT Wednesday for SDZ050-054>071. Freeze Warning until 8 AM CDT Wednesday for SDZ038>040-052-053. MN...Frost Advisory until 8 AM CDT Wednesday for MNZ071-072-080-081- 089-090-097-098. IA...Frost Advisory until 8 AM CDT Wednesday for IAZ001>003-012>014- 020>022-031-032. NE...Frost Advisory until 8 AM CDT Wednesday for NEZ013-014.