textproduct: Sioux Falls

KEY MESSAGES

- Fog, including dense fog, continues to expand tonight. Dense Fog Advisory in effect through 8 AM CST for portions of the area with visibility below one quarter of a mile. Expect quickly changing conditions if traveling.

- A strong storm system will bring widespread showers and a few thunderstorms to the region late in the work week. Chances of more than a half inch of rain are over 50% from about Yankton to Windom southeast.

- A few strong to severe storms may occur with this system as well, focused south of I-90.

- On the back side of the system, the best chances for minor winter weather impacts will be across eastern South Dakota north of Sioux Falls.

UPDATE

Issued at 1143 PM CST Tue Mar 3 2026

Fog, including dense fog with visibility below a quarter of a mile, has continued to expand over the area. Dense Fog Advisory in effect for portions of eastern SD, southwestern MN, and northwestern IA until 8 AM. Further areal and temporal extensions may be needed overnight. Be prepared for quickly changing visibility if traveling tonight.

DISCUSSION

Issued at 136 PM CST Tue Mar 3 2026

Through Thursday:

Cloud cover has eroded somewhat over areas east of I-29 and north of I-90 early this afternoon, with the low stratus deck gradually increasing in height south of I-90. While some modest improvement is expected over the remainder of southeast South Dakota by early evening, NAM forecast soundings for Sioux City show a stout inversion just above 5,000 feet that sticks around through Wednesday. Think any clearing that takes place will begin to fill in again later in the night, before a more substantial clearing trend works from west to east across the area later on Wednesday.

Morning deterministic guidance moves an upper low eastward across Nebraska Wednesday into early Thursday, with a surface boundary getting hung up in the upper flow near the North/South Dakota border. The southerly flow will bring a steady warming trend Wednesday and Thursday, with high temperatures topping out in the lower 70s in south central South Dakota.

Thursday night through Friday night:

As the low pulls further away from the region later in the week, an upper trough moving out the Pacific Northwest will deepen across the Rockies. This will introduce surface cyclogenesis across eastern Colorado, with the low lifting northeast through Friday evening. The GFS track is more on the northern periphery of the guidance envelope, but not overly so, and the broader model suites continue to favor the highest rain chances from central Nebraska into south central Minnesota. On the back side of the system, a changeover from rain to snow is expected in a deformation zone of precipitation, with WPC's probabilistic Winter Storm Severity Index showing highest potential for some minor winter impacts (20-30%) across the I-29 corridor north of Sioux Falls.

The GFS track would suggest the best thunder potential from about Mitchell/Sioux Falls south and east on Friday, though a number of European ensembles have CAPE's over 500 J/kg in this area as early as Thursday night. SPC Day3 convective outlook brings the level 1 (marginal) risk as far north as I-90, for some elevated storms Thursday night that may produce large hail The CSU probabilistic guidance has the I-29 corridor on the periphery of any strong to severe weather potential for Friday, with the corresponding SPC Day4 outlook more focused from about Sioux City east and south. Thunder chances from the NBM initialization seem reasonable for Thursday night and Friday, but may be hanging onto it a bit too long Friday evening, with any higher CAPE's east of the South Dakota border at that point.

In terms of rainfall amounts, overnight LREF guidance shows a greater than 50% chance of seeing more than a half inch of rain southeast of a Yankton- Windom line, areas that are in moderate drought on last week's Drought Monitor update. Chances of more than an inch are around 25% in an area focused over northwest Iowa and far southeast South Dakota.

Saturday through Tuesday:

Looking through the weekend into early next week, an upper trough will move through the Dakotas on Saturday, with the flow behind it becoming more zonal. Another surge of milder weather should result in temperatures getting into the lower 70s by Monday near the Missouri River. With a large upper low cutting off near the Baja Peninsula, the longer range GFS suggests the zonal flow will persist into the middle of next week, but the international model suite opens it up into a long wave trough. That solution would lean toward another storm system similar to the one that's coming up in a couple of days, but there's plenty of time to keep an eye on it.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1050 PM CST Tue Mar 3 2026

Latest satellite shows a mix of low level stratus sitting at MVFR/IFR/LIFR levels and fog across the area. The low level stratus is sitting across parts of southwest Minnesota, northwest Iowa, far northeast Nebraska, far southeast South Dakota. The fog is along and north of this area of stratus with visibilities also spanning MVFR/IFR/LIFR thresholds. The fog and stratus will persist through the entire night and into the morning hours tomorrow. Despite light winds in place, fog looks to lift during the morning hours due to diurnal heating. The main uncertainty is how much the low level stratus will dissipate. Currently have it lasting into the afternoon hours but trends will be monitored. Additional low level stratus and fog looks to develop tomorrow night but at this time, it looks to come just after the TAF period ends.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Dense Fog Advisory until 8 AM CST Wednesday for SDZ039-040- 054>056-061-062-066-067. MN...Dense Fog Advisory until 8 AM CST Wednesday for MNZ071-072-080- 081-089-090-097-098. IA...Dense Fog Advisory until 8 AM CST Wednesday for IAZ001>003- 012>014-021-022-032. NE...None.