textproduct: Sioux Falls

KEY MESSAGES

- Low stratus and fog returns into Monday morning, mostly along and east of the James River. At times, dense fog may be possible.

- A warm and mostly quiet forecast persists through Thursday. Outside of minimal (less than 20%) precipitation risks Monday night into Tuesday evening.

- A great deal of uncertainty continues in the potential for another storm system arriving Friday into Saturday, with probabilities for measurable wintry precipitation remaining around 30%.

DISCUSSION

Issued at 149 PM CST Sun Jan 4 2026

THIS AFTERNOON: Mid-lvl trough crossing the Dakotas this afternoon continues to push warmer air eastward. At the surface an area of low pressure has developed over the northeastern portions of South Dakota, with a trailing cold front sweeping into the James River valley as of 1pm. As shortwave energy begins to move into Minnesota late this afternoon, we'll continue to see that aforementioned cold front slide southeast pushing a narrow corridor of upper 40s and 50s ahead of it. We'll also begin to see stratus return and slip southeast along Highway 14 by sunset.

TONIGHT: Most guidance is in good agreement that as low level flow turns more to the northwest, stratus will build southeast along the Coteau des Prairies. Given the weak surface flow, areas of fog and even dense fog will form. Currently, highest probabilities for dense fog reside east of the James River valley. Depending on the coverage of dense fog, advisories may be needed into Monday.

MONDAY: Stratus and fog may be slow to erode until low-lvl winds begin to shift back to the southwest by mid-morning. With surface winds turning southerly through the day, and a considerable amount of low-lvl warm air advecting overhead, we should again see highs in the 40s most everywhere with 50s along the MO River valley. Mid-lvl clouds will also be on the increase through the day.

TUESDAY: Mid-lvl vorticity will continue to stream through the region Monday night into Tuesday. Questions remain on overall column saturation overnight and into Tuesday, so any QPF is anticipated to stay on the very light side through Tuesday. Temperatures may also stay near or above freezing through Tuesday, likely meaning that most precipitation will just fall as a cold rain/sprinkle/flurry.

WEDNESDAY-THURSDAY: Quasi-zonal flow on Wednesday will gradually begin to shift more to the southwest by Thursday as troughing enters the West Coast. Southwesterly surface winds will lead to a very pleasant day on Wednesday with highs nearing the 50s. Only a slight cooldown is expected Thursday as a weak low-lvl cool front drops in from the northwest.

FRIDAY-SATURDAY: We're still watching the potential return of a wintry mix of precipitation to end the work week. A large spread in deterministic and ensemble guidance continues today, mostly due to the inconsistencies in guidance to resolve the phasing between troughs crossing the CONUS. The GFS/CMC are more phased with a digging northern stream and eastward tracking secondary trough crossing the Southwest Thursday. This would result in a deeper developing low over the Southern Plains to Mid-Mississippi River valley. Meanwhile the ECMWF/ECE support less phasing, a more positively tilted northern stream trough, stronger Southeast ridging, allowing the southern stream system to track further north and deepen in the Upper Midwest. All that to say...further fluctuations in guidance can be expected as both of these features and driving jets remain over the Pacific until Wednesday.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1049 PM CST Sun Jan 4 2026

Fog has finally developed across the area, generally along and north of I-90. Chances for fog at KHON have dwindled so have omitted from its TAF. The fog will continue to expand to the south and east before dissipating during the morning hours. KFSD is the only TAF site that is expected to see fog so have included fog from tonight into tomorrow morning. Once the fog dissipates by tomorrow morning, a mostly quiet afternoon is in store. There could be some light rain/freezing rain showers tomorrow afternoon and evening along highway-14, especially along its southwest Minnesota portion. As of now, these showers are not expected to affect any TAF sites. A second round of fog is possible towards the end of the TAF period. Confidence is not high enough to include mention of fog in a TAF at this time interval but trends will be monitored.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Dense Fog Advisory until 9 AM CST Monday for SDZ039-040-055- 056. MN...Dense Fog Advisory until 9 AM CST Monday for MNZ071-080-089- 097-098. IA...None. NE...None.