textproduct: Sioux Falls

KEY MESSAGES

- A strong warming trend is on the way into the weekend. The degree of warming however will be determined by how quickly snow melts.

- Fog, possibly dense, more likely to develop Thursday morning, focused primarily along the higher elevations of the Coteau des Prairies but could extend to the James River.

- Depending on fine fuel moisture (grass and brush), fire conditions may become elevated along the Missouri River Valley Friday and Saturday.

DISCUSSION

Issued at 1219 PM CDT Wed Mar 18 2026

THIS Afternoon: Winds continue to slowly turn to the west this afternoon, ushering in steadily warmer temperatures. We're seeing a good response to the warmth at the surface as temperatures surge towards the 60s and 70s along and southwest of the James River. Areas with more snow cover are slower to respond, but still quickly rising into the 40s and 50s, a good indication of the power of mid- March sun.

TONIGHT: Upr-mid level clouds will persist through the evening and overnight hours as the CWA remains under mid-lvl northwesterly flow aloft and slightly south of a building upper jet. These clouds will help temperatures stay near the freezing mark, and could even stay in the 40s in some areas. High resolution guidance again hints at low stratus/fog development along the Ridge areas by daybreak Thursday. While the NAM based solution may be too aggressive, we're also seeing signals of snowmelt fog developing in additional model data. Should fog develop, it could turn dense rather quickly and advisories may be needed as far west as the James River valley.

THURSDAY-SATURDAY: The weather for the end of the week will be dominated by a large 592DM upper ridge centered over the Four Corners region. The expansion of this ridge eastward will allow climatologically significant low-lvl temperatures to advect eastward. As noted yesterday, minimal change in medium range models when it comes to the overall significance of the airmass, with ESAT data indicating that 850mb temperatures approach the 90th and then exceed the 99th percentile of climatology centered around mid- March by the weekend. At the surface, temperatures will be most impacted by lingering snow cover, wet grounds, and depth of mixing but are still expected to surge into the 70s by Friday, and 70s and 80s on Saturday. These temperatures may approach or exceed record values, with the greatest potential focused around Friday afternoon.

The rise in temperatures and advection of drier low-lvl air through the Plains may introduce some minor fire danger risks. However, surface winds remain less than RFW criteria Friday and Saturday, and may only produce elevated conditions near the Missouri River valley region.

SATURDAY NIGHT: One minor variance in the medium range forecast continues to be the timing of a stronger cold front surging southward through the Plains Saturday afternoon and evening. Timing differences in model data are producing a 10+ degree range in the 25/75th percentile temperatures at 7pm Saturday, mostly north of I- 90. Winds behind the passage of this Saturday night may gust between 30-40 mph based on the 35 knots of wind at the top of the shallow mixed layer overnight. LREF histogram data would suggest at least a 35% probability of >30 mph winds. Populated NBM guidance is likely too low, and heading towards the 75th percentile is reasonable given the strong cold advection behind the front.

SUNDAY-TUESDAY: A brief spell of near normal temperatures arrives for Sunday and Monday as high pressures moves into the Great Lakes early next week. However, latest model trends project a period of fast northwest to westerly flow into next week, keeping the region susceptible to a roller coaster ride of temperatures and periodic windy days into the middle of the week. At this time, no large impactful systems are expected.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 639 PM CDT Wed Mar 18 2026

Currently VFR conditions with some mid-to upper clouds moving in. Clouds are expected to linger for the majority of the period before scattering out near the end.

Winds are light and variable, gradually becoming southerly to southwesterly beginning late morning and continuing through the end of the period. Some gusts of 15-20 kts are possible mainly along areas of elevation along and west of the James River Valley, and the Coteau des Prairies.

Fog, possibly freezing fog, is expected to develop overnight and may be dense at times. Especially for areas north of I-90 and along and east of the James River Valley, where VFR to IFR visibility and ceilings are possible. Conditions at times may even decrease to LIFR. Both KHON and KFSD are expected to be impacted by the very low ceilings and visibility. KSUX may experience some patchy fog and slight reductions in visibility but should remain at or above MVFR. Fog may linger into the late morning before burning off in the early afternoon.

CLIMATE

Issued at 1220 PM CDT Wed Mar 18 2026

Extremely warm air will try to move eastward late this week into this weekend. These temperatures may result in the top 10 earliest 75 and 80 degree highs at long term climate locations. Here is a look at records for Friday and Saturday

Record High Temperatures:

March 20: KFSD: 73/2022, KSUX: 79/2015, KHON: 75/1911, KMHE: 77/1994

March 21: KFSD: 83/1910, KSUX: 85/1910, KHON: 84/1907, KMHE: 88/1907

Record High Minimum Temperatures:

March 21: KFSD: 49/1938, KSUX: 48/2012, KHON: 45/1938

FSD WATCHES/WARNINGS/ADVISORIES

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