textproduct: Sioux Falls

KEY MESSAGES

- Critical fire weather expected to return Thursday, along with a risk for isolated to scattered thunderstorms. Severe storms are not expected.

- Winds Thursday may also break the 40+ mph mark, leading to periods of blowing dust in rural areas. Use caution if traveling as visibility may be impacted

- Temperatures continue to warm though the weekend, with high temperatures expected to be 10 to 20 degrees above normal.

- Regional rain chances increase Saturday and especially Sunday. A great deal of uncertainty remains, but signals remain present for strong storms Sunday and Monday.

UPDATE

Issued at 910 PM CDT Wed May 13 2026

The forecast remains on track with critical fire conditions expected Thursday, and near critical conditions Friday. Tonight into Thursday modest mid-level moisture will flow in on southerly winds. WAA behind a warm front provides enough lift to result in clouds and possibly light elevated showers to thunderstorms Thursday mid- morning. Showers are most likely to form along or slightly west of I- 29 and move east through the early afternoon. A very dry subcloud layer will likely limit how much reaches the ground. So, this is unlikely to impact fire conditions. But persistent clouds may limit highs a little bit. Hot on the heels of the WAA is a cold front that will enter central South Dakota around mid-day. With the front come additional low chances for showers and thunderstorms. Ahead of the front winds will increase rapidly in response to the tightening SPG. Winds look to reach their peak in the late morning to early afternoon with widespread gusts 35-45 mph. Areas between the James River Valley and I-29 may see occasional gusts to 50+ mph. Behind the front winds drop off rapidly from west to east through Thursday afternoon. In addition to the winds relative humidity values will fall as low as 19-25% for portions of the region. The timing of the winds and lowest humidity remain slightly offset for areas along and west of the James River. Here the gusty winds will ease before the lowest humidity is met, therefore this region remains out of the Red Flag Warning at this time. East of the James River Valley the strongest winds and lowest humidity values will be better aligned. Despite the low rain chances, the Red Flag Warning from 10 am until 7 pm Thursday looks to be in good shape.

For Friday winds will be out of the northwest and breezy with gusts 15-25 mph. Very dry surface conditions continue with minimum relative humidity values of 15-19% for the entire region. Near critical fire conditions will be possible for areas along and north of Highway 34, where the strongest gusts are expected. At this time no changes are needed for the Fire Weather Watch in effect from 9 am until 7 pm Friday.

DISCUSSION

Issued at 155 PM CDT Wed May 13 2026

THIS AFTERNOON: An absolutely beautiful afternoon across the region as winds remain light and variable, temperatures have risen into the 70s and plenty of sunshine is around. Expect these conditions to persist into the evening.

TONIGHT: Shortwave ridging moves east of I-29 by daybreak Thursday, with modest low-lvl moisture convergence on the nose of a 50 knot LLJ trying to focus along I-29 by mid-morning. The overnight hours are expected to remain dry but with a mixy wind, temperatures may fail to fall below 50 degrees.

THURSDAY: Multiple hazards likely on Thursday. Early in the morning, guidance shows a narrow tongue of low-mid lvl moisture streaming up I-29. CAMS are a bit split in further development of this moisture into a few showers/sprinkles but feel potential is high enough to warrant slight chc PoPs into NW Iowa and SW MN for a brief period of time. Meanwhile a surface front will approach central SD by daybreak, gradually moving east through the day. A channel of 50+ knots of low-lvl flow ahead of this boundary will begin to mix downward quickly in the morning. Have trended wind gusts towards the 90th percentile of the NBM which aligned well with winds on Tuesday. Peak gusts may break the 45 mph mark at times into the afternoon. Surface based moisture will be extremely limited ahead of this boundary, but another wedge of elevated moisture may be enough to produce high based sprinkles to showers as this front passes east into the afternoon. Slight inhibition at 850 mb will likely prevent any surface based convection from forming. The combination of strong winds Thursday will also produce some patchy blowing dust and minor air quality issues in the afternoon. For fire weather concerns, please see separate discussion below.

THURSDAY NIGHT-FRIDAY NIGHT: The aforementioned boundary will be east of the CWA by daybreak Friday, with winds switching to the west northwest behind the boundary Thursday night. VERY dry air will advect southeast behind this boundary, setting the stage for RH values near 15% in the afternoon of Friday. Latest trends have pushed the strongest wind potential along or north of Highway 14 in the afternoon as high temperatures rise into the 80s. One thing to monitor for Friday evening will be the on/off potential in guidance of some weak low-lvl convergence across northern Nebraska and western Iowa in the evening. This area will be on the edge of some slightly deeper moisture and MUCAPE AOA 800-1000 J/KG. While its an intermittent signal in CAMs, can't discount a thunderstorm or two trying to form south of I-90 or towards Highway 20 if we somehow reach convective temps in the low 90s.

SATURDAY: A brief rise in mid-lvl heights and influence of drier Canadian airmass will prevent moisture and meaningful instability from racing northward Saturday. For most of us, expect a dry and rather nice Saturday as highs rise into the 80s.

SATURDAY NIGHT-MONDAY: Guidance is still quite uncertain, but trends continue to shove a trough into the Plains Saturday night. The speed at which low-lvl flow turns more meridional remains in question, however both the GFS/ECMWF lift an elevated warm front northward by Sunday morning. Convergence and upper dynamics would support growing shower and thunderstorm risks moving northward through the Tri-State area into Sunday morning. While the severe weather risks overnight may be low, elevated parcels might have upwards of 500-1000 J/KG supporting some hail growth through mid-morning Sunday.

Even more uncertainty builds through the day on Sunday, focused on the northward push of the warm sector into the Plains. GFS/EC/CMC ensemble guidance all remains split 50/50 with the warm sector or deeper instability either staying south of I-90, or on the flipside spreading well north and bringing even moderate to strong instability towards the Tri-State area by Sunday afternoon. AI based models and CIPS analog guidance support the potential that does exist for this event, further supporting early SPC day 4 outlooks. Continue to monitor Sunday's forecast if you have outdoor events planned, as this remains a very conditional severe weather forecast.

The upper trough deepens and pivots eastward into Monday, pushing a surface front into the CWA overnight. Several waves of convection could be possible into the morning hours of Monday, with stronger convection potential focused east of I-29. A great deal of uncertainty remains into Monday and it's certainly possible the greatest potential of redevelopment along the front could be pushed east of the CWA.

This entire system should bring meaningful rain to the CWA by time it exits the region. NBM 10/90 percentile QPF over the 72 hour period does range from a quarter inch to nearly 2", with a mean around 0.75" in most locations. Of course convection can influence these locations significantly, which is why the NBM probability of >0.50" is only around 50% in any given location.

TUESDAY-WEDNESDAY: Drier weather and cooler conditions are expected as we move into the middle of next week. High temperatures Tuesday could struggle to climb through the 60s.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 703 PM CDT Wed May 13 2026

Light and variable winds are expected to become southwest and increase through the evening and overnight. Sustained winds of 20-26 kts with gusts 35-40 kts with occasional gusts to 50 kts are possible. In addition a period of LLWS is expected beginning around midnight and continuing through about sunrise. There is potential for weak showers and thunderstorms Thursday morning, and again Thursday afternoon. Confidence in storms impacting TAF sites was too low to include at this time.

FIRE WEATHER

Issued at 703 PM CDT Wed May 13 2026

Strong southwesterly winds will begin Thursday ahead of an approaching font from the west. Gusts 40+ mph are likely to develop by daybreak and slide eastward into MN/IA by mid-afternoon. While a few sprinkles may be present at times, relative humidity values will still fall near 25 percent in areas east of the James River. West of the James River, a front will arrive by mid-day, trending winds quickly downward or turning to the west. RH values near the front may rise slightly lowering the risks. Recent drought conditions have significantly slowed the Spring greenup, leading to increased fire potential in tall and even some short grass areas. Will issue a RFW for areas with a longer duration of sustained high winds and near criteria RH.

On Friday, a very dry airmass will work southward, lowering afternoon relative humidity values towards the 15% mark. Winds will be lower in most areas, but could flirt with RFW criteria north of I- 90 and especially along and north of Highway 14. Will issue a FWA to advertise this potential.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from 10 AM to 7 PM CDT Thursday for SDZ039- 040-054>056-060>062-065>071. Fire Weather Watch from Friday morning through Friday evening for SDZ038>040-052>056. MN...Red Flag Warning from 10 AM to 7 PM CDT Thursday for MNZ071- 072-080-081-089-090-097-098. Fire Weather Watch from Friday morning through Friday evening for MNZ071-072-080-097. IA...Red Flag Warning from 10 AM to 7 PM CDT Thursday for IAZ001>003-012>014-020>022-031-032. NE...Red Flag Warning from 10 AM to 7 PM CDT Thursday for NEZ013- 014.