Area Forecast Discussion

KEY MESSAGES

- Severe storms are expected this morning and are possible again from midday into the early evening. All severe hazards are possible including damaging winds (potentially up to 80 mph early this morning), large hail, and tornadoes, as well as heavy rain bringing a threat for Flash Flooding.

- Gusty winds behind the storms may have 30-40 mph gusts, with 50 mph gusts not out of the question from late morning into late afternoon west to east respectively.

- Cooler, drier conditions develop on Friday.

- Thunderstorm chances return Saturday, some of which may be severe.

UPDATE

Issued at 1111 AM CDT Thu Jun 11 2026

Our morning thunderstorms have pushed through the area, and we now look ahead to additional development through mid-day into the early afternoon. The surface low currently resides over south central Iowa, with the cold front draped over southwest Iowa and the warm front extending east from central into eastern Iowa. This wave will be tracking east northeast through the next few hours, continuing to advect warm, moist air up into southern Iowa. There are scattered clouds/showers muddying the skies in southern Iowa, which may limit atmospheric recovery some, but this system is likely dynamic enough to overcome the patchier sunshine.

Models and forecast output from SPC mesoanalysis all show destabilization occurring in southern Iowa today, reaching nearly 3000 J/kg of surface based CAPE. To compliment this unstable air mass will be an impressive wind field showing strong speed and directional shear through the entire layer, thanks to a stout 60 kt 500 mb jet, a 30 to 40 kt 850 mb jet, and south southeasterly surface flow. The result, is large, looping hodographs in the lowest 3 km and good tilting of updrafts. Where the winds are more southeasterly, storm relative helicity values through that 0 to 3 km layer will be in the 300 to 400+ m2/s2 range with strong streamwise ingest. Therefore, the tornado threat looks high for any storms that do develop this afternoon, especially in areas farther south and east in the area. With supercells being the most likely storm mode, large hail (2"+) and damaging winds (up to 75 mph) will also be possible, in addition to the tornado threat. Of course, this is all contingent on the atmosphere recovering as models suggest. The tornado watch remains in place until 3 pm for southeastern Iowa where the highest risk resides.

Finally, heavy rainfall will also accompany storms over southern Iowa this afternoon. Portions of south central Iowa are already experiencing flooding issues at this time, and additional rainfall amounts of 1 to 2 inches will exacerbate these conditions. For this reason, the flood watch has been extended through 4 pm.

SHORT TERM /THROUGH TONIGHT/

Issued at 315 AM CDT Thu Jun 11 2026

Upper level trough crosses through the Central Plains this morning before swinging through the Upper Midwest this afternoon into tonight and then arriving in the Great Lakes region late tonight. At the surface, a low over western Kansas early overnight is expected to move towards and then into Iowa this morning as it heads for the southern Great Lakes area into tonight. Additionally, the boundary is stalled out around central Iowa that will later on today continue to progress eastward as a cold front while the warm front/modifying outflow has begun to activate in central Nebraska early this morning and will continue to lift back northward. With ample forcing as noted already aided further by a 40-50+ knot LLJ we're looking at another round of severe storms this morning with some chance for additional development along the eventually progressing cold front/any lingering boundary from this morning's activity from around midday through this afternoon.

We've already coordinated a Severe Thunderstorm watch with SPC and surrounding offices for this first round early this morning with the risk of large hail, some very large hail possible early, with all guidance and expectation in the clusters of storms growing upscale into a severe MCS as they progress eastward across Iowa bringing the threat for damaging wind gusts up to 70 mph, potentially even destructive and up to 80 mph. Although early storms are generally expected to be elevated, a tornado could be possible early with supercell structures but certainly with time storms are expected to become surface based as moisture surges back in this morning sending instability values by mid morning back to 2000-4000 J/kg and with nearing 50 knots or more of 0-6 bulk shear. Thus, tornadoes along the line near and then after sunrise are possible as the storms cross through southern into portions of central Iowa. The bulk of this first round should be through by 15 or 16Z (10 or 11A) and is the highest severe risk of the day.

Additional storms may be able to reactivate along the cold front as previously mentioned or any lingering outflow depending on our atmosphere recovery. This looks most likely in the far east/southeast but could also occur in portions of central to north central Iowa if this first round is able to push through quickly (south central), or with locations that stay dry in the first round (portions of central into north central Iowa) or further east altogether if morning storms hold on longer. All hazards are on the table again - damaging wind gusts, large hail, and tornadoes, with the tornado threat highest near the triple point into east central/northeast Iowa, but should not be discounted elsewhere given the environment. Showers have already started in northwest Iowa and showers, occasional storms, are expected to prevail a good portion of the day over northwest into northern Iowa where the severe risk is much lower (severe weather not expected in northwest Iowa).

Behind these 2 rounds of storms, environmental winds on the back side of the low look to increase with gusts of 30-40 mph common, and 50 mph gusts not out of the question. Considered a wind headline but confidence in location and timing is not quite there to do so but this will be something we will watch closely into midday with these winds expected to move in west to east from mid morning west. through late afternoon to early evening in the east

The Flood Watch also remains in effect this morning, see the hydro discussion for further details on the hydro threat with these storms today.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 301 PM CDT Wed Jun 10 2026

Behind the cold front on Thursday, conditions become cooler and drier through Friday. Thunderstorm chances then return again on Saturday, with severe storms possible once again Saturday afternoon. With so much ongoing in the short-term, will discuss this risk more thoroughly once we are through the current active period.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 559 AM CDT Thu Jun 11 2026

A complex of thunderstorms in southwest IA will continue to race east this morning, likely growing upscale with time. DSM and OTM are the most likely to take the brunt of this system within the next couple of hours. Strong westerly winds will coincide with the storms' arrival with gusts reaching 35-45 knots. These gusts may be too conservative of an estimate but we'll see how observations and radar trends evolve. IFR conditions are expected during storms with showers and MVFR cigs likely continuing afterwards for much of the region into this afternoon. CAMs suggest a another round of storms is possible this afternoon at OTM so have kept PROB30 while slightly adjusting timing. VFR conditions expected this evening onward as skies clear. Southeasterly winds flip to northwesterly after a cold frontal passage in the wake of the precip with speeds increasing to 15-20 knots this afternoon. Gusts will reach 30-35 knots. Winds turn westerly and slow to 5-10 knots this evening.

DMX WATCHES / WARNINGS / ADVISORIES

Flood Watch until 4 PM CDT this afternoon for IAZ061-062- 073>075-083>086-093>097.