textproduct: Des Moines

KEY MESSAGES

- Dense fog this morning, especially in portions of central and southern Iowa.

- Marginal Risk (Level 1 of 5) for severe storms today in much of the area. Damaging wind gusts are the primary threat though some isolated large hail is also possible.

- Additional Marginal Risks (Level 1 of 5) for severe storms on Saturday and Sunday. Damaging wind gusts remains the primary threat, but storm timing and location is somehwat dependent on the previous day activity.

- Heavy rain potential with Marginal Risk (Level 1 of 4) Excessive Rain Outlooks all weekend in addition to the severe threat.

- Rain and storm chances linger at times through next week.

SHORT TERM /THROUGH TONIGHT/

Issued at 310 AM CDT Fri Aug 7 2026

Light winds and clear skies have led to the development of fog again early this morning mainly over southern, eastern, and into portions of central and northeast Iowa. This fog is patchy in places and locally dense in others with some observations under 1/2 mile. A Dense Fog Advisory was hoisted in portions of southern to central Iowa and some adjustments may still be needed as this fog continues to develop with fog likely lingering until after sunrise this morning. Winds in parts of northern Iowa are slightly more elevated (around 7 mph compared to under 5 mph) so fog may have a little harder time developing/maintaining with the slightly higher winds, though some patchy fog is noted early this morning on satellite in portions of north central/northeast Iowa as well where winds are near to under 5 mph.

Attention then turns upstream to the approaching cold front which is noted in northern Minnesota arching back through far southeast North Dakota and into central South Dakota early this morning. Upstream radar has noted a few showers and storms trying to develop just ahead of this front but have been weakening as they move eastward. The moisture axis will arch into Iowa by mid morning and the combination of these will lead to continued developing storms this morning into midday. Northern Iowa seems to have the best chances for storms from around mid morning to midday, though CAMS continue to have a difficult time with how long storms will maintain into portions of central and southern Iowa and what the severity will be. Initial storms may be elevated and contain a hail threat with the overall line looking to grow upscale with time with a greater wind threat. If an MCS is able to develop and maintain, this wind threat may be a bit higher as it reaches into Iowa this afternoon to evening. However, with fog/clouds this morning, peak heating/instability will be delayed so it will all depend on the timing of storms developing. Earlier development into Iowa will have less instability/shear to work with thus keeping storms weaker/having a harder time maintaining. Shear and instability both increase into this afternoon. Will continue to watch storm development closely this morning into midday with a well-placed SPC Day 1 Marginal (Level 1 of 5) Risk for the largely isolated strong to severe storms that may be able to develop with a hail or wind threat. There may be a little more development this evening behind the main line in portions of central to eastern Iowa where pockets of instability remain, but dry conditions largely return by mid evening into Saturday morning.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 141 PM CDT Thu Aug 6 2026

Saturday: The warm sector gradient orients northwest to southeast across Iowa, and extending further into Nebraska. The next shortwave will spawn an MCS on this gradient early Saturday with its remains entering Iowa by Saturday afternoon. It will be caught by the retreating surface front, the highest confidence in afternoon severe storms in southwest Iowa. The LLJ will intensify Saturday afternoon and overnight, igniting the elevated reflection of the front. It will veer east through the night and offer a chance for heavy rain in central and eastern Iowa, reflected by the Marginal ERO. PWATs will rise over 1.5" and the mean wind will point to the east, favoring some training on the flattening boundary. If storms lean more organized, training will happen less.

Sunday: While dependent on weather the previous two days, Sunday night looks representative of a Maddox frontal setup for heavy rain. With model simulations placing the front in southern Minnesota. At this range, due to cold pools from storms days prior, this QPF axis is possibly predicted to be too far north. PWATs will approach 2 inches and both the mean wind and Corfidi vectors mirror the front, meaning training is possible even with organized MCSs. It's worth monitoring trends to see if the front does indeed sink south into Iowa. Rain rate-driven flash flooding would become possible in urban areas.

The forecast beyond features northwest flow with relatively higher deep-layer shear in northern Iowa. This is due to enhanced flow across the Upper Midwest. Precipitation chances will gradually sink south through the week due to repeated storms shoving the boundary more into the ridge. Nearby instability will keep storms in play.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1056 PM CDT Thu Aug 6 2026

Areas of patchy to locally dense fog are expected to develop through the overnight hours, with lower visibilities more likely over KALO, KDSM and KOTM where winds are expected to be lighter. Lowered visibilities and ceilings will lead to IFR and periods of LIFR conditions through about mid-morning before improving. A frontal boundary is expected to follow, entering northwest Iowa mid to late morning and sink southeast across the state through the rest of the period. Showers and storms are possible with this passing feature, with higher confidence over the northern terminals where PROB30 mentions remain, but also at KDSM later in the afternoon. As mentioned previously, would expect slight adjustments to be made based on trends and overall confidence. Winds shift northwesterly after 18z with this passing boundary.

DMX WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM CDT this morning for IAZ047>050- 057>062-070>074-081>085-092>096.