textproduct: Des Moines

KEY MESSAGES

- Highs warm today to near 80 degrees and winds become breezy this morning, especially in western Iowa.

- Localized patchy fog is possible Wednesday morning, but the day will again be dry and mild.

- Scattered showers and thunderstorms possible Thursday night

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 159 AM CDT Tue Oct 6 2026

Clear skies stretch across Iowa tonight with the continued domination of ridging across the southern US. The difference today is the trough approaching from southern Canada, and associated surface trough stretching from North Dakota to Colorado. This trough will advance across Iowa this afternoon and bring across a wind shift boundary. The 850mb trough can be seen across South Dakota and Nebraska tonight, and here in Iowa a 30kt LLJ is forecast overhead by morning as the 850mb moves east. This is the reason for lower fog concerns tonight, as the the added mixing should prevent a river fog scenario like what was seen last night. With clear skies expected this morning, PBL growth will be unrestricted and there will be a window of a few hours this morning where gusty LLJ winds mix down to the surface. Gusts of 20 and perhaps up to 25 knots are forecast this morning, mainly in northwest Iowa, but lingering 15-20kt gustiness may continue across the state through the afternoon. Dry moisture profiles will likely keep precip chances near-zero with this frontal passage.

Highs this afternoon have a few added factors from yesterday. On the one hand, NBM highs have come in too low, and dewpoints too high, for the last several days, and forecast 850mb temps are several degrees higher than yesterday with decent mixing likely. On the other hand, moisture advection will be present and dewpoints may approach 60 locally, and there is also a frontal passage. As a result, have opted to raise highs to ~78-80 and lower dewpoints. Although with the caveat of knowing that the continued NBM bias may be less applicable today as the previous few days given the synoptic pattern change.

On Wednesday, the front continues to advance south and exits the state by evening. Surface winds are expected to be calm Wednesday morning and skies mostly clear, which could introduce the potential for morning river fog. Highs in the mid to upper 70s are expected once again, with the highest temps in southern Iowa. Cirrus may limit high temps in central to northern Iowa.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 234 PM CDT Mon Oct 5 2026

Little change in the overall pattern through Friday as the upper level flow remains a modified westerlies leading to mild and mostly dry conditions. The caveat being Thursday night and Friday morning as a few showers and storms could develop by another round of moisture return with surface low pressure moving to the east and return flow commences. Upper low pressure will descend into the Pacific Northwest this weekend leading to a gradual amplification of southwest flow into Iowa. This will lead to warmer temperatures this weekend, with more widespread 80s possible. A bit beyond the 7 day forecast and perhaps the next widespread weather potential for Iowa arrives mid next week as the upper low shifts east into the Plains and may bring thunderstorms back to Iowa.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1110 PM CDT Mon Oct 5 2026

VFR conditions are forecast to prevail through the TAF period. Winds are starting to slacken across all TAF sites; however, over the next few hours, an upper-level trough will arrive and bring increasing winds later Tuesday morning. There's a small window where LLWS will exist before turbulent mixing occurs. However, confidence is low on where that window exists and LLWS was left out of the TAF. Lastly, river valley fog is possible overnight and impacts to terminals are possible.

DMX WATCHES/WARNINGS/ADVISORIES

None.