textproduct: Des Moines

KEY MESSAGES

- Showers in the southeast continue to move out/dissipate this afternoon. A few low (<25%) chances for showers in move back into far southern Iowa tonight.

- Patchy fog is possible overnight, especially in portions of northern Iowa.

- More seasonal temperatures in the upper 70s to low 80s continue on Thursday. Slight warm up Friday, another push of heat looks to move in for Monday.

- Additional thunderstorm chances late Friday into Saturday, Saturday into Sunday, with more widespread chances Sunday into Monday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 226 AM CDT Thu Sep 10 2026

Tuesday's cold front has stalled to our south this morning and thunderstorms are ongoing from Ohio to Colorado. High level cirrus from storm outflow is traversing southern parts of the state, but most locations have clear skies this morning. The calm winds and clear skies have allowed for another morning of radiation fog conditions. Visibility reductions have been occurring in southern Iowa, where humidity is higher, but a low level cloud deck has held off fog in some spots temporarily at the time of writing. Patchy fog may form further north as well near sunrise given prolonged clearing.

High pressure dominates today and conditions will be quite mild today and tomorrow. Highs are expected to reach the upper 70s or lower 80s this afternoon and Friday afternoon. Worth noting that NBM highs both today and tomorrow are near the 25th percentile of guidance, with bias corrected models several degrees higher than NBM, so perhaps highs in the low 80s will be more widespread than output by the NBM. Precip chances will remain low today through the day Friday as profiles will be quite dry.

By Friday evening, the pattern begins to shift again. A shortwave crosses the Dakotas, associated with a surface low centered over western Minnesota by evening. Low level winds across the state shift to southerly, advecting higher theta-e back in, particularly in a narrow zone just ahead of the cold front. The front does not arrive into Iowa until 6-12z, so any precip chances likely hold off until the late evening or overnight. There is decent confidence across global ensembles in some elevated convection developing along the front overnight, and this is likely the reasoning for inclusion of northwest Iowa in the marginal/slight convective risk per SPC and is the justification for maintaining 30-40% PoPs overnight across a large part of the state. However, worth noting that the few CAMs that run out to that hour by this point (RRFS/FV3) have very little if any robust convection occurring across the northwest portions of the state overnight which would fit the conceptual model of being in the jet streak right exit region and in the divergent entrance region of the LLJ (like what is being forecast). RAP/NAM suggest the thermodynamic environment will be decent, with 7-8 C/km mid-level lapse rates and 1000-2000 J/kg MUCAPE. Shear is unlikely to be very strong above the LLJ. So, the environment is supportive of cells with hail and strong wind.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 226 AM CDT Thu Sep 10 2026

The weekend then looks to remain active with several additional chances for showers and storms from later Saturday into Sunday, and then again with more widespread chances Sunday through Monday. Although temperatures remain in the 70s to 80s through the weekend (though with the higher dew points), we'll get one more bigger push of heat into Monday before cooling back into the 70s early next week behind another cold front. Will continue to evaluate the potential for severe storms and heavy rain with these subsequent rounds over the coming days but conditions at first glance to remain more favorable for heavy rain with pwats over 1.5" through much of the weekend.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1055 PM CDT Wed Sep 9 2026

Main challenge remains the fog, which is starting to become more widespread over southern Iowa. Started the time for fog at KOTM sooner. Will need to monitor developing stratus, although it looks to remain VFR as it spans across southern Iowa.

Went less aggressive on fog in the north, and changed FOD to BCFG. This was after watching KEBS bounce between vsby categories from fog this evening. A TEMPO group will be re-added if conditions show they'll worsen. Not expecting fog to impact KDSM due to cloud cover tonight, but patchy fog could develop near the terminal.

DMX WATCHES/WARNINGS/ADVISORIES

None.