textproduct: Des Moines

KEY MESSAGES

- Hot and humid conditions continue this week. Heat indices in the upper 90s to near 100 expected.

- Patchy fog possible again tonight into early Wednesday morning.

- Isolated shower and thunderstorm chances return late Thursday and Friday. Severe threat looks low.

SHORT TERM /THROUGH THURSDAY/

Issued at 250 PM CDT Tue Jul 14 2026

Our pattern remains status quo once again today with warm and dry conditions persisting. Skies are clear and winds are light over Iowa, with temperatures once again a few degrees higher than where they were yesterday. Likewise, we have seen dewpoints creep a bit higher again today as well. This trend has been discussed in just about every discussion this week but, with little change in air mass or advective features under the surface high, our air mass is simply warming and moistening with each day of heating and evapotranspiration (ET). Temperatures across central Iowa as of 2 pm are in the upper 80s to low 90s, with heat indices generally in the mid to upper 90s. Since conditions will remain generally unchanged again tonight (clear skies, calm winds), expect more shallow, patchy fog development by Wednesday morning. This fog likely won't be widespread, but could become locally dense in some areas. Fog is once again most likely over eastern Iowa directly beneath the surface high, and within low lying areas throughout the state.

NBMs bias-correction has struggled a bit with the balance between moisture and temperatures these last few days, with forecast highs yesterday being 2 to 3 degrees above observations, likely caused by the moist surface layer limiting mixing. Little change in air mass is expected through Wednesday and Thursday, so have started to correct for the ET contribution/higher dewpoints by bumping forecast dewpoints up and nudging forecast highs down. Still, highs in the low to mid 90s are expected tomorrow and Thursday, warming by a few degrees each day. Heat indices will also stay quite warm, especially with the upper 60 to low 70 dewpoint air. The highest dewpoints will be over northeastern Iowa, where heat indices are expected to near 100F. These values will remain below the 105F criteria, however, multiple days of heat indices near 100F and overnight lows only falling into the mid 70s may still lead to cumulative effects from the heat. More on that in the long term discussion below.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1229 PM CDT Tue Jul 14 2026

VFR conditions prevail over the area today. Winds are calm to light. Patchy fog development is expected again overnight into early Wednesday morning. Highest confidence in fog is at eastern sites (KOTM and KALO) but development is possible at all TAF sites. Have included visibility reductions and/or 6SM BR for the most likely timeframe.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 620 PM CDT Tue Jul 14 2026

VFR conditions prevail for much of the period. Early morning patchy fog is again possible with highest likelihood in eastern Iowa at sites KALO/KOTM. Have included modest reductions at all sites with MVFR reductions at KALO/KOTM/KFOD. As confidence increases further adjustments are likely.

DMX WATCHES/WARNINGS/ADVISORIES

None.