textproduct: Des Moines

KEY MESSAGES

- Warm and dry conditions today through at least mid-week. Highs in the upper 80s and 90s this week.

- Shallow, patchy fog possible again early Saturday morning.

SHORT TERM /THROUGH TUESDAY/

Issued at 225 PM CDT Sat Jul 11 2026

After yesterday's showers and storms, the weather will now trend drier today through at least the beginning of the work week. The upper level pattern depicts a broad 500 mb ridge building it's way eastward into the central U.S. The surface pattern will reflect this, as high pressure establishes itself over much of Iowa through Tuesday. The resulting weather will be typical late summer conditions, with multiple days of warm temperatures, light winds, and mostly clear skies. Likewise, these conditions will be favorable for strong radiational cooling overnight, suggesting at least patchy fog may once again develop Sunday morning. Guidance isn't necessarily hammering the fog risk, but with moist antecedent conditions and cooling expected overnight, shallow fog is certainly possible.

With dry conditions expected through the next few days, the primary forecast challenge in the short term is the temperature and dewpoint trends. With the surface high pressure building over the Mississippi River Valley region, drastic air mass changes aren't expected but temperatures will be steadily warming through mid-week. This will be a slow process, as our east southeasterly low level flow will generally promote either neutral or very weak cool air advection, keeping the main thermal ridge and higher 850 mb temperatures just off to our west and north. However, with multiple days of peak heating and no significant advective components, the air mass overhead will sill warm with each day. Resulting high temperatures at the surface will generally be in the mid- to upper- 80s Sunday, then creeping into the low to mid 90s during the work week.

In addition to the temperature trends, our moisture profile will also be influenced by the high and the east southeasterly flow. This flow regime will allow drier air to be advected into the state from the east through Sunday, helping promote more efficient thermal mixing. This better mixing could allow temperatures to overperform by a degree or two tomorrow, but the lack of those higher 850 temperatures aloft will put a ceiling on how warm temperatures are able to mix out to. At the surface, this drier air would also suggest lower dewpoints and relatively less humid conditions, which is being seen over eastern Iowa today. That said, we are also nearing peak evapotranspiration time as corn begins to tassel and crops throughout Iowa reach maturity. Recent rainfalls and wet soils will likely also contribute to higher dewpoints, at least locally. This added surface moisture won't influence the entire boundary layer, but it will contribute to what we feel right at the surface. Regardless, any relief we get from the dry easterly flow will be short-lived, as better moisture advection returns during the work week and pushes dewpoints back into the upper 60s and low 70s again. Fortunately, forecast temperatures and dewpoints should stay low enough to negate the need for any heat headlines in the short term, but conditions will still be on the warmer side of normal for mid- July in Iowa (normal being roughly 82F north to 86F south).

LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/

Issued at 225 PM CDT Sat Jul 11 2026

The warm and humid conditions generally stick around through the remainder of the week, although the influence of the surface high and upper ridging begins to weaken through the second half of the work week. An amplified Canadian trough will begin to push the 500 mb ridge back westward, putting Iowa on the periphery between the northwest flow to our northeast and ridging to our west. At the surface, this will equate to a messy surface pattern with weak high pressure overhead and low pressure to our west, favoring south southwesterly flow. This transition will take place Wednesday and Thursday, ultimately not resulting in much noticeable change at the surface aside from continued warming both days. Highs are expected to reach the mid-90s with dewpoints around 70, pushing heat indices into the upper 90s and near 100F. With the weakening high, subsidence also won't be as strong and the potential for diurnally- driven thunderstorms could creep back into the forecast through the second half of the week. With the lack of any prominent systems, guidance and NBM are struggling to resolve this, but a signal does exist when looking at the longer range models. There's of course no shortage of instability this time of year but the flow in this regime should be fairly weak, so the severe risk appears low at this time. With the low uncertainty, the forecast remains dry through mid-week, but will be something to watch for as we get closer.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1159 AM CDT Sat Jul 11 2026

Generally VFR conditions today, although a scattered to occasionally broken cloud deck around 2500 to 3500 ft is impacting KFOD, KDSM and KOTM. Fortunately, these clouds should be lifting and any MVFR conditions should be brief. Otherwise light winds and mostly clear skies persist overnight. Isolated fog may develop, but confidence is too low to include in TAFs at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.