985
FXUS63 KDMX 100348
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1048 PM CDT Sun Aug 9 2026

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- A few thunderstorms possible again tonight, mainly over
  southern Iowa. Severe weather and heavy rain potential looks
  low at this time.

- On and off thunderstorm chances through most of the upcoming
  week.

- Warm and humid conditions Monday through Wednesday with heat
  indices near 100 at times over central and southern Iowa.

- Wildfire smoke will likely be over Iowa through Wednesday.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 206 PM CDT Sun Aug 9 2026

An outflow boundary from the morning thunderstorms is stretched from
far southeast Iowa to just south of the Des Moines metro to near
Denison. This has created a pseudo warm front with breezy southerly
winds over south central Iowa. The 18z SPC MesoAnalysis is
suggestion 4000 J/kg of uncapped CAPE over south central Iowa. This
is way overexaggerated with a stout elevated mixed layer (EML)
capping over the area. MLCAPE values are much more realistic with
150-200 J/kg of CIN. This capping will prevent any surface based
thunderstorm development for the rest of the day.

The low level jet (LLJ) will intensify again to 50+ kts tonight and
point into southern and central Iowa after midnight. A ribbon of
MUCAPES over 3000 J/kg does develop along the nose of the LLJ.
Similar to the daytime now, much of that instability will not be
realized, for a different reason. Utilizing the 850-300 mb MUCAPE is
lifting the parcel from 850 mb. The EML will be situated just above
this lifted parcel and will prevent ascent. While there is some
saturation of the EML overnight with the moisture transport, it does
not appear to be enough saturation to overcome this capping. Much
like last night, any storms will have to be rooted above the EML and
in this case with less MUCAPE available. Much of Monday will be dry
outside of any lingering morning convection as the EML again
reintensify.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 206 PM CDT Sun Aug 9 2026

Little change in the upper level pattern as westerlies aloft prevail
through at least mid-week before a trough develops over the Western
CONUS leading to weak ridging into Iowa. Expect wildfire smoke to
persist over Iowa until the trough develops to the west and changes
the source region of the upper flow. This smoke remains dense
enough for solar filtering and perhaps will result in slightly
cooler temperatures than forecast. The little change in the
pattern will also keep the surface boundary in the vicinity of
Iowa through Wednesday then it will shift a bit south into
Missouri. On and off chances for thunderstorms will occur during
this period, especially during the overnight hours as the LLJ
fuels thunderstorm development in addition to the periodic short
wave passages. Thunderstorm chances will continue to end the
week despite the arrival of cooler air as an overrunning event
of the surface boundary appears possible. Heat index values may
eclipse 100 degrees Tuesday and Wednesday over central and
southern Iowa but at this time, should remain below headline
criteria.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1048 PM CDT Sun Aug 9 2026

Primary aviation concerns this period are patchy fog in northern
Iowa and precipitation in southern Iowa. Patchy fog is
possible in northern Iowa overnight and have maintained an MVFR
mention at KMCW Monday morning. In southern Iowa storms are
expected to move along and just south of the Iowa-Missouri
border overnight. Closer to sunrise these may lift into southern
and central Iowa, weakening with less lighting activity. At
KOTM maintained the prob30 mention but removed the thunder.
There is still a possibility this expands north to KDSM but
confidence at this time was too low to include.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...Hagenhoff