307
FXUS63 KDMX 211145
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
645 AM CDT Fri Aug 21 2026

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Marginal Risk (Level 1 of 5) for severe storms across southern
  Iowa. Damaging winds and large hail are the primary hazards.

- Highs across central Iowa climb into the lower to mid 80s.

- Mostly dry and sunny through the weekend!

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 202 AM CDT Fri Aug 21 2026

Mostly dry conditions will prevail across central Iowa on Friday. A
slow moving cold front currently positioned across southeastern
South Dakota will continue pushing southeastward throughout the day.
While pre-frontal convection remains possible along the boundary in
Minnesota, activity is expected to dissipate as it moves into
central Iowa and encounters a more stable air mass. A stray shower
or storm will still however be possible during the early morning
hours in northern Iowa.

By Friday afternoon, diurnally-driven destabilization ahead of the
boundary will build MLCAPE to 2000-3000 J/KG. Combined with 35-45
kts of 0-6km bulk shear, the environment will be conditionally
favorable for organized severe convection. However, convective
initiation confidence remains low due to two primary limiting
factors: high pressure to the north advecting mid-level dry air and a
weak thermal gradient across the front resulting in broad- weak low-
level convergence. Despite these inhibition factors, the Storm
Prediction Center has issued a Marginal Risk (Level 1 of 5) across
southern Iowa. If an isolated parcel manages to break the cap,
robust updrafts could produce damaging wind gusts and large hail.
The highest precipitation chances (10-20%) will align with late
afternoon into evening (generally after 6pm). Post frontal high
pressure will build in overnight, clearing skies from north to
south.

Elevated haze will persist today as northwesterly flow aloft
advects upper level wildfire smoke from the Pacific Northwest. This
smoke layer will remain elevated aloft, with no surface air quality
impacts anticipated.

Friday Night

Northwesterly flow will reinforce a dry, subsidence airmass across the
region, setting up quiet conditions overnight through Saturday
morning. The next window for organized precipitation arrives Sunday
evening.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 222 PM CDT Thu Aug 20 2026

Another embedded shortwave will move across Iowa late Sunday
evening into Monday, slowing from model solutions 24 hours ago.
The upcoming work week looks to remain active with embedded
shortwaves continuing to ride along the western US ridge with
northwest flow across Iowa. A more robust system looks to move
across the area on Tuesday and will be the next opportunity for
more organized convection. At this time range differences remain
with the GFS favoring a southerly track over the Euro northerly
track.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 641 AM CDT Fri Aug 21 2026

VFR conditions expected to prevail through the period with
departing clouds in southern Iowa early. There will be a wind
shift that will sink from north to south through the day. Winds
will become northerly behind its passage. Low chance for
thunderstorms for KOTM late this afternoon, but confidence
continues to trend lower, so have maintained no mention in the
TAF.

&&

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

&&

$$

SHORT TERM...TDR
LONG TERM...Hagenhoff
AVIATION...Jimenez