357
FXUS63 KDMX 111157
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
657 AM CDT Tue Aug 11 2026

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

.KEY MESSAGES...

- Thunderstorms linger this morning.

- Smoke aloft and hot, humid conditions across southern and
  portions of central Iowa continue through Wednesday, with heat
  indices at or just above 100 degrees possible.

- Another potential window for severe weather returns tonight
  into early Wednesday. Shower and thunderstorm chances continue
  through the week with severe weather and heavy rain possible
  at times.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 233 AM CDT Tue Aug 11 2026

Another night with continued storm chances with moderate uncertainty
continues. This morning, the MCS which was originally forecast to
form and move across the Dakotas has not yet formed and guidance is
now split on the potential scenarios as we move into this morning.
At a first glance, radar and some of the previous solutions in the
convective allowing models (CAMs), there is a possibility for
ongoing storms in north central Nebraska to hit the Low Level Jet
(LLJ), merge with the ongoing messy cluster in southeastern South
Dakota, and barrel across northern Iowa over the next several hours.
This solutions appears unlikely at the moment, as the cluster of
storms in Nebraska is currently trending down. Part of the
difficulty is that the disorganized cluster in southeastern South
Dakota has not been captured by models, safe for the 06z WoFS run.
If the 06z WoFS run is to be believed, this cluster will make its
way across Iowa ahead of potential development farther northwest in
South Dakota. This potential development, aided by the LLJ, will
quickly organize into an MCS and move across northern Iowa through
the morning.

Whether anything can grow upscale into an MCS and whether an MCS can
sustain itself across northern IA this morning remains to be seen,
as this is highly dependent on the LLJ and its strength.
Deterministic guidance has backed off on the magnitude of the LLJ,
while the NAM remains persistent that a strong (~50kt) jet will set
up and be pointed into Iowa around 09z. If a stronger jet has formed
and is pointed into Iowa, storms will be in an unstable and highly
sheared environment, and a damaging wind threat will remain through
the morning hours today. If a stronger jet hasn`t formed or is not
favorably oriented, thunderstorms across the northern half of the
state would be weaker to marginally severe.

The rest of today looks to be dry, hot, and humid again. Heat will
be felt the most across southern and portions of central Iowa, where
highs are once again forecast to be in the low to even mid 90s and
heat indices could ever so slightly exceed 100 degrees in spots.
While not as dense, smoke overhead will dampen heat from being more
extreme and reaching advisory criteria. That said, a few
observations could reach advisory level, but not anticipating
widespread heat indices over 105. For now, a Heat Advisory was not
issued but trends will be monitored through the morning. If
overnight showers and storms do not occur in portions of southern
Iowa, heating could begin earlier and this will need to be
reevaluated. Going further with the enhanced heat and humidity, warm
700mb temperatures will once again hinder any convection during the
daytime hours despite ample instability and shear across the state.

Attention then gets turned toward the overnight hours tonight into
Wednesday. The potential exists for another MCS to form and move
across the state. Solutions at this point are still highly varied.
More questions about the LLJ and its strength, orientation, and
position come up. For now, the GFS shows the most robust LLJ at
4am/09z Wednesday, while the NAM and Euro are less favorable. Much
like tonight, the atmosphere will still be unstable and highly
sheared. In CAM land, solutions where an MCS is not realized instead
points to the potential for early-morning convection to form along a
boundary. If this is the case, initiation will be much earlier than
`normal,` beginning in the hours just after sunrise rather than in
the afternoon with better diurnal heating.

Once again on Wednesday, hot and humid conditions are expected
across southern and portions of central Iowa with heat indices
nearing or barely exceeding 100 degrees possible. Shower and
thunderstorm chances will return again after sunset.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 307 PM CDT Mon Aug 10 2026

Most of Wednesday morning will be dry but we are watching the
potential for showers and storms Wednesday afternoon into Thursday.
Medium range guidance look to bring ample moisture in and with PWATs
over 2", heavy rainfall could occur.. Excessive Rainfall Outlooks
has central Iowa in a Slight Risk for flash flooding. Embedded
shortwaves look to track across the Plains and into central Iowa
keeping us active with showers/storms through the end of the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 642 AM CDT Tue Aug 11 2026

VFR to LIFR conditions ongoing across the area early this
morning with thunderstorms dropping visibilities at KALO and a
few showers may still impact KOTM imminently and with less
confidence may drop south and impact KDSM. These storms in the
KALO area have brought some gusty winds. Showers/storms are
mostly past KMCW and will finish shortly at KFOD. Behind the
showers/storms there remains some fog in far northwest Iowa but
is northwest of TAF sites. The storms are expected to largely
clear the area over the next few hours with dry conditions and
rising ceilings to move in behind. Winds will be quite variable
today but largely under 10-12 knots. There may be more
opportunities for storms overnight into Wednesday morning but
confidence is too low at this time to include any mentions. If
storms don`t pan out, then patchy fog may in play.

&&

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

&&

$$

SHORT TERM...67
LONG TERM...TDR
AVIATION...05