248
FXUS63 KDMX 112341
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
641 PM CDT Tue Aug 11 2026

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Hot and humid this afternoon with highs pushing into the 90s
  and heat indicies near 100F.

- Another chance for severe storms possible Tonight into early
 Wednesday morning. A Marginal Risk issued (Level 1 of 5) with
 damaging winds the primary concern.

- Another round of storms expected Wednesday night into
  Thursday. Locally heavy rainfall possible.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 253 PM CDT Tue Aug 11 2026

Our County Warning Area (CWA) missed the main convective event by
one county this morning, as the primary wind threat developed just
east of Waterloo and tracked into eastern Iowa. Dry conditions will
persist this afternoon, with highs climbing into the 80s and 90s
across central Iowa. Given the lack of morning convection across
southern Iowa, enhanced diurnal heating combined with mid level dry
air and deeper boundary layer mixing, highs could climb into the mid
90s across southern Iowa during peak heating hours. Dew points in
the upper 60s and lower 70s may briefly push heat index values into
the lower triple digits in isolated spots; however, no heat
headlines are anticipated due to low confidence in widespread 105
heat indicies. Similar to yesterday, robust afternoon instability
will be present across the area. A few CAMS attempt to develop
isolated storms, but most guidance maintains a strong 13-15C cap
that should suppress initiation. This area will continue to be
monitored through the afternoon.

Tuesday night

Attention shifts to Tonight for another potential severe storm
threat. Similar to Monday, the scenario remains highly dependent on
upstream evolution and whether key ingredients overlap. Initial
supercellular development is expected across northern Nebraska and
the southern Dakotas Tuesday afternoon. As these storms mature and
generate strong cold pools, upscale growth into a MCS is expected.
However, uncertainty remains regarding the track and longevity of
the MCS. Model guidance depicts 2500 to 3500 J/kg of MLCAPE
extending into central Iowa late tonight into Wednesday morning.
However, synoptic forcing across the local area appears relatively
weak, meaning storms will require additional mesoscale lift to tap
into elevated instability. Furthermore, several models indicate mid-
level dry air as convection approaches, which could cause storms to
decay without sufficient forcing. Ultimately, storm evolution hinges
on the positioning and strength of the LLJ. High Resolution guidance
(HRRR,NAM and RAP) maintains the LLJ axis further south across
southern Iowa, keeping it detached from the primary storm track.
Conversely, the RRFS and GFS has the axis further north, allowing
the MCS to latch onto better forcing. IF this northern solution
materializes, the risk for severe weather increases, with damaging
wind gusts being the primary concern. The highlight the severe
potential the Storm Prediction Center has placed most of Iowa in a
Marginal Risk (Level 1 of 5).


Wednesday

Any lingering morning convection should exit the CWA by late morning,
giving way to another warm and humid day. Highs will range from the
upper 80s to lower 90s. Factoring in the humidity, heat indices will
climb into the mid to upper 90s, with a few spots approaching the
triple digits. Attention then turns to a weak surface boundary
progged to stall across southern Iowa by Wednesday afternoon. While
a few CAMS attempt to initiate convection along this boundary,
modest CIN will likely suppress widespread development, keeping
confidence low. However, this bears watching; forecast soundings
depict dry low level air, suggesting a localized severe threat if
any sustained updrafts can break the cap.

Wednesday Night

Precipitation chances increases significantly Wednesday night into
Thursday. An upper-level shortwave originating over the Rockies will
eject eastward across the Plains. Ahead of this feature, a
strengthening LLJ will advect a surge of moisture into the region,
pushing surface dew points well into the 70s by early Thursday
morning. As highlighted in the previous discussion, PWATs will pool
near 2" across the CWA. The high moisture profiles will support
highly efficient rainfall rates as storms move into central Iowa. A
localized flash flooding threat will exist.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 249 PM CDT Tue Aug 11 2026

Active weather persists into Thursday night as another shortwave
traverse into the Plains, The SPC currently highlights the southern
CWA in a Marginal Risk (Level 1 of 5) for Thursday. The active
pattern remains in place through Saturday, maintaining low-end
severe storm probabilities. A more robust cold front will finally
sweep through the region on Sunday, bringing a cooler and drier
airmass. Highs look to top out in the upper 70s in northern Iowa to
lower 80s in southern Iowa.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 629 PM CDT Tue Aug 11 2026

Scattered showers are streaming across northern Iowa this
evening, albeit with minimal impacts. That said, occasional
MVFR ceilings are being observed. Expectation is for brief
showers to impact KMCW and KFOD through the next few hours. KALO
may also be impacted but confidence isn`t high enough to
include in TAF at this time. Sporadic lightning has been
observed upstream but this thunder threat doesn`t appear
imminent at TAF sites.

There is also potential for another complex of storms to move
through the area early Wednesday morning. However, confidence
is quite low in details pertaining to this activity. Therefore,
have included the current expected time period for each TAF, but
refinements will be necessary as confidence increases.

Finally, patchy fog may develop over northern Iowa near KMCW
tonight, but not expecting widespread impacts, especially given
current clouds and showers. 6SM BR is included at KMCW for the
most likely window.

After storms move through and fog dissipates tomorrow morning,
VFR conditions and light east to southeasterly winds prevail
through the day.

&&

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

&&

$$

SHORT TERM...TDR
LONG TERM...TDR
AVIATION...Dodson