693
FXUS63 KDMX 241150
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
650 AM CDT Mon Aug 24 2026

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

.KEY MESSAGES...

- Early showers will continue to fade as they head east leaving
  a dry afternoon.

- Isolated severe storms are possible with a passing cold front,
though dry air may limit coverage.

-A more active weather pattern will return with additional
thunderstorm chances next weekend, but any further details remain
unclear at this range.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 312 AM CDT Mon Aug 24 2026

Monday

Monday morning will begin with a slight increase in cloud cover
compared to Sunday, alongside a localized light fog that will yield
minimal operational impacts. Recent mesoscale analysis reveals a
strengthening LLJ positioned over north-central Nebraska and south-
central South Dakota. Along the nose of this LLJ axis, where richer
low level moisture return is concentrated, showers and thunderstorms
have begun to initiate. Overnight, the LLJ and associated convection
will shift gradually eastward. Areas near and west of Omaha and
Sioux Falls will maintain 30-50% PoPs through the morning hours. As
showers propagate eastward into central Iowa, they will increasingly
decouple from the primary moisture transport axis and encounter a
significantly drier airmass. Consequently, precipitation will
diminish rapidly, with the highest remaining chances (~30%)
confined to Crawford and Sac counties. PoPs drop to near 10% toward
Des Moines, where any surviving activity will be limited to trace
amounts of light sprinkles.

By Monday afternoon and evening, deep layer mixing and dry air
entrainment will continue to scavenge lingering morning moisture,
yielding dry surface conditions. Synoptically, a 500 mb trough
currently centered over the Great Lakes will slide eastward,
clearing the way for a shortwave to approach the region by Wednesday
morning. Further west, a shortwave traversing the Pacific Northwest
and southern British Columbia will ride along the upper level ridge,
carving out a surface trough across the Northern Plains and Upper
Midwest. An associated cold front is projected to cross the Plains
and Midwest Tuesday morning into the afternoon.

Tuesday

Isolated showers and storms remain possible across northern Iowa
Tuesday morning, though the most favorable forcing will reside over
southern Minnesota along the LLJ axis. Heading into Tuesday
afternoon diurnal destabilization will increase; however, forecast
soundings indicate a notable thermal cap that could suppress
convection. Where storms manage to initiate, 30-35 0-6 km bulk shear
will be sufficient to support isolated strong to severe storms. The
Storm Prediction Center has places portions of northwest and Central
Iowa in a Marginal Risk (Level 1 of 5), with damaging wind gusts and
large hail as the primary hazards.

A key forecasting challenge remains moisture availability across
central Iowa. Forecast soundings depict a prominent dry slot in the
mid levels. Furthermore, upstream convective development across
central and northwest Nebraska could effectively rob low level
moisture transport into the local area. Given these uncertainties
over the next 36 hours, updates to the convective risk profile may
be necessary as high resolution guidance arrives. Following the
cold front passage Tuesday night, quiet and dry conditions will
return Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 108 PM CDT Sun Aug 23 2026

By Wednesday the large 500 MB heat dome will remain in place
over the southwestern/south central CONUS, while the trough
described in the SHORT TERM section above moves away to our
east. This will allow deep-layer ridging to reassert itself just
to our west, leading to a period of dry, quiet, and seasonally
mild weather with daily highs in the low to mid-80s for the
remainder of the week. By Friday and Saturday the pattern will
begin to shift a bit, as two large 500 MB lows develop over
Canada and shunt the ridge southward, with the heat dome
retrograding more over the far southwestern CONUS near Arizona
and New Mexico. This will cause 500 MB flow over Iowa to become
more zonal, with multiple shortwave impulses moving through the
flow and providing several opportunities for thunderstorms from
Friday or Saturday into early the following week. While the
details of any such storms are very uncertain at this range, it
is fair to say that overall the weather pattern will be more
active by next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 639 AM CDT Mon Aug 24 2026

VFR conditions to prevail through the end of this TAF period.
Light rain showers are passing thorugh central Iowa this morning
with a scattered clouds present around 5,000 ft. Showers should
taper off over the next few hours. Scattered clouds between
5000 and 7000 feet will continue into the afternoon before
things clear out tonight.

&&

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

&&

$$

SHORT TERM...TDR
LONG TERM...Lee
AVIATION...TDR