540
FXUS63 KDMX 222314
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
614 PM CDT Fri Aug 22 2025

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

.KEY MESSAGES...

- Showers and storms possible into this evening, mainly over
  northern to western Iowa, with a conditional severe threat

- Dry and cooler weather is expected Saturday and beyond, with
  highs generally in the 70s

&&

.DISCUSSION...
Issued at 253 PM CDT Fri Aug 22 2025

Much of the state remains dry this afternoon, thanks to the
influence of high pressure remaining into portions of central to
eastern Iowa as its center sits over into Illinois/Indiana. Cloud
cover has increased over portions of the state, with the thickest
clouds over northern Iowa due to the morning shower and storm
activity in South Dakota that has largely weakened, with showers and
some storms trying to make their way eastward into northern and
western Iowa near the boundary that is draped from northeastern
Nebraska into far northwest Iowa and southern Minnesota. The showers
over the CWA have been struggling to actually bring any
precipitation to the surface, with many observation sites reporting
dry weather, outside of Estherville, which did see some light rain
briefly so far. In terms of expectations later this afternoon, the
overall strong to severe storm potential remains quite conditional,
as cloud cover has kept temperatures a bit cooler in the low to mid
70s over northern Iowa, while further south values have increased
into the upper 70s to low 80s. The higher moisture content remains
generally near and west of the NE/SD/IA border, but should
gradually move into western Iowa later this afternoon to
evening, along with the frontal boundary gradually dropping
across the northwest half of the state into the early evening.
Analysis indicates MLCAPE values generally over
northwest/western Iowa in the 500-1000 J/kg range, with bulk
shear values around 25-30 knots, though the EML has been
limiting much in the way of storm development as indicated
above. There is the potential of clouds clearing out over
west/northwest Iowa by late afternoon to early evening, and a
slight increase in instability and less influence of the EML to
increase the chance for more storms to develop. Trends among
models generally have shower and storms reaching west-central
Iowa into the evening, though the potential for stronger storms
decreases further south and east so concerns remain lower at
this time and will continue to closely monitor conditions
through the rest of today. The SPC Marginal Risk, which
generally hinges on the potential being conditional, remains
over the northwest half of Iowa. Any severe storms would pose a
threat for damaging winds, and less so for hail. Lingering but
weakening showers and storms would generally remain over south-
central to southern Iowa as the front drops into the area late
tonight into Saturday morning, before conditions gradually dry
out for all areas by or just after sunrise.

A large area of surface high pressure from western Canada will then
slide into the Central Plains Saturday and gradually track directly
overhead by Monday/Tuesday, with northwesterly flow bringing cooler
and drier air overhead that will greatly limit any rain chances,
keeping any activity further south and west. Breezy winds with a
tightened pressure gradient from the departing Canadian low pressure
are also expected over the weekend. High temperatures will generally
be in the 70s during over the next several days. By midweek, there
is a low signal of a shortwave dropping behind the departing high
pressure that may bring the next chance for showers and some storms,
though any concern for stronger storms is low given limited
instability over the area. Will continue to monitor over the next
several days. Otherwise temperatures midweek next week will be just
slightly warmer in the upper 70s to low 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 614 PM CDT Fri Aug 22 2025

While TAFs advertise VFR conditions through the period, the main
challenge is the shower and storm trends in the next 9 hours or
so. Much of the shower and thunderstorm activity has been
focused near and west of OMA so far early this evening. Chances
for storms over the central Iowa terminals is decreasing so
have removed PROB30 groups at DSM, ALO, and OTM given less than
30% chance. Have maintained PROB30 at MCW and FOD, but have
shortened these groups with an AMD just before these TAFs,
shortened the period on the back side, and transitioned to SHRA.
Will be monitoring trends and may remove these groups over the
next hour or two. Behind the cold front passing tonight, winds
will be from the northwest Saturday morning with winds
averaging 10 to 15 knots with gusts approaching 20 to 25 knots
Saturday afternoon.

&&

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

&&

$$

DISCUSSION...Bury
AVIATION...Ansorge