663
FXUS63 KDMX 231131
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
631 AM CDT Sat Aug 23 2025

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

.KEY MESSAGES...

- A few areas of fog early this morning central and south.

- Mostly dry and cool for this weekend and for much of the
  upcoming week.

&&

.UPDATE...
Issued at 345 AM CDT Sat Aug 23 2025

A few showers are lingering over far southeast Iowa and will be
ending soon. Fog has developed in some areas immediately in the
clearing area behind the departing clouds over central Iowa.
Some of this fog is locally dense. The cold front is over the
northern third of Iowa and is moving south and is bringing much
drier dew points in the state. Visible satellite imagery is
showing the fog dissipating quickly as the boundary passes. The
fog area will have the appearance of settling south as it
reforms in the clearing and dissipating to the north. No
headlines are expected due to the transient nature of the fog.
Once the boundary is through, expect cooler conditions for the
weekend. Shallow cumulus clouds with very little vertical extent
due to an inversion aloft, will form both days. Cool and mostly
dry conditions for much of the upcoming week.

&&

.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 /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 626 AM CDT Sat Aug 23 2025

Fog and stratus beginning to clear out of KDSM with the arrival
of a cold front. A brief period of stratus possible at KOTM
through 14z but the residence time is expected to be short
enough to not include in the forecast. VFR conditions for most
locations otherwise through the period. A period of MVFR bkn
cigs may occur at KMCW this afternoon as stratus settles out of
Minnesota. Breezy northwest wind at times late this morning and
in the afternoon.

&&

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

&&

$$

UPDATE...Donavon
DISCUSSION...Bury
AVIATION...Donavon