308
FXUS63 KDMX 281823
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
123 PM CDT Thu Aug 28 2025

.KEY MESSAGES...

- Dry through tonight, with lows in the mid to upper 50s Friday
  morning.

- Isolated showers and non-severe storms (~20% chance) possible
  over northern Iowa on Friday afternoon and evening. Additional
  low rain chances (20-30%) at times this weekend, but low
  confidence in details. Severe weather not anticipated.

- Cold front to sweep through roughly around Tuesday night next
  week, ushering in cooler weather in the latter half of the
  week.

&&

.DISCUSSION...
Issued at 123 PM CDT Thu Aug 28 2025

A surface high pressure ridge is draped across the region today,
resulting in light and variable winds and mostly sunny skies
throughout Iowa. A nebulous, mostly washed out boundary sagged
into our service area overnight and is providing a focus
mechanism for some cumulus development this afternoon from
around Pocahontas down to Grinnell. A few model solutions
attempt to generate light showers within this cumulus field,
however, forecast soundings show very limited moisture so will
hold any rain mention out of the forecast through tonight. Of
note, however, is that diurnal heating will promote seasonally
strong low-level lapse rates and 0-3 km AGL CAPE values in
excess of 100 J/kg near the boundary across northern Iowa this
afternoon and evening. This may promote some weak landspout-type
funnel clouds in that area, though with the shallow nature of
the clouds and high LCLs, any brief touchdowns appear unlikely.

From Friday through Sunday the surface ridge will slowly retreat
eastward, while a weak mid/upper level low pressure center
meanders from South Dakota southward or southeastward toward
Nebraska and Iowa. This results in a gradual return of clouds
and rain chances to our forecast area, but with ill-defined
focus mechanisms and uncertainty in where the mid/upper low will
track as it becomes trapped in a larger scale ridge, there is
low confidence in the timing and location of any resulting POPs.
By Sunday the GFS is moving the mid/upper low across Iowa, while
the GEM and EC wander it southward into Nebraska and have
relatively drier solutions in our area. In any event, severe
weather is not expected but obviously any showers or storms may
have an effect on outdoor plans over the holiday weekend.

Looking ahead into next week, a deep gyre will sink from south
central Canada down into the Great Lakes region around Tuesday
night or so, bringing a pronounced surface cool front sweeping
through with it. There will likely be a return of rain chances
in association with this system, then once the front pushes
through we will see cooler temperatures as we remain beneath
brisk northwesterly steering flow for the remainder of the week.
Long-range temperature guidance points to daily highs only in
the 60s to lower 70s during that time, so not a major blast for
early September but still noteworthy after the warmth of much of
August.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1209 PM CDT Thu Aug 28 2025

VFR conditions will prevail through the TAF period. There is a
low probability (10-20%) of fog/low clouds around sunrise
Friday, mainly in northeastern Iowa around MCW, but the
likelihood is too low to advertise in the 18Z TAFs. Will monitor
this possibility tonight.

&&

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

&&

$$

DISCUSSION...Lee AVIATION...Lee