358
FXUS63 KDMX 041136
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
636 AM CDT Sun Oct 4 2026

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

.KEY MESSAGES...

- Dry conditions are expected to remain over the next several
  days, with a slow warming trend through the first part of the
  upcoming work week.

- A few periods with overnight/early morning fog are possible.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 145 AM CDT Sun Oct 4 2026

The upper level pattern features a ridge of high pressure in the mid-
levels over the Southwestern US with its axis extending up into the
British Columbia province of Canada. Downstream of this ridge is the
shortwave trough that swung through our region that is now moving
over the western Great Lakes early this morning as viewed on GOES-
East upper level water vapor imagery. In the wake of this trough,
RAP analysis shows low level cold air advection (CAA) ongoing over
the region into the state. Fog is not likely this morning as
forecast soundings show too much dry air; however, do note winds are
calm in the Nishnabotna River Valley and with small dewpoint
depression cannot rule out isolated fog in a sheltered area like
this. After morning lows in the upper 40s to low 50s, high
temperatures will be lower than yesterday with 850mb
temperatures about 2 degrees lower due to the aforementioned
CAA. Thus, highs today will be around 70 degrees - seasonable
for early October - with plenty of sunshine. Similar to
previous days, boundary layer mixing will entrain drier air
aloft to the surface so have lowered dewpoint temperatures below
the initial National Blend of Models guidance toward the 25th
percentile of available guidance.

Tonight, the sky remains clear and winds become calm as a region of
high pressure moves over the state. Given the recent wetness, this
points to fog potential. This is indeed shown in the 0z HRRR
forecast soundings as well as LAMP visibility probabilities around
20-25%. However, the rest of the guidance and forecast
soundings show the near surface layer too dry for fog. Similar
to this morning, cannot rule out fog development in sheltered
locations such as river valleys and will be monitoring this
morning for possible inclusion. Otherwise, the signal for
widespread fog is not apparent.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 221 PM CDT Sat Oct 3 2026

Into the beginning of the upcoming work week, the forecast will
remain dry, with a large area of high pressure over the Upper
Midwest that will slowly depart the region, especially into Tuesday.
Outside of an embedded shortwave passing over Winnipeg/Ontario,
with any rain chances staying well north of Iowa into midweek,
quasi- zonal upper level flow is expected to persist, keeping
conditions dry. The main story otherwise will be a gradual
increase in temperatures, with values into the low to mid 70s
becoming common Tue/Wed. The late work week will see an
intensifying area of ridging over the western CONUS where a heat
dome will dominate, which will put Iowa into a northwest flow
pattern aloft. This will likely introduce at least some
potential for passing weak shortwave energy at times from the
north, where long range guidance is starting to show by late
Thursday/early Friday, which could bring the first chance for a
return of rain chances back into the state. Given low confidence
on specific track and evolution of features at this time
though, have left conditions dry, but this will be something to
keep a casual eye on in the coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 634 AM CDT Sun Oct 4 2026

VFR conditions will prevail through the period. Some high clouds
will pass overhead FOD, DSM, and OTM through the day as winds
from the northwest or north prevail under 10 knots. Winds will
become calm tonight and while there remains a roughly 20%
chance of fog development at any given location, this is too low
to include any mention.

&&

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

&&

$$

SHORT TERM...Ansorge
LONG TERM...Bury
AVIATION...Ansorge