700
FXUS63 KDMX 240508
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1108 PM CST Sun Nov 23 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Areas of dense fog likely tonight. Dense Fog Advisory in
  effect for about the northern and eastern half of our area
  overnight into Monday morning.

- Gray and soggy Monday, with fog giving way to light rain and
  thickening clouds.

- Much colder from around Tuesday night through the end of the
  week, with blustery winds Tuesday night through Wednesday.
  Precipitation chances return around next weekend, with a
  potential for accumulating snowfall but details of timing and
  magnitude still unclear.

&&

.DISCUSSION...
Issued at 233 PM CST Sun Nov 23 2025

It has been another mild and sunny day, with light south breezes
and temperatures soaring well into the 50s once again.
Unfortunately, today will be the last hurrah for such
pleasantness for quite some time.

A 500 MB low is moving east northeastward across Colorado this
afternoon, and will meander eastward across Kansas on Monday.
Meanwhile, an energetic shortwave trough will come ashore over
the Pacific Northwest coast later tonight and move quickly
across the northern U.S. Rockies on Monday. At the surface, a
low pressure center has developed in eastern Colorado and a
broad trough will extend northeastward from it tonight, acting
as a weak warm front developing over Iowa and nearing the IA/MN
border by Monday. Within broad but modest south southwesterly
flow ahead of this system, forecast soundings indicate
substantial warm air and moisture advection overnight, as well
as clouds associated with the approaching trough spreading in
late. Rising surface dewpoints, weak but organized SSW low-level
flow, increasing clouds, and warming aloft will all support
steady or slowly rising temperatures overnight and have
maintained that trend in the ongoing forecast. Meanwhile, fog
and stratus that developed across parts of Iowa last night
dissipated after sunrise this morning, however, a large fog bank
has persisted across central Missouri and is beginning to creep
northward this afternoon per visible satellite imagery. This fog
bank should advect northward and expand across Iowa this evening
and overnight. With skies clear across our forecast area
initially, once the sun sets temperatures should fall pretty
quickly, even with winds not calm, then as higher dewpoints
surge northward conditions will be quite conducive for fog
expansion. High-res guidance is all over it with the NAM, HRRR,
RAP, and HREF all indicating areas of dense fog across at least
portions of our area tonight. Confidence is highest in our
northern and eastern counties, where clouds and light rain from
the approaching system will arrive later, and in the north where
the effective warm front mentioned earlier will likely set up
later tonight into Monday morning. HREF probabilities of <1/4
mile visibility are 60-80% in that area and forecast soundings
almost unanimously indicate a fully saturated layer from the
surface up to an inversion around 1000-2000 ft above the
surface. Given the set-up, model guidance, and climatology, have
chosen to be aggressive in issuing a Dense Fog Advisory for
generally the northern and eastern half of our service area,
beginning late this evening in the southeast and at Midnight in
the north and northeast.

On Monday and Monday night, the trough approaching from the
west/southwest will slide eastward across Iowa and Missouri,
making for a gray and soggy day as areas of light rain or
drizzle move through and fog is slow to dissipate beneath
thickening clouds. Rainfall amounts will be light and no impacts
from that are expected, but it will make things dreary. On
Monday night, even as this system begins to move away to our
east, the previously discussed and more robust 500 MB shortwave
will emerge from the northern U.S. Rockies and dig southeastward
into the Dakotas, then close off and deepen further over
Minnesota and Wisconsin on Tuesday-Tuesday night. Snow is
forecast to develop in the deformation zone on the back side of
the deepening cyclone, but will primarily track across Minnesota
with light snow just scraping far northern Iowa. At this time we
are forecasting negligible accumulations right along the border
and nothing farther south into our area, however this will bear
watching to ensure no southward shift in the forecast which
could have some impact on our northern counties. Of greater
consequence to most of Iowa is that this second system will
produce blustery northwest winds and send temperatures
plummeting from late Tuesday onward. Highs on Wednesday are
forecast to be 15-20 degrees below Tuesday levels, and by
sunrise Thursday readings will fall into the mid-teens to lower
20s across our entire forecast area. The result will be the
first real taste of winter air for most of Iowa from Tuesday
night onward.

The cyclone over the Upper Midwest will move away to our east
from Wednesday onward, but leave brisk northwesterly steering
flow overhead supporting a continuation of cold but dry weather
for a couple of days. Around Friday morning or so another
energetic 500 MB trough will come ashore over the Pacific
Northwest coast, and quickly carve out a deep western U.S.
trough by this weekend. This will bring our flow aloft around to
southwesterly, promoting increasing moisture and ejecting
ribbons of vorticity out of the larger trough up through the
Midwest and a region of broad forcing for ascent. This leads to
increasing precipitation chances for several days at the end of
next week into early next week, and forecast surface
temperatures generally support snow as the dominant
precipitation time for much of that period, but with rain or a
mix certainly being possible at times. At this range however,
the details of when and where regions of enhanced lift will
allow for any impactful precipitation amounts, and to what
extent those opportunities could manifest as accumulating
snowfall, are still quite uncertain. Anyone with travel plans
around next weekend should monitor the forecast updates in the
coming days as we gradually begin to refine these details and
determine any potential for meaningful snowfall that could
impact post-Thanksgiving travel plans.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1106 PM CST Sun Nov 23 2025

Main change was tapering off some of the fog intensity for sites
like KDSM and KFOD, although do have a TEMPO group to account
for periods of restrictive fog that remains possible, at times
tonight. IFR/LIFR cigs will expand overnight and lift to MVFR
across the south for a time after 18z. Rain will be likely for
all sites through after 12z and beyond. Fog and IFR/LIFR stratus
return after 00z for all sites.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST Monday for IAZ004>007-
015>017-023>028-035>039-047>050.
Dense Fog Advisory until 10 AM CST Monday for IAZ061-062-074-
075-083>086-094>097.

&&

$$

DISCUSSION...Lee
AVIATION...Jimenez