464
FXUS63 KDMX 201140
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
540 AM CST Thu Nov 20 2025

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

.KEY MESSAGES...

- Stratus and areas of fog again today will impact high
  temperatures.

- Rain possible over southern Iowa late tonight through Friday
  evening.

- A mild weekend ahead though much colder weather may be on the
  horizon by mid next week.

&&

.DISCUSSION...
Issued at 357 AM CST Thu Nov 20 2025

Another day and another forecast discussion focused on stratus
trends in the near term.  The low level flow has turned southerly
across much of Iowa. That has led the stratus to be lifting north as
well and its advancement has accelerated the past few hours. This
clearing is reaching the Interstate 35 corridor except for northern
Iowa. A trough of low pressure has reached far western Iowa and
there is another area of stratus across South Dakota that is
dropping southeast. That stratus has just entered far northwest Iowa
and outside of a small break, it extends to far southern Manitoba.
Reduced visibilities in fog is common under much of this stratus.
Most locations have visibilities greater than 1sm though there are
pockets less than this. The main area to monitor for dense fog
potential is over south central Iowa where lighter winds are in
place along with the clearing skies. The nighttime microphysics
satellite imagery appears to be showing lower visibility river
valley fog may already forming in that area. Should the dense fog
indeed form with greater coverage, then headlines may be required.

It should be no surprise that the stratus trends are again the major
factor for high temperatures for today. The steepening low level
inversion this morning will help trap any moisture below it whether
it is stratus or the fog which will delay the erosion of either.
Therefore utilized a blend of NBM 10th and 25th percentiles for most
of the area. Perhaps a bit warmer west central and southwest which
could have some early sun pending the fog development and the moist
layer does become quite then and perhaps breaks. Moisture depths are
more shallow than yesterday all around and that should limit any
drizzle potential despite a bit of turbulence within that layer.

Fog could return tonight but at this time, cloud cover should again
limit any dense potential. Pops later tonight thorugh Friday evening
are coming into better focus with chances confined to southern Iowa.
High pressure will be moving into the area from the north with the
drier air arriving into northern Iowa Friday morning but it will not
reach central and southern Iowa until the afternoon. This delay will
allow for the precipitation to enter southern Iowa before eroding.

The weekend is setting up to be mild for this period in November.
Another system brings rain chances Monday into Monday night. There
is increasing confidence that colder to much colder weather will
arrive around Wednesday and for Thanksgiving day as a large trough
carves out through the region. Strong and gusty winds could
accompany the cold front passage and any moisture with this system
appears limited across the state.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 535 AM CST Thu Nov 20 2025

Widespread fog is over Iowa this morning. Dense fog has
developed over parts of central Iowa and will impact KDSM and
may impact KOTM/KFOD yet this morning. This fog will be slow to
erode through mid morning and expect LIFR conditions to persist
in these areas through that time. IFR to LIFR stratus is over
the eastern half and northern Iowa and will also persist much of
the day. A few breaks with VFR area possible at times but it
will be brief. Some erosion in the stratus field is likely from
the north overnight but most locations will remain MVFR or
lower through 12z. Rain may reach KOTM late tonight. The wind
will become more northerly today and remain less than 10 kts.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST this morning for IAZ044>048-
057>062-070>075-081>084-092>094.

&&

$$

DISCUSSION...Donavon
AVIATION...Donavon