357
FXUS63 KDMX 201739
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1139 AM CST Thu Nov 20 2025

 ...Updated for the 18z 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 /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1131 AM CST Thu Nov 20 2025

Fog and stratus around 200 to 500 ft continues over the area
today, although visibilities are improving. Fog will continue to
improve today. Expecting this stratus to stick around through
most of the afternoon and evening, although ceilings should lift
a few hundred feet as the afternoon progresses, before falling
again tonight. Therefore, mostly IFR conditions prevail at
southern sites (KDSM and KOTM) while northern sites (KFOD, KMCW,
and KALO) could see some periods of MVFR as drier air works in
from the north. Additional fog development is possible again
tonight and into Friday morning, but haven`t included visibility
restrictions in TAFs yet due to low confidence in location. Low
clouds stick around through this TAF period, with improvement
beyond this period through Friday afternoon and evening.

In addition to clouds and visibilities, light winds are steadily
transitioning to more west then northwesterly behind the
boundary today.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST today for IAZ033-044>046-
057>062-070>075-081>085-092>096.

&&

$$

DISCUSSION...Donavon
AVIATION...Dodson