452
FXUS63 KDMX 041128
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
528 AM CST Thu Dec 4 2025

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

.KEY MESSAGES...

- Very cold this morning, with daily record low temperatures a
  near certainty. See climate section below for record
  temperature values.

- Friday will be more mild, with highs approaching 30 degrees
  and a light dusting of snow crossing far northern Iowa.

- Chances for accumulating snowfall late Saturday through
  Saturday night have increased to 50-70% across most of the
  area. Amounts are still uncertain, but there is the potential
  for several inches in some area. The relatively short duration
  of the event limits potential for higher amounts, but in any
  event, travel impacts are increasingly likely.

&&

.DISCUSSION...
Issued at 205 AM CST Thu Dec 4 2025

A large surface high pressure area has settled across the region
overnight, bringing clear skies and light winds that are
allowing temperatures to fall well below zero this morning. Wind
chill values of around 15 to 25 below zero are anticipated, but
any readings reaching advisory levels are marginal and fleeting
thus no advisory has been issued. Even so, it will be very cold
and anyone venturing outside should take appropriate
precautions. The high pressure area will slide off to the
southeast today, allowing for a return of modest south breezes
by this afternoon and bringing relatively milder weather on
Friday.

Meanwhile, on the synoptic scale, a large gyre is spinning over
Hudson Bay and a string of shortwave impulses rounding its
western periphery will cross western and southern Canada and the
Midwestern U.S. this weekend into early next week, making for a
more active weather pattern in our area. The leading impulse in
the approaching train is currently located over the
Alberta/Saskatchewan border and will eventually cross Minnesota
and northern Iowa on Friday. A reflective surface low will cross
Minnesota during the day Friday, bringing light to moderate snow
north of Iowa and likely just scraping our far northern counties
with a quick shot of light snow. Have increased POPs to 30-50%
roughly north of Highway 18, mainly Friday morning, but expected
accumulations are very light at only a few tenths of an inch or
so.

A deeper and somewhat more robust trough will cross the region
late Saturday through Saturday night, and long-range model
solutions have been picking up on this feature for many days now
but with varying solutions as to timing and latitudinal extent.
With it now only being 2-3 days away the model suite is
achieving better resolution and we have a better idea of how
things will play out. By Saturday afternoon the 500 MB wave will
be crossing eastern South Dakota and Nebraska, with a surface
trough extending along the southern High Plains from the Texas
panhandle up to the Nebraska/Kansas border. The broad forcing
for ascent associated with the shortwave will overlay a band of
frontogenetical forcing in the northern/northeastern hemisphere
of the developing surface cyclone, generating a swath of snow
that will cross our forecast area around Saturday night. The EC
has been the most consistent in its track for this storm, with
accumulating snow focused across about the northeastern two
thirds of Iowa, while the GFS has been more erratic and the NAM
has so far been taking things more over the southwestern half of
Iowa. In any event, the probability of snowfall in our area is
increasing and we are now carrying 50-70% POPs on Saturday
evening/night accordingly. Amounts are still uncertain due to
variations in the location, elevation and magnitude of
frontogenetical forcing as well as the larger storm track, but
it is fair to assume a few inches of snow will affect at least
portions of the area. The system will be moving through pretty
quickly though, which should limit the potential for higher
accumulations. We will be closely watching this system over the
next couple of days as some travel impacts are likely from late
Saturday into early Sunday. The wave train will then continue
into the first half of next week, with several more impulses
expected between Monday and at least Wednesday, but the details
during that time are hazy at this range.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 528 AM CST Thu Dec 4 2025

VFR conditions will prevail through the TAF period. A large area
of low stratus clouds, based around FL015-025, is currently
blanketing much of Nebraska and eastern South Dakota and has
moved very little overnight. These clouds should gradually pivot
east and northeastward today, and may reach FOD and MCW from
around midday into the afternoon. However, confidence is low and
also the ceiling heights within the cloud bank will be rising
through the day and may reach VFR levels even by the time they
approach FOD. For now have advertised only VFR ceilings there,
but if the clouds move more quickly or rise more slowly then
MVFR ceilings may be possible. Otherwise, the aviation
forecast is quiet through Friday morning.

&&

.CLIMATE...
Issued at 205 AM CST Thu Dec 4 2025

     Forecast and Record Low Temperatures for Select Central Iowa Cities...

===============================================
            |      Wednesday       |  Period  |
            |  Forecast   Record/  |    of    |
City        |    Low       Year    |  Record  |
===============================================
Des Moines        -9      -6/1886      1878-
Lamoni            -5       2/1991*     1897-
Mason City       -14      -9/1991      1903-
Ottumwa           -5       1/2005*     1923-
Waterloo         -12      -7/1991      1895-
===============================================

*Record occurred in multiple years

&&

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

&&

$$

DISCUSSION...Lee
AVIATION...Lee
CLIMATE...Dodson