543
FXUS63 KDMX 291724
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1124 AM CST Sat Nov 29 2025

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Major Winter Storm underway. Snow will fall, heavily at times,
  through today before tapering off around this evening. Storm
  total amounts of 8-12 inches will be common, with some areas
  receiving more than 12 inches.

- Increasing, gusty winds later today and tonight will cause
  blowing and drifting of the fresh snowpack and prolong recover
  times into Sunday.

- Much colder temperatures move in on Sunday, with wind chills
  in the single digits above and below zero.

- Additional light snow is forecast on Monday into Monday night,
  mainly across the southern half of Iowa.

&&

.DISCUSSION...
Issued at 216 AM CST Sat Nov 29 2025

     Major Winter Storm ongoing across Iowa...

A large mid/upper level trough is moving over the High Plains at
this time, with a large attendant surface low centered near the
Oklahoma Panhandle. Within a large region of isentropic lift and
forcing for ascent in the northeast quadrant of the surface low
and leading flank of the approaching trough, a precipitation
shield has developed and is blanketing Nebraska, Iowa, and much
of neighboring states. The system will advance eastward today,
with the surface low pivoting northeastward across Missouri and
the far southeast corner of Iowa by this evening, while slowly
filling as it does so. Tonight it will then deepen again as it
moves away into the Great Lakes region. The primary impact of
this scenario is that our forecast area will remain squarely
beneath the large precipitation field today, resulting in
prolonged accumulating snowfall with rates approaching an inch
per hour at times when pockets of stronger forcing move
overhead. In relative lulls between these bursts ice
introduction aloft may be briefly lost, and we have seen spotty
observations of sleet/freezing drizzle tonight, but any icing
would be minimal and not as impactful as the heavy snow
accumulations that are expected. Earlier tonight a pronounced
band of heavier snow, evinced by radar returns, set up roughly
along Highway 20 and we received several reliable reports of
around 5 inches of snow by midnight. It is expected several more
such bands will impact transient portions of the area today, and
overall storm total snowfall amounts remain on track in the 8-12
inch range for most of our service area, with a swath of more
than 12 inches likely somewhere roughly between Interstate 80
and Highway 18, tapering southeastward into eastern Iowa. No
changes have been made to the ongoing headlines tonight.

Another notable forecast wrinkle is that some recent guidance,
particularly HREF runs, have pegged potential for wind gusts of
35+ MPH late today into tonight as the low begins to pull away.
With the low deepening during that time and pressure falls in
our eastern counties, and a tight surface pressure gradient
moving squarely across the CWA with good mixing and modest cold
air advection, we should see a surge in winds progressing from
west to east from around late afternoon into early tonight. This
will occur as appreciable snowfall is ending, but with such a
deep fresh snow pack forecast to be in place by that time the
strong and gusty winds will still cause issues with blowing snow
re-covering roads and reducing visibility. However, most
deterministic guidance keeps the speeds/gusts below 35 MPH, and
almost no output is predicting visibility falling to <1/4SM.
Even so, this potential will be monitored closely today in case
blizzard conditions become feasible, and in any event the winds
and blowing snow will extend very hazardous travel conditions
through tonight and possibly into Sunday, as it will prolong the
time needed to clear roads across the area.

From Sunday onward the forecast is considerably colder. A large
500 mb gyre will set up over Hudson Bay for much of the coming
week, and troughs will rotate around the base of the gyre and
swing across the central U.S. The first of these will cross the
High Plains and Midwest Monday into Monday night, and likely
spread light snow across at least parts of Iowa. The highest
chances for accumulation will be across the southern half of our
forecast area, where currently 1-2 inches is forecast but there
is variability in model solutions. Certainly nothing as heavy as
the current event is anticipated, but even a couple inches of
snow may cause impacts when it is hot on the heels of the first
system, adding to a pre-existing snowpack, and coming on a
weekday with many returning to work and school. With forecast
snow amounts being what they are no headlines are being
considered at this time, but we will be keeping one eye on the
Monday timeframe this weekend in case one becomes warranted. The
forecast after Monday night is mostly dry for the week, but
additional nebulous shortwaves could result in low POPs/light
snow at times as the week progresses.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1125 AM CST Sat Nov 29 2025

Widespread snow continues to impact all sites this afternoon
with IFR to LIFR conditions. Conditions will persist into the
evening. Snow tapers off from west to east around 00z. Wind
increases as snow comes to an end, transitioning from falling
snow to blowing snow. Northwest winds are forecast to gust 25-30
kts through Sunday morning. Visibility reductions from blowing
snow should begin to taper off late morning. Conditions should
begin to improve towards the end of the TAF period as skies
begin to clear and winds diminish.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM CST Sunday for IAZ004>007-
015>017-023>028-033>039-044>050-057>062-070>075-081>086-
093>097.
Winter Weather Advisory until 6 AM CST Sunday for IAZ092.

&&

$$

DISCUSSION...Lee
AVIATION...Hagenhoff