421
FXUS63 KDMX 052326
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
526 PM CST Wed Nov 5 2025

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Breezy south wind on Thursday with gusts of 25-30 mph.
  Scattered rain across eastern and southeastern Iowa Thursday
  evening into Friday morning.

- Rain across the area on Saturday with snow possible across the
  northern half of Iowa. Turning much colder Sunday into Monday
  with highs in the 30s.

&&

.DISCUSSION...
Issued at 123 PM CST Wed Nov 5 2025

A breezy start to the day as a shortwave pushed across the
area, with subsidence and cold air advection helping to pull
stronger gusts down to the surface. As the surface high
continues to slide across the area this afternoon and the
pressure gradient relaxes winds will continue to diminish. As
high pressure continues to shift east overnight a surface low
shifts towards the area from South Dakota. This places Iowa
within the warm sector and winds will shift back around to
southerly. The enhanced pressure gradient across the area will
result in another breezy day, but without subsidence and cold
air advection the highest gusts will likely not be realized.
Even so, gusts of 25-30 mph are expected through Thursday. And
with warm air advection into the state, temperatures will warm
into the mid 50s to near 60. By Thursday evening the boundary
will trail across eastern Iowa as deeper moisture transport out
of the gulf phases with the system. While soundings show dry air
in place, with increasing moisture into the area do expect to
see light scattered shower activity across east to southeast
Iowa Thursday evening into Friday morning. Brisk northwest winds
pick up again on Friday behind the boundary, but with a weaker
pressure gradient expect winds to be not quite so high with
gusts to around 20-25 mph.

Our attention then turns to the larger system set to impact the area
this weekend. The overall synoptic setup remains similar as has been
seen the last few model cycles. A vigorous shortwave will drop out
of Montana and across Iowa on Saturday, embedded within the broader
longwave trough. This wave will arrive Saturday morning with the
surface low expected to track across southern Iowa with good
agreement between the GFS, Euro, and 12z NAM (note the 06z NAM was
substantially further north). This places the deformation zone
across central to southern Iowa as cold air begins to rush into the
area on the back side of the low. Expect to see temperatures fall
through the day as cold air pushes south. The GFS is faster with the
push of cold air into the area, more closely timed with the
shortwave bringing the precipitation. The Euro is slower, bringing
the precipitation first and the bigger surge of colder air in a
separate wave a little later. This has notable impacts on
precipitation amounts and accumulations. While the deterministic
Euro and associated ensemble members favor a broad 1-2 inch swath of
snow across the northern half of Iowa, the GFS is more vigorous with
a band of 3-5 inches setting up in northern Iowa. An important note.
A look at model soundings across the area shows a dry layer at the
surface with saturation occurring over 900 mb. With the surface
temperature above freezing, the model determines this is rain. But
thermodynamics tells us that as precipitation falls through this
layer evaporative cooling will quickly pull the temperature down to
the wetbulb - which is below freezing. Expect that this will bring a
quicker transition over to snow than models currently project and
this would result in higher snow accumulations than model currently
project. Much colder air filters in Saturday night with overnight
lows in the teens to 20s across the area. This brings another set of
impacts as any precipitation that fell as rain, or as a sloppy wet
snow, will freeze solid. With this setup, worsening road conditions
are possible as temperatures continue to fall overnight and Sunday
morning. Sunday temperatures will not offer much relief, only
reaching the low to mid 30s. Monday morning lows are also frightful
in the teens with wind chill in the single digits.

What does this mean, accounting for various scenarios and
uncertainties? We know that there is an increasing probability for
accumulating snow across the northern half of Iowa on Saturday.
Temperatures fall through the day, turning very cold overnight.
These cold temperatures may result in worsening road conditions as
liquid on the ground freezes. Still unknown is how quickly we will
shift from rain to snow, exactly how much snow we will receive, or
where exactly the heaviest amounts might fall. Details will continue
to be refined in the next couple days. Anyone with weekend plans
should monitor closely.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 525 PM CST Wed Nov 5 2025

VFR conditions are expected to remain through the period across
the terminals, though clouds will increase into Thursday ahead
of a system that will move across the region. Mid-level clouds
are expected near or just after the current TAF forecast, with
rain showers possible in eastern Iowa around or after 00z
Thursday. Otherwise, winds will increase through Thursday
morning out of the south, with gusts up to 20-25+ knots through
the afternoon.

&&

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

&&

$$

DISCUSSION...Hagenhoff
AVIATION...Bury