900
FXUS63 KDMX 052356
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
556 PM CST Wed Feb 5 2025

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

.KEY MESSAGES...

- Winter Weather Advisory Remains for Freezing Drizzle Into
  Tonight. Some slick travel possible through the evening
  commute, especially on elevated or untreated surfaces. Fog
  development tonight behind the end of drizzle.

- Windy Thursday.

- Next system Saturday with snow in the north and a mix south.

- Return to seasonal winter temps Sunday into Tuesday with
  additional systems nearing Iowa Tuesday.

&&

.DISCUSSION...
Issued at 253 PM CST Wed Feb 5 2025

Light icing began early this morning in southern Iowa, as seen on
Iowa DOT plow cameras, with a few roads also noted to be partially
covered with ice near US-34 in southwest Iowa. Since then, moisture
has been increasing northward decreasing dew point depressions and
leading to saturation/the start of the freezing drizzle. Into early
afternoon, road treatments seem to largely be working with
temperatures in the 20s and road temperatures in the upper 20s to
low 30s through much of southern into central Iowa, a few cooler
road temperatures in the north. Some snowflakes were also noted this
morning, likely due to some seeder feeder effects as a band of
higher clouds moved across the state. With overall depth of
saturation near to below 2 km, as noted in soundings in much of
central through southern Iowa, freezing drizzle should remain the
primary precipitation type through the evening in the Winter Weather
Advisory footprint which was left in place with no changes other
than starting the headline sooner this morning with saturation
occurring a bit faster. The peak moisture and forcing is still
expected here this afternoon into mid evening which will also
coincide with loss of diurnal heating and thus could increase
the extent of the freezing drizzle impacts. However, elevated
and untreated surfaces will remain the primary concerns with
slick sidewalks, driveways, or bridges, as a few examples.
Certainly use caution and slow down this afternoon and evening
in case you encounter slick roadways. Ice accumulation amounts
remain unchanged with a a few hundredths/a glaze in much of the
area, and some higher amounts in the far southeast where
moisture coincides with lift for longer, thus leading to higher
ice accretion amounts. To the north, some deeper saturation is
possible this evening leading to some snow mixing in, or even
becoming the primary type, though with little to no
accumulations expected. Further south, some snow flakes could
still be seen at times as saturation flirts with ice nucleation
zone closer to freezing, but as noted light freezing drizzle
should be the main precipitation type.

The mid-level trough moves off to the east around 06Z bringing the
drizzle to an end in the east by about midnight (06Z), but as the
drizzle ends, fog will likely develop with the low level saturation
remaining leading to some continued reduced visibilities and
potentially extension of impacts on elevated surfaces with lows
tonight in the teens to 20s. The fog should gradually clear west to
east through the overnight hours as winds increase into Thursday
morning as another quick moving passes to our north and a surface
high pressure moves in from the north. The pressure gradient
increases in especially the northeast with cold air advection and
mixing helping to send gusts towards 30-40 mph, the highest gusts in
the far north to northeast. At this time, winds look to remain sub
advisory. Despite the cold air advection aloft, temperatures
Thursday warm some in many locations with highs mainly in the 30s
and the return of sunshine.

The mid-level ridge passes over on Friday with another dry day and
temperatures in the 30s. Then, an approaching system Friday night
into Saturday will bring two distinct areas of precipitation, one to
the north and one to the south with potentially some areas in the
middle even staying dry. While the north favors snow, up to a couple
inches, areas to the south look to see a mix again. Will continue to
evaluate over the next couple with updates to come, though at this
point any ice amounts look to remain on the light side, up to about
a glaze at this time range.

High pressure moves in again for Sunday with a dry and seasonal end
to the weekend before some additional precipitation chances move in
early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 556 PM CST Wed Feb 5 2025

Conditions varied from LIFR south to MVFR north at 00z with
light freezing drizzle central and south advancing northward
and likely reaching KMCW and KALO shortly. At least IFR
conditions in visibility and/or fog, as well as light freezing
drizzle, can then be anticipated at all sites through the
evening. The precipitation should end by the early morning hours
however, with winds becoming westerly and conditions improving
to VFR as the stratus exits. Brisk west winds with gusts >=30
kts may occur north, including near KMCW, by mid to late
afternoon as well.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 PM CST this evening for
IAZ034>039-044>050-057>062-070>075-081>086-092>097.

&&

$$

DISCUSSION...KCM
AVIATION...Small