223
FXUS63 KDMX 222317
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
617 PM CDT Thu May 22 2025

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

.KEY MESSAGES...

- Cool temperatures through early next week.

- Precipitation chances return Friday afternoon and will be on
  and off into early next week. Severe weather chances are near
  zero through Sunday.

&&

.DISCUSSION...
Issued at 241 PM CDT Thu May 22 2025

The transition to northerly flow aloft has fully occurred today as
an upper low has moved into the western Great Lakes while high
pressure ridging is occurring through the Dakotas and Manitoba.
The northerly flow allowed the northern Iowa/Minnesota stratus
to move south today and a few areas of light rain occurred south
to near Interstate 80 before diminishing. The stratus also
transitioned to more cellular clouds with cumulus developing
upstream in the clearing which has now moved into northern Iowa.
The main area of stratus that has become cellular will be
slower to erode overnight with clearing occurring from north to
south overnight. This will allow temperatures to cool overnight
as the wind diminishes with surface high pressure arriving.

The upper flow will undergo another transition Great Lakes upper low
moves a bit more east allowing for some 500 mb height rises and a
pseudo zonal flow. A short wave will pass over the Rockies overnight
and will carry Pacific moisture into the region on Friday. Clouds
will be on the increase on the lee side of the Rockies as the
moisture lifts over the mountains. This process will eventually lead
to high to mid-level cloudiness to increase from west to east over
Iowa on Friday. Enough saturation will occur during the day for rain
chances to increase across parts of central and western Iowa,
especially during the afternoon. In addition, the increasing cloud
cover will lead to another cool day. Guidance is suggesting highs in
the mid 60s which are likely overdone. Little change in the pattern
through Sunday which will keep cool weather and some shower/non-
severe thunderstorm chances going through Sunday. By Sunday night,
an upper low will develop over western South Dakota and this will
initially lead to a more southwest flow into Iowa before the upper
low moves and settles over Iowa by late Tuesday. This again will
lead to cool temperatures and keep precipitation chances going
across the state. This setup can also lead to funnel cloud
development. Will need to further evaluate the near surface
parameter space as this event draws closer. The uncertainly for
mid to late next week is how quickly that upper low will move
out of the area and western ridging and warmer air arrives. At
this time, a more delayed departure is favored but possibly back
to warmer weather at the end of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 617 PM CDT Thu May 22 2025

VFR conditions are forecast for the next 24 hours. A few light
showers may be possible on Friday evening, right around or just
after the end of the 00Z TAF period, but probability of impacts
is too low to include in the TAFs at this time.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Lee