688
FXUS63 KDMX 052358
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
658 PM CDT Tue May 5 2026

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

.KEY MESSAGES...

- Cool through mid week. Frost possible north tonight and
  perhaps more widespread Wednesday night into Thursday
  morning.

- Low chance (30-40%) for showers south Thursday night and
  Friday, then more widespread chance (50-60%) for showers and
  thunderstorms Saturday into Sunday.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 230 PM CDT Tue May 5 2026

The cold that passed across Iowa has stalled out across Missouri,
leaving Iowa in a cold air advection regime as high temperatures
this afternoon sit in the mid to upper 50s. Light radar returns
across southern Iowa through today for residual post-frontal
showers, though with very dry low levels and 20+ degree dewpoint
depressions, this is not reaching the ground. High pressure begins
to nudge into Iowa overnight, helping reduce cloud cover across the
area. While clouds thin out in northern Iowa, soundings still
indicate a high saturated layer and expect these clouds will persist
through the overnight. Temperatures in northern Iowa are still
expected to fall into the mid to low 30s, but cloud cover will
prevent better radiational cooling that would otherwise have
them fall even lower. With these cold temperatures anticipated
overnight through Wednesday morning a Frost Advisory has been
issued for northern Iowa.

Cooler temperatures hang around through Wednesday with another day
in the 50s across Iowa. Overnight low will fall to the mid to upper
30s across much of Iowa on Wednesday night through Thursday morning.
The trough axis begins to push east overnight and on Thursday,
allowing for southwest flow and warm air advection into the area,
sending temperatures back to the mid 60s on Thursday.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 230 PM CDT Tue May 5 2026

As for the long term, two embedded waves will push through the area
Thursday night/Friday morning and again on Saturday through Saturday
night. Both of these waves will bring our next chances for
precipitation. The strength of the system on Friday has some
uncertainty. An 850mb jet will bring a plume of low-level moisture
to southern/southeastern Iowa, while mid-level moisture is coming
from the west. Uncertainty lies with the placement and the strength
of the 850mb jet. Current guidance has been trending south, which
suggests most of the activity Friday will be confined south of I-80
or even south of US-34. Sounding profiles on Friday support the
potential for lightning, though there is very little CAPE to work
with here - around 150 J/kg. At the same time, sounding profiles
show an inverted-V with dry air near the surface to around 700mb
which may result in gusty winds with showers or thunderstorms.

Saturday presents its own challenges. Better moisture transport from
the gulf leads to higher dewpoints across the area and current
sounding profiles look more saturated, although there is more
uncertainty with how widespread mid-level forcing will be. The GFS
and Euro paint a picture of widespread rainfall across much of Iowa,
while Canadian guidance keeps it confined to a narrow corridor in
southern Iowa. With both this system and Friday`s system, a complete
washout is not expected across the state. For Friday, the LREF Grand
Ensemble mean shows around 0.1 inches of rainfall across southern
Iowa, while the same guidance shows around 0.1 inches of rainfall in
northern Iowa and around 0.25 inches of rainfall in southern Iowa.

Beyond the weekend, ridging sets up over the western United States.
Locally, this translates to temperatures being slightly warmer than
average. The average high for this time in May is in the low 70s,
while the NBM ensemble mean is teasing highs in the mid 70s to low
80s as the ridge builds. That being said, this pattern will be
monitored for the potential to be more active than this week has
been.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 651 PM CDT Tue May 5 2026

VFR cumulus and gusty winds will quickly diminish in the next
one or two hours. Light winds overnight will shift to northerly,
then to northwesterly through the morning. 20kt gusts return in
the north after 18z.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM CDT Wednesday for IAZ004>007-
015>017-023>028.

&&

$$

SHORT TERM...Hagenhoff
LONG TERM...Hagenhoff/Rotter
AVIATION...Jimenez