852
FXUS63 KDMX 311738
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1238 PM CDT Sat May 31 2025

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

.KEY MESSAGES...

- Temperatures warm into the 80s through the weekend with upper
  level smoke making for hazy skies. Some may mix down to the
  surface at times this afternoon into Sunday.

- Thunderstorms return to the area Tuesday into early Wednesday.
  The potential for any severe weather will continue to be
  monitored over the next few days.

&&

.UPDATE...
Issued at 325 AM CDT Sat May 31 2025

Smoke continues to be the main forecast feature through the
weekend. Few changes from previous except extended smoke
mentions through Sunday with RAP/HRRR smoke guidance in good
agreement of smoke remaining aloft through the weekend keeping
skies hazy. Lowered high temperatures a few degrees both days as
a result, though highs still in the 80s. Some of this smoke may
be brought down to the surface this afternoon, especially
towards northern Iowa, but may become more widespread by Sunday
afternoon. Any smoke that does make it to the surface could
lead to a reduction in visibilities at times or the smell of
smoke. Any air quality impacts will continue to be evaluated by
the Iowa DNR.

&&

.DISCUSSION...
Issued at 229 PM CDT Fri May 30 2025

While most of Iowa is cloud free this afternoon, one cannot look up
into a blue sky. Smoke from wildfires across Canada has pushed
into Iowa today and satellite imagery shows this blanketing a
large swath of the midwest. This smoke has remained aloft with
no observational sites reporting reductions to visibility that
would indicate smoke making it to the ground. HRRR and RAP smoke
data continues to indicate that this will last through Saturday
as well. There is a chance with a passing shortwave on Saturday
that some of this smoke may be pulled down to the surface, and
this is indicated with slightly elevated concentrations in both
RAP and HRRR surface smoke variables. Any impacts to air quality
across Iowa will be monitored by the Iowa DNR. Aside from smoke
impacts, the passing shortwave should have little tangible
impact to Iowa weather with CAMs keeping the area dry. A stray
shower my be possible in the afternoon with marginal instability
in some HRRR soundings, however confidence to include this in
the forecast at this time is low.

Meanwhile, temperatures through the weekend and into Monday will
soar through the mid to upper 80s with theta e advection into
the area as the thermal ridge shifts east.

At the same time, a western US trough will dig across the Rockies
with an associated surface low ejecting across the midwest by Monday
into Tuesday. Impacts to Iowa look to arrive on Tuesday and this
will be the next window for thunderstorms. The current track
takes the low across Missouri and lifting into Illinois to
Wisconsin. That would keep the more robust impacts to the south,
however southern Iowa could see some triple point action as the
surface low skims southern Iowa. GFS soundings at Lamoni and
Des Moines indicate 1200-1500 J/kg surface based CAPE with
100-200+ m2/s2 0-1 km SRH and nicely curved hodographs through
roughly the lowest 3 km. While better deep layer shear lags the
instability axis in current model runs, this environment remains
more than sufficient for supporting organized convection. We`ll
continue to fine tune the forecast in the coming days, but this
will likely be the next window for severe storms in Iowa.
Another system will pass over the area late this week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1230 PM CDT Sat May 31 2025

VFR conditions prevail through the period, with Canadian wildfire
smoke being the most notable weather condition this period.
Smoke remains in place aloft, although satellite imagery has
shown considerable thinning over the last few hours. Therefore,
have stuck with only BKN (KFOD and KDSM) or SCT (KMCW, KALO,
KOTM) VFR ceilings for all sites through the afternoon. Expect
there to be another push of smoke tonight into Sunday, primarily
aloft. Confidence is still quite low in whether smoke will
reach the surface at any sites during this period, so have
continue to leave it out of TAFs. Reduced visibilities and
surface smoke look to be more likely farther to our west, but we
will continue to monitor for changes in these trends through
the day and evening.

&&

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

&&

$$

UPDATE...05
DISCUSSION...Hagenhoff
AVIATION...Dodson