480
FXUS63 KDMX 292000
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
300 PM CDT Fri May 29 2026

.KEY MESSAGES...

- Shower chances (30-50%) build across the state tonight.
  Embedded thunderstorms are also possible, particularly in
  western Iowa.

- Showers and storms are possible across much of the state on Saturday
  (20-40% all day). Any slow moving thunderstorms that form
  could bring isolated pockets of heavy rain. Winds will also be
  stronger, particularly in northwest Iowa, with winds gusting
  from 25- 30 mph.

- Chances for severe storms exist on Sunday in western Iowa,
  though potential is low at this time.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 256 PM CDT Fri May 29 2026

The pattern today once again fits the omega block model, with
troughing in the western US, ridging through the central US, and
troughing across eastern Canada. The exception is the prominent
shortwave meandering its way towards Iowa. For today`s daily check
in with the shortwave, we see the axis is sitting over central
Nebraska to northern Mississippi. Ahead of the shortwave and over
Iowa, height falls have been in place most of the day, forming some
mid and upper level cloud cover that has limited high temps today.
RAP analysis and visible satellite reveals a vorticity max embedded
within the shortwave over Kansas City. This, combined with some
meager instability has already begun to initiate some scattered
convection from Kansas City and northwest towards Omaha. Meanwhile,
stratiform rain in central Missouri is being advected northward
towards the Iowa border. Translating this to a PoP forecast is
challenging, but generally 10-35% PoPs have been introduced through
the rest of the afternoon in southwest Iowa.

Through the overnight, the shortwave will continue to advance over
the state. This will at last overcome the dry airmass from the Great
Lakes high pressure and bring in gulf moisture with PWATs over 1.5
inches. Saturation in the mid levels over central Iowa is expected
in the evening and showers may become more prevalent in the evening
and overnight over most of the state. Thunder is possible with these
showers in the southwest portion of the state where some elevated
instability is expected.

Similar conditions continue through the day Saturday, with chances
for showers and thunderstorms expanding across the rest of the
state. 1-1.5 inch PWATs will be in place much of the day, and
instability nudges further into Iowa. The REFS ensemble brings 1000
J/kg just into our southwest, but some individual members like the
HRRR have up to 2000 J/kg. However, 0-6km shear will likely not
exceed 20 knots. Consensus amongst the morning CAMs is most of state
will remain dry for much of the day, but there will likely be a few
pockets of showers and sub-severe thunderstorms. Signal for heavy
rain from these slow moving storms still exists, with some NBM
members showing totals over 1 inch (though fewer than this time
yesterday), but pockets of heavy rain will be very isolated. Winds
will be more gusty tomorrow as 25-30 knot 850 mb winds could be
mixed down by intermittent heating/mixing or storm downdrafts,
particularly in northwest Iowa.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 256 PM CDT Fri May 29 2026

Some consensus is coming into view on Sunday`s synoptic pattern,
though convective evolution is still highly variable across the mid-
range CAMs. The western trough will finally pivot northeast over the
high plains, with waves of energy perhaps far enough east to
influence storms in Iowa Sunday. Lee cyclogenesis to the west and
associated southerly flow will likely advect in a warm sector with
upper 60s and 70s dewpoints. EPS/GEFS ensembles show Iowa on the
edge of meaningful 500 mb flow in the exit region of the trough,
meaning improved shear may be in place, though it certainly isn`t a
guarantee. Latest GEFS runs have 50% chance of supercell composites
>5 in southern Iowa. SPC now has a marginal risk in western Iowa as
a result of these trends, and some of the machine learning guidance
suggests low end severe probabilities. Convective evolution in
Nebraska/Kansas will be important for sorting out details for our
storm chances Sunday, and CAMs show too much uncertainty to discuss
at this time.

By early and mid week, ensembles show some agreement that the
western trough will continue to lift out to the northeast, and
central US ridging/eastern troughing will hold their positions. If
the lifting trough can pull moisture across Iowa and overcome the
dry airmass sitting under the eastern troughing/Great Lakes high
pressure, scattered storm chances will continue through the mid-
week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1222 PM CDT Fri May 29 2026

VFR conditions will prevail through the TAF period. Chances for
SHRA/TSRA will slowly increase overnight into Saturday,
primarily at FOD/DSM overnight and at OTM later. Even at those
three sites, POPs are generally 30-40% so have maintained PROB30
groups targeted around the time periods of highest chances. That
being said, most SHRA will be light and a reduction to MVFR or
lower ceilings/visibilities or TSRA is a lower probability (10%
or less) at any given terminal, so advertised only VFR
conditions with 6SM -SHRA in the PROB30 groups.

&&

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

&&

$$

SHORT TERM...De Bruin
LONG TERM...De Bruin
AVIATION...Lee