574
FXUS63 KDMX 291722
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1222 PM CDT Fri May 29 2026

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

.KEY MESSAGES...

- Much of central Iowa dry today with highs a few degrees either
  side of 80.

- Chances for scattered showers and a few storms spread into
  central Iowa tonight into Saturday up to around 50%. Not an
  all day washout. Severe weather is not forecast, but lightning
  a concern for those with outdoor plans. Highly localized
  rainfall amounts up to 2 inches possible on Saturday, but also
  highly uncertain if and where this may occur. In addition,
  winds will be breezy on Saturday.

- Seasonal temperatures through this weekend, then a bit above
  normal into next week. Occasional shower and storms chances
  persist through late this weekend into next week with low
  chances for severe weather or widespread heavy rainfall.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 155 AM CDT Fri May 29 2026

Early morning GOES-East upper level water vapor imagery shows an
amplified, stagnant omega blocking pattern in place with troughing
over the western CONUS and also from the Great Lakes into the
Northeastern US with a ridge from the Deep South into the south
central Canadian prairies. Lifting northeastward ahead of the
western CONUS trough, there is an elongated area of shortwave
energy. The aforementioned GOES imagery shows a good plume of Gulf
moisture with this energy, which is reflected in objective RAP
analysis at 925mb and 850mb. This moisture has already spread into
southwestern and western Iowa with higher content over Kansas, but
that will be lifting into the state later today into Saturday as the
shortwave energy moves toward the state. With the forecasted
increase in cloud cover, did taper back high temperatures a degree
or two today from the initial National Blend of Models (NBM) closer
to the 50th percentile of available guidance. This kept highs in the
middle and upper 70s in southwest Iowa to the low 80s in eastern
Iowa. Chances for any rain today are higher west of our forecast
area in western Iowa and points west closer to the approaching
shortwave energy and moisture plume. Forecast soundings show that
dry air, especially in the mid-levels and lesser so in the low
levels, will keep conditions dry farther into central and certainly
eastern Iowa. Instability is quite limited and shear is almost non-
existent so much of this will be rain showers with intermittent
rumbles of thunder at best.

As we move into tonight and Saturday, the shortwave energy lifts
over the state with forecast soundings showing the saturating
effects of the arrival of the plume of moisture with precipitable
water values up to around 1.5 inches. The forcing and moisture will
lead to more widespread chances for showers and storms spreading
from western into central Iowa during this time frame. However,
examining convective allowing model (CAM) guidance`s reflectivity
fields shows that this will not be a washout for any given location
with spotty to scattered activity. Instability up to around 1000
J/kg may reach our far western or southwestern forecast area with
higher instability farther west and weak instability perhaps as far
northeast as our northeastern forecast area. The highest shear of
around 25 knots will be focused over southwest Iowa. The lack of
shear and saturated profiles point to little if any severe weather
potential, which aligns with the latest SPC day 2 outlook, but
lightning is still possible and could interrupt outdoor plans as a
storm moves through a given location. Warm cloud depths are
seasonally high and with weak 850-300mb flow, storms will be slow
moving. Latest HREF localized probability matched mean (LPMM) shows
a few bullseyes of 1.5 to 2 inches of rainfall with NBM PMM showing
up to an inch. The cloud cover will keep highs a bit lower for much
of the area Saturday with highs in the upper 70s. In addition, winds
from the southeast will turn breezy by mid to late morning through
the afternoon hours. BUFKIT soundings show winds within the limited
mixing depth still supportive of gusts of 20 to 25 mph over central
Iowa and may top 30 mph up towards Estherville. While CAMs are not
showing this at the moment, a shower or storm could entrain these
types of winds to the surface as well.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 133 PM CDT Thu May 28 2026

Uncertainty in the long range is high as the trough in the west is
trying to eject, shortwaves around the western fringe of the eastern
Canada longwave trough are pivoting south, and remnant central
US shortwave will dissipate or merge with the next shortwave.
Regardless, as the western trough attempts to eject, it looks
likely southerly flow will bring a more robust warm sector into
or near Iowa. Latest GEFS guidance brings moderate CAPE into
Iowa by Sunday and Monday. On a large scale, period of
thunderstorms look possible in the long term. EPS/GEFS position
Iowa atop a decaying ridge and a shortwave off the the west,
making weak to moderate shear possible. Any severe weather
through the period will become highly contingent on mesoscale
details, particularly convective evolution closer to the
shortwave further west, and require more model certainty to
untangle.

&&

.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...Ansorge
LONG TERM...De Bruin
AVIATION...Lee