649
FXUS63 KDMX 310650
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
150 AM CDT Sun May 31 2026

.KEY MESSAGES...

- Slow moving, efficient rainfall storms with isolated heavy
  rainfall this morning diminishing toward midday, then a dry
  interval through this afternoon.

- There is a chance of a few severe storms this evening into
  tonight, but the question is if storms can develop. If storms
  do develop, gusty winds, hail, and locally heavy rainfall
  will be the main threats.

- Monday is favoring drier conditions with capping in place to
  limit if not prevent storms. However, similar to Sunday, if
  storms can develop, a few severe storms with large hail or
  gusty winds are possible.

- High pressure drifts southward through the Great Lakes into
  the Ohio Valley, which pushes rain and storm chances west of
  the state Tuesday and Wednesday and perhaps Thursday. Highs
  above normal in the 80s.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 150 AM CDT Sun May 31 2026

Early morning radar imagery has shown convection blossoming over
southwestern Iowa into our southwestern forecast area, which is
within a broad area of 850mb low level warm air advection. These
storms are moving ever so slowly to the north around 10 to perhaps
15 mph. The 0z KOAX RAOB measured precipitable water (PWAT) values
at 1.51", which is between the 90th percentile and the daily max.
So, there is an impressive reservoir of atmospheric moisture where
these storms have developed with relatively drier air sitting over
eastern Iowa with the 0z KDVN RAOB just under an inch and closer to
the median PWAT value. An earlier line of convection, which early in
the day (May 30) convective allowing models (CAMs) showed pushing
through, has now fizzled while a stronger area of convection is
ongoing over eastern Kansas pushing into Missouri. CAMs show the
activity over southwestern Iowa generally moving to the east and
northeast through the forecast area and losing intensity as it does
so. There may be credence to this idea given the upper level pattern
that has a lobe of shortwave energy (associated with the
left/upstream part of the omega block) lifting northeastward over
the central Rockies while in the low levels the jet focuses more
over Kansas. While there is no severe weather threat with this
activity due to the weak effective shear, locally heavy rainfall
will remain possible in this favorable environment. Unlike this time
yesterday, CAMs and the HREF and REFS have gone full retreat on the
higher magnitude rainfall amounts previously discussed last night.
Isolated totals by midday today could near 2 to 3 inches (RRFS (both
cores)/REFS) to 1 to 1.5 inches in most other CAMs and the HREF.
Thus, the concern for flash flooding is quite a bit lower than this
time yesterday.

Any lingering convection should be lifting northeast of our forecast
area by early this afternoon. This will be pulling the mid and high
level clouds away from the area, though there looks to be plenty of
lingering low level moisture per RAP cross sections so the amount of
sunshine looks to be limited at this point. So, it does look like a
dry period from sometime this morning for some to many by this
afternoon. With warm level aloft capping the atmosphere and the
cloud cover, it remains to be seen how much storm development could
occur this evening given the weak low level thermal lift and QG
convergence. Models differ on where the LLJ may be pointing with
some towards southwest Iowa while others veer into central Missouri.
If isolated to scattered storms are able to develop, the environment
features between 2000 and 3000 J/kg per forecast soundings and plan
view models. However, deep layer shear looks to be marginal between
20 to 30 knots (RAP) to at best 30 to 35 knots (GFS). Soundings
persist good saturation in the lowest 1km while the mid-levels dry
out yielding favorable downdraft CAPE values for gusty winds to be
possible. Thus, any severe risk looks contingent on 1) storms
developing and 2) there being sufficient shear to sustain
convection. Heavy rainfall parameters will still be favorable with
PWATs above normal and between 1.25 and 1.5 inches and deep warm
cloud depths. Storm motions will be faster though around 20 to 25
mph with storms pushing generally to the east or perhaps southeast.
Again, if storms are able to develop, isolated rain totals from any
Sunday night storms could be between 2 to 3 inches on the upper end
by Monday morning. However, most are unlikely to see these amounts
with some places perhaps seeing no rainfall.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 239 PM CDT Sat May 30 2026

Upper ridging is maintained to start the new work week with
moisture largely shunted to the south and west until closer to
midweek when shower and storm chances again return to the
forecast. Details at this time range remain uncertain with a
surface high over the Great Lakes to contend with. Temperatures
remain in the 80s through the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1055 PM CDT Sat May 30 2026

A line so scattered showers and thunderstorms has reached far
southwest Iowa and will spread across the state overnight,
lingering through Sunday morning. This is expected to weaken as
it moves into central Iowa, though thunderstorms are still
possible. Have included prevailing mentions at KFOD/KDSM/KOTM on
the mostly likely window for showers with a prob30 group to
time out the thunder chances. Introduced prob30 -shra groups at
KMCW/KALO as data has trended towards showers reaching farther
east on Sunday. There is uncertainty as to how long the
scattered activity will linger into Sunday and adjustments are
likely. Additional thunderstorms are possible SUnday night just
beyond the current TAF period.

&&

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

&&

$$

SHORT TERM...Ansorge
LONG TERM...05
AVIATION...Hagenhoff