574
FXUS63 KDMX 120342
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1042 PM CDT Fri Sep 11 2026

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Occasional shower and storm chances possible tonight and
  Saturday. Overall severe risk is low, but a few stronger
  storms could produce hail or gusty winds.

- More widespread shower and storm chances on Sunday. A few
  stronger storms are possible.

- Increased severe weather and heavy rain chances on Monday.
  Heavy rain potential continues through mid- week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 249 PM CDT Fri Sep 11 2026

Surface high pressure over the Great Lakes region is being slowly
pushed eastward as a subtle 500 mb shortwave brings surface low
pressure eastward into the state today into tonight. Current
conditions are reflective of this transitioning pattern, as skies
remain clear and temperatures warm, but with breezy winds signal the
tightening pressure gradient ahead of the approaching low pressure.

As we get into this evening and overnight, the low pressure to our
north and west will continue eastward, advecting low level moisture
northward ahead of it and eventually dragging a boundary through the
state. Models have been progging at least isolated showers or storms
overnight as this system passes through the area, although the
best chances for rain certainly reside farther north over
Minnesota nearer to the synoptic lift and where mid-level
moisture is more plentiful. Farther south over Iowa, any
showers or storms that occur will need to overcome dry mid-
levels and primarily rely on convergence along the passing
boundary for lift. There will be some instability in the layer
(~500 J/kg), so it`s certainly possible a displaced parcel or
two is able to overcome the dry air and produce a few showers or
a brief storm, but this will be far from widespread. Therefore,
have maintained low end rain chances (15 to 30%) in the
forecast, with the best chances over northern Iowa. The storm
prediction center does still have a marginal risk for severe
weather over northwest Iowa (wind and hail), but the overall
severe risk looks low.

The wave and associated boundary generally push through Saturday
morning, flipping us to northerly surface flow and bringing in drier
surface dewpoints and low level moisture. However, despite this low
level drying trend, another push of mid-level moisture may leave the
door open for additional showers and storms in southern Iowa. This
appears to be mostly post-frontal and elevated, which should help
mitigate the concern for surface based convection. However, 1500 to
2000 J/kg of elevated instability and moderate amount of shear
could certainly promote a few stronger storms in southern Iowa
Saturday. With thunderstorm activity being elevated, wind and
hail will be the main concerns with any organized storms. Again,
a marginal risk for severe weather will be in place on
Saturday, this time over southern and southwestern Iowa. A
marginal risk of excessive rainfall marks the same area, as
heavy rain could occur with any of these storms. For the rest of
the state, Saturday will bring cooler temperatures and drier
conditions as dewpoints generally fall into the 40s and 50s by
Saturday afternoon.

Upper level ridging begins to develop to our west as a trough digs
in over the pacific northwest on Saturday into Sunday. For Iowa,
this will bring another slug of mid level moisture into the state
and the potential for more widespread rain and isolated
thunderstorms on Sunday. This activity will once again be fairly
elevated, as high pressure and cool air will still be in place at
the surface. Therefore, expectation is activity will be scattered
light to moderate rain associated with the mid level moisture and
theta-e advection. The severe risk appears low but thunderstorms are
certainly possible with 1000+ J/kg of elevated instability. A
stronger storm also can`t be ruled out given the increasing flow
aloft but hail and wind would be the only concerns, as any storms
will be quite elevated.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 249 PM CDT Fri Sep 11 2026

The pattern turns quite active starting Sunday night, as deep layer
moisture increases ahead of an approaching 500 mb trough and
multiple subsequent waves keep the gulf moisture stream open through
the first part of the week. The first day of concern will be Monday
as the aforementioned 500 mb trough passes through the northern
CONUS. This will bring a push of low level moisture and
increasing temperatures up into Iowa, along with strong mid and
upper level flow. Instability values in our area will maximized
Monday afternoon, with plenty of shear for organized storms.
Fortunately, a warm nose aloft will work to keep the atmosphere
capped off and activity surface based, at least at this lead
time. Still, strong 850 mb winds could certainly support some
damaging winds. The storm prediction center has already started
to key in on Monday, with a Day 4 15% risk over central Iowa.

The active weather continues through at least Tuesday and Wednesday,
although the pattern looks to transition to more of heavy rainfall
threat through these next two days. Modeled PWATs around 1.9 to 2"
will be conducive for efficient rainfall, and multiple days of
convection along a quasi-stationary boundary could lead to some
flooding concerns. It`s still a bit early to get too ingrained
in details, as mesoscale factors could cause this boundary to
sink or move around, but the current synoptic setup certainly
points towards potential hydrology concerns through next week.
The weather prediction center is already on top of this as well,
with slight risks for excessive rainfall spanning from Sunday
to Tuesday of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1042 PM CDT Fri Sep 11 2026

Currently a line of showers is entering northwest Iowa bringing
a fleeting shot for showers to impact most of the TAF sites
early Saturday morning. After the passage of this boundary winds
will shift from SE to SW and then to NW by Saturday morning.
There also is the possibility of a brief lowering of cloud
heights after this frontal passage, but they will generally
rebound quickly. Winds during the day on Saturday will generally
be around 10 kts except for KMCW which has gusts up to 20 kts
possible. Winds are expected to become light and variable by
Saturday evening for all the TAF sites.

&&

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

&&

$$

SHORT TERM...Dodson
LONG TERM...Dodson
AVIATION...Lee/Wyss