115
FXUS63 KDMX 121141
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
641 AM CDT Sat Sep 12 2026

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Widespread shower and storm chances expected on Sunday.

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

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 333 AM CDT Sat Sep 12 2026

As of the latest surface analysis, a cold front and pre-frontal
trough are moving across the area. Showers and thunderstorms
continue to advance across the DMX CWA early this morning. Based on
0700Z surface observations, the cold front is draped across the far
northwestern corner of the CWA and is slowly dropping southeast.
Ahead of the front, temperatures remain in the upper 60s to lower
70s with dewpoints in the upper 60s. Behind the front, northwesterly
winds are advecting cooler air and dewpoints in the low to mid 50s
as weak surface high pressure builds in from the northwest.

Through the remainder of the overnight hours and into the day,
showers and isolated thunderstorms will continue to move southeast
before dissipating later this morning. A lull in activity is
forecast before re-development takes place in southeastern Nebraska
as a vort max moves from southeast Nebraska through southern Iowa
into northern Missouri. The SPC previously placed the area under a
Day 2 Marginal Risk, but with cooler low-level temperatures and a
stout cap in place, the strong to severe thunderstorm threat is near
zero. However, should a parcel break through the cap, a weak EML
could support isolated convection. Otherwise, the remainder of the
area should stay dry, with high temperatures ranging from the lower
70s in the northwest to the lower 80s in the southeast, and
dewpoints ranging from the upper 40s in the north to the mid to
upper 60s in the south.

Beginning late Saturday night into Sunday morning, a surface low is
progged to lift north toward the region, bringing increasing chances
for showers and thunderstorms throughout the day on Sunday. While
the severe weather threat for Sunday has been downgraded to general
thunder, increasing moisture advection will drive PW values near the
90th percentile into the area. This abundant moisture, combined with
skinny CAPE profiles on forecast soundings, will support efficient
heavy rainfall, particularly Sunday night. High temperatures on
Sunday will generally range from the mid-60s to the low 70s.

A cold front is bringing showers and thunderstorms to the region
this morning, followed by cooler and drier air from the northwest.
Severe weather risks remain near zero today due to strong low-level
capping, though isolated showers remain possible. By late Saturday
night into Sunday, an approaching surface low will increase rain
chances, with high atmospheric moisture levels creating the
potential for heavy rainfall through Sunday night.&&

.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.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 638 AM CDT Sat Sep 12 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 /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 638 AM CDT Sat Sep 12 2026

VFR TAFs are on tap through the TAF period as weak surface high
pressure builds in from the northwest. However, post-frontal
MVFR CIGS may sneak into the TAFs this morning as the front
drops southeast through the area. Post-frontal northwesterly
winds will start to pick up with gusts upwards of 20 knots and
persist through the day before starting to diminish toward
00Z/Sunday especially at KFOD, KMCW and KALO.

&&

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

&&

$$

SHORT TERM...Vorst
LONG TERM...Dodson
AVIATION...Vorst