163
FXUS63 KDMX 071138
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
638 AM CDT Mon Sep 7 2026

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

.KEY MESSAGES...

- Lingering showers and weak storms are expected to continue
  generally over the western half of Iowa this morning, drying
  out into the afternoon.

- A front moving through Tuesday will lead to continued chances
  for showers and storms. This looks to occur over two rounds;
  The first over north/north-central Iowa through the morning,
  and a second later in the afternoon to evening. Isolated
  strong to severe storms, as well as heavy rain are possible,
  with higher chances Tuesday evening/early Wednesday.

- Cooler temperatures and lower humidity arrive late week.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 305 AM CDT Mon Sep 7 2026

Lingering showers with some isolated areas of embedded weak storms
are ongoing over portions of western Iowa this morning. This
activity is elevated and is being fueled by deep moisture
convergence within a ribbon of relative weak instability around 500
J/kg, as a 25-30 knot low level jet sits overhead. The expectation
is that with little change in the environment over the next several
hours, similar activity is expected to continue generally west of
the I-35 corridor, before slowly decreasing in coverage by late
morning and especially into the afternoon. Additional rainfall
amounts this morning should generally read under an inch. Drying
conditions will return as forcing aloft decreases, along with the
push of drier air as surface high pressure currently centered over
the Great Lakes dominates overhead, pushing the instability axis
westward. While the mid-level ridge becomes more centered over the
Midwest briefly today, a push of 850mb warm air advection is
expected to occur, with efficient mixing and a tightening pressure
gradient allowing for surface winds to become breezy by late morning
and through the afternoon. Gusts up to 20-25 mph will be common,
with locally higher gusts up to 30-35 mph over northern Iowa. Highs
are expected to remain cooler compared to the recent hot conditions
experienced, as thick cloud cover is slow to decrease into the
afternoon, with forecast values reaching into the low to mid 80s.

As a potent trough moves into Manitoba, Canada late tonight, an
associated boundary extending from Minnesota through the Dakotas is
expected to gradually track into Iowa through Tuesday. Ahead of this
boundary, showers and thunderstorms are forecast per guidance to
arrive into north/northwest Iowa around if not just after midnight.
A strengthening low level jet is expected to have more of an
influence into Iowa as it expands across the state, along with a
push of theta-e advection overhead. A closer look at the environment
features relatively limited instability amounts across northern Iowa
of less than 1000 J/kg, along with shear around 25-30 knots and
lapse rates around 6.5-7 C/km, which would indicate a low severe
risk into Iowa with this morning activity. Cannot rule out some sub-
severe wind gusts, and periods of heavy rain though as PWATS are
indicated around 1.5-1.75 with deep warm cloud depths. Lingering dry
air overhead may delay the timing of showers and storms slightly as
soundings indicate, so will be something to monitor and adjust as
needed.

As the jet fades through the morning, the coverage of showers and
storms looks to decrease as the front slowly descends southeast,
with a continued low severe threat. Attention however turns to the
late afternoon to evening timeframe Tuesday, as the cold front
itself arrives into central Iowa, paired with stronger forcing for
lift given a restrengthening LLJ and higher moisture levels pooling
ahead of the boundary. Temperatures in the warm sector (central to
southern Iowa) are expected to be quite warm in the upper 80s to low
90s, paired with dewpoints in the upper 60s to low 70s. Higher
instability values around 2000-3000 J/kg, along with shear values
around 30-40 knots are indicated per soundings overhead, which would
be more favorable for potential severe weather. Isolated severe
storms with damaging wind gusts and large hail are possible. There
is an increasing potential as well per latest guidance for heavy
rainfall Tuesday into early Wednesday, given the indication for
training storms along the boundary and high PWAT values overhead
around 2-2.5 inches. Rainfall amounts around 1-2 inches are expected
at this time, though slightly higher amounts near 3 inches could
occur in areas where repeated stronger storms pass through. Details
will continue to become more clear in future forecast updates.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 322 PM CDT Sun Sep 6 2026

Storms will exit the region behind the cold front on Wednesday,
ushering in cooler temperatures and lower humidity. Highs in
the lower 80s are expected through Thursday, with precipitation
chances potentially returning by Friday.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 627 AM CDT Mon Sep 7 2026

Showers with isolated storms are currently moving towards KFOD/KDSM.
These will likely remain showers and only last a couple of hours,
but there is a slight chance that they briefly produce some
lightning. Rain is expected to last until 15z, but could linger
longer and will be monitored. VFR conditions prevail from the midday
into the evening, but the 6z-12z period will become more active.
LLWS is likely across the state during that period, though it
appears too marginal for inclusion in this TAF issuance.
Thunderstorms also become more likely across the northern terminals
but kept PROB30 for now.

&&

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

&&

$$

SHORT TERM...Bury
LONG TERM...TDR
AVIATION...De Bruin