894
FXUS63 KDMX 082347
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
647 PM CDT Tue Sep 8 2026

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Reintensification expected along a cold front moving across
  Iowa this afternoon and early evening. A few strong to severe
  storms may produce gusty winds a pockets of heavy rain.
  Showers linger across southern/southeastern Iowa through
  Wednesday morning.

- More seasonal temperatures in the upper 70s to low 80s the
  rest of this week.

- Additional thunderstorm chances later Friday into Saturday and
  again Sunday into early next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 226 PM CDT Tue Sep 8 2026

A line of showers has lingered across north central Iowa through the
morning and into the early afternoon, very slowly sinking toward
central Iowa. Warm air advection in the warm sector of the low is
ongoing with station in far southern Iowa reporting temperatures
into the low to mid 90s this afternoon. This has allowed for
destabilization ahead of the boundary with MLCAPE around 1500-2000
J/kg already. This prefrontal convection will continue to bubble
this afternoon ahead of the main cold front that has just reached
far northwest Iowa around 2 pm. Daytime heating should help to
reinvigorate the ongoing convection as it reaches central Iowa and
there is a window from around 21-03z for stronger storms to develop.
Any stronger cores would primarily present a damaging wind concern
with dry low levels noted in soundings lending a microburst
potential. Those would be fairly short lived. Shear is largely
parallel to the boundary, but if a bowing segment could orient
moving ENE with the shear a more organized wind signal could
develop. SPC has also outlined a 2% tornado risk. This would be
difficult to come by in this environment with parallel shear and
LCLs over 1200 m but stretching with initial updrafts may carry
some risk.

There is also a hydro concern this evening and overnight. The
environment is fairly supportive with PWATs of 2-2.25" (very high
for this time of year) and deep warm cloud layers over 4500 m for
efficient rain production. The 12z HREF indicated a widespread
1- 1.5" for much of the area with areas east of I-35 potentially
seeing pockets of 2-4+". CAMs through today have consistently
indicated pockets of 4-5+" are possible, though placement is
tougher to nail down. After the initial increase in
strength/coverage with daytime heating, secondary rejuvenation
of cores is anticipated as the LLJ increases overnight. Shear
parallel to the boundary will help allow for training cells,
tough the boundary itself will continue to sink south overnight
with not current indication of it stalling out. Based on where
ongoing convection is lining up and expectations for diurnal
strengthening and LLJ enhancement, somewhere in the highway 30
to I-80 corridor seems to be the most expected area. While
antecedent conditions are quite dry, areas in town with poorer
drainage could see a flash flood concern later this evening and
overnight.

Post-frontal showers linger across southern Iowa Wednesday morning
before finally exiting the area. In northern Iowa, patchy fog
is possible Wednesday morning behind the front and cooler air
filters into the area. Wednesday highs will be more seasonal in
the low 80s and these temperatures are expected to last through
the end of the week.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 226 PM CDT Tue Sep 8 2026

After a drier period Thursday and much of Friday, our next system
arrives later Friday into Saturday as a deepening shortwave
traverses the area. SPC has outlined a Day 4 risk area for this as a
plume of instability increases in conjunction with better kinematic
forcing. Another more robust system looks to move across the area
Sunday into early next week. Both system will help to bring
temperatures down and by early next weeks highs may be in the
upper 60s to low 70s areawide.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 638 PM CDT Tue Sep 8 2026

Showers and thunderstorms are moving across Iowa and will impact
all sites early in this TAF period. Around 02z, storms are
expected to clear KFOD and KMCW, before a slower departure at
KALO. At KMCW and KALO, low ceilings are possible as clouds
build in and conditions are favorable for patchy fog leading to
visibility reductions. KDSM and KOTM will see visibility
reductions through the period due to showers and storms as they
move through the state. A wind shift will occur behind showers
and storms as a front passes through the state, leading to winds
generally from the northwest by the end of the TAF period.

&&

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

&&

$$

SHORT TERM...Hagenhoff
LONG TERM...Hagenhoff
AVIATION...67