035
FXUS63 KDMX 141130
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
630 AM CDT Fri Aug 14 2026

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

.KEY MESSAGES...

- The heavy rainfall threat for Iowa continues due to ongoing
  convection with efficient rainfall production, and further
  still by convection expected tomorrow.

- Severe weather is possible tomorrow, with damaging wind gusts
  and heavy rain as the primary threats. Large hail and a
  tornado or two are also possible.

- The pattern remains active with storm chances through the
  weekend and mid next week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 325 AM CDT Fri Aug 14 2026

Convection is ongoing across central Iowa which the HRRR has been
struggling to assimilate over the past several hours (up to 06z/1am
Friday). The Friday 00z suite of CAMs has the basic footprint down
for the ongoing convection, however, they have been struggling with
timing for convection. One potential reason for this is that CAMs
are not properly modeling the Elevated Mixed Layer (EML). Model
soundings suggest decent capping up to around 700mb. Looking at
mesoanalysis, these storms are forming in an area with decent deep
moisture convergence. The expectation through the night is that
these storms will continue to develop and push to the
north/northeast into the mid to late morning hours. Models show the
low level jet weakening around 12z/7am, which would lead to any
remaining convection decaying as it loses its forcing. Until that
happens, the ongoing convection will have fairly high rain rates, as
they are not moving particularly quickly. SO far, these storms have
already produced over 1in of rainfall in an hour, with one swath of
just over 2in in an hour. Unseasonably high dewpoints and PWAT
values exceeding 2in aid to the heavy rainfall potential, however,
with convection being elevated updrafts would not be as deep to take
advantage of the whole warm cloud layer (around 13500ft).

Due to the poor representation of ongoing convection, more
uncertainties crop up as we move through the day today, where the
bulk of our heavy rain potential lies. In central Nebraska, an MCS
driven by a shortwave is in the process of decaying. As it decays,
an associated MCV will move towards Iowa which will serve as the
focus point for the next round of storms. There is some severe
potential with convection in the afternoon, given decent shear (25-
35kts) and a strong push of instability into Iowa. Damaging winds
looks to be the primary threat, with large hail and a tornado or two
possible. See SWODY1 for details. The uncertainties are with the
location of the MCV and how convection behaves as it forms. The most
likely scenario is cells that quickly grow upscale before moving
east along the instability gradient that sets up, which looks to
mainly be south of the Highway 20 corridor. The northward or
southward extent of this line will have implications on which areas
receive the most rainfall. As mentioned before, PWAT values are
quite high and there is another push of moisture through the day.
This, combined with warm cloud depths will lead to efficient
rainfall production.

As the MCS exits the area, the rest of tonight looks to be fairly
dry. Most of the day tomorrow will be fairly dry before more shower
and thunderstorm chances return Saturday night into Sunday
morning.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 252 PM CDT Thu Aug 13 2026

The ring of fire pattern continues through Saturday night. PWATs
over 2" linger until a cold front sweeps through Sunday morning.
GEFS/EPS guidance highlights Saturday into Sunday morning as another
period of storm chances, with similar potential for marginal severe
chances and flash flooding as we have seen most of this week. High
pressure and drier canadian air may bring a brief break from any
rain chances before the ridge breaks down a bit and shortwaves and
enhanced flow return to our part of Midwest by midweek. This will
need to be monitored for renewed severe weather and heavy rain
concerns.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 544 AM CDT Fri Aug 14 2026

Prevailing IFR to MVFR conditions are expected through this TAF
period. Showers and thunderstorms are lifting north across Iowa
this morning and are currently impacting KDSM and KOTM. As
thunderstorms lift north, terminals across northern Iowa could
see impacts from this activity, although storms should weaken
through the morning. Otherwise, lower ceilings will linger
through the morning before recovering slightly pending another
round of showers and thunderstorms beginning around 20z.
Depending on how quickly the next round of storms clears the
area, fog will be possible overnight Friday into Saturday
morning. Due to low confidence in storm timing, the only mention
of fog is at KDSM.

&&

.HYDROLOGY...
Issued at 326 AM CDT Thu Aug 13 2026

Periods of heavy rainfall remain possible through tonight.
Cumulative impacts from several rounds of moderate to heavy rainfall
beginning Thursday morning and another round currently ongoing
across central Iowa followed by more storms later today and tonight.
These may lead to river and/or flash flooding and certainly will
lead to significant ponding.

WPC has carried the previous Day 2 excessive rainfall outlook (ERO)
to moderate risk for Today into the Day 1 outlook and includes much
of central and southern Iowa. The primary concern with the current
convection is it is moving across areas that received 2-4 inches of
rainfall less than 24 hrs ago. In addition, this heavy rain may move
into the Des Moines metro and lead to urban impacts. Will also be
monitoring Walnut Creek, which responded to the previous rainfall
and reach action stage. Additional heavy rainfall will increase the
potential for flooding along these faster responding streams
including Walnut Creek.

Little change regarding the potential for river flooding, as
significant within-bank rises are still expected on many streams. At
least isolated to scattered minor river flooding is possible, with
more significant flooding possible as well. Since QPF will be around
rainfall-runoff inflection point, just a little more QPF than
forecast may produce more significant flooding. For example, if QPF
averages around 0.5 to 1 inch more than forecast, then widespread
minor river flooding with multiple locations seeing moderate or
possibly major flooding may occur.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday morning for IAZ023>028-033>039-
044>050-057>062-070>075-081>086-092>097.

&&

$$

SHORT TERM...67
LONG TERM...De Bruin
AVIATION...67
HYDROLOGY...Donavon/Zogg