219
FXUS63 KDMX 111226
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
726 AM CDT Fri Jul 11 2025

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

.KEY MESSAGES...

- Flood Watch for Flash Flooding between US Highways 34 and 20
  through 7AM CDT this morning. Widespread rainfall totals
  between 2 and 3 inches with locally higher amounts.

- Flood Watch for Flash Flooding for the remainder of the day
  Friday from the Waterloo through Corydon areas and points east
  for another round of heavy rainfall this afternoon and
  evening.

- Scattered Severe Thunderstorms this afternoon and evening
  across portions of central Iowa (risk level 2 out of 5).
  Damaging winds and a tornado or two are the primary threats in
  addition to heavy rain.

&&

.DISCUSSION...
Issued at 104 AM CDT Fri Jul 11 2025

A long lived MCS with damaging winds will continue to propagate
east across the I-80 corridor early this morning, sustained by
a low level jet and along a gradient of steep mid level lapse
rates and downdraft CAPE. In this wake of this leading MCS,
training convection along a stationary front sustained by the
low level jet with a precipitable water axis around 2.00 inches
will yield heavy rainfall and a flash flood threat between US
Highways 34 and 20. Rainfall totals between 2.00 and 3.00 inches
are likely for many locations, with locally higher amounts in
excess of 4.00 inches. A Flood Watch remains in effect for these
areas until 7 am CDT this morning.

For this afternoon and evening, another round of strong to
severe storms with heavy rainfall is expected. Issued a second
Flood Watch for the Waterloo through Corydon areas and points
east for another round of heavy rainfall with precipitable water
values remaining near 2.00 inches with training convection
likely along the slow moving frontal boundary. Additional rainfall
amounts of one and a half to three inches are possible for
these areas, supported by the HREF LPMM QPF, MPAS CAMS and RRFS.
This also aligns well with the WPC Slight Risk in the Excessive
Rainfall Outlook for today (level 2 out of 4).

Regarding the Severe Risk for today, SPC has much of south
central into eastern Iowa in a Slight Risk for severe
thunderstorms (level 2 out of 5). Plentiful moisture and
buoyancy with MLCAPE on the order of 2000-3000 j/kg with
daytime heating will be in place along and ahead of a slow
moving frontal boundary. Deep layer shear around 30-40kts
augmented by an approaching shortwave this afternoon will
promote another round of severe thunderstorms. Outflow
boundaries from morning convection will have to be sorted out
for their mesoscale impacts on the thermodynamic and kinematic
setup. Still, initial supercell structures are favored with a
tornado or two possible with large low level curvature in the
forecast hodographs and low cloud bases. As storms become more
numerous in the late afternoon and evening, upscale growth is
expected with damaging winds becoming the primary threat.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 716 AM CDT Fri Jul 11 2025

We still have some overrunning showers going this morning to the
north of the stationary boundary down near the MO border. We
still expect these showers to dissipate by 15Z, with a short
breather from storms before the next round of thunderstorms and
heavy rain gets going this afternoon. By 18Z, we should be
seeing the next round developing near DSM and ALO, and sliding
toward eastern Iowa from there. Given the placement of the
front, MCW will likely be on the outside looking in for this
round of storms, with it being a close call for FOD. We leaned
the TS timing toward the HRRR, though it is possible storms get
going a couple of hours earlier. Tonight, RAP soundings show a
saturated boundary layer, with the LAV as developing MVFR/IFR
visibilities and IFR cigs. However, HREF probs from MVFR or
lower conditions really lights up eastern Iowa, so we were not
as aggressive with the lower cigs and vsbys as what the LAV has.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for IAZ059-060-072-073-
084>086-095>097.

&&

$$

DISCUSSION...Jimenez
AVIATION...MPX
HYDROLOGY...Ansorge