590
FXUS63 KDMX 260739
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
239 AM CDT Sun May 26 2024

.KEY MESSAGES...

- Showers and storms to continue through the morning with a
  waning severe weather threat. A few thunderstorms possible
  southwest this afternoon.

- Additional rain chances Monday and Tuesday. Some Monday storms
  could be strong in the east.

- Midweek dry period with seasonal temperatures with rain
  returning Thursday night. On and off rain through next
  weekend.

&&

.DISCUSSION...
Issued at 225 AM CDT Sun May 26 2024

Convection progressively coated the state overnight, overrunning the
surface warm front found in Missouri. 00z upper air analysis placed
the nocturnal jet into central Iowa, bringing plenty of upgliding
moisture into the state with mostly elevated thunderstorms with
sparse hail reports. Expect instability to wane southward through
the night as the MCS in Kansas takes over and sinks southeast, which
will largely diminish severe weather chances for us.

Otherwise, showers and storms will form from the jet-influenced
theta-e advection, the passing shortwave, and the left exit region
of the upper level jet. Southern Iowa can expect amounts between a
half inch to an inch of rain with higher amounts with thunderstorms.
The HREF probability matched mean QPF has a max along the H850 warm
front between the Highway 20 and Highway 30 corridors where
localized amounts nearing 2 inches will be possible. Rain and cloud
cover will focus more south through the day Sunday under the
influence of the deformation axis and pressure trough, finally
exiting after sunset. Enough instability will remain for these to
become thunderstorms, but northwesterly winds will inhibit the
amount of moisture available. CAA will keep highs in northern Iowa
near 70 for the day. Southern Iowa will be in the mid 70s.

Additional rain will be possible along passing waves on Monday and
Tuesday. CAMs build in an instability axis along the cold front
on Monday, bringing thunderstorm chances mostly east. Effective
shear at 40kts could organize some of the storms and produce
hail and gusty winds. Tuesday`s rain will be focused north. A
tightening pressure gradient and dry boundary layer will make
for a breezy Monday with 30 mph gusts possible in the west.
Upper level ridging will build in by midweek and spare the state
from rain until Thursday night when upper level troughing
influences the weather pattern again through next weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1126 PM CDT Sat May 25 2024

While end of VFR conditions remains expected across all sites,
the extent and duration of non-VFR has trended downward as hi-
res models grapple with ongoing convection in
Nebraska/Kansas/Missouri. Trend has been such that northward
extent and duration of TSRA/SHRA have been less robust. Guidance
has also eased a bit on the areal extent and duration of IFR
ceilings. With all that in mind, have attempted to target best
opportunity windows for prevailing thunder and vicinity mentions
otherwise. Also have not fully dropped the hammer on IFR
ceilings with current/upstream obs tending to be higher than
guidance would suggest. VFR conditions then return late in the
period.

&&

.HYDROLOGY...
Issued at 243 PM CDT Sat May 25 2024

The latest river forecasts utilizing QPF over the next 24 hours
(7am Sat-7am Sun) mainly suggest either steady or falling river
levels. Even higher end QPF simulations based on recent HEFS
30% exceedance probabilities yield similar results as sites
either have 1) sufficient storage capacity, or 2) are already
at such elevate flows that more appreciable precip would be
needed for additional rises.

The only exception to this would be locations below Lake Red
Rock where the combination of runoff and Corps of Engineer
releases may bring more significant within bank rises, or
potentially minor flooding. Ottumwa may reach minor Flood Stage
Sunday night, but confidence is medium at best and is dependent
on rainfall and future reservoir release changes, so a River
Flood Watch has been issued for Ottumwa for the time being until
confidence in flooding increases.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Curtis
HYDROLOGY...Small