657
FXUS63 KDMX 130000
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
700 PM CDT Mon Aug 12 2024

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

.KEY MESSAGES...

- Lingering showers this afternoon will taper off, then patchy
  fog expected overnight into Tuesday morning.

- Showers and thunderstorms return late Tuesday evening into
  Wednesday and again Wednesday into Thursday. Heavy rain and a
  few strong storms are possible, but the overall severe threat
  is low.

&&

.DISCUSSION...
Issued at 230 PM CDT Mon Aug 12 2024

Showers have lingered across central Iowa for much of the day, due
in part to a trailing vorticity lobe behind the main shortwave that
passed over the area overnight and early this morning. CAMs have
struggled with this precipitation all day, squashing precipitation
with each new run. While models struggle with the evolution,
extrapolation of satellite and surface observations shows the weak
wave should pass out of the area late this afternoon. In the wake of
the system, overnight patchy fog is expected to develop  and last
into Tuesday morning. Widespread dense fog is not anticipated,
however the HREF does indicate pockets of visibility under 1 mile
are possible.

Tuesday will see a brief break from the activity, but as the upper
ridge shifts east it will bring with it a little more upper level
smoke from western US wildfires. Meanwhile, a low will deepen across
the central plains and lift out of Nebraska late Tuesday night and
into Wednesday across the area. Instability is fairly weak
overnight with modest shear around 30-40kts as the the nose of
the LLJ into SW Iowa helps fuels activity through the overnight.
While widespread severe storms are not expected, a few stronger
storms are possible as this passes over the area.

Quickly on it`s heels is a second more robust shortwave that will
move across the area Wednesday into Thursday. Timing and placement
inconsistency continue with the GFS a little slower and further
north than the EC. Shear and instability are displaced which
may limit more robust severe storms, but the slower flow will
contribute to a heavy rain set up, along with deep warm cloud
layers and PWATs over 2". In most cases rivers can take this
much precipitation, but there may be instances of ponding or
flash flooding, particularly in urban areas. Despite model
differences, at this time it appears both solutions are mainly
dry Friday into the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 658 PM CDT Mon Aug 12 2024

Lingering drizzle through 06z with fog already developing across
the southern half of the area. Have left out of KDSM and KOTM
for now as vsby restrictions appear more likely after 06z for
these sites. IFR fog and stratus to develop after 08z and last
through sunrise with MVFR cigs likely lasting through the TAF
period for KDSM and KOTM.

&&

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

&&

$$

DISCUSSION...Hagenhoff
AVIATION...Jimenez