859
FXUS63 KDMX 131732
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1232 PM CDT Tue Aug 13 2024

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Patchy fog early this morning with some lingering drizzle/mist
  possible southwest half.

- Showers and thunderstorms return late tonight into Wednesday
  and again Wednesday into Thursday. Heavy rain and a few strong
  to severe storms are possible.

&&

.DISCUSSION...
Issued at 358 AM CDT Tue Aug 13 2024

Active pattern ahead over the next several days with multiple rounds
of showers and storms starting late tonight and continuing into
Thursday.

Prior to that, we start the day today with patchy fog that
has been locally dense at times with visibilities as low as 1/4 to
1/2 mile. Lowest visibilities have mainly been transient through the
early overnight hours precluding a fog headline at this point but a
SPS remains in place. Fog should dissipate shortly after sunrise
though some lingering drizzle/mist is certainly possible underneath
the stratus deck which is firmly in place over roughly the southwest
half of the state. With additional cloud cover moving in later today
into tonight, sunshine may be harder to come by for all but the
northeast but even then may be filtered today with upper level smoke
moving into the state from western wildfires. Temperatures as a
result remain below normal through much of the area and in the 70s
with areas northeast potentially seeing the highest max
temperatures.

Theta-e advection increases late tonight into early Wednesday with
showers and storms returning to the forecast ahead of a low lifting
out of KS/NE overnight into Wednesday. The nose of an increasing 35-
45 knot low level jet will help keep rain/storms going through the
night and although can`t completely rule out some stronger storms
with moderate shear, generally weak instability should limit storm
strength. Pwats of 1.5 to nearing/exceeding 2" will keep a locally
heavy rainfall threat nearby, but guidance into 12Z Wednesday mainly
keeps the highest QPF values just outside of our area for the most
part with a localized 1-2" amount possible in the far southwest.

How activity evolves through the night and the amount of lingering
cloud debris Wednesday morning will have a significant impact on our
next storm threat Wednesday night into early Thursday as the next
wave moves through. Forcing overall looks a bit stronger with the
potential for much higher values of instability if atmospheric
recovery can occur. Soundings suggest the potential for long,
looping hodographs with low LCLs putting all hazards on the table if
surface-based convection can be realized. Depending on storm mode
and the effects of early day activity/clouds, some strong to severe
storms are certainly possible with wind or hail, as well as another
heavy rain threat with pwats near to exceeding 2" again fueled by a
stronger low level jet. Will need to continue to monitor trends
through the day but see SPC Day 2 Marginal (Level 1/5) to Slight
(Level 2/5) Risk for further details.

Additional storms are possible on Thursday into early Friday before
another break in activity occurs through at least part of the
upcoming weekend as an upper level ridge builds in.
Temperatures return to more normal levels with increasing
humidity values by mid-late week into the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1232 PM CDT Tue Aug 13 2024

MVFR to IFR stratus across the area is starting to break up but
will continue to impact sites through the afternoon. Winds will
start to increase tomorrow morning ahead of the next approaching
system, with gusts around 20kts. A few showers may reach
KFOD/KDSM/KOTM at the end of the current period as overnight
storms in southwest Iowa weaken and lift into central Iowa
through the morning. For now have kept from TAF as there is
uncertainty as to how scattered they will become by the time
the reach TAF sites.

&&

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

&&

$$

DISCUSSION...KCM
AVIATION...Hagenhoff