677
FXUS63 KDMX 121747
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1247 PM CDT Sat Jul 12 2025

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

.KEY MESSAGES...

- Mainly dry this weekend, with a low potential (<20%) for
 showers and storms north Sunday afternoon to evening

- Looking more active Tuesday and beyond with on and off chances
  for showers and thunderstorms

- Late next week, cooler temperatures arrive for Thursday and
  Friday.

&&

.UPDATE...
Issued at 358 AM CDT Sat Jul 12 2025

Conditions have generally turned quiet across the state, with
surface high pressure currently over Nebraska and South Dakota,
which will continue to pass over the Midwest today. Given previous
rainfall and light winds over portions of east/southeast Iowa,
patchy dense fog has developed, with a handful of sites reporting
visibilities less than a mile. Given little change in conditions
expected over the area until after sunrise when winds increase, have
issued a Special Weather Statement to highlight these low
visibilities. While expansion in coverage of this fog is not
anticipated, drivers should be extra careful in the affected area
this morning. Otherwise, winds today will turn breezy out of the
northwest, with gusts expected up to 20-25 mph while temperatures
reach into the low 80s. Sunday will see a shift in winds back
southwesterly, leading to slightly higher temperatures in the mid
80s. Model guidance generally hints at an increasing potential for
showers and possibly a few storms reaching into northern Iowa as a
boundary drops into the state Sunday afternoon into the early
evening. Given that the signal is fairly weak, have only introduced
low PoP mentions across the north in coordination with neighbors,
and will continue to monitor for further changes. Soundings indicate
favorable shear and instability over the area that point to storm
development, though given weaker forcing, the overall potential is
lower end at this time. General thunder per SPC guidance is
highlighted over northern Iowa to highlight the potential. Rainfall
amounts look to remain generally under a half inch with any
showers/storms that are able to develop.

&&

.DISCUSSION...
Issued at 147 PM CDT Fri Jul 11 2025

TODAY...Thunderstorms capable of heavy rain, damaging wind, and
event a few tornadoes are expected this afternoon and evening.
Early afternoon satellite and radar imagery shows storms across
much of the region as of 2PM. For the rest of today, multiple
rounds of storms could lead to heavy rain and flooding. There is
also a severe weather threat with these storms, with damaging
wind and a few tornadoes being the primary threat.

A weak surface low was centered across southern Iowa, with
southeast winds ahead of it.Temperautres were in the mid 80s,
with dewpoints in the mid to upper 70s. This warm and unstable
airmass will be the main driver for thunderstorms today, while
upstream an upper level wave along the IA/NE border will
provide the forcing for ascent.

The main question will be how long storms will be discrete in
the warm sector, vs how quickly they will grow upscale into a
line. This is one of the key factors for whether or not
tornadoes or damaging wind will be the primary threat. Even if
storms do develop into a line, the low level shear could support
QLCS tornadoes, so have a Tornado Watch in effect for mainly the
Southeast part of Iowa, including the Des Moines metro. North of
this, a severe thunderstorm watch is in effect, where confidence
is higher in a wind and/or hail threat.

In addition to the severe threat, heavy rain is also a concern
given the PWAT values near or above 2 inches. Training storms
along an ill-defined warm front could produce rainfall totals
of 2 to 3 inches, with a few pockets close to 4 inches based on
the local probability matched mean of the HREF.

SATURDAY THROUGH FRIDAY...Storms will move east tonight, and the
weather will dry out over the weekend and into early next week.
The next chance for storms will be Tuesday into Wednesday as a
cold front moves through the region. A few storms could be
strong to severe, but as of now there isn`t a signal that this
will be anything noteworthy. Looking ahead, if the cold front is
able to push through, temperatures will cool off toward the end
of week, with highs closer to 80s. If it hangs up across the
region, then expect continued chances for showers and
thunderstorms.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1243 PM CDT Sat Jul 12 2025

BKN deck across the southeast will become SCT and VFR this hour
as the atmosphere mixes. Short-lived MVFR from HZ possible at
times this afternoon. Transient enough to leave it out of the
TAF, but will monitor the short term. Additional smoke should
stay aloft across the north, hence the high-level ceiling
preserved for the period. KALO and KDSM may see fog tonight as
winds become light. Have left as BCFG for now, but will evaluate
for VSBY restrictions for the next issuance.

&&

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

&&

$$

UPDATE...Bury
DISCUSSION...
AVIATION...Jimenez