616
FXUS63 KDMX 141139
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
639 AM CDT Mon Jul 14 2025

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

.KEY MESSAGES...

- Dense fog expected over southeastern Iowa this morning

- Muggy conditions return to start the week with dew point
  temperatures rising back to near 70F

- Next widespread chance (40-70%) of rain returns to the region
  beginning early Wednesday through the rest of the work week.

&&

.UPDATE...
Issued at 345 AM CDT Mon Jul 14 2025

Isolated areas of patchy fog has developed once again in Iowa this
morning, considering very light winds and clear skies, with most
areas in the CWA seeing around 3-5 statute mile visibilities.
However, higher moisture content over the southeastern portion of
the state has led to the formation of dense patchy fog, with the
Ottumwa ASOS reporting visibilities around a quarter mile as of 3am.
HREF and latest HRRR guidance has trended upward on dense fog
covering much of southeast Iowa, which makes sense given conditions,
so have decided in coordination with neighboring eastern and
southern offices to issue a Dense Fog Advisory until 9am for
portions of southeast Iowa. Low visibilities around or below a
quarter mile are expected at times, so extra caution will be needed
when traveling this morning. After sunrise, winds will increase and
the inversion will fade, leading to dissipating fog and improving
conditions.

Outside of the fog this morning, the forecast remains on track to
remain dry today and throughout Tuesday, with temperatures generally
in the upper 80s as southwest flow remains overhead. Of note is that
the timing for the next chance for showers and storms per latest
model guidance has slowed slightly, with most members generally
keeping Iowa dry until closer to midnight into Wednesday. Increasing
moisture advection into the Midwest and a gradually sinking frontal
boundary draped over central Nebraska into northwest Iowa and
southern Minnesota, along with the development of a 30-35 knot LLJ
into western Iowa will result in the forcing necessary to develop
showers and storms into the region, with a MCS looking to drop
into northwest Iowa and track southeastward as it gradually
weakens through Wednesday morning. Model soundings indicate
elevated convection, with gusty winds looking to be the main
concern given DCAPE values around 1000+J/kg, outside of
favorable shear and instability into northwest Iowa, and
becoming less favorable further southeast. The Marginal Risk
into northwest Iowa early Wednesday per the SPC seems reasonable
given that isolated severe weather may occur from this given
the above setup as discussed. Following the weakening system,
model guidance gets quite messy, as solutions range from mostly
dry to seeing scattered lingering showers and storms until late
Wednesday, when the boundary then somewhere over
central/southern Iowa looks to kick off more widespread
activity. This variation in solutions makes sense, as activity
later on will largely depend on how the morning system evolves.
A close eye will remain on this activity, with more details
expected over the next few days as more models capture this time
period.

&&

.DISCUSSION...
Issued at 240 PM CDT Sun Jul 13 2025

The anomalously dry air mass (PWAT of 0.71" on OAX`s 00z
sounding puts it in just the 10th percentile per SPC`s
sounding`s climatology) that made a brief appearance yesterday
and today disappears quickly tonight as moisture advection and
typical mid-summer Iowa humidity returns to begin the week. As
this begins, short-range CAMs consistently depict a decaying
low-level boundary and weak convection initiating & dropping
thru S MN late this evening and overnight. However, unable to
sustain moisture enough to overcome the drier air mass, no
solutions sustain this activity into northern sections of the
CWA. So for now - will keep silent precip chances across the far
north. Additionally, added patchy fog mention in far southern
Iowa late tonight & early Monday as clear skies combine with
light winds to narrow dew point depressions to near saturation.

Flow turns zonal for Monday & southwesterly for Tuesday as the
pattern buckles ahead of the next wave moving into the Pacific
Northwest. Continued low-level warm-air thermal advection both
days will push afternoon highs back into the upper 80s to near
90F. In the absence of any forcing the bulk of both days will
remain dry. However, it`ll feel noticeably muggier both days as
surface dew points return back to around 70F.

By Tuesday night, the first shortwave kicks out into the
region, bringing perhaps a MCS and next shot of moisture into
the state late. The boundary will remain in the vicinity for
Wednesday and into Thursday. This will be our best window of the
week for widespread precipitation. Another week, another shot
at several inches of rainfall. Deep layer shear makes a return
as well during this period as right entrance of upper-level jet
moves across the state. This will aid convective organization
through the period. Any severe potential will be refined in the
coming days as the mesoscale details can be resolved.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 639 AM CDT Mon Jul 14 2025

Dense fog will continue to impact KOTM over the next few hours,
then will improve as fog dissipates later this morning.
Otherwise, more isolated patchy fog across much of Iowa this
morning will also fade over the next few hours, with widespread
VFR conditions expected across the terminals by mid morning and
remain through the rest of the period. Winds will generally be
light out of the south, with mostly clear skies today.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CDT this morning for IAZ062-074-
075-083>086-094>097.

&&

$$

UPDATE...Bury
DISCUSSION...Hahn
AVIATION...Bury