335
FXUS63 KDMX 151918
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
218 PM CDT Wed Jul 15 2026

.KEY MESSAGES...

- Hot and humid conditions continue through the weekend with
  heat indices nearing 100 degrees on Friday.

- Patchy fog development is possible once again tonight, mainly
  across northern and northeastern Iowa.

- Low (~30%) precipitation chances return tomorrow and again on
  Friday to southern and southeastern Iowa.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 217 PM CDT Wed Jul 15 2026

A high pressure system pancaking much of the central United States
right now hasn`t gone anywhere, leading to another hot and humid
evening with light and variable winds. Both temperatures and
dewpoints were changed for the short term period. Temperatures were
poked down a degree or two across much of the state, while dewpoints
are being nudged up a degree or two. Heat indices will still be
nearing the mid to upper 90s across much of Iowa today. Otherwise,
diurnal cumulus has formed across much of the state, which is
anticipated to dissipate around sunset.

Moving into tonight, plenty of moisture, calm to light winds, and
clear skies means patchy fog could develop overnight. For now, the
best area looks to be across northern and northeast Iowa. As with
previous nights, fog that does develop will be pretty shallow and
minimal impacts are expected with the fog burning off after sunrise.

Tomorrow will be more of the same; hot, humid, and light winds. As
an upper-level trough swings across the northern US, the high which
has been sitting over the plains will be shunted west slightly. With
this, low rain chances return with the potential for popcorn
thunderstorms in southern and southeastern Iowa. CAPE is plentiful,
the moisture is there, except shear is lacking. Anything that does
manage to pop up will be short-lived and isolated. With this
potential for thunderstorms, cloud cover is expected to be increased
slightly. The forcing mechanism for this looks to be a vort max that
lifts up into Iowa from Missouri. At the same time, forcing looks to
be pretty limited from this. The potential for thunderstorms will
diminish after sunset, leading to clear and dry conditions tomorrow
night.

More precipitation chances return Friday as the high continues to be
shunted west, putting us on the periphery of the upper level ridge.
At the moment, the influence of the ridge looks to be too great for
widespread precip in our forecast area, with the same area from
Thursday having the highest (30-50%) chances. It`s the same story
with plenty of CAPE and moisture, but little to no shear or forcing.
Otherwise, Friday looks to be the warmest day of the week with highs
currently forecast to be in the low to mid 90s. Combined with high
dewpoints in the 60s and 70s would lead to heat indicies reaching
for 100 degrees across parts of Iowa. Depending on trends through
the rest of today and tomorrow, combined with warm overnight lows,
heat headlines will need consideration for Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Issued at 217 PM CDT Wed Jul 15 2026

Over the weekend, the ridge which has been over the region will
continue to break down as the high weakens, putting us on the
periphery of it through the weekend and into early next week. The
most notable feature currently in the long term forecast is the
potential for a shortwave to affect the region Sunday night into
Monday which could lead to shower and thunderstorm potential
returning to the area. At the same time, LREF ensemble clustering
shows the ridge may continue to hold out which would lead to a
higher potential farther to the east. At this point, it`s too far
out to try and pinpoint a location. Otherwise, warm and humid
conditions continue before the ridge breaks down further, bringing
some amount of relief from the heat during the early part of the
workweek.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1224 PM CDT Wed Jul 15 2026

VFR conditions are expected to prevail at all sites through
much of this period. Fair weather cumulus have developed with
bases as low as FL025, although with limited coverage, TAFs have
been left in VFR. After sunset, the cumulus clouds will
dissipate, leading to clear skies overnight. As has been the
case for several nights this week, there is a potential for
patchy fog to develop, mainly in northern and northeastern Iowa.
Confidence is too low to mention in TAFs at this time, but will
be monitored for future issuances.

&&

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

&&

$$

SHORT TERM...67
LONG TERM...67
AVIATION...67