523
FXUS63 KDMX 130749
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
249 AM CDT Mon Jul 13 2026

.KEY MESSAGES...

- Our slow warmup continues each day this week, with actual
temperatures in the low and possibly mid 90s. Heat indices may
approach 100 at times, particularly mid to late week.

- Shallow, patchy fog possible early this morning, particularly
  in southeast Iowa.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 246 AM CDT Mon Jul 13 2026

High pressure and subsidence dominates across the central US this
overnight as revealed by GOES channel 13 with a near perfect circle
of clear skies from Colorado to Indiana. The sfc high is sitting
over southeast Iowa, and the most calm winds are expected there
tonight into early this morning. Radiative cooling is well on track
currently, and brings in another sunrise timeframe with patchy fog
potential. The near term forecast is quite similar to last night`s
conditions that produced some shallow patchy fog in north and west
Iowa. However, calm winds may be more favorable in southeast Iowa
this time. Fog is not expected to be widespread, but some low lying
portions of southeast Iowa highways could see steep visibility
reductions until 7am. Similar conditions are possible Tuesday
morning.

Surface heating should have no issues recovering through the day
today. Highs may be somewhat uniform across the state for today and
tomorrow, though it will be a balancing act of a couple factors.
850mb temps will be a bit warmer across the north, where westerly
winds dominate and remnants of an EML clip our CWA. However, this
sits above an area of the state that has better soil moisture, and
like yesterday is expected to retain higher dewpoints which may
reduce the ability to mix down the warmer 850mb temps. In central
and southern Iowa, dewpoints and soil moisture may be just a tick
lower, and allow extra heating to match or exceed that in northern
Iowa. Highs Tuesday will increase by a few degrees more as the
stagnant airmass is heated further.

As far as dewpoint forecasting over the next few days, pick your
favorite boundary layer scheme, models are all over the place. The
dewpoint near DSM for example is anywhere between 60 and 75 across
the model suite Tuesday afternoon. Expectation is that widespread
evapotranspiration will be enough to counter mixing down of fairly
dry mid-levels. Most areas will keep mid 60s dewpoints, even at peak
heating, and areas with better soil moisture, crop maturity, and
reduced turbulent mixing will break into the 70s. Regardless, this
is generally too low to have a large effect on heat indices.
Therefore, headlines will not be needed in the short term. However,
wet bulb globe temperatures will be near 85 on Tuesday given heat,
lack of breeze, humidity, and ample sunshine. So, despite not
meeting heat headline criteria, the middle of the afternoon,
particularly Tuesday, will be a sweltering time to be doing
work or exercise outside.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 228 PM CDT Sun Jul 12 2026

A Canadian long wave trough will dig southeastward into the
northeastern CONUS through mid- to late- week, which attempts to
shunt the 500 mb ridge overhead back to the west. As this occurs,
the surface high pressure will begin to weaken, transitioning us to
a more transient surface pattern over Iowa. This increases the
spread in temperature solutions among deterministic and ensemble
guidance through the end of the week. The general trend seems to be
continued warming into the weekend, although NBM may be running too
hot with forecast highs in the mid 90s and dewpoints in the 60s.
Should dewpoints increase into the 70s, highs would likely be closer
to the low 90s. Adjustments have been made to the forecast to
account for this, but will need to continue to monitor trends.
In addition to temperatures, the weakening high and increased
moisture Thursday into Friday may bring back rain chances to the
state. This is a low confidence scenario, especially with the
late week pattern still in flux, so the forecast remains dry at
this time. Severe chances will be better assessed in the coming
days, but weak flow should help mitigate severe chances through
this period.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1052 PM CDT Sun Jul 12 2026

No changes from previous with light winds and clear skies
expected to prevail through the TAF period outside of the low
chance for patchy fog development into Monday morning. Best
chances still remain near KOTM and left 6SM BR from previous TAF
issuance. Although visby could drop lower at times, confidence
in those impacts within 5SM of the terminal is too low for
inclusion.

&&

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

&&

$$

SHORT TERM...De Bruin
LONG TERM...Dodson
AVIATION...05