620
FXUS63 KDMX 271941
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
241 PM CDT Thu Aug 27 2026

.KEY MESSAGES...

- Dry conditions to continue tonight into Friday. Patchy fog
  possible in the early morning.

- Shower and storm chances return late Friday into Saturday,
  with a low risk of severe weather. Additional storm chances
  will continue at times into early next week.

- A pattern change will lead to warming temperatures and higher
  humidity. Heat indices will be in the 90s.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 240 PM CDT Thu Aug 27 2026

A big picture look at the upper level flow pattern shows a large
ridge across the northwestern CONUS, while a broad trough covers the
Great Lakes, with its western fringe over eastern Iowa. This setup
is leading to the continuation of northwesterly flow overhead, with
surface flow light out of the northwest as a vertically elongated
area of high pressure slowly sinks into the Midwest. As a result,
drier air continues to filter into the state, leading to benign and
rather comfortable weather conditions as dewpoints sit in the mid to
upper 50s. Despite the drier airmass overhead, diurnal cumulus has
developed over much of the forecast area per satellite imagery, with
efficient warming between the clouds allowing for temperatures this
afternoon to reach into the upper 70 to low 80s. After sunset, winds
will generally turn variable and very light to calm into the
evening, paired with expected clear skies. These conditions should
lead to optimal viewing of the partial lunar eclipse. Some presence
of at least surface moisture could lead to patchy fog formation by
early Friday morning, with areas of eastern Iowa signaled in CAMs to
see formation of fog, but could also occur in river valley areas.

Something to keep an eye on is the signal for the development of
showers and thunderstorms over eastern Nebraska per CAM guidance
into Friday morning, which occur as the low level jet (LLJ)
strengthens over the western Great Plains. This activity looks to
sink southeast with time through the morning, which has a low
potential to skim southwest Iowa near sunrise through mid-morning.
Limiting factors working against this activity making it into Iowa
though is comparatively weaker forcing further east, along with
the surface high pressure remaining overhead keeping drier air
in the state. Have kept the forecast dry in the southwest as a
result, but will continue to monitor.

Dry weather is expected to continue throughout Friday as the surface
high pressure system remains present across much of Iowa, but will
see a gradual shift back to southwesterly flow in the low levels
ahead of an approaching area of low pressure entering the western
Central Plains. Highs will be slightly warmer as a result, paired
with mostly sunny skies as highs reach in the mid to upper 80s. An
increase in theta-e advection is noted by Friday evening into
Saturday morning, maximized over far western Iowa into eastern
Nebraska/South Dakota. At the same time, the LLJ will develop again,
but further eastward as models depict it nosing directly into
central Iowa. This setup will be much more favorable for the
development of showers and thunderstorms, which are expected into
Iowa late Friday and especially through Saturday morning.
Model consensus in terms of coverage of this activity indicates
highest probabilities (60-70%) over northern Iowa through the
morning hours, while areas into central Iowa have slightly increased
chances (40-60%) with this forecast package, followed by drying
conditions into the afternoon. In terms of the environment
overhead, while shear increases to values around 40-45 knots,
MLCAPE values are rather meager being less than 1000 J/kg as any
storms would be elevated, given the low level warm layer
present in model soundings. Outside of some potential for sub-
severe winds with any storms, any severe weather risk remains
low.

Outside of the precipitation Saturday, a tightening pressure
gradient into western Iowa and the aforementioned increased
southwesterly flow will lead to breezy winds, with values expected
to top out around 25 to 30 mph across the forecast area, especially
over western Iowa throughout much of the day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Issued at 240 PM CDT Thu Aug 27 2026

Through the remainder of the weekend, the upper level ridge is
expected to shift further eastward over the Central CONUS, but also
become more squished south as a rather potent trough moves across
the Pacific Northwest. The net result will be a return of even
warmer and humid conditions through early next week as southwest
flow persists, with various shortwaves suggested to ride the upper
ridge, ultimately putting Iowa into a more active pattern for
various chances of showers and thunderstorms. With Iowa well into
the warm sector, capping looks likely at least on Sunday, keeping
chances for precipitation rather low (20-30%) until around Monday
evening/Tuesday when a cold front is suggested to push into Iowa.
More specific details are expected to become more clear in the
coming days for this time period. Temperatures will generally
top out in the upper 80s through the 90s, with central and
southern Iowa reaching near 100 degrees for heat indices Sunday
and Monday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1232 PM CDT Thu Aug 27 2026

Cumulus development continues to expand in coverage over the
forecast area, with ceilings near MVFR in spots but should
generally remain VFR. Clear skies are expected to return after
00z this evening, with winds becoming variable and very light to
calm into Friday morning. A signal exists at this time for
patchy fog development into the morning, though confidence on
this development and coverage is quite low at this time, so
have not included at any terminals and will continue to monitor
trends.

&&

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

&&

$$

SHORT TERM...Bury
LONG TERM...Bury
AVIATION...Bury