335
FXUS63 KDMX 192018
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
318 PM CDT Sun Jul 19 2026

.KEY MESSAGES...

- Hot and humid today and tomorrow. Heat peaks on Monday, with a
  Heat Advisory across the entire forecast area from noon to 8pm.

- Two rounds of storms are possible on Monday: The first in the
  morning and again in the later afternoon through the evening.
  Severe storms are expected and may produce damaging winds,
  along with hail and heavy rain. There is also a low tornado
  threat, highest in northeast Iowa.

- Cooler temperatures return into midweek in the upper 70s to
  80s and dry until Wednesday evening

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 318 PM CDT Sun Jul 19 2026

A look at surface conditions this afternoon per GOES satellite
imagery shows a blanket of smoke covering much of roughly the
eastern third to half of Iowa, but especially into Wisconsin and
Illinois where it is notably thicker. This is thanks to an area of
high pressure that is centered over the Great Lakes, which is moving
this lingering wildfire smoke from the Ohio Valley into Iowa from
the southeasterly flow. Sites such as Mason City, Waterloo and
Ottumwa were reporting visibility values anywhere between 2-5
statute miles due to this smoke, with light wind also reported. This
smoke per guidance is expected remain over these areas due to little
change in the flow pattern, before gradually departing through
Monday morning given an expected pattern change. The Iowa Department
of Natural Resources has issued an Air Quality Alert through 11am
Monday for the eastern half of Iowa due to this smoke. Those
especially sensitive to smoke should limit time spent outdoors as
needed. Outside of the smoke, seeing a streak of clouds over
southwest Iowa that is associated with pooling theta e advection
against the dominant area of high pressure. The instability gradient
in this strip of clouds is indicating values generally less than
1000-2000 J/kg, paired with weak flow that will allow for clouds to
remain in this area, along with a very low chance for a diurnally
driven isolated shower or storm into the early evening. A larger
area of clouds moving across northwest Iowa from decaying
morning convection over the Dakotas will allow for a general
increase in upper level cloud cover across Iowa, along with the
development of scattered diurnally driven cumulus, but shouldn`t
hinder highs today from reaching forecast values in the mid 80s
to low 90s, warmest south.

Into this evening, the high pressure system will slowly dive further
southeast out of the region, with attention turning to a rather
potent shortwave over southern Canada that is expected to move
east/southeast to the Upper Midwest into Monday morning. Ahead of
this feature, a boundary will extend down through Minnesota and into
northern Iowa, which per guidance will bring the next chance for
showers and thunderstorms. Latest CAM guidance has slowed the
arrival of this boundary, with dry conditions likely holding on
until near/after sunrise when scattered showers and storms push into
northern Iowa. While the better forcing is located further north and
east of the state, should still see enough lift near the boundary to
allow for elevated storm development that will be aided by
environmental conditions of shear around 30-40 knots and MUCAPE
values around 1000-2000 J/kg to produce sub severe to isolated
severe wind gusts and small hail. Could also see localized areas of
efficient rainfall with this activity, given PWATS around 1.75-2
inches and high warm cloud depths, leading to rainfall amounts up to
an inch and potentially locally higher amounts.

This activity is only the first round of storms for the day, as
additional activity is expected to occur into the afternoon and
especially through the evening/overnight. Before we get into those
details, lets discuss the setup. The low-level flow will increase
out of the southwest, increasing theta-e advection across the entire
forecast area, which will bring much warmer and humid air into the
region. Despite the morning storm potential in northern Iowa, should
see a window of returning dry conditions and decreasing clouds in
these areas that will allow for temperatures to increase
substantially into the mid to upper 90s over much of Central Iowa,
paired with dewpoints through the 70s. This will allow for heat
indices to top out in the 100-105 degree range across the forecast
area into the afternoon, with high enough confidence resulting in
the coordination and issuance of a Heat Advisory that is in effect
from noon to 8pm. Heat safety measures need to be practiced to avoid
negative impacts from these conditions.

The hot and humid conditions, paired with the closer proximity of
better mid and upper level support from the deepening trough
traveling southeast across the Midwest will lead to returning
chances for scattered showers and thunderstorms into Iowa with and
near the surface boundary later in the afternoon and especially
evening/overnight. Regarding the specific details, could see initial
isolated storm development just ahead of the boundary around mid-
afternoon over northern Iowa, followed by more scattered activity by
evening. Model guidance has been struggling to agree on how fast
this boundary sinks through the area, with variations of the front
anywhere from north central to south central Iowa after sunset.
While timing details will need to be watched over very closely, the
environment regardless of position of this front will be more than
conducive for strong and even severe thunderstorm development
as organization takes place, given instability values over 4000
J/kg and shear values around 50-60 knots, along with steeper
lapse rates near 7-7.5 C/km. The main hazard of concern remains
damaging wind gusts, especially later on as storms congeal into
a line, though large hail initially is possible, as well as a
few tornadoes mainly in northeast Iowa given closer proximity to
the surface low. Heavy rain is also expected at times due to
PWATS around 2-2.25 inches and warm cloud depths over 15 kts,
with rainfall amounts in spots possible up to 1-2 inches and
slightly higher amounts in localized areas. However, the
flooding threat is minimal given antecedent dry conditions and
the expected progressive movement of any storms.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 318 PM CDT Sun Jul 19 2026

Showers and thunderstorms will likely carry primarily a wind threat
into the night, before decreasing near/after sunrise. With the front
through the majority, if not all of Iowa, northwest flow and cool
advection will spread across Iowa, leading to slightly cooler
temperatures and drier air. With this shift in the flow, HRRR smoke
guidance indicates the return of wildfire smoke into Iowa from
Minnesota, leading to additional hazy skies and at least some
possible lowering of visibilities. Surface high pressure though will
lead to dry conditions through the rest of the day as this feature
descends across the Central Plains and through much of Wednesday.
Conditions will remain comfortable through midweek as northwest flow
remains, with temperatures largely in the upper 70s to 80s and
dewpoints in the 50s to low 60s. A weak wave skimming southwest Iowa
Wednesday evening looks to bring returning chances for rain and
possible thunderstorms, while additional waves riding the upper
level flow follow this activity that will bring additional periods
of active weather through late work week. Details regarding these
systems will be better known in the coming days. Ridging then builds
over the southwestern CONUS that will slowly influence temperatures
through the weekend as highs gradually return into the 90s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1248 PM CDT Sun Jul 19 2026

Haze due to smoke will continue to linger at/near the KALO and
KOTM terminals in the near term, then gradually lift through
this evening and especially Monday. Otherwise, generally VFR
conditions are expected outside of some potential short-lived
MVFR ceilings due to spotty cumulus development. Otherwise mid
to upper level clouds increase most notably near the latter
portion of the period, with a low potential for storms in
northern Iowa and therefore the addition of PROB30 mentions in
this issuance. Further details regarding exact timing and
coverage will need to be refined in future updates. Light
southeast winds will gradually shift SW late in the period and
become breezy.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 8 PM CDT Monday for IAZ004>007-
015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097.

&&

$$

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