623
FXUS63 KDMX 300757
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
257 AM CDT Tue Jun 30 2026

.KEY MESSAGES...

- The heatwave continues, with extreme heat running through the
  4th of July weekend. The Extreme Heat Warning continues area-
  wide today.

- Additional daily thunderstorm chances run through the week,
  with the potential for severe weather today (Marginal/1 of 5),
  Wednesday (Slight/2 of 5), and Thursday (Slight/2 of 5).

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 254 AM CDT Tue Jun 30 2026

In the immediate term this forecast period, a complex of
thunderstorms in Nebraska and southeastern South Dakota is making
its way to the east/northeast and is expected to clip the northern
fringes of the forecast area, which may bring some localized relief
to tomorrow`s heat. These storms are currently riding a Theta-E
gradient which will limit coverage greatly to northwest and north
central Iowa. This activity is expected to move through the area in
the very early morning hours and exit a couple of hours after
sunrise. The primary hazard is damaging winds with D-CAPE values on
the order of 1500 J/kg. Mid-level lapse rates of 7-7.5 C/km would be
supportive of smaller hail, but this is negated by a high freezing
level.

The highest point of confidence going forward in the short term is
the ongoing heatwave continuing. The high is still sitting over the
Southeastern U.S. This leads to another day of ample southwesterly
flow. Highs forecast in the lower to mid 90s. Combined with
dewpoints in the upper 60s to the mid 70s across Iowa, heat indices
will be hovering in the low 100 degree range. The high isn`t
expected to go anywhere come Wednesday, although slightly less
moisture is fed into the area leading to slightly lower dewpoints
and slightly lower heat indices. While we are expected to remain in
southwesterly flow, little relief is still expected as overnight
lows are still expected to stay in the mid to upper 70s, mainly in
areas along and south of I-80. Areas further north may have more
overnight relief due to lingering effects of overnight thunderstorms.

Of lower confidence this forecast period is continued low
thunderstorm chances as another shortwave is expected to ripple over
part of Iowa. There will be plenty of CAPE around with deterministic
guidance showing MLCAPE values in the neighborhood of 2500-3000 J/kg
across much of the area and mid-level lapse rates as high as 8 C/km
will support some level of convection, but weaker shear across Iowa
will be the limiting factor. Additional thunderstorm chances exist
on Wednesday with a greater severe potential across our CWA.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 256 PM CDT Mon Jun 29 2026

A similar pattern remains in place through Saturday. High pressure
to our southeast will keep the heat and humidity in place,
especially across the central and southeast part of the state. Heat
indices may drop a tad, but the danger may lie more in the continued
days of heat, and the lack of overnight relief with lows in the
upper 70s. Therefore, the extreme heat warning has been extended for
a large part of the state through at least Wednesday with
anticipation of possible further extension in the coming days. As
has been talked about the last few days, the heat is expected to
continue through the 4th of July weekend, where heat indices on the
order of 100 are still being forecast. Storm chances will continue
each day, particularly in the western and northern part of the
state, as the ring of fire pattern continues. The usual pattern will
continue to be large instability built up during the day, LLJ surges
at night, and initiates storms overnight that attempt to push east
through the highly capped environment over our CWA. Though marginal,
it is also worth mentioning the excessive rainfall outlooks across
Iowa. With large PWAT and storm chances, chances for flash flooding
can`t be ruled out on any given day. Per the usual for this time of
year, these storm chances will be highly uncertain in their exact
timing and intensity.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1109 PM CDT Mon Jun 29 2026

VFR conditions are expected to prevail through the end of this
TAF period. Confidence is high that LLWS will be present at all
sites during the early morning hours. Storms will be possible
in NW Iowa this morning but confidence is too low to issue
PROB30s at KFOD and KMCW. Winds will begin to increase Tuesday,
with gusts reaching up to 25kts.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 9 PM CDT this evening for
IAZ004>006-015-023-024-033-034-044-045-057-070.
Extreme Heat Warning until 10 PM CDT Wednesday for IAZ007-016-
017-025>028-035>039-046>050-058>062-071>075-081>086-092>097.

&&

$$

SHORT TERM...67
LONG TERM...De Bruin
AVIATION...Bury/TDR