269
FXUS63 KDMX 032330
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
630 PM CDT Thu Jul 3 2025

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Hot and humid today with a low chance (15% or less) for
  isolated storms east and northeast this afternoon/evening. If
  a storm develops, they could produce gusty winds and hail.

- Warm conditions continue tomorrow with increasing cloud cover
  into the afternoon and evening. Shower and thunderstorm
  chances return overnight into Saturday morning.

- Scattered showers and thunderstorms expected on Saturday,
  especially in the afternoon. A few stronger storms are
  possible, but widespread severe weather is not expected.

&&

.DISCUSSION...
Issued at 243 PM CDT Thu Jul 3 2025

It`s a hot and humid afternoon over Iowa with blue skies and light
to breezy winds. Dewpoints have skyrocketed into the mid 70s this
afternoon with ambient temperatures already in the upper 80s to low
90s early this afternoon. This has bumped heat indices up to the
upper 90s to even over 100 in some locations, further emphasizing
the hot conditions. While there is likely some minor advective
component to these moist conditions, the main driver of these higher
dewpoints today is likely evapotranspiration from the corn. As
the boundary layer continues to mix this afternoon, drier air
aloft should mix down and slow or reverse the increasing
dewpoints. That said, temperatures will continue to increase,
which could bring a few hours of heat indices between 100 to 105
still this afternoon. Along with these warm, moist temperatures
this afternoon is a very unstable airmass overhead.
Fortunately, a small amount of capping and the lack of any
forcing/lift to displace parcels will help to negate widespread
thunderstorm development this afternoon and evening. A pop up
shower/storm or two could still crop up in the east as winds
back slightly from southwestern into northeastern Iowa this
afternoon, although convergence would be very weak if any occurs
at all. If a storm does develop, there is a marginal risk for
severe weather (level 1 of 5) across the northeast, with the
main concerns being wind and hail, although the lack of shear
means pulsey, isolated storms. Moderate rainfall would also be
produced by any stronger updrafts that develop, but again, the
risk of anything developing in our forecast area is low (15% or
less).

Temperatures remain warm into Friday, as the approaching upper level
wave (and coincident clouds/precipitation) has slowed down a bit now
arriving a bit later in the day on Friday. This should keep skies
clear through at least mid-day for much of the forecast area,
allowing temperatures to again climb into the upper 80s to near 90.
Dewpoints will be similar to slightly lower, putting heat indices in
the mid 90s to near 100 again. By the afternoon and into the
evening, cloud cover will move in ahead of the approaching wave. The
slower and drier arrival of the wave should keep conditions dry
through much of the Fourth of July/Friday.

Shower and thunderstorm chances then return late Friday night to
early Saturday morning as theta-e advection increases and a low
level jet noses into the state. The profile will have plenty of
moisture present as this occurs, with 2+" PWATs and strong moisture
transport. That said, models continue to trend downward with
precipitation coverage and amounts as the trailing front moves into
the state, likely due to the better forcing departing north and east
with the main wave. This should help mitigate prolonged heavy
rainfall from this system, as the environment will be favorable for
heavy rainfall but likely won`t have the lift to produce consistent,
widespread storms. However, will want to keep an eye on high
resolution guidance as it comes in for Saturday afternoon and
evening, as the atmosphere will be quite unstable and any lift along
the cold front will be enough to produce storms over central Iowa.
The wind profiles are relatively benign, which should limit
organized convection, but could still see some small hail and gusty
winds with any more efficient updrafts. Likewise, locally heavy
rainfall will be likely under any stronger storms. Of course, severe
or not, thunderstorms always have lightning, so it`s important to
stay weather aware this weekend if you have any outdoor holiday
plans. Intermittent precipitation chances continue Saturday night
and mostly depart by Sunday, barring a few lingering showers/storms
in southeast Iowa. With the cloud cover and scattered precipitation
on Saturday and northerly flow behind the front on Sunday,
temperatures will be slightly cooler through the weekend with highs
reaching the mid to upper 80s. More precipitation chances return
then toward the start of next week as weak shortwaves pass through
what will be a zonal flow pattern. However, the spread between
models in regards to timing and location is quite large, so will
discuss that more as we go through the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 625 PM CDT Thu Jul 3 2025

Main terminal of concern in the short term in KALO.
Thunderstorms will linger near and over the site through sunset.
Highest gust seen was ~44kts. KMCW will have mostly showers
nearby over the next 2 hours and instability is focusing further
south. The rest of the TAF period will be dry with increasing
clouds from the west.

&&

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

&&

$$

DISCUSSION...Dodson
AVIATION...Jimenez