363
FXUS63 KDMX 041949
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
249 PM CDT Fri Jul 4 2025

.KEY MESSAGES...

- Warm and dry today with increasing cloud cover overnight.

- Showers and thunderstorms move in from west to east late
  tonight into early Saturday. Small hail and gusty winds are
  possible.

- Another round of thunderstorms will develop over northwest
  Iowa and drop southeastward through the state tomorrow
  afternoon into the evening. Damaging winds and small hail are
  the main concern, as well as locally heavy rainfall.

- Cooler and drier on Sunday, then active pattern continues through
  next week.


&&

.DISCUSSION...
Issued at 230 PM CDT Fri Jul 4 2025

It`s been a beautiful Independence Day so far, with photogenic,
cumulus filled skies, warm temperatures, and breezy winds. Dewpoints
have stayed a bit more steady today, thanks to the better
mixing/breezier winds helping to disperse the corn`s moisture.
Temperatures are in the upper 80s and will make a run for the
low 90s, but still a degree or two less. All this to say, heat
indices should be a bit more manageable compared to yesterday,
peaking in the mid to upper 90s. Tough to draw up a better
summer day for holiday plans, especially those that involve a
body of water!

This warm summer day comes thanks to a narrow upper level ridge
parked over Iowa, which will slowly drift eastward as an upper level
wave ejects around it from the west. As this occurs, a better fetch
of gulf moisture will pivot into western Iowa. This moisture,
combined with warm south southwesterly flow and synoptic forcing
around the wave will bring the return of shower and thunderstorm
chances beginning late tonight into early Saturday morning. The
overnight/early morning storms will be elevated and only working
with around 1000 to 1500 J/kg of most unstable CAPE, which should
help limit severity. This is especially true with warm and moist
vertical profiles which will inhibit large hail production.
That said, with 1000+ J/kg instability, can`t rule out at least
small hail with stronger updrafts. Likewise, wind can always be
sneaky overnight, even with elevated storms. DCAPE values
overnight will still be over 1000 J/kg out ahead of any storms,
so could certainly see some gusty winds out of storms into the
morning. Fortunately, weak, unidirectional flow through the
column will limit the amount wind shear overnight and into the
morning, decreasing the risk of organized storms/widespread
severe weather.

As the wave continues northeastward through tomorrow, a cold front
will be pulled through the state, eventually firing off a second
round of storms in northwest Iowa as the atmosphere continues to
destabilize through mid-day. This roughly southwest to northeast
oriented line will make its way southeastward through the afternoon
and evening hours, bringing storm chances to most of the state.
Instability values will work to recover from any residual morning
storms, eventually increasing to the 1500 to 2000+ J/kg range by the
afternoon. This will increase the chances for stronger storms, but
the flow through the column never really improves through Saturday
afternoon. With a lack of any shear, strong, organized storms appear
unlikely, but the risk for a few severe wind gusts and hail remains,
especially as storms initially develop. Due to the unstable, but
weakly sheared environment, cold pools will also struggle to stay in
balance. This will likely lead to storm outflows outrunning the
synoptic boundary and coincident convection, limiting the wind
threat with any storms behind the outflow. The storm prediction
center has a marginal risk for severe weather over the area,
reflecting this weakly sheared but unstable boundary passage. In
addition to the severe weather chances, heavy, efficient rainfall is
possible with any thunderstorms. Convection should be progressive
enough to avoid prolonged periods of heavy rainfall over one area,
but will still be monitoring for potential hydrological impacts due
to heavy rain.

The boundary will depart the southern portions of the area by around
midnight tomorrow night, leaving generally dry and slightly cooler
conditions on Sunday. Unfortunately, this will only be a brief break
from precipitation as next week again looks active with zonal to
northwesterly upper level flow overhead with multiple shortwaves
producing convection in vicinity to the state. The next chances in
proximity to the state look to be late Sunday into Monday, but
predictability is quite low in these zonal flow regime.
Therefore, the important takeaway is more active weather with
multiple thunderstorm chances around the state lasting through
the remainder of the forecast period.


&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1231 PM CDT Fri Jul 4 2025

VFR conditions prevail with breezy south southwesterly winds.
Scattered cumulus at around 5000 to 6000 ft has begun to
develop early this afternoon, and will likely persist through
sunset. Winds die down overnight, but cloud cover and
precipitation will increase from west to eat into the morning
hours. Showers and thunderstorms are possible at all sites
tomorrow morning and into the afternoon, but confidence is
highest in sites over northern Iowa. Storms will also be
accompanied by MVFR to potentially IFR ceilings, again most
likely over northern Iowa.

&&

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

&&

$$

DISCUSSION...Dodson
AVIATION...Dodson