663
FXUS63 KDMX 302324
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
624 PM CDT Mon Jun 30 2025

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

.KEY MESSAGES...

- Showers and storms possible mainly across southern and eastern
  Iowa this evening (<30% chance). Gusty winds possible with
  storms, mostly in the southeast (<10% chance).

- Next best window for storms Wednesday night across the north
  (~40% chance).

- Showers and storms to be a common theme over the holiday
  weekend.

&&

.DISCUSSION...
Issued at 250 PM CDT Mon Jun 30 2025

Morning objective analysis highlighted the shortwave trough
over the region, this being the culprit for the shower and
storms in the north this afternoon. Instability in the north
being generated by the steepening lapse rates from the cooling
profile. The bulk of the instability has been squashed south of
the state due to the MCS this morning, but some will hold across
southeast Iowa this afternoon and evening, hence the marginal
threat for wind. Storm mode within the Marginal Risk will be
disorganized clusters, updraft columns that will collapse on
themselves. Inverted-V soundings will allow for strong cold
pools during the storm decaying cycle mentioned above,
contributing to the severe wind threat. Nonsevere gusty winds
will also be possible with showers in the north. The wind threat
statewide will diminish after sunset. PoPs have been kept low
as models have generally been too robust on precipitation
coverage through this morning and early afternoon.

High pressure follows the CAA regime and holds highs in the 80s for
another day. Its upper air reflection in the form of a ridge will be
building over the High Plains, keeping us in northwest flow for the
next several days. We`ll get a mixture of warming and synoptic
forcing in this regime, along with moisture return inching its way
in along the LLJ axis. An instability axis exceeding 2,000 J/kg
MUCAPE sets up in northwest Iowa, forming a N-S gradient somewhere
through central Iowa. An MCS will form along the LLJ nose, slowly
progressing southeastward through the night. It will initially
have an EBWD of ~30kts to work with, meaning there could be an
early window of severe storms. The instability axis itself
serves as another point of convergence, meaning some scattered
storms with some hail potential may form. The MCS will drop
south and east through the night as the jet veers, but will
encounter the apex of a ridge, a region of weak flow, causing
storm motions to slow down. If this setup played out, there will
be a narrow region of heavy rainfall in northern Iowa that will
last much of Wednesday night. The instability axis won`t move
far for Thursday evening and may offer another chance at storms
at peak heating.

The upper-level ridge centers over the state by Friday and will be
followed by another shortwave trough for the holiday weekend. The
first round of associated precipitation will be on Friday evening.
The synoptic evolution differs in deterministic runs at this point
in time, but would expect mesoscale features that fall out of prior
convection to add another facet to the kinematics available for the
warm, moist, and weakly capped summertime airmass all weekend. The
NBM PoPs are high, but have the right idea for spatial coverage in
the afternoon beneath the main instability axis.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 624 PM CDT Mon Jun 30 2025

VFR conditions will prevail through the TAF period. Spotty
showers are southeast of KOTM and clearing of lingering high
ceilings will occur there over the next couple hours.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Hagenhoff