407
FXUS63 KDMX 300506
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1206 AM CDT Mon Jun 30 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Thunderstorm chances (20-50%) remain yet this
  afternoon/evening, but coverage and magnitude has decreased

- Isolated storm chances (20%) have been added to the region
  Monday, but coverage won`t be all that great

- Cooler air mass for Monday & Tuesday, followed by warmer
  conditions and storm chances returning as early as Wednesday
  and perhaps into next weekend.

&&

.DISCUSSION...
Issued at 240 PM CDT Sun Jun 29 2025

Morning Mesoscale Convective System (MCS) and residual blow-off
clouds has put quite the damper on temperatures today - about 5
degrees cooler than was expected at this time yesterday. Lack
of insolation and resultant cooler temperatures has
significantly reduced storm prospects and severe potential
across the CWA this afternoon/evening; a trend that was
captured well in 1630z SWODY1 Slight-Marginal shift. All of the
12z CAMs captured this well, with only the 12z HRRR and FV3
convecting along a relatively diffuse "cold" frontal which is
progd to be located roughly from Waterloo to Lamoni by mid-
later afternoon. If storms are able to materialize along this
boundary, northeast portions of the CWA would be best
positioned for best thunderstorm organization given proximity
to the mid-level shortwave trough. The best updrafts of which
would be capable of producing primarily damaging wind (DCAPEs of
1000 j/kg) and brief heavy rain. So - have made wholesale
forecast changes to reduce rainfall chances across the board for
this afternoon and evening - generally into the 20-50% range.
Of course, this will mitigate flooding threat as well, so no
longer anticipate a widespread flooding concern. Storms will
depart quickly this evening, giving way to drying thru much of
the overnight.

MCS Fest is set to continue once again later tonight as the next
one moves out of Nebraska and into the Midwest. 12z output has a
bit more consensus compared to last night`s tracking it mainly
into SW Iowa and MO. It doesn`t look to get into the region
until sunrise Monday; and have adjusted precipitation chances
accordingly. As for Monday, did maintain low storm chances as
the mid-level thermal trough moves overhead, steepening mid-
level lapse rates, and likely allowing for at least isolated
convection. Although expect most areas will stay dry for
Monday.

A drier air mass works in for Tuesday. Medium range guidance
differ on timing and magnitude of thunderstorm chances into the
holiday weekend, so confidence decreases after Wednesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1152 PM CDT Sun Jun 29 2025

VFR conditions ongoing across much of the area. A few locations
have started to see patchy fog develop which may continue
through the overnight especially in the northeast, towards
KALO/KMCW. Confidence in timing and impacts is not high, but
started with some patchy fog mentions, though adjustments may be
needed should fog become more dense. For later Monday
morning/early afternoon, although confidence has diminished in
shower/storm chances with time and associated impacts, for
consistency left prob 30 groups at KDSM and KOTM. Will continue
to evaluate trends and adjust or add mentions to other sites if
needed/confidence increases in shower/storm timing and impacts.
Light and variable winds expected through the overnight before
winds settle out of the northwest and increase during the
daytime Monday to around 10-15 knots, with a few higher gusts.

&&

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

&&

$$

DISCUSSION...Hahn
AVIATION...05