582
FXUS63 KDMX 291940 CCA
AFDDMX

Area Forecast Discussion...CORRECTED
National Weather Service Des Moines IA
240 PM CDT Sun Jun 29 2025


.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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1246 PM CDT Sun Jun 29 2025

Morning complex of showers and thunderstorms has shrouded the
state in thick layer of clouds today; which has limited warming
and thus rain chances. So, although isolated shower and storms
will still be a possibility yet later this afternoon, coverage
and strength will be much more limited compared to earlier
expectations. What does that mean for terminals? Well, we left
in Prob30 groups highlighting this possibility although with
uncertainty. Best time will be generally 22-03z. Should storms
materialize, they won`t take long to dissipate and/or move east
this evening. MVFR CIGS at KDSM will likely persist for the next
1-2 hours as well, but with better daytime mixing as clouds
move east, expect them to lift by around 1930z. Otherwise, VFR
conditions can be expected through the period. There may be
isolated shower/storms on Monday, however, coverage will be very
limited - similar to today.

&&

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

&&

$$

DISCUSSION...Hahn
AVIATION...Hahn