643
FXUS63 KDMX 311124
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
624 AM CDT Sat Oct 31 2026

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Shower and thunderstorm chances continue this morning, then
  gradually diminish later today and tonight.

- Next chance of rain returns Monday, with thunderstorms
  possible Monday afternoon/evening. Rain will linger through
  Tuesday.

- Highs in the 60s common, though rain and clouds could drop
  highs into the 50s in spots.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 115 AM CDT Sat Oct 31 2026

A broad, positively-tilted 500 MB trough is making its way
gradually northeastward across the central U.S. at the current
time and will cross Iowa later today into tonight. At the
surface, a large high pressure area is situated far to our east
over the eastern Great Lakes region, while broad low pressure
sits along the western High Plains in the lee of the Rockies.
This will keep Iowa within modest southeast to south breezes
through the weekend. A weak and nebulous near-surface boundary
is currently located from northwest to southeast across Iowa and
is serving as a focus mechanism for convective development early
this morning as it very slowly lifts north/northeastward. Away
from this band isolated showers and storms are also developing
elsewhere around the region, as broad but modest forcing for
ascent associated with the approach of the 500 MB trough
overlies increasing 850-925 MB winds within a moist airmass.
This will be the rule for today as isolated to scattered
convection continues, but trying to pin down details of location
and timing for shower/storm development becomes rapidly more
difficult more than a few hours in advance and have thus
maintained broad mid-range (30-60%) POPs through about midday.
Thereafter, with the aforementioned low-level boundary lifting
north of our forecast area and the bulk of the forcing aloft
also shifting northeastward as the 500 MB trough axis
approaches, rain coverage and intensity will gradually decrease
from the afternoon through the evening and into tonight with
POPs more in the 10-20% range after dark.

On Sunday the first 500 MB trough will move away toward the
Great Lakes and Ohio River valley, but a deeper and stronger
trough will come ashore over the U.S. Pacific coast. Between
these two systems, a brief period of mid-level ridging will
provide a break and the forecast is dry during the day. This
will also support some breaks in the clouds and at least
periodic sunshine to return, but any resultant warming will be
tempered by humid conditions and light southeasterly breezes.
Highs will peak somewhere in the 60s in most areas.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 159 PM CDT Fri Oct 30 2026

A prolonged period of rain and some storms will arrive to start
next week. The western U.S. trough will eventually eject into
the plains, enhancing the low and midlevel jet in the warm
sector. At this range, deterministic runs bring MUCAPE values
around the 300 J/kg range into southern Iowa. The potential for
surface- based severe weather is heavily challenged by morning
rain and lingering cloud cover. Moderate wrap-around rain stays
in the state for Tuesday and partially into Wednesday. NBM QMD
guidance shows that much of the state has around a 50% chance of
exceeding 2" of rain, which matches the early convective nature
as well as the very high PWATs (1.5") by November standards.
The progressive nature of convection and the long-duration of
rain will reduce potential hydrologic impacts. Highs will cool
into the 50s following the system`s departure and the upstream
pattern will remain active and amplified.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 624 AM CDT Sat Oct 31 2026

Scattered SHRA are crossing the area this morning and have
included TEMPO groups in the first few hours of the TAFs
mentioning these. Most associated visibility restrictions will
be MVFR. Low ceilings are also impacting most of the area with
MVFR and occasionally IFR heights, IFR being more likely in the
northwest at MCW/FOD. Coverage of showers should gradually
diminish, and ceiling heights should gradually increase, as we
move through late morning and into this afternoon.

&&

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

&&

$$

SHORT TERM...Lee
LONG TERM...Jimenez
AVIATION...Lee