067
FXUS63 KDMX 121747
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1247 PM CDT Sun Oct 12 2025

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Highs around 80 today, with gusty southeast to south breezes.
  Mostly dry, with a slight chance of showers (20%) in the west
  and northwest.

- More widespread rain chances (20-40%) tonight, with a few
  thunderstorms possible, lingering into Monday in southern
  Iowa.

- Rain chances commonplace in the coming week, mainly around
  Tuesday and Friday-Saturday.

&&

.UPDATE...
Issued at 202 AM CDT Sun Oct 12 2025

Overall forecast for today through tonight remains on track. An
approaching low pressure trough is preceded by a tight surface
pressure gradient working into western Iowa early this morning
and central Iowa before noon, resulting in increasing southeast
to south breezes and have maintained forecast speeds above
median guidance. The breezy conditions combined with warm air
advection aloft ahead of the system will support warmer
temperatures today, though tempered a bit by widespread high
cloud cover. Still expect highs generally in the upper 70s to
lower 80s southwest. Made small adjustments to POP trends, but
rain still appears unlikely during the day due to a stout low-
level dry layer apparent in all forecast soundings, with perhaps
a few light showers scraping our northwestern counties. More
scattered showers will accompany the trough passage tonight, but
there is negligible instability and any thunder will be isolated
and of little to no impact, with only spotty light rain
anticipated.

&&

.DISCUSSION...
Issued at 241 PM CDT Sat Oct 11 2025

The beginnings of moisture advection could be seen over Iowa today,
but moisture resides up high for now. Cloud bases are around 20kft,
moisture originating from the monsoonal flow over the eastern
Pacific. The low level moisture fetch is locked in step with the
cyclone over Colorado. The feature will be ushered northeast along
the strong 500mb flow that will round the trough base, placing the
main area of forcing in the Dakotas for Sunday. The pressure
gradient will tighten over Iowa during the day Sunday with gusts
over 30mph likely (70% confidence) over portions of western and
northern Iowa. Wind maxes will be spurious through the afternoon as
WAA and synoptic lift will limit momentum transfer to the surface.
It will also be warm with highs again approaching 80 degrees. Fire
weather conditions will be dampened by increasing dew points,
holding RH values in the 40s.

Theta-e advection picks up ahead of the front, but profiles continue
to fight a lot of dry air. Precip output in models has an eastern
flank of precip along the theta-e gradient and a western counterpart
on the synoptic front. A look at profiles on the eastern flank shows
that moisture will be anchored at around 700mb and above, meaning
that if there was rain associated with it, it will be very light.
This is why rain chances south of Highway 20 are below 25%, and near
0% in southern Iowa. Better saturation, albeit for a short duration,
will come Sunday night along the synoptic front. The chance for
thunderstorms overnight is low (~15% in the south) as MUCAPE values
are under 200 J/kg.

Monday will bring a welcomed change to temperatures as highs in the
60s return for a short increment. Our front won`t be far away as it
stalls near the IA-MO state line. Its 850mb reflection looks to stay
right over the state, hence the increase in PoPs Tuesday and
Wednesday. Forcing and instability will be at a minimum, but
wherever the front sets up, it will produce light rain and cloud
cover for an extended period. A deep trough from the west will
grab a hold of it in the second half of the week and it remains
to be seen what dynamics will be in play for Iowa this far out.
WPC cluster analysis shows that around 60% of members favor a
northern stream track for the deepest height falls, but a look
at both deterministic GFS and ECMWF give credence for some
leakage deeper into the CONUS.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1247 PM CDT Sun Oct 12 2025

Coverage of rain shower activity this afternoon is quite
isolated and struggling to reach the surface, though still
will see slightly increased chances to see more scattered
activity across most terminals this evening into early Monday.
PROB30 mentions therefore remain at all sites except KDSM but
trends will be monitored and adjustments made as needed.
Otherwise, ceilings will decrease this evening into Monday with
mid-level clouds with this shower activity, though cannot rule
out brief periods of MVFR at times, but generally expecting VFR
conditions. Breezy S-SE winds will remain through the rest of
the afternoon, turning slightly less breezy this evening, as a
frontal passage brings a windshift across the state from
northwest to southeast Iowa becoming north/northwesterly.

&&

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

&&

$$

UPDATE...Lee
DISCUSSION...Jimenez
AVIATION...Bury