930
FXUS63 KDMX 181911
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
211 PM CDT Sat Oct 18 2025

.KEY MESSAGES...

- Period of rain for most locations beginning northwest this
  afternoon and moving east overnight.

- Gusty winds, sunny and cooler Sunday

- Next strong system will impact the area Monday and Tuesday.

&&

.DISCUSSION...
Issued at 209 PM CDT Sat Oct 18 2025

Two areas of precipitation ongoing early this afternoon with
widespread showers and thunderstorms from southern Illinois, central
Missouri and into eastern Oklahoma. A more narrow area of
precipitation is lagging behind the main system to the south with
light rain over southwest Minnesota, southeast South Dakota and
Nebraska. These systems are being forced by several factors and are
in association with a couple strong PV anomalies that are showing up
well in the water vapor imagery. The first is across north central
OK with the other over southwest South Dakota though it does have
short wave energy extending to the northeast. A couple of upper
level jet maxes are also in vicinity of these anomalies. The lead
130 kt jet streak is centered over southeast Iowa and lifting
northeast while the other 120 kt jet max is diving southeast through
Wyoming and Montana. This will create a coupled jet structure
leading to enhanced upper levels divergence and mid-level ascent over
parts of central and eastern Iowa by this evening. That forcing will
be enhanced by the approaching short wave energy and should lead to
an expansion in precipitation as the energy of the southern and
western systems combine. The Gulf moisture will remain secluded to
the south meaning the precipitation into central Iowa will be
reliant on any residual Pacific moisture that is tagging along with
the system. While it may be a struggle to saturate enough for cloud
bases below 4-6 kft, enough forcing and precipitation loading is
expected for widespread precipitation that will impact areas from 1-
4 hours, with the greatest time periods over the east.

Gusty north winds will develop today and will persist tonight into
at least Sunday morning before diminishing begins in the afternoon
as mixed layer winds lower with high pressure ridging arriving
from the west. Sky conditions will clear out later tonight for a
mostly sunny albeit cool Sunday with highs in the upper 50s to
low 60s. Upper level default ridging will move across Iowa
Sunday night into early Monday then will transition to a brief
period of southwest flow Monday ahead of the next strong system.
Strong mid-level theta-e advection will commence as this occurs
while a connection to Gulf moisture is reestablished with high
pressure moving east of the Mississippi River. Another strong PV
anomaly arrives late Monday into Monday night along with low
static stability. Precipitation chances will be contingent on
available moisture. Given the amount of forcing and the
reestablished moisture connection, the NBM and similar
deterministic solutions are likely underdone on PoPs. Should
enough moisture and saturation occur, thunderstorms could be
possible given the low static stability and strong supporting
forcing.

An upper low will be established over northern Wisconsin by Tuesday
morning leading to pronounced cyclonic flow over Iowa. Again, the
NBM is likely struggling with this time period in several
aspects. Given it is mid to late October, strong cyclonic flow
very often results in a broad stratus field over the area.
Strong and gusty northwest winds are likely, though the
aforementioned stratus may limit those mixed layer depths.
Several deterministic soundings do have low level instability
and pending that instability depth and the strength of the
inversion above this layer, showers may very well occur on
Tuesday. The cyclonic/northwest flow will persist into Wednesday
and most of Thursday before gradually relaxing late Thursday.
High temperatures much of next week will be in the 50s and 60s
and there will be some periods with freezing overnight lows,
especially over the north.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1240 PM CDT Sat Oct 18 2025

An area of showers and perhaps isolated thunderstorms will move
across central Iowa late this afternoon over the northwest and
over the rest of the area overnight. Cigs will remain mainly VFR
but local MVFR may occur. Vsby restrictions in rain may occur.
The period of rain at sites will range from 2-4 hours. Gusty
north winds will develop as well later this afternoon and
overnight. Expect clearing late tonight and into Sunday.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Donavon