273
FXUS63 KDMX 141126
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
626 AM CDT Tue Oct 14 2025

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

.KEY MESSAGES...

- Shower chances increase from southwest to northeast today into
  tonight, then persist mainly north into Wednesday.

- Warmer weather returns in the latter half of the week, with
  highs Thursday and Friday in the mid-70s to lower 80s.

- A few showers and storms possible Friday and Saturday.

&&

.UPDATE...
Issued at 223 AM CDT Tue Oct 14 2025

Light radar echoes are being observed as moisture advection
aloft attempts to promote showers early this morning, but
stubborn low-level dry layer has proven too much to overcome so
far. Forecast soundings indicate it will take some time yet,
with light rain beginning in our west/northwest later this
morning and pivoting across about the northern half of the state
by tonight. Have adjusted POPs to delay onset accordingly and
capped at likelies (60-70%) overnight in deference to concerns
about the coverage of measurable precipitation. Still, we should
see at least scattered if not widespread sprinkles/light showers
tonight, again, mainly north, before they gradually fade out on
Wednesday and Wednesday night. Limited instability may support a
few thunderstorms at times the next couple of days, but severe
weather is not expected.

&&

.DISCUSSION...
Issued at 229 PM CDT Mon Oct 13 2025

Very slow moving surface boundary is just to the south and east of
the area this afternoon. Dew points in the upper 50s and 60s are
pooled along the boundary. Ridge of high pressure is moving in
behind this boundary and it has brought much drier air into central
and northwest Iowa with dew point values dropping into the 30s this
afternoon. A portion of the dew point drop this afternoon can be
attributed to diurnal mixing so there should be a modest bounce back
up towards sunset. Theta-e advection will commence overnight into
Tuesday and will begin to overrun the surface ridge as winds aloft
above 4 kft turn southerly. This will lead to descending cloud bases
overnight and Tuesday with increasing chances for showers from south
to north during this period. Continued the trend of delaying the
onset of precipitation due to the saturation process and the dry
layer beneath cloud bases. The precipitation chances will become
more focused over the northern third of Iowa Tuesday night and in
vicinity of the theta-e advection focus. Light rain may linger into
Tuesday evening in central and southern Iowa as some saturation
remains before some dry air entrainment arrives. Thunderstorm
chances through this period remain quite low. Mid-level lapse rates
remain below 6 C/km much of the period and while very low MUCAPEs
may develop with ideal particle lift points, the vertical extent of
lift is quite shallow and likely will not result in lightning. This
process is already occurring over eastern Kansas and Oklahoma where
the latest lightning data is not returning anything.

Clouds will keep conditions cool over northern Iowa while highs over
the south will be dependent if some sunshine can occur which despite
the arrival of the drier air, is not a certainty.

Upper level ridging will become reestablished on Wednesday then a
transition to steeper southwest flow to end the work week as the
ridge moves east. This will result in seasonably warm conditions
return on Wednesday with highs back into the mid to upper 70s for
the southwest half of Iowa. High may reach the 80s in some areas on
Thursday then slightly cooler on Friday. The moisture return
profiles for both low level Gulf moisture advection and the combined
Gulf and Pacific mid-level moisture contribution is more favorable
with the enhances southwest flow. This environment will be more
favorable for a few thunderstorms as the main boundary and short
wave pass through the area. At this point though, any activity will
likely be sub-severe. A long wave trough and upper northwest flow
follows for the weekend. At this point, the NBM forecast for Sunday
looks a bit on the warm side unless extreme mixing can occur, which I
should note is possible. Gusty winds in this type of setup would
seem likely as well.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 626 AM CDT Tue Oct 14 2025

VFR conditions will prevail this morning, however clouds will
generally thicken and lower gradually today and tonight,
especially across northern Iowa, resulting in MVFR ceilings at
FOD/MCW/ALO by later this afternoon, and potentially IFR
ceilings late tonight, toward the end of the 12Z TAF period.
Confidence is lower in these conditions affecting DSM/ALO
farther south so have only included VFR at those terminals.
Light SHRA is also expected at times, again mainly at the
northern terminals later today and tonight, but in general
visibility restrictions will be modest and intermittent. While
these general forecast trends are reflected in the outgoing
TAFs, amendments are anticipated later today and especially
tonight.

&&

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

&&

$$

UPDATE...Lee
DISCUSSION...Donavon
AVIATION...Lee