Carl Iowa Weather Forecast Discussion

875
FXUS63 KDMX 151125
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
625 AM CDT Wed Oct 15 2025
...Updated for the 12z Aviation Discussion...
.KEY MESSAGES...
- Isolated to scattered showers will persist at intervals today
  and tonight, but rainfall will mostly be spotty and light. A
  few thunderstorms are also possible, but no severe weather is
  expected.
- Warmer weather returns in the latter half of this week, with
  highs Thursday and Friday in the mid-70s to lower 80s.
- More showers and thunderstorms are forecast between Friday and
  Saturday night when a cool front will move across the region.
  The severe weather potential is low at this time.
&&
.UPDATE...
Issued at 204 AM CDT Wed Oct 15 2025
Rain largely cleared out from the area on Tuesday evening, but
more showers and storms then developed over eastern Nebraska and
are moving from western toward central Iowa early this morning.
Most CAM solutions are not even depicting this feature, with the
FV3 being a notable exception, and it is clear that within this
regime of saturated lower levels and ripples of forcing moving
through, it will not take much to generate patches of light
showers and a few thunderstorms from time to time. Models are
having a hard time resolving this in terms of pinning down the
time and location of any resulting rainfall, but they nearly all
generate sporadic scattered echoes across our forecast area
through much of the next 24+ hours, with perhaps consensus on
somewhat of a lull this afternoon and evening. Given these
various considerations, have opted to carry POPs right through
today and tonight in most of our forecast area, however, from
late today through tonight have only included slight chances
(20%) of rain due to low predictability and expected low
coverage at any given time. Aside from POP trends, the forecast
remains on track and little to no change was made overnight.
&&
.DISCUSSION...
Issued at 239 PM CDT Tue Oct 14 2025
Analysis of the large scale weather setup today shows a large area
of upper-level ridging that covers much of the central CONUS, with a
mid-level high pressure area circulating over the Southern Plains,
while two troughs are located on either side of this high pressure:
the first now over the Atlantic and the other just arriving onto the
California coast. Closer to the surface, high pressure is centered
over northern Minnesota/Wisconsin, covering much of the upper
Midwest into the Central Plains. Despite this high pressure, a
frontal boundary is draped across southern Iowa, with moisture
pooling into the state by increased theta-e advection that lead to
saturation to occur over northern into central Iowa, bringing rain
showers over the area. This afternoon, the showers are more isolated
in nature mainly over northern Iowa. Temperatures are quite varied
this afternoon with values in the 50s across the northern two-thirds
of the state, while southern Iowa has values through the 60s. Given
the slow movement of the boundary north through the day, on and off
showers are expected to continue through the remainder of the day
mainly over northern Iowa, while southern Iowa generally remains
dry, outside of a low chance for sprinkles if the drier air overhead
is able to saturate. Thunderstorms are not expected with this
activity given the lack of instability overhead. Temperatures
tonight into Wednesday are expected to fall into the upper 40s to
mid 50s north and in the upper 50s to low 60s south.
By Wednesday, lee cyclogenesis is expected to occur per model
guidance, as the large-scale trough finally starts to eject out of
the western CONUS eastward, which will push a thermal ridge over the
Midwest, leading to warming overhead. This ridge will try to push
the aforementioned boundary out of the state, keeping near surface
weak convergence mainly over northern to north central Iowa, with
additional but more isolated chances (20-30%) for on and off showers
mainly over western and northern Iowa by the afternoon. Into
Wednesday evening and Thursday morning, the aforementioned low
pressure is expected to lift northeast into Nebraska and the
Dakotas, with Iowa in the warm sector and a push of moisture with
the initial advection wing arriving into Iowa. This will result in
more scattered shower activity mainly over northern late Wednesday
into Thursday, along with breezy conditions as low level
southwesterly flow increases. This stronger push of warmer air will
lead to above normal temperatures as values are expected to reach
the upper 70s to low 80s across the state Thursday, along with
higher dewpoints in the mid to upper 50s. A return of instability
paired with favorable shear will bring the potential for some storms
with this activity, though not expecting any severe weather at this
time.
Additional rain chances will continue to end the work week Friday as
a cold front in relation to the lifting surface low into the Upper
Midwest moves into Iowa. Additional shower and storm chances return
once again, with the front tracking slowly eastward through the day,
though weaker forcing looks to keep any activity fairly light in a
rather broken line, before an increase in low-level jet activity
late Friday into Saturday will lead to some more widespread
development mainly over eastern Iowa. However, model variations
remain on the extent of coverage and timing so a close eye remains.
Instability increasing mainly over the southeast portion of the
state with more favorable shear would lead to some potential for
storms as well later in the day Friday, so will be keeping on eye on
this over the next few days.
Brief drying across the state looks to occur following the front`s
departure Saturday, though a quick moving shortwave dropping into
the Midwest within the circulating mid-level low pressure system
over Canada brings yet another opportunity for rain, before dry
conditions look to settle Sunday into early next week as
northwesterly flow becomes common. A return to more seasonal
conditions is expected this weekend with highs in the upper 60s
to low 70s Saturday, and a touch cooler Sunday in the low to mid
60s.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 625 AM CDT Wed Oct 15 2025
LIFR/VLIFR ceilings continue at FOD/MCW early this morning and
will be slow to lift today, but should eventually rise to IFR by
late morning or early afternoon. ALO will likely remain VFR
before eventually rising to VFR, and farther south at DSM/OTM VFR
conditions should prevail through the day. Aside from these
larger-scale cloud/ceiling trends, widely scattered light
showers will persist at intervals through the TAF period.
However, predictability of timing/location is unusually low, and
even when a shower does affect a terminal any reduced
conditions/impacts will be very brief. Therefore, SHRA is not
mentioned in the TAFS and will be handled with amendments if
appropriate.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
UPDATE...Lee
DISCUSSION...Bury
AVIATION...Lee

NWS DMX Office Area Forecast Discussion