642
FXUS63 KDMX 161109
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
609 AM CDT Thu Oct 16 2025

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

.KEY MESSAGES...

- Low chances (20-40%) of intermittent showers and thunderstorms
  early today, tapering off toward the northeast and ending by
  this afternoon.

- Warm and breezy to end the week, with highs today and Friday
  in the mid-70s to lower 80s.

- An approaching cool front will bring more showers and
  thunderstorms at times from Friday through Saturday. The
  overall severe weather threat is low, but a few storms could
  be strong mainly across the southeastern half of Iowa late
  Friday.

- Dry and breezy conditions on Sunday may promote elevated fire
  weather concerns.

&&

.UPDATE...
Issued at 203 AM CDT Thu Oct 16 2025

Ripples of forcing moving through a relatively saturated column
continue to produce additional rounds of isolated to scattered
showers and thunderstorms overnight. This will continue through
the morning but then the rain will finally depart to our
northeast during the afternoon as deep-layer ridging builds in
overhead. Have thus expanded POPs initially this morning but
maintained a decreasing trend exiting our northeastern counties
around mid-afternoon. Thereafter, dry conditions will set in
through tonight. Also, forecast soundings indicate that as we
dry out somewhat in the afternoon, particularly in our
southern and western counties where clouds will clear earlier,
mixing depths should increase and winds will become gusty. Have
maintained a wind speed/gust forecast above median guidance but
this will still be below hazardous levels.

&&

.DISCUSSION...
Issued at 236 PM CDT Wed Oct 15 2025

Broad mid-level ridging continues to track slowly eastward across
the central CONUS today, with a large area of surface high pressure
centered over far northern Wisconsin, covering the Upper Midwest
into the Ohio Valley. Further analysis of surface observations shows
the very slow moving frontal boundary overhead, draped just north of
I-80. Plenty of moisture remaining overhead with weak forcing
allowed for isolated to scattered shower activity this morning,
which has largely faded this afternoon with the main shower activity
in southern to eastern Iowa. On and off showers are expected to
continue at times for the remainder of the day and into Thursday,
with the highest chances (25-35%) over northern Iowa where the
higher moisture content remains. Little instability overhead will
keep storm chances low into Thursday, though a few lightning strikes
here and there may occur with a stronger shower. A look at
temperatures across the state shows a large difference of values
from north to south, with much cooler conditions over northern Iowa
in the 50s to low 60s where thicker clouds are located, while south
of the boundary, values are in the upper 60s through the 70s where
some patchy clear skies are noted per satellite imagery. With little
change anticipated in the overall setup, have lowered the previously
anticipated high temperatures today mainly across the north as
thicker cloud cover will limit the extent of warming for the rest of
the day, though the initial push of warm air advection ongoing
should allow for values to increase a bit more this afternoon to
reach the 60s in northern Iowa, while the southern half reaches
the mid to upper 70s. Further west of the aforementioned ridge,
a defined mid- level low pressure area within the large trough
over California today is expected to eject east/northeast into
the Northern Plains by Thursday, which will gradually push the
current boundary and ridge out of the area later in the day.
Lingering rain showers are expected to remain at least through
the morning over northern Iowa, before drying occurs across the
state through the rest of the day. The thermal ridge will
continue to build into Thursday, with low level southwesterly
flow increasing across the state, with increased warm air
advection overhead. Temperatures therefore will increase with
highs expected in the 70s to low 80s across Iowa. With the
increased southwesterly flow, breezy winds are expected with
gusts up to 25-30 mph, isolated to 35 mph in northern Iowa.

By Friday, the surface low is expected to track further
northeastward into the Dakotas, with Iowa remaining in the warm
sector as the warm front remains well north of the state, keeping
the area dry at least into the morning. However, just west into
Nebraska, a cold front moving eastward is expected to arrive into
Iowa as moisture returns into the state, which will bring the next
notable chance for showers and thunderstorms. Initial development
looks to occur Friday morning into western Iowa, tracking slowly
eastward across the state into the afternoon. By the evening, better
forcing for lift and an increase in theta-e advection sets up
into central to eastern Iowa, with more scattered to widespread
development of showers and storms. Models indicate instability
values generally less than 500J/kg though better shear around 30
knots or so over east/southeast Iowa Friday evening, leading to
at least low chances of pulse storms, though not expecting
severe weather at this time. Lingering showers and storms look
to continue through Saturday morning mainly over eastern Iowa,
while at least much of western Iowa dries out. Later in the day,
a shortwave trough over the Southern Plains looks to lift
northeast and become ingested by the larger trough circulation
over southern Canada, which looks to bring an enhancement to the
larger system. Coming from this looks to be the potential for
yet another though stronger surge of forcing and moisture into
east/southeast Iowa Saturday afternoon to evening as the front
still looks to remain over that area, developing a heavier band
of rain showers over the Ohio Valley and extending into eastern
Iowa, and lingering into Sunday. In terms of storm potential,
higher shear values increase a bit to 30-35 knots, along with
slightly higher instability, so this could hold the highest
potential for some stronger storms. There still however remains
some slight differences between long-range guidance on the
overall timing, placement and intensity of the previously
mentioned features, so there will likely be changes over the
next few days as additional model members capture these time
periods and more details are better known.

Northwesterly flow takes over with much drier air overtaking the
region later Sunday into early next week. Ridging develops into the
Central Plains into early next week before models diverge on
solutions beyond this, where the GFS keeps the region dry until
Tuesday when the next trough arrives in the central CONUS, whereas
the Euro has an earlier arrival by Monday. Therefore, not much to
really be specific on at this time and will be monitored over the
coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 609 AM CDT Thu Oct 16 2025

IFR/LIFR ceilings will affect MCW early this morning, and
FOD/ALo at times, before gradually rising and moving away to the
north. VFR conditions will prevail by 18Z, except perhaps at MCW
where MVFR ceilings may linger into the afternoon before
improving. Widely scattered SHRA/TSRA are also ongoing early
today and will slowly diminish by the afternoon, but even this
morning any impacts will be infrequent and brief and thus are
not included in the 12Z TAFs except for a couple of TEMPOs.
Overnight tonight, toward the end of the TAF period, VFR
conditions are forecast but LLWS of 30-40 KT is anticipated as
winds increase just above the surface.

&&

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

&&

$$

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