414
FXUS63 KDMX 032318
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
618 PM CDT Fri Oct 3 2025

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Elevated fire weather concerns remain this weekend,
  particularly for field fires with windy and warm conditions
  both days. Any spark could cause a fire, which could spread
  quickly!

- Unusual early October warmth continues along with dry weather
  through Saturday if not much of the daytime Sunday.

- Increasing chances for scattered showers and storms into
  Sunday night through early Tuesday. No strong signal for
  severe weather.

- Cooler next week with more seasonal conditions.

&&

.DISCUSSION...
Issued at 225 PM CDT Fri Oct 3 2025

It is a warm Friday afternoon across Iowa with just a few clouds in
southwest and southeast Iowa. More broadly, there is little in the
way of an area of substantial clouds over much of the eastern and
central US as these reside beneath the now again dominate mid-level
ridge and surface high pressure. GOES-East upper level water vapor
imagery shows that a sharp, amplified trough has moved over the
western US. This trough will move eastward and then northeastward
this weekend with surface cyclogenesis over the central Rockies.
With the high pressure to the east of Iowa and low pressure
developing to the west, winds will increase as the pressure gradient
tightens. Winds are just a bit breezy this afternoon, mainly over
western Iowa, but there is a lack of stronger winds at the top of
the mixed layer to tap into and mix to the surface. That won`t be
the case on Saturday as winds in the low levels will be stronger,
especially from Nebraska into Minnesota clipping northwest Iowa, and
this raises the concern for elevated fire weather conditions in
cropland. Cloud cover is expected to be at a minimum with perhaps a
few high-level cirrus clouds passing over in intervals in the
afternoon per latest HREF. With near full sunshine expected, deep
boundary layer mixing is anticipated. Pick your model forecast
soundings show this warming and drying that deepens the boundary
layer up to 7000 feet or so. Thus, the stronger low level winds at
the top of the mixed layer around 40 knots in western and parts of
northern Iowa should be able to be mixed to the surface with surface
gusts of 30 to 40 mph common with a few gusts over 40 mph in a few
places. Even warming and mixing in drier air at the surface, surface
dewpoints remain in the 50s with relative humidity staying largely
above 30%, though a few spots may drop into the upper 20 percents.
Calling around to fire weather partners yesterday and today, the
consensus in our service area is that grassland fuels remain green
enough to not warrant a Red Flag Warning/concerns of rapid grassland
fire spread. However, cropland in many areas is dry with the
cropland fire danger showing very high or extreme in central Iowa in
the warm and windy conditions. With harvest in full progress, the
concern is for field fires that develop and spread rapidly in these
conditions and keep fire departments busy. We will continue to
message this concern in our public facing forecasts and likely issue
a Special Weather Statement focused on the cropland fire danger
Saturday morning in conjunction with at least some of our
neighboring offices.

Winds will diminish into Saturday night and relative humidity will
rise ending this round of elevated fire weather conditions. Through
Sunday, the upper level trough and associated surface low will lift
through northern Minnesota into the southern Manitoba and Ontario
provinces. With the stronger low level flow and pressure gradient
moving away from the state on Sunday, winds won`t be quite as
strong, but will still be quite breezy. So, another day of elevated
fire weather conditions will once again be present with very high
cropland fire danger. In addition, cloud cover is expected as a
surface cold front - attached to the departing low - is dragged
through the state. This will yield a slightly less warm day with
highs in the low and middle 80s. As stronger low level QG
convergence arrives and waves of theta-e advection pass over the
state, scattered showers and thunderstorms should develop in the
afternoon if not Sunday night in most areas with the exception being
parts of northwest and north central Iowa that may miss out on much
of this rainfall. Nothing has changed in the parameter space or
AI/ML guidance to suggest a strong setup for severe weather given
the marginal at best instability and largely out of phase shear.

Moving into early next week, conditions will be more seasonal with
highs in the upper 60s or low 70s through at least midweek. The
front that looked to somewhat stall south of the state is more
progressive in today`s deterministic guidance. There will still be a
period of scattered showers and storms in the wake of this front as
QG convergence lingers and weaker waves of theta-e advection pass
over Iowa Monday through early Tuesday. With the expected more
progressive pattern, deterministic guidance not surprisingly has
lower QPF generally between 1 and 1.5 inches. National Blend of
Models probability of an inch or more of rainfall in this period
focuses the highest probabilities at 20 to near 40% over the
southern half of the state. Any rainfall will be welcomed by the
recent stretch of dry weather that has soils showing at or below the
30th percentile in many areas.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 610 PM CDT Fri Oct 3 2025

VFR conditions will prevail through the period as skies remain
mostly clear through tomorrow afternoon. Increasing southerly
winds through tonight and into Saturday will be the main weather
through this timeframe. First, have added some LLWS to KFOD for
a few hours tomorrow morning, as a 40 to 45 kt low level jet
develops over northwestern Iowa. After sunrise, these winds
will begin to mix down to the surface, eliminating the LLWS,
but translating to strong, southerly surface winds over much of
Iowa tomorrow. Wind gusts of 30 to 40 mph are possible at all
sites, but the strongest gusts will be in the afternoon near
KFOD, KMCW, KALO, and KDSM. Winds will still be gusty at KOTM
as well, but not as strong as areas farther north and west.
Gusty winds will persist through the end of the TAF period.

&&

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

&&

$$

DISCUSSION...Ansorge
AVIATION...Dodson