Lacelle, Iowa Weather Forecast Discussion

409
FXUS63 KDMX 182349
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
649 PM CDT Thu Sep 18 2025
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Scattered showers and thunderstorms continue this afternoon
  and evening. A few stronger storms may produce smaller hail
  and gusty wind. Pockets of heavy rain are also possible, but
  widespread hydro concerns are not anticipated.
- Scattered shower and thunderstorm chances will continue
  through Friday and the weekend.
&&
.DISCUSSION...
Issued at 247 PM CDT Thu Sep 18 2025
An area of scattered showers and thunderstorms has lifted from
southern to central and eastern Iowa through this afternoon. If we
zoom out to a big picture view, satellite makes it easy to pick
out the key features impacting the area today and through the
weekend. This afternoon a large surface low is in place across
Nebraska to South Dakota, visible as a big swirly across the
midwest on satellite. Meanwhile, another smaller vorticity
maxima is lifting out of Kansas and Nebraska into Iowa. This
will pull the next round of showers and thunderstorms into the
area this afternoon and through the evening. Convection so far
has been fairly weak with little lightning activity thus far.
Instability does continue to increase however, and a few
stronger cores are expected through the afternoon and early
evening. MLCAPE is around 1000 J/kg or less and 0-6 km shear is
under 25 kts, similar to the last few days. With little
organizing shear we will see more pulse thunderstorms the
develop quickly and then collapse. As such, expectations are
similar to what we`ve seen on both Tuesday and Wednesday with
marginally severe hail and gusty winds possible. One additional
area to consider today is the proximity of the surface low,
supplying additional low level vorticity while 0-3 km CAPE
analyzed on the SPC mesoanalysis page has reached 50-100 J/kg
already this afternoon. This increased stretching potential
could induce brief funnel cloud development this afternoon with
updrafts.
Scattered convection continues across the north overnight as the low
consolidates with another surface low further north across Montana.
With plenty of available moisture from recent rains, patchy fog
development is expected once again on Friday morning. As the
upper level trough finally begins to pass across the area
scattered convection is expected to continue across the area.
Most activity will be confined across northern Iowa, expanding
into central Iowa through the afternoon. With increased cloud
cover on Friday and the instability axis pushing east, stronger
storms are less likely on Friday, though a few are still
possible. These would be most likely east of I-35 with 500-800
J/kg of MLCAPE or less.
Convection lingers across northern Iowa into Saturday and a
reinforcing shortwave drops across the area on Sunday into
Monday. Another larger wave then drops across the area Monday
into midweek. While details are not clear at this time range,
what is clear is that the active pattern will continue through
much of the upcoming week with several chances for showers and
thunderstorms across the area.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 648 PM CDT Thu Sep 18 2025
Scattered showers with more isolated storms are expected to lift
across central Iowa this evening into Friday morning, with
higher confidence over KFOD, KDSM and KOTM in the near term
before gradually lifting northward near 06z. Given the isolated
nature of storm potential, have left out direct mention for most
sites, mainly including -SHRA mentions. Amendments would occur
if changes are anticipated given trends in the activity.
Otherwise, patchy fog is expected given recent moisture from the
rainfall, with higher coverage over western Iowa but could
extend more across the state, with lower visibility at times
through the morning. Low ceilings are also expected in the
morning into MVFR and possibly IFR at times.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Hagenhoff
AVIATION...Bury

NWS DMX Office Area Forecast Discussion