643
FXUS63 KDMX 180504
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1104 PM CST Mon Nov 17 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Rain shower chances increasing into tonight. A few non- severe
  thunderstorms with small hail are possible this evening. A
  brief period of snowflakes mixing in near the Minnesota border
  is possible after midnight tonight into early Tuesday
  morning.

- Highs lowered on Tuesday due to lingering stratus clouds.

- Next rain chance late this week, but trends are pushing these
  chances farther south in the state and lower in percentage.

&&

.DISCUSSION...
Issued at 228 PM CST Mon Nov 17 2025

Early afternoon satellite imagery shows a cyclonic spin over
the Nebraska panhandle, which is associated with a compact PV
anomaly. Ahead of it, low level thermal lift is increasing over
the state and this will result in cloud cover increasing through
the remainder of the afternoon. There is some MUCAPE associated
with this wave this afternoon and simulated reflectivity shows
attempts at showery activity. However, forecast soundings reveal
low level dry air being funneling into the state on
southeasterly flow so expecting this first wave this afternoon
to mainly be saturating the mid-levels and increasing cloud
cover with perhaps a shower or two here or there that can break
through the dry air. As we head into the nighttime hours,
another wave of low-level thermal advection will push over the
state as the PV anomaly reaches Iowa. This will help to
generate more widespread shower activity. Further, MUCAPE values
ranging from 500 to 1000 J/kg will pass through the state
allowing for embedded thunderstorms to occur, particularly in
the evening hours to a few hours after midnight. The deep layer
shear is unimpressive, but the instability would be sufficient
for small hail growth or graupel production with the stronger
instability. While SPC did introduce a marginal risk of severe
weather over Missouri, the lack of stronger kinematics will
likely preclude any severe hailstones or a marginal risk this
far north. The showers will push into far northern Iowa and
northeastern Iowa by sunrise Tuesday. Near the Minnesota border,
a few snowflakes may work in as the column cools overnight, but
at the same time drier air will be working to deplete the ice
introduction. So, the time window for any snowflakes mixing in
is narrow. With the warm ground temperatures, any snow that
does survive will melt on roadways. As the drier air does arrive
in the column and ice introduction is lost, we may be left with
just a period of drizzle. The depth of this saturation thins
with time such that drizzle production will end and will be left
with low stratus clouds through much of the day. Thus, have
lowered temperatures a few to several degrees away from the
initial National Blend of Models (NBM), which was closer to the
75th percentile of available guidance and too high.

While clouds will linger Tuesday night into Wednesday morning,
the recent moisture and light winds may allow fog to form in
some areas. MOS and NBM text guidance shows this potential,
though will have to see if this occurs given the lingering
stratus clouds. Soundings do not show the typical low level/near
surface inversion and would favor the stratus.

The next window for rain will be late this week as a amplified
trough over the Western CONUS pivots east and northeastward.
Meanwhile, a trough will pass over the Canadian prairies and
over the Great Lakes. This latter feature will force a cold
front through the state with high pressure following it. With
this high over the northern states helping to push dry air into
at least northern Iowa, the moisture from the southern stream
amplified trough will be focused more southward in the state if
not south of the state. This is also shown in the NBM data over
the last day or so and will see if this trend continues to
hold in the coming days.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1104 PM CST Mon Nov 17 2025

Light rain showers with embedded weak storms are expected to
continue this morning, with storm potential highest at KDSM over
the next hour or so given radar trends, with any additional
activity lifting into northern Iowa near sunrise as this
activity gradually weakens. Some drizzle is also possible this
morning, especially over northern Iowa given the saturated air
and low ceilings expected. This low stratus is expected to
extend across Iowa, with MVFR and even IFR ceilings likely
throughout the day. Winds out of the east will turn more
northeasterly through the day as this system drops southeast out
of Iowa, with light winds mainly expected.

&&

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

&&

$$

DISCUSSION...Ansorge
AVIATION...Bury