Numa, Iowa Weather Forecast Discussion

730
FXUS63 KDMX 070740
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
240 AM CDT Sun Sep 7 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms return to the forecast
  between Monday into Tuesday. Severe weather is not
  anticipated.
- Temperatures continue to rise in the latter half of the week,
  with daily highs well into the 80s in most areas.
&&
.UPDATE...
Issued at 240 AM CDT Sun Sep 7 2025
High pressure centered across the is making for another quiet night
across Iowa. GOES-east nighttime microphysics imagery indicates
cloud-free conditions with a couple spots of patchy light fog.
With dry air in place more widespread develop is not anticipated
through the morning. As high pressure shifts east today winds
will shift to southerly, marking a return of warm air advection
into the area. Effects will be minor today with highs still
cooler than average for this time of year, but still a few
degrees warm than those recorded on Saturday.
By Monday a weak shortwave pushes into western Iowa, bringing with
it our next chance for showers and thunderstorms. The instability
axis remains largely west of the area with under 1000 J/kg of MLCAPE
reaching western Iowa and 0-6km shear around 30kts or less. This
should preclude severe storms, but thunderstorms are expected. The
wave is slow to pass across Iowa, lingering through Tuesday. Model
soundings indicate quite a bit of dry air in place and struggle to
saturate, so robust QPF amounts are not forecast. In most cases 0.1-
0.25" or less is expected. The thermal ridge builds across the area
behind this wave, sending temperatures back into the 80s for the
middle to end of the week.
&&
.DISCUSSION...
Issued at 204 PM CDT Sat Sep 6 2025
The forecast remains quiet overall, with cool weather through
Sunday morning then a gradual warming trend through next week,
and rain chances returning at intervals beginning around late
Monday.
Currently cyclonic northwesterly steering flow covers most of
the region, with a shortwave trough swinging through the flow
over Minnesota and Wisconsin. This is generating some
stratocumulus clouds extending down into our service area, but
any associated sprinkles/light showers will remain well to our
northeast today. At the surface, modest northwest breezes are
helping to keep temperatures in the 60s throughout central Iowa.
Meanwhile a large, cool area of surface high pressure is
building down across the Dakotas and will spill into Iowa
tonight, centering right over us by sunrise Sunday. As the high
spreads in this evening winds will drop off and the clouds will
largely dissipate after sunset, resulting in mostly clear and
nearly calm conditions overnight. This will support efficient
radiational cooling and have maintained a low temperature
forecast in the bottom 25% of the guidance envelope, with Sunday
morning lows ranging in the upper 30s to lower 40s. Frost is not
included in the forecast, however, not only because lows remain
around 38 or above, but also due to the very dry conditions in
place.
From Sunday into Monday the surface ridge will steadily move off
to the east, bringing a return of southeasterly and then
southerly low-level flow across Iowa. Meanwhile the 500 mb flow
will become more zonal, promoting slow but steady warming with
highs climbing into the upper 60s to lower 70s Sunday, then well
into the 70s on Monday. A broad mid/upper trough will then move
slowly eastward across the region between late Monday and late
Tuesday, with broad forcing for ascent generating thicker clouds
and bringing a return of rain chances mainly around Monday
night. The forcing is not overly strong however, deep-layer
shear is only predicted to be around 15-25 KT with modest CAPE
of less than 1000 J/kg mostly confined to western Iowa. This
scenario does not support severe weather, and in general more
scattered showers and isolated thunderstorms are expected with
PoPs capped at 50% for now due to uncertainties in timing and
location of rainfall.
On Wednesday and Thursday a deep-layer ridge will build across
the Midwest, with temperatures rising well into the 80s across
central and southern Iowa each afternoon. Some model solutions
generate spotty light QPF during this time frame, but given the
large-scale subsidence within the ridge overhead, have
maintained a dry forecast these two days. From around Thursday
night into next weekend, however, it appears the ridge will
become more flattened and perhaps shunt just a bit eastward,
allowing overtopping impulses to bring some potential for
additional rainfall and resulting in a return of low (20-30%)
PoPs to the forecast. This evolution will also likely lead to
a little more airmass modification and temperatures could
approach 90 degrees in a few southern areas at the end of the
week. The last few days have provided a sneak preview of autumn,
but it`s not here yet.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1047 PM CDT Sat Sep 6 2025
Confidence remains high in VFR conditions through the period at
all terminals. Winds are calm to light from a generally
northwesterly direction and will continue light and variable
into Sunday before becoming from the southeast late in the
period. A few cumulus clouds around FL050 or higher may develop
over eastern Iowa Sunday afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hagenhoff
DISCUSSION...Lee
AVIATION...Ansorge

NWS DMX Office Area Forecast Discussion