885
FXUS63 KDMX 060000
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
700 PM CDT Sat Jul 5 2025

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

.KEY MESSAGES...

- Second round of thunderstorms dropping southeastward through
  the area this afternoon into the evening. Isolated strong
  storms are possible, with strong winds the main concern. A few
  funnel clouds are possible initially in the afternoon.

- Seasonal and mostly dry on Sunday although a few isolated
  showers/storms are possible east.

- Thunderstorms return to the forecast on Monday, with active
  period through much of the week.

&&

.DISCUSSION...
Issued at 257 PM CDT Sat Jul 5 2025

Our morning convection produced some healthy rainfall over the area
today, with a few bands of 2 to 3 inch rainfall over the northern
and western portions of the forecast area. This convection was
fueled by a very moist low level jet nested within an upper level
wave (and coincident surface low pressure) which is currently
drifting north and east of the area early this afternoon. This
morning activity has all but departed our forecast area, with
showers and storms developing sporadically in it`s wake. However, as
this first round departs, our second round of storms is already
starting to develop along the cold front draped behind the surface
low. While most of the storms today have only produced brief gusty
winds and heavy rainfall, this second round of storms will have the
potential to produce a few stronger storms now that skies have
cleared out some and the atmosphere is destabilizing. Fortunately,
shear still remains fairly low, and storms will struggle to
organize. The main severe risk will be small hail, as well as
damaging winds as the initial cores develop and collapse. However,
as convection occurs, cold pools/thunderstorm outflow will race out
ahead of storms. New storms will then develop on the progressing
outflow, but any severe threat should be limited to new storms
developing in the untapped air ahead of the outflow. Also a product
of the low shear environment will be the potential for funnel clouds
and even a brief landspout with initial updrafts along the boundary
this afternoon, especially in northwest Iowa. That said, expect this
threat to diminish as more storms develop and cold pools negate the
processes involved in stretching vorticity into a funnel. Finally,
heavy rainfall is expected with additional convection this evening.
Storms today should remain progressive with the movement of the
boundary and outflow, but will still continue to monitor for
hydrological concerns, especially as storms move through areas that
already saw heavy rain this morning.

Storms move out of the area through the overnight hours, although
the boundary will stall out just to the southeast of the forecast
area. This may lead to additional scattered showers in far southeast
Iowa through tomorrow, but these should generally be weak and
transient. As mentioned in the previous update, weak surface high
pressure fills in behind the wave on Sunday. Northerly flow will
keep temperatures seasonal in the low to mid 80s through the day and
drier conditions behind the boundary will drop dewpoints into the
60s, helping to alleviate the humid feel we`ve had recently. Some
model output does still imply the development of diurnally driven
showers and isolated storms, mainly south and east on Sunday
afternoon as the atmosphere destabilizes. However, this would be
contingent on there being a source of lift to displace parcels,
which there is little of in our area. If anything is going to do it,
it would be the slight wind shift over the eastern half of the
state. Regardless, instability will generally be around 1000 J/kg or
less and wind shear will be non-existent, meaning any convection
would be pulsey and disorganized. This type of convection could
still produce gusty winds and small hail, but generally won`t pose a
significant severe risk. Aside from this low potential for isolated
precipitation, Sunday will remain dry for most, giving us brief
reprieve before another active week starting on Monday.

The upper level pattern overhead becomes more zonal through the
first half of the week as ridging sets up over the southwest CONUS.
This will see multiple waves of convection developing around the
northern periphery of the ridge and over the Plains region, which
will progress eastward toward the state, either in the form of an
MCS or remnant MCV/shortwave which will refire over the state. The
first of these waves begins Sunday night into Monday morning. Short-
range guidance implies this will grow upscale over Nebraska but
eventually dissipate as it loses support from the low level jet on
Monday morning. However, remnants from this system then drift into
Iowa, becoming the source for convection on Monday afternoon. That
said, it`s get too attached to this solution, as it`s dependent on
multiple upstream factors. Since this zonal pattern is so weakly
forced, what happens in Iowa on Monday will depend on the mesoscale
factors that play out with thunderstorms firing off the front range
all the way over in eastern CO/WY Sunday afternoon then it`s
progression and evolution through Nebraska Sunday night and then
into Iowa Monday morning. If you`re familiar with the butterfly
effect, that applies here. Needless to say, it`s a low confidence
scenario, so will be keeping an eye on model and observational
trends through the coming days. Fortunately, this will once
again be an environment with plenty of CAPE but minimal shear,
helping to negate organization and sustainment of storms.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 644 PM CDT Sat Jul 5 2025

Main aviation concern in the short term is the scattered showers
and storms ongoing across portions of the area which have led to
some isolated MVFR to even LIFR conditions temporarily with
reductions to CIGs or visibilities. Although these
showers/storms will persist at times through the next several
hours, most activity should be clear of all sites by 06Z with
areas north/northwest clearing first and areas south/southeast
lingering the longest as storms move northwest to southeast. Few
hints at some fog potential behind the showers/storms overnight,
but not enough agreement in guidance to include at this time.
Winds out of the south to southwest will shift to be out of the
northwest behind the front which continues to move through the
area tonight with winds out of the north on Sunday as well as
some increasing clouds by the evening.

&&

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

&&

$$

DISCUSSION...Dodson
AVIATION...05