796
FXUS63 KDMX 061908
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
208 PM CDT Fri Jun 6 2025

.KEY MESSAGES...

- A 20% chance of a few showers, a storm this afternoon over
  northern Iowa ending this evening.

- 50% to 70% chance of showers and thunderstorms Saturday over
  southern into central Iowa. Another round of showers and
  storms Sunday, but highest chances over 40% are over northeast
  Iowa. Any appreciable severe weather is unlikely.

- Gusty winds of 20 to 30 mph after a front passes Sunday and again
  during the day Monday.

- Seasonal to a bit below normal temperatures through Tuesday, then
  warmer.

&&

.DISCUSSION...
Issued at 208 PM CDT Fri Jun 6 2025

Low amplitude and largely zonal flow is over the central part of the
United States with a jet streak passing to the north and one over
the southern Rockies. While jet streak dynamics are favorable for
lift over Iowa, low level thermodynamics and focused convergence are
rather weak and nebulous. This has resulted in clouds with a bit of
sunshine with a few attempts at sprinkles. A few showers or a
storm is possible this afternoon, likely over northern Iowa,
with an expectation that this activity will diminish overnight.
A stronger shortwave trough that is currently over Wyoming will
move into Iowa by Saturday morning. This along with a weak
surface low just south of Iowa will increase QG convergence with
a higher chance of showers and isolated thunderstorms through
the day. The highest chances over 50% will be over southern into
central Iowa due to the proximity of the shortwave and low
tracks with all chances lowering in the evening as the shortwave
moves east of the state. Severe weather is not forecast with
weak lapse rates and instability.

Right on the heels of this shortwave will be a larger trough that
will be moving out of Canada Sunday into the western Great Lakes. At
the surface, low pressure will be over Canada ahead of the trough,
but a cold front will extend southwestward and move through Iowa
Sunday morning. While low level theta-e advection looks to be at
least modest ahead of the front, the best phasing of this forcing
with mid-level thermodynamics will be over northeastern Iowa into
Wisconsin and northern Illinois. Thus, the highest chances for
showers and storms will be over these areas with lower chances,
generally less than 30%, over central into southern Iowa. While at
first glance deep layer kinematics look impressive, there is a lack
of effective shear, lapse rates are weak, and instability is at most
around 250 J/kg meaning that severe weather continues to look
unlikely. After the front passes, winds from the northwest will
increase. The pressure couplet is weak and while there is a surge in
advection right behind the boundary, sustained winds of 10 to 20 mph
with gusts between 20 and 30 mph will be common. These winds will
draw drier air into the state with dewpoints falling from the middle
50s to low 60s Sunday morning to the middle 40s to low 50s by Monday
morning.

The fitful and gusty winds look to return on Monday as the
trough moves east over the Great Lakes and the southeastern
Ontario province. Another lobe of vorticity will spin
cyclonically around the trough and drop over northeastern Iowa.
This will bring another shot of showers from north central into
northeastern Iowa on Monday. As this trough`s influence departs
the region, mid-level ridging and increasing heights look to
replace it. This will bring rising temperatures with conditions
above normal from mid-week to the end of the week. It will also
result in a mainly dry forecast from Tuesday until at least late
Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1210 PM CDT Fri Jun 6 2025

While VFR conditions are forecast at the terminals, there will
be varying amounts of clouds around this afternoon with most
bases at or above FL030. Spotty showers or storms will form this
afternoon as well, particularly over northern Iowa, but impacts
at any given terminal are too low to include. This activity
will end this evening. The next round of showers and isolated
storms will arrive toward the end of the period. Confidence is
highest at OTM so have included PROB30 mention, but more
widespread and/or prevailing conditions will be needed in
future updates at other terminals.

&&

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

&&

$$

DISCUSSION...Ansorge
AVIATION...Ansorge