764
FXUS63 KDMX 010624
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
124 AM CDT Mon Jun 1 2026

.KEY MESSAGES...

- Ongoing storms over western Iowa will pose a risk of large
  hail, gusty winds, and locally heavy rainfall as they move
  into our forecast area in the next few hours. These should
  wane in intensity through the remainder of the night though.

- Today/Monday is favoring drier conditions with capping in
  place to limit if not prevent storms. However, similar to
  yesterday/Sunday, if storms can develop late this afternoon or
  early this evening, a few severe storms with large hail,
  gusty winds, and locally heavy rainfall are possible.

- High pressure drifts southward through the Great Lakes into
  the Ohio Valley, which pushes rain and storm chances west of
  the state through Wednesday. Highs above normal in the 80s.

- Storm chances look to return late in the week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 124 AM CDT Mon Jun 1 2026

Monitoring ongoing convection over western Iowa that is just
beginning to push into our forecast area. Storms west of a Sac
to Cass County line have had warnings the last few hours with
hail reports up to an inch with radar indicating larger sized
hail. SPC mesoanalysis shows these storms have 2000 J/kg of
MUCAPE and effective shear around 30 knots. They are also moving
slowly around 15 to 20 mph. There are several storms lined up
west to east and while they are not moving due east, will have
to watch for repeat rounds of rainfall if they occur over our
forecast area with the heavy rainfall parameters favorable with
precipitable water values around 1.5 inches and deep warm cloud
depths. WPC just recently issue mesoscale precipitation
discussion 291 that highlights the risk of flash flooding as
well. To the north, another storm cluster is pushing in from the
Spencer area, which had a wind gust to 45 mph around 1230am.
These storms are expected to remain below severe limits as the
outflow boundary has already pushed out ahead of this cluster.
Outside of the next few hours when storms are expected to be
their strongest to possibly severe, it is expected that the
storms over Iowa will trend downward through sunrise as the low
level jet (LLJ) is forecast to veer and point over Missouri the
rest of the night.

Thereafter, forecast soundings show a warm capping layer aloft,
which should suppress storm develop through much of the afternoon.
Thus, the daylight hours today will have a good deal of sunshine and
it will be warm. As was the case on Sunday, the question becomes
whether there is enough forcing to overcome the cap. If so and
storms are able to develop, there will be sufficient instability
with mixed layer CAPE values between 1500 and 2500 J/kg and deep
layer shear near 30 knots (RAP) to a bit above (NAM/GFS). However,
it remains unclear what the forcing will be for storms tonight with
the LLJ focused west of the state. The omega block pattern remains
over the CONUS and there is subtle shortwave energy approaching the
top of the ridge axis, which will be center over roughly the Iowa
Nebraska border late today. So, that is a possible mechanism.
Looking at convective allowing models (CAMs) for possible scenarios,
they generally show storms trying to develop late this afternoon or
early this evening over some portion of western Iowa. The exception
is the RRFS (both cores) that initiate storms over south central
Iowa. This would seem less likely given that it would be more
removed from the shortwave energy just discussed. If storms can form
and sustain for any appreciable time in the evening, gusty winds,
large hail, and heavy rainfall will be the main hazards. Much
farther west of the state, storms are forecast to develop on the
High Plains and push towards the state as a mesoscale convective
system (MCS). This is expected to weaken as it nears Iowa with drier
air pushing into the state and also outrunning the LLJ axis.

After any storms dissipate tonight/Monday night, attention will be
on a zone of high pressure dropping south from Hudson Bay over the
Great Lakes region on Tuesday. With drier easterly flow pushing into
the state, this will also shunt the higher moisture axis west of
Iowa providing for dry and warm conditions on Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 253 PM CDT Sun May 31 2026

Warm conditions continue this week with highs in the 80s. A Great
Lakes high looks to keep conditions dry Tuesday into Wednesday with
storm chances returning later in the week as the upper ridge finally
breaks down. By the end of the week, temperatures may warm further
as southwest flow kicks in with additional storm chances into the
weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1053 PM CDT Sun May 31 2026

A scattered line of storms is beginning to develop in eastern
Nebraska and will move east into western Iowa overnight. Current
expectations are for activity to diminish before reaching TAF
sites and have not included any mentions, however will need to
monitor for possible later adjustments. Patchy fog development
remains a possibility on Monday morning, however uncertainty
with cloud cover and degree of cooling was too high to include
at this time. Light wind under 10 kts will be from the ESE this
evening, becoming variable overnight, then from the ENE on
Monday.

&&

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

&&

$$

SHORT TERM...Ansorge
LONG TERM...05
AVIATION...Hagenhoff