724
FXUS63 KDMX 250010
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
710 PM CDT Mon Jun 24 2024

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

.KEY MESSAGES...

- Heat Advisory into the evening across central and west. Heat
  Advisory in the southwest on Tuesday

- Severe potential and heavy rain potential return central and
  south on Tuesday into Tuesday night.

- More convection potential on Thursday night into Friday with
  additional heavy rainfall across portions of central Iowa.

&&

.DISCUSSION...
Issued at 305 PM CDT Mon Jun 24 2024

Sultry airmass has pushed back into the state this afternoon with
heat index values of 100-110 across much of central into western
Iowa.  The heat advisory has been extended up to the I35 corridor to
include the Des Moines metro and Ames areas.  Otherwise, warm mid
level temperatures with +12C at 700mb has pushed across much of the
forecast area during this afternoon.  This has effectively capped
convection for the moment across central Iowa despite MUCAPE values
of +6000 J/KG in western Iowa.  Convection is more likely to develop
farther north into Minnesota later today along the northern edge of
the cap and then scoot southeast, possibly clipping the far
northeast counties of the forecast area but more likely remaining to
the northeast of our area.  This convection is expected to produce
strong to damaging winds as it pushes to the southeast into the
overnight along with locally heavy rainfall.  Otherwise, the airmass
remains very warm and muggy into tonight with lows in the 70s.

Tuesday into Tuesday night is setting up as a complex forecast as a
weak boundary settles into the state during the day.  The hot and
muggy conditions persist south of the front with near heat advisory
conditions once again in far southwest Iowa and have included a
small advisory for that area. Otherwise, CAMS continue to indicate
some convective development by mid to late morning near the
convergence boundary in central Iowa somewhere near the Highway 30
or Interstate 80 corridor.  Some training of this appears possible
into the afternoon and some locally heavy rainfall may occur.
Outflow from this and the placement of the boundary are likely to
affect the eventual evolution of convection into Tuesday evening and
night with central and southern Iowa remaining the most likely areas
for storms.  Damaging wind remains the biggest concern with the
storms later in the day into Tuesday night given the strong
instability and decent downdraft CAPE.  Some large hail may also
occur as well.  This convection moves swiftly to the southeast on
Tuesday night and exits into Missouri and Illinois.

Wednesday into Wednesday night is quiet with drier and cooler air
overspreading the state in the wake of the front. The bulk of
Thursday is also relatively tranquil, however moisture and warm
advection return with a vengeance by the evening as strong low
level flow from the southwest pushes into western Iowa.
Convection is likely to spread into the west during the evening
and push across much of central Iowa during the overnight. A
strong low level jet around 50kt will feed moisture rich air
into the state maintaining convection overnight along with PWATS
around 2" leading to locally heavy rainfall and the potential
for some severe weather. This convection lingers into Friday
with possible redevelopment ahead of a boundary pushing across
the state. Eventually, subsidence arrives by late day into
Friday night with cooler and drier air for much of the weekend.
However, the active pattern returns into early next week with
additional chances of rainfall.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 710 PM CDT Mon Jun 24 2024

Main challenge early will be wind and LLWS overnight into
Tuesday. Expecting cap to hold at H700 overnight, but may see a
line of storms developing along old outflow along I80 corridor
near 17z. Coverage/extent uncertain for now. Additional develop
aft 00z Wednesday is possible over more of the region. Will need
to continue to evaluate that for later packages. /rev

&&

.HYDROLOGY...
Issued at 305 PM CDT Mon Jun 24 2024

Major to historic flooding continues along portions of the West Fork
Des Moines River as well as mainstem Des Moines River above
Saylorville Lake. There has not been much in the way of changes to
going forecasts, however the river may fall more slowly in expected
due to upstream readings in Minnesota. If we do make any changes to
the forecast in the Des Moines basin or elsewhere the changes would
likely be downward slightly.

Looking ahead to potential rainfall through the week, the most
immediate concern for heavier rainfall will be Tuesday, as most of
the rainfall today is expected to avoid our forecast area.
Fortunately for those being impacted by river flooding in northern
Iowa, the higher QPFs currently favor southern Iowa, and even if
heavier rainfall develops north, it will quickly drop south with the
front. That being said, any heavy rainfall could still delay
improvement to flood conditions, if only briefly. Additional shower
and thunderstorm chances are expected again Thursday night into
Friday. That additional rainfall may either result in quicker rises,
higher crests or slower falls. When it comes QPF its location,
amounts and timing are everything in terms of the river response.

Make sure to stay up to date on the latest forecasts and river
information, and use extreme caution in flooded areas.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for IAZ004>006-015-
016-023>025-033>036-044>048-057>060-070>073-081>083-092>094.
Heat Advisory from noon to 7 PM CDT Tuesday for IAZ070-081-082-
092>094.

&&

$$

DISCUSSION...Cogil
AVIATION...REV
HYDROLOGY...Zogg