099
FXUS63 KDMX 052335
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Fri Jun 5 2026

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

.KEY MESSAGES...

- A lull in the storm activity for much of today, but storms return
  this evening and tonight, mainly across southern and central
  Iowa. There are renewed concerns for flash flooding and severe
  storms with all hazards possible.

- Much of Saturday will be dry but muggy, with scattered late
  day and evening storms again possible across central and southern
  Iowa.

- Heavy rain is a concern for renewed showers and thunderstorms
  on Sunday into Monday. Then heat builds next week with many
  areas exceeding 90 degrees.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 1214 PM CDT Fri Jun 5 2026

Upper air pattern early this afternoon features a low amplitude
upper trough moving through the northern Plains and upper
Midwest. Still seeing rather thick cloud cover across much of
Iowa due to abundant low level moisture (enhanced by yesterdays
rainfall) trapped under the developing inversion. The storms
from overnight pushed the effective sfc boundary into Missouri
this morning, but the latest sfc obs show winds shifting back
southerly across portions of southern and central Iowa. Some
breaks in the cloud cover have allowed temps to climb into the
70s, and expect some additional heating the remainder of the
afternoon.

With the expected high temperatures (upper 70s to lower 80s)
model soundings continue to show at least a weak cap /MLCIN of
-25 J/kg/ remaining over much of the CWA through early evening.
With generally weak background forcing/ascent, any CI will
likely be tied to moisture convergence along the sfc boundary.
Several of the CAMs /HRRR, RRFS/ try to initiate isolated storms
across far southern Iowa from 22-00Z. While very conditional, if
any storms can initiate in that region, strong MLCAPE /2000-3000
J/kg/, steeper mid-level lapse rates, and effective deep layer
shear values of 25-35kts could lead to supercell development.
Large hail and damaging winds would be the primary threat,
although an isolated tornado is possible, especially near any
locally backed flow and enhanced SRH near the boundary.

The more robust severe threat will occur later in the evening
and then continue into the overnight as stronger lift develops
due to the strengthening nocturnal LLJ. Good model consensus
shows storms developing over ern NE/swrn IA from 9-11pm CDT and
then expanding eastward along the sfc boundary. Highest threat
for storms will generally occur along and south of I-80, but
will be ultimately dependent on where the sfc boundary ends up.
Even during these overnight hours, favorable MUCAPE/effective
shear will continue at least an isolated severe weather threat
/mainly hail and wind/ along with an escalating heavy rain
threat, see Hydro Discussion below. Storms will likely persist
until around sunrise Saturday before gradually weakening. See
the SPC Day 1 Slight Risk (Level 2 of 5) and any forthcoming
SWOMCDs for further details.

Saturday and Saturday Night..

Any remaining storms will be diminishing on early Saturday
morning. Shortwave upper ridging is then expected to develop by
Sat afternoon, with broad subsidence and little in the way of
forcing noted. As such, still expecting much of Saturday to be
dry, warm, and muggy, with highs again in the 80s. The
deterministic models and CAMs do indicate the possibility for
isolated/scattered late afternoon or evening storms, potentially
along any sfc or residual outflow boundaries. The most likely
location of storms is again across central and southern Iowa,
where the strong instability will reside, MLCAPE of 2000-3000
J/kg. Wind shear in that same area remains generally weak /less
than 20 kts/ so mainly pulse or perhaps multicell storms being
the most likely mode, with marginally severe hail or wet
microbursts possible. A SPC Day 2 Marginal Risk (Level 1 of 5)
appears reasonable for now. Any storms will be diurnally driven,
with activity waning after sunset.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 1214 PM CDT Fri Jun 5 2026

An upper level cutoff low across the southern plains on Sunday
morning will lift into the midwest by the afternoon and evening.
Deep moisture transport out of the gulf increases into Iowa,
especially southern Iowa. Scattered daytime showers and
thunderstorms may linger with renewed thunderstorms developing
in the evening and continuing overnight into Monday morning as
the upper low/trough tracks across Iowa. The threat for severe
storms appears low at this time with deeply saturated soundings
exhibiting very little instability (500 J/kg) or shear (20 kts
or less). The primary concern this period will be additional
heavy rain across southern Iowa, following heavy rain Thursday
and Friday nights. With PWATs near 2 and deep warm cloud layers
exceeding 4000m, expect efficient rain fall across southern into
central Iowa.

The upcoming week should be mainly dry, though few weak waves
skimming the area could bring renewed showers or thunderstorms
to the area. Heat builds through the week as the thermal ridge
expands and shifts into the midwest. While NBM guidance has
rockets up into the mid to upper 90s by the middle to end of
next week, this seems overdone from over mixing and with weak
waves thwarting the highest temperatures. NBM has been on the
highest end of the guidance envelope the past several cycles and
will continue to need nudging down unless the pattern changes.
Despite the overzealous NBM, temperatures will still be quite
warm and reach the upper 80s to low 90s. The next more organized
chance for precipitation arrives late in the week around
Thursday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 632 PM CDT Fri Jun 5 2026

Thunderstorms are expected to develop tonight which will impact
terminals in southern to central Iowa (KDSM and KOTM) while
northern terminals will not be impacted, though a stray shower
or two can`t be ruled out in the north. With these
thunderstorms, KDSM and KOTM may have intermittent MVFR
conditions as thunderstorms move through. At northern terminals,
however, IFR fog may develop overnight tonight. After sunrise
and any fog dissipates, MVFR to VFR conditions are expected
across Iowa through the day tomorrow.

&&

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

&&

$$

SHORT TERM...05
LONG TERM...Fowle
AVIATION...Rotter