637
FXUS63 KDMX 051746
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
Issued by National Weather Service Twin Cities/Chanhassen MN
1246 PM CDT Fri Jun 5 2026

.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 NIGHT/...
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 /SUNDAY THROUGH THURSDAY/...
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 /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1214 PM CDT Fri Jun 5 2026

While cloud cover from early morning storms is lifting, pockets
of MVFR to IFR conditions remain within the broader VFR cloud
deck. VFR conditions are expected to last through this afternoon
and into the evening. Then additional thunderstorms develop
across southern Iowa late tonight, lifting into central Iowa
overnight into early Saturday morning with most likely impacts
at KDSM/KOTM. Winds today are from the west-southwest at 10-15
mph with direction becoming variable in the vicinity of
thunderstorms later this evening.

&&

.HYDROLOGY...
Issued at 1244 PM CDT Fri Jun 5 2026

Short and long term flooding concerns exist through this
weekend. In the short term (tonight through Saturday morning),
additional heavy rainfall tonight will lead to flash flood
concerns mainly along and south of U.S. Hwy 30, where WPC
indicates a slight risk of flash flooding from excessive
rainfall, with a marginal risk generally as far north as U.S.
Hwy 20. Comparing NASA SPoRT-LIS 10 cm (4 in) soil moisture
percentiles at 6/4 00Z and 6/5 00Z, as well as comparing event
QPE through 6/5 00Z with 6/5 12Z, suggest soil moisture
percentiles in the slight risk area are at or above the 70th
percentile for this time of year, which indicates soils
predisposed to increased runoff from additional heavy rain
tonight. FLASH CREST and SAC-SMA soil moisture percentiles
concur with elevated soil moisture shown in those areas.
National Water Model rapid onset flooding (ROF) probabilities
have also been persistently elevated mainly in south central and
southeast Iowa. Finally, WPC Urban Rain Rate Dashboard (URRD)
for Des Moines indicates a moderately elevated risk of flash
flooding there.

The above information means an elevated risk of flash flooding
exists tonight mainly along and south of U.S. Hwy 30, both from
sheer rainfall intensity as well as rainfall amounts. The
greatest risks will be in towns and cities (including the Des
Moines metro area) where the heavier rain falls. Creeks and
smaller streams that rose from last nights rain will have
reduced capacity for additional runoff as well, so less rain
will be needed tonight to increase flooding concerns on those
smaller waterways.

Longer term, additional risks of flash flooding exist into the
weekend, especially Sunday into Sunday night, where WPC
indicates another slight risk of flash flooding from excessive
rainfall over far southern Iowa, with a marginal risk elsewhere.
To an extent, however, the evolution of tonights event will
affect the risk of flash flooding later in the weekend. If
tonights event underachieves then the risk will be lower. The
opposite will be true if tonights event overachieves.

The risk of river flooding over the next several days is
minimal, with HEFS probabilities of reaching flood stage
generally less than 10-20%. The most likely scenario is runoff
from rainfall tonight through early next week leading to minor
to moderate within-bank rises.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 7 PM CDT this evening through Saturday
morning for IAZ081>084-092>096.

&&

$$

SHORT TERM...Fowle
LONG TERM...Hagenhoff
AVIATION...Hagenoff
HYDROLOGY...Zogg