Iowa City, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

607
FXUS63 KDVN 100728
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
228 AM CDT Sun Aug 10 2025

.KEY MESSAGES...

- Active weather is expected through the beginning of next week with
  periods of showers and thunderstorms likely.

- Flash flooding is the main concern through the next several
  days with a 25% for excessive rainfall. The strongest storms
  could produce torrential rainfall rates between 1-3" per hour
  and locally damaging winds.

- Widespread 2 to 4 inches of rain are possible through Monday
  with some areas receiving higher amounts.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 220 AM CDT Sun Aug 10 2025

Current radar shows some scattered showers forming across IA as a
warm front extends across the region early this morning. Farther
west there is a larger complex of storms along the NE and MO border
that are being driven east by a compact shortwave. We may see some
additional development within the warm sector of the aforementioned
warm front as our atmosphere remains quite moist and surface dew
points still hitting in the 70s. The main show however will likely
be associated with the thunderstorm complex out west. A
strengthening low level jet will further aide in propelling this
into our forecast area. While CAMs are struggling with the current
set up the HiResW-ARW seems to be initializing the best and brings
the storms into our western borders after 5AM. The environment
remains quite moist with PWATs of around 2" which is around the
90th percentile of climatology for this time of year. Sounding
profiles showcase a deep column of saturation with a warm cloud
depth of over 12,000 ft which will lead to the efficient
production of large raindrops and higher rainfall rates. The
latest HREF PMM precipitation totals continue to favor areas
west of the Mississippi with totals ranging from 3-7."
Unfortunately the CAMs have a lot of descrepancies for
initiation time leading to a larger spread in solutions with an
average spread of 2-3" between the 25th and the 75th percentile.
With this system looking slightly more progressive then
previous forecasted the higher rain totals may be overly
optimistic. Overall, the atmosphere is primed for heavy rain.
WPC has a 25% chance of exceeding flash flood guidance draped
through areas west of the Mississippi.

The initial convective environment boasts higher instability courtesy
of our high dew points. But we are lacking in overall bulk shear.
Any storms firing off of the warm frontal boundary will have a hard
time getting any tilt for sustainability. Shear profiles do start
to improve as the shortwave and storms out west approach in the
morning. This would be the most likely time for any severe storms to
develop. Primary hazards would be damaging winds and large hail.

While the main activity is largely expected to move off to the east
by the afternoon we maintain some higher PoPs through the day. The
environment remains very moist and capable of producing scattered
showers. Additionally, another potent shortwave is projected to slide
in from the west in the late afternoon and evening hours. This will
lead to another round of storms and heavy rainfall. Depending on how
much rain we receive from this first set of storms the soils may be
primed for quick runoffs. For now, we will continue to maintain our
Flash Flood Watch through Monday morning. Severe weather threat will
also still be present with adequate shear and buoyancy to work with.
The primary threat will most likely be damaging winds from heavy
precipitation loading storms.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 220 AM CDT Sun Aug 10 2025

There remains some disagreement among the 00Z suite of deterministic
guidance for the overall departure of rain chances. The NAM is the
most progressive with having rain chances tapering off completely on
Monday as a cold front starts to move in from the NW. However, this
seems to be the outlier with the other models showing a much slower
progression in the pattern. For the time being we will maintain PoPs
of 30-50%.

Once this front moves through we will have a stretch of quieter and
cooler weather over the region. Highs will be in the low 80s on
Tuesday and begin to gradually warm through the week. Towards the
end of the week southerly flow returns over the region and high
temperatures will begin to climb back into the 90s. The southerly
flow will also promote an increase in humidity with our heat
index soaring back into the triple digits by Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1231 AM CDT Sun Aug 10 2025

Convection is likely to blossom across Iowa overnight and develop
northeastward with time. Recent trends have slowed the onset, but it
still seems likely to get going by 08z particularly closer to KCID.
A second wave of convection over Nebraska likely will congeal with
the initial activity and impact the terminals during the morning on
Sunday with IFR/MVFR cigs/vsbys likely. A lull is then expected by
midday/early afternoon, but additional scattered showers and storms
are possible later in the afternoon and evening.

&&

.HYDROLOGY...
Issued at 1236 PM CDT Sat Aug 9 2025

Several rounds of storms are forecast in the next 24-36 hours across
the forecast area. Widespread rain totals between 1-3 inches will be
possible, with some localized totals over 4-5 inches. Some of this
rain could also fall in a very short amount of time resulting in
flash flooding over very wet ground or in urban areas.

There remains high uncertainty where exactly the higher totals
are expected to fall. Where this occurs will be key how high
and how fast the rivers will respond over the coming week. With
the new 24- hr QPF forecasts today and with most streamflow
values in the Iowa tribs running above normal, new flood watches
have been issued for the Fox River at Wayland and for the Des
Moines River at St. Francisville. Additional changes can be
expected in subsequent forecasts as water falls into the river
system.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through Monday afternoon for IAZ040>042-051>054-
     063>068-076>078-087>089-098-099.
IL...Flood Watch through Monday afternoon for ILZ001-002-007-009-
     015-016-024>026-034.
MO...Flood Watch through Monday afternoon for MOZ009-010.

&&

$$

SHORT TERM...Britt
LONG TERM...Britt
AVIATION...NWS
HYDROLOGY...Gross