Coralville, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

447
FXUS63 KDVN 192001
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
301 PM CDT Sat Jul 19 2025

.KEY MESSAGES...

- Flash Flood watch remains in effect through 1 PM Sunday for
  parts of the area. Additional rounds of heavy rain through
  Sunday may lead to areas of flash flooding.

- A ring of fire pattern will set up over the Midwest. This will provide
  daily thunderstorm chances through mid-week. Some of which
  could be strong to severe with heavy rain and flash flooding.

- Seasonable temperatures through Tuesday before the heat returns
  mid-week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 PM CDT Sat Jul 19 2025

Mostly clear skies have allowed temperatures to warm back into the
80s after this morning`s MCS & heavy rain. High temperatures should
top out in the mid 80s with dew points in the 70s. The remainder of
the afternoon should be quiet with a much needed break from active
weather. That break will end this evening with an additional round
of thunderstorms & heavy rain potential on tap. SPC maintained a
slight risk for severe storms this evening & tonight with the main
threat being damaging winds. Potential for another round of heavy
rainfall is expected tonight into Sunday morning. This round of rain
is concerning given it will fall on saturated soils due to our
current stretch of active weather. The Weather Prediction Center has
much of the area outlooked in an upper end slight risk for excessive
rainfall. Tropical-like moisture is over the region with
precipitable water values of 2.0 to 2.2 inches. Add in favorable
warm cloud layer depth and we have ingredients to support the heavy
rain & potential for flash flooding. I`ve opted to maintain the
flash flood watch in effect across the area through Sunday
afternoon. Please read the hydrology section below for a more in-
depth discussion on the flash flood potential tonight & Sunday.

Our focus turns to the severe potential this evening into tonight. A
differential heating boundary is present across Iowa that should act
as a focus point for additional convective development this evening.
Initial storms should form upstream over western & central Iowa
before moving eastward overnight. Forecast soundings depict a
favorable environment with moderate instability with 2000-3000 j/kg
MLCAPE & 50+ knots of effective wind shear. There is a notable cap
in place that will need to erode before convection can develop. The
combination of CI attempts & strengthening LLJ should lead to
successful CI across W/WC Iowa that`ll track eastward
overnight. These storms will be initially capable of gusty winds
& hail before transitioning to a primary heavy rain threat.
Further upstream a shortwave will promote convective initiation
across NE that`ll congeal into an MCS/MCV that`s forecast track
into the Quad Cities area around daybreak early Sunday morning.
The unknown is if we`ll see this evening`s convection move
across the same area`s as the MCS/MCV later tonight/Sunday AM.
If that occurs - there will be increased potential of flash
flooding over the area that is impacted by BOTH rounds of
thunderstorms & heavy rain.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 259 PM CDT Sat Jul 19 2025

The pattern remains favorable through early next week for additional
thunderstorm potential. An upper level ridge remains in place over
the central CONUS with DVN on the northern periphery on the ridge.
This pattern is typically referred to as a "Ring of Fire" that
supports daily thunderstorm complexes moving along the northern edge
of the ridge. There is a daily chance for these complexes to impact
the area with potential severe & heavy rain. By mid-week, there is
good agreement that the upper ridge will build into the region -
pushing the severe thunderstorm threat northward into the Upper
Midwest (Dakotas/MN/WI). This will also lead to the return of warmer
temperatures (upper 80s/lower 90s) & higher humidity. Heat indices
of 100+ appear possible given the additional low level moisture in
place due to evapotranspiration (corn sweat) across the region.
A cold front is progged to move through late week that should
return more seasonable temperatures & additional PoP chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1235 PM CDT Sat Jul 19 2025

Skies will continue to clear out this afternoon. IFR/MVFR
ceilings are lingering at KMLI but conditions will improve to
VFR shortly after TAF issuance. Another round of storms remains
possible this evening and overnight.There is some uncertainty on
where thunderstorms develop this evening, but I`ve adjusted the
PROB30 group to reflect period of best confidence across each
taf site.Latest HRRR fires TS to the west of our sites in C IA
before tracking into E IA & the Quad Cities area. Confidence in
timing has increased with possibly in the window from 5 to 12
UTC. MVFR to IFR ceilings and visibilities will be possible in
the strongest storms. Showers may linger into late Sunday
morning.

&&

.HYDROLOGY...
Issued at 1053 AM CDT Sat Jul 19 2025

What has changed...

A flood warning has been issued for the Iowa River at Marengo,
IA.

A flood watch has been issued for the North Skunk River near
Sigourney, IA.

Discussion...

Overnight bands of 1 to 3 inches of rain fell across parts of
eastern Iowa and west central Illinois. Within those bands were
localized pockets of 3+ inches.

Another round of heavy rainfall is expected tonight into Sunday
morning. This round of rain is concerning as the Weather
Prediction Center has much of the area outlooked in an upper end
slight risk for excessive rainfall. The risk of excessive
rainfall will continue into Monday night.

As mentioned yesterday atmospheric moisture levels will be
near 2 inches tonight which is greater than the 90th percentile
for July. With a tropical moisture connection developing with
the Gulf, warm rain processes have a high probability of
dominating which will lead to very efficient rainfall production.
There is a high probability of rainfall rates of 1 to 2+ inches
per hour.

Data so far this morning from weather models is pointing to the
general area of along or south of I-80 as being the focus for
the heavy rainfall tonight into Sunday morning. There will
likely be more bands of 1 to 3 inches of rain with locally
higher amounts. If storms repeat over the same areas (there is a
50-60% probability of this occurring) then rainfall rates of 2+
inches per hour would lead to rapid runoff and resultant flash
flooding. This additional round of heavy rainfall will produce
general rises on area rivers with the potential for river
flooding.

The following tributary rivers will need to be watched carefully
through the end of July since they already have above to much
above normal streamflows; Cedar, English, Iowa, North Skunk,
Skunk and Wapsipinicon.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through Sunday afternoon for IAZ051>053-063>068-
     076>078-087>089-098-099.
IL...Flood Watch through Sunday afternoon for ILZ015-016-024>026-
     034-035.
MO...Flood Watch through Sunday afternoon for MOZ009-010.

&&

$$

SHORT TERM...BPH
LONG TERM...BPH
AVIATION...BPH
HYDROLOGY...08