643
FXUS63 KDVN 250545
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1245 AM CDT Wed Jun 25 2025

.KEY MESSAGES...

- An upper level front will keep the heat and humidity across
  the area the remainder of the week along with a daily risk of
  showers and thunderstorms. Some relief may be seen next week.

- Isolated strong to severe storms with heavy rainfall will be
  possible at times late this afternoon and evening, mainly in
  southern/eastern areas.

- Please see Hydrology section regarding potential river
  flooding.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 201 PM CDT Tue Jun 24 2025

Last night`s storms and overnight rains (northwestern areas
received 1-3"!) that fell into the mid morning hours have
provided cloud cover and a weak chaotic wind flow over much of
the CWA today. Only our far east and south remain hot and humid,
and with that, near advisory heat. With clouds increasing in
those areas as of 1 PM, I`ve opted to go with an SPS to cover
the near advisory heat index.

This afternoon and this evening, the differential heating boundary
in the south is expected to serve as a focus for new strong storm
development. CAPE over 3K is over Missouri and central IL, while
under 1K over much of Iowa. Though there`s little shear (<25kts 0-
6km) available, the nearby DCAPE of 1K-1100 will have us watching
for isolated wet microburst activity.  Activity is unlikely to
organize due to the weak flow, but could move the axis northeast
with time this evening both on the upper flow and on outflow
boundary interaction. By mid to late evening, increasing 900-850mb
winds from the southwest are expected to push showers and storms
north, and help them become more widespread in the north 1/2 of the
area into the night. Tonight`s heavy rainfall is not expected to be
as organized as last evening, and with that, no flood watch has been
issued.  The areas in our far west and northwest would be
susceptible to heavy rainfall, but do not appear likely to get
prolonged storms tonight.  The broad picture of having PWAT values
over 2 inches has not changes, thus any storm could produce heavy
rain totals if it moves slowly.

Wednesday, a continuation of lifting the boundary  slowly north is
expected, and without strong forcing, any storms along the front are
hard to predict timing on.  We have continued to advertise a chance
to lower end likely pops along the front as it lifts north.

Despite rain chances, increasingly hot and humid weather is again
forecast in the south 1/2 of the CWA, and we`ll be near advisory
level (100 HI) in the afternoon. Since clouds and precipitation
remain a problem for building the heat, we`ll hold off on an
advisory for now. Thursday will have this similar issue, but
appears to be a mainly dry day through mid afternoon, and is
more likely to see a headline needed for heat.

Thursday has good support from many models for a day which we`ll
build heat / instability through the afternoon, then see a trigger
arrive in the afternoon  and evening. Due to the higher CAPE around
3-4K J/KG forecast, an event similar to last evening is possible,
maybe a bit farther southeast per some CAMS. Low confidence on this
exists, but the broader picture shows that we could have strong to
severe storms between 3 PM and 10 PM Thursday.

Friday, heat and humidity appear to temporarily shift east,
though we`re still quite hot. Westerly winds arriving will
hopefully shift the afternoon storm threats east of our CWA, but
for now we`re maintaining some pops into the afternoon.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Issued at 201 PM CDT Tue Jun 24 2025

Saturday night through Monday

The active weather pattern looks to continue through the
weekend and early next week before a larger scale pattern change
occurs.

The global models are signaling the heat dome over the Midwest will
sink south early next week with a pattern change aloft. This pattern
change will bring a seasonably strong system through the Midwest
late this weekend (generally centered around Sunday) that will cool
down temperatures to near normal by early next week.

As a result, the daily risk of rain will continue for the area
through early next week. As mentioned earlier, the best rain chances
look to be centered around Sunday and Sunday night.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1240 AM CDT Wed Jun 25 2025

Weak lift has developed an area of SHRA/TSRA across eastern Iowa
and northern Illinois. Very short range models have this area of
rain slowly decaying through 12z/25 similar to yesterday. After
12z/25 there is a 20-30% chance of SHRA and possibly an isolated
thunderstorm through 00z/26 that may result in brief MVFR
conditions. The numerous weak boundaries around will keep winds
light until after 18z/25. After 00z/26 more nocturnal convection
will develop from the MN/IA border into southern Wisconsin.

&&

.HYDROLOGY...
Issued at 1138 AM CDT Tue Jun 24 2025

     RIVER FLOOD WATCHES HAVE BEEN ISSUED FOR THE CEDAR RIVER AND
PORTIONS OF THE IOWA RIVER...

Heavy rainfall of 1 to 3 inches fell across portions of central and
eastern Iowa Monday evening, June 21. The combination of heavy rain
this past week, and potentially heavy rains across Iowa and southern
Minnesota in the next 3 days has brought the potential for
significant river flooding on the Cedar River and Iowa River. As
this rainfall materializes the next few days, forecasts for rivers
will become more confident, and flood warnings may be required.

HEFS guidance continues to show a wide spread at the upper end
of forecasts for many Iowa tributary rivers, especially the
Cedar River, including Cedar Rapids. There is a 10-25% chance of
exceeding major flood stage on the Cedar River at Cedar Rapids
early next week. Other points along the Cedar River have similar
potential in the 5-10% range of exceeding major FS. The Iowa
River also continues to see a forecast for potential flooding,
with 10-25% chance for exceeding moderate levels of flooding at
Marengo.

All of this information is 4+ days away from reaching flood
stage, and models are not greatly skilled at determining the
exact latitude/location of heavy rainfall events. However, due
to the potential significant impact of forecast rainfall on
rivers, the RFC is using a 72 hour forecast rainfall amount,
rather than the normal 24 hour amount (QPF). As this rainfall
verifies, or falls into another basin rather than the
Iowa/Cedar, these forecasts are subject to considerable change.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Ervin
LONG TERM...Ervin/08
AVIATION...08
HYDROLOGY...Ervin