512
FXUS63 KDVN 240542
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1242 AM CDT Tue Jun 24 2025

.KEY MESSAGES...

- Near daily chances for showers and thunderstorms are found in
  the week ahead. Some strong to severe storms and heavy
  rainfall will be possible at times.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 305 PM CDT Mon Jun 23 2025

As of 1 PM, a cold front with a strong temperature gradient along
and behind it is positioned from southeast NE through central Iowa
to near LaCrosse Wisconsin. Ample moisture is found along and ahead
of this front, with surface dew point values of 70 to 75 common over
the Midwest. Lower 90s temperatures are in place over our CWA, with
near 100 degree heat index readings at 1 PM.  A Heat Advisory will
continue through 8 PM tonight.

These warm and humid conditions are helping the surface based
instability become extreme, with SPC mesoanalysis showing 3-4K J/KG
CAPE as of 1 PM over areas ahead of the front.   This energy has
been held in check by weak capping and lack of forcing so far, but
as the front nears the area this afternoon/early evening storms are
expected to initiate along the front and along any outflow boundary.
While storms are expected to move boundary parallel initially, a
cold pool is expected to drop storms to the south this evening, with
gusty winds from downburst around 60 mph likely, and heavy rainfall.
Heavy rains are more certain than severe weather after 7 PM.  The
question on how far south the storms will migrate tonight remains in
question, but near I-80 seems like a good cut off in confidence.
PWAT values remain forecast by models near 2 inches, near our the
daily max for all DVN RAOBs on June 23 per SPC sounding climatology.
00z HREF ensemble mean shows 1-2" amounts for the 24 hour period
ending 12z Tuesday across parts of the aforementioned area, with the
Localized Probability Matched Mean (LPMM) depicting a signal for
some pockets of higher amounts of 3+ inches. This would lead to a
greater concern for flooding if this were to occur over an urban
area.

Heat continues to be the most widespread threat in our area through
8 PM, and could continue tomorrow, but with nearly all guidance
showing more clouds and rainfall tomorrow, I`m not planning on any
additional Heat headlines at this time for tomorrow.  Tomorrow`s
heat (or not heat), is 100% driven by tonight`s convection/cold
pool, and resultant cloud cover tomorrow as the synoptic cold front
is not expected to bring CAA to our area.

Tomorrow continues to be represented by a day of convective debris
clouds, light winds, and scattered showers and storms. Heat index
readings of 90-97 are currently forecast, mainly south of a Keokuk
to Princeton Illinois line.

Depending on how tonight unfolds, a flood watch may be needed for
much of the CWA, especially in Iowa. Please see the Hydrology
section for more details on flooding potential.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 305 PM CDT Mon Jun 23 2025

Tuesday night into next weekend looks to remain
active/unsettled with the frontal boundary meandering in or near
the area, while aloft also residing on the edge of stronger
southwesterly mid level flow shuttling periodic disturbances
through the region. This will result in episodes of showers and
storms at times. Trying to pin down exact placement and timing
of the greatest rain chances is exceedingly difficult in this
regime. However, wherever the boundary resides will look to
serve as the focus for some strong to possibly severe storms and
heavy rain potentially at times. Some of our northern tributary
rivers (Cedar/Iowa/Wapsipinicon) are experiencing rises from
recent heavy rains in the head waters, and so this will bear
watching throughout the week as depending on where the heavy
rain lays out these rivers could be more susceptible to flooding
with already high flows. Otherwise, it looks to be
quintessential June with very warm/ hot and muggy conditions
throughout the period, which may actually feel more oppressive
than our current heat wave given the added moisture from
rainfall juicing the boundary layer dew points while a weaker
flow regime promotes a more stagnant airmass. Can`t rule out
some areas near advisory level heat index readings of 100+ at
times, particularly southern areas on Tuesday, and then perhaps
expanding again midweek area-wide, but there`s too much
uncertainty with the boundary placement and potential impacts
from precipitation/clouds to extend the current heat headlines.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1236 AM CDT Tue Jun 24 2025

Current round of convection across eastern Iowa is slowly
dissipating as daytime instability wanes. Outflow boundaries
from the convection will result in variable winds through
12z/24. Very short term models suggest a minima in any
convection during the daylight hours Tuesday due to expected
cloud cover. At the very worst it would be 20-30 percent
coverage across eastern iowa and northern Illinois. TS
probability looks low (<20%) so no TS was included in any of the
TAFs.

&&

.HYDROLOGY...
Issued at 305 PM CDT Mon Jun 23 2025

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

Eastern Iowa tributary rivers are currently already running high,
with portions of the Iowa/Cedar/Wapsipinicon near action stage/bank
full today. While the antecedent soils are not overly wet, and
in some areas could really benefit from rains, the boundary
parallel flow and high PWAT (atmospheric moisture content) will
provide a set up for repeating thunderstorms with very heavy
rain. This heavy rain is forecast to be highest over eastern
Iowa through the headwaters in northern Iowa, which is rising
confidence in at least minor flooding on these tributaries in
the days ahead. We have issued a flood watch for the Cedar River
at Conesville IA, and the Iowa River at Marengo, which both are
forecast to reach flood stage Wednesday.


WPC is forecasting a marginal to slight risk over eastern Iowa and
northwest Illinois tonight, with much of the area in that Tuesday
and Wednesday. As soils become wetter, especially in Iowa, we are
moving into a situation where flash flooding is more likely. Right
now, our urban areas are most at risk for flash flooding, but in
days ahead, this threat could include rural areas that become
saturated.

&&

.CLIMATE...
Issued at 313 AM CDT Mon Jun 23 2025

Record High Temperatures:

June 23:
KBRL: 100/1911
KCID: 100/1931
KDBQ: 96/1923
KMLI: 97/1931

Record Warm Low Temperatures:

June 23:
KDBQ: 79/1874
KMLI: 77/1950

&&

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

&&

$$

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