990
FXUS63 KDVN 072312
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
612 PM CDT Mon Sep 7 2026

...Updated for 00z Aviation...

.KEY MESSAGES...

- A storm system passing through the Upper Midwest Tuesday
  evening into Wednesday will bring widespread showers and
  storms to the area. There will be a low-end risk for strong-
  severe storms, with heavy rainfall accompanying storms.

- Quiet weather Thursday into Friday, as high pressure passes
  overhead. Seasonal conditions will remain, with mostly clear
  skies.

- Another stretch of potentially active weather this weekend
  into the next work week, bringing daily chances of
  precipitation for some.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 214 PM CDT Mon Sep 7 2026

Weak upper ridge will start to break down overhead tonight, with
surface high pressure over the Great Lakes Region getting shunted
east. As this pushes east, llvl southwesterly flow increases
overhead in response to a shortwave trof digging into the north-
central CONUS. Overnight tonight, plenty of llvl dry air will
remain, with increasing mid-high clouds resulting from this return
flow. Overall dry conditions will remain through the night, with
temperatures in the 60s and a light breeze.

Tuesday into Tuesday night, we will start to see a stronger response
from the increasing warm advection overhead, especially later in the
day. Prior, we will see temperatures increase well above seasonal
norms once again. Areas along and south of Interstate 80 will near
90s degrees, if not reach the low 90s, with areas north in the mid-
upper 80s. Fortunately, the better moisture will not move in until
late in the day, which should largely keep heat indices below 100
through the afternoon. Areas south of Interstate 80 in Eastern Iowa
will have the better chance of seeing  heat indices approaching the
mid-upper 90s. So, even though we might not be oppressively hot like
last week, we will still be quite warm tomorrow. Later Tuesday
afternoon and through the evening, the LLJ will increase to near 25-
35+ KTs. This will increase moisture quite a bit, pooling
along/ahead of a cold front approaching from the northwest
overnight. This increase in moisture will result in PWATs nearing
2.00"+. Thus, with plenty of moisture in place and sufficient
upper/lower level forcing moving in, widespread showers and storms
are likely Tuesday evening into Wednesday.

There will be a low-end severe threat with these storms, but
confidence remains low. Short term guidance favors meager
instability (<1000 CAPE) with deep layer shear around 30 KTs. Thus,
while an organized storm cannot be ruled out, the threat for a
strong to severe storm should be relatively isolated. The primary
threat with any strong-severe storm will be damaging wind gusts,
largely influenced by precipitation loading in the thunderstorms.
Secondary threat would be hail, but confidence in this occurring is
low at this time. Another expected impact from these storms is heavy
rainfall. The increasing jet overnight will converge into the
approaching cold front, where we will also see streams of vorticity
ahead of the main wave providing forcing for rounds of potential
showers/storms. Widespread rainfall can be expected in eastern Iowa,
with lesser coverage east of the Mississippi River. Some areas may
see repeated rounds of showers/storms through the night, where
localized areas may see 1.00-2.00" of rain. Given the recently dry
and hot conditions, soils should have capacity for much of this to
easily infiltrate the ground. Although, with PWATs around 2.00"+
(well above seasonal norms), quick and efficient rainfall
accumulation is possible in areas. Thus, a localized flash flood
threat cannot be ruled out, especially for eastern Iowa. As such,
the WPC has highlighted these areas in a Slight Risk, level 2/5, for
Excessive Rainfall.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 214 PM CDT Mon Sep 7 2026

Cold front isn`t expected to be out of our area until early
afternoon on Wednesday, which will keep precipitation chances over
much of the area through the first half of the day. We will see
shower/storm coverage decrease from northwest to southeast through
the morning, with best chances for precipitation in the afternoon
hours for areas in western Illinois and northeastern Missouri. At
this time, we are not expecting much in the way of strong-severe
storms. Much of the remaining instability will have been worked
through, leaving us with a shield of stratiform rain and little/no
embedded thunder. Otherwise, we will see mostly cloudy conditions
through the day, with temperatures in the low 80s and light west to
northwest winds.

Thursday into Friday, upper level flow becomes more northwesterly as
a weak wave passes through and weak ridging builds over the Central
CONUS. This wave will be through our area by midday Thursday, with
surface high pressure moving in behind. A brief period of quiet and
seasonal weather will result, with mostly clear skies and
temperatures around 80 on Thursday into Friday. Overnight
temperatures will cool off a bit compared to recent nights, with
most in the mid 50s. Friday, the weak ridge will pass east of the
area, with southwesterly flow increasing ahead of a quickly-
approaching shortwave trof. This wave is due to come through Friday
night into Saturday, prompting our next chance of precipitation (30-
60% chances). Showers and storms will be possible along the
associated cold front, but accumulations should be on the lower-end
due to the quick movement of this wave. There remains some
uncertainty, owing to moisture availability.

Saturday and beyond appear to be a continuation of potentially
active weather, with us falling largely under upper level zonal to
southwesterly flow. This patten would favor us falling under the
path of passing shortwaves through the weekend and into next week.
Thus, daily PoPs (20-40%+) are in the forecast through this stretch,
with temperatures remaining above seasonal norms.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 605 PM CDT Mon Sep 7 2026

Predominantly VFR conditions expected through the TAF period.
Easterly winds around 10 kt tonight will turn more southerly on
Tuesday gusting to 20+ kt. PROB30 mention for a shower was
included at CID/DBQ Tuesday 13z-17z for decaying precipitation
from central and northern Iowa moving in attendant to a waning
nocturnal LLJ. Redevelopment of shower and storms are possible
toward the end of the period (<30%) northwest, but the better
chances (60-80%+) will be found mainly 03z-18z Wednesday area-wide.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...Gunkel
AVIATION...McClure