586
FXUS63 KDVN 151922
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
222 PM CDT Tue Sep 15 2026

.KEY MESSAGES...

- While there is a Marginal, level 1 out of 5, Risk for severe
  storms through this evening, the weak forcing and warm air
  aloft may limit any severe risk to a few isolated storms.
  Damaging winds are the primary risk.

- An active weather pattern will persist through the weekend
  with rounds of rain, some potentially heavy, expected. There
  will be brief respites in the active pattern the second half
  of the week.

- With each round of rainfall, the risk of flash flooding will
  be on the increase the second half of the week and weekend,
  especially if storms repeat over the same areas. There is a
  medium to high chance (40-75%) for portions of eastern Iowa to
  see over 2 inches of rainfall, with localized areas of 4+
  inches possible (5-10%). By the weekend, general rises are
  expected on area waterways.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 220 PM CDT Tue Sep 15 2026

Convergence at 850 mb is allowing a band of light rain/sprinkles to
persist across the northwest part of the area. Said convergence of
moisture/wind will slowly weaken through sunset and allow the rain
to dissipate.

Convergence and lift along the southward moving front is weak, and,
combined with warm temperatures aloft raises questions regarding the
potential for convection this afternoon/evening. However, given the
energy potential building in the atmosphere and recent radar trends,
isolated to low end scattered (15-35%) coverage of some diurnal
convection is reasonable. The energy potential is there for severe
storms, but as mentioned earlier, the warm air aloft may limit the
severe potential.

Late tonight and into Wednesday morning the LLJ will increase the
lift and moisture convergence across the front. From a QPF and
reflectivity standpoint the CAMs are struggling. Internally,
however, the models are suggesting the better potential for rain and
storms is south of a line from Ottumwa, IA to Sterling, IL. Given
PWATs progged to be 2+ inches in this area, heavy rainfall is a
given. The saving grace is that this area received little or no rain
the past 24 hours and thus should be able to take this round of rain
with not much problems, save urban areas.

Thus tonight into Wednesday morning areas of 1-2 inches of rain
across the southeast half of the area is fairly high. Locally
heavier amounts of 2-3+ inches are definitely possible.

As the LLJ weakens Wednesday morning the areal coverage of rain and
embedded thunderstorms will slowly decrease. Residual showers and a
few storms will be possible through the afternoon but will be
isolated to scattered (20-40%).

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 220 PM CDT Tue Sep 15 2026

Wednesday night through Thursday night
Assessment...medium confidence (40-50%) confidence on rain occurring.
Low (<20%) confidence on where rain will occur.

A frontal boundary will vacillate across the area through Thursday
night. Both nights the LLJ will increase and help initiate new rounds
of storms across the area. The signal for this is a given. The
uncertainty is where each round of showers/storms develops and moves
during the overnight hours of Wednesday night and Thursday night.

During the day on Thursday, the nocturnal round from Wednesday night
will slowly dissipate during the late morning. Thursday afternoon
looks to be mainly dry with some isolated diurnal convection
occurring on boundaries left over from the morning rain.

Friday-Saturday...The mid-level trough moves into the Dakotas and
Minnesota, dragging the Colorado low with it towards Iowa. A
WAA wing will likely develop along the warm front moving into
our CWA and force more scattered storms (50-70% coverage).
Muggy conditions are likely (60-90%) to return Friday into
Saturday with dew points back into the upper 60s and 70s
areawide. By Saturday, the low pressure slowly meanders across
the Upper Mississippi River Valley as another round of
scattered storms (40-70% coverage) is forecast to form from the
enhanced surface convergence.

Sunday-Tuesday...The trough over the western CONUS finally
ejects eastward into the Northern Plain on Sunday, introducing
the upper- level flow needed to kick the low pressure sitting
over the region eastward towards the Great Lakes. With the
return to northerly surface flow/dry air advection on the
backside of this low, PoPs should decrease on Sunday with Monday
likely (80-95% chance) being the first area-wide dry day in
over a week as seasonable conditions resume!

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1230 PM CDT Tue Sep 15 2026

Weak front will stall out across northern Missouri and central
Illinois by sunset with some isolated TSRA in southeast Iowa and
west central Illinois. Increased lift across the front will
bring another round of rain with embedded TSRA after 03z/16 that
will continue through 16z/16 before decreasing in areal
coverage. Probability is high (>80%) of widespread MVFR with
areas of IFR developing by 12z/16 across eastern Iowa and
northern Illinois.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08/Delaune
AVIATION...08