172
FXUS63 KDVN 142324
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
624 PM CDT Mon Sep 14 2026

.KEY MESSAGES...

- Active pattern this week with numerous rounds of showers and
  storms with heavy rainfall at times.

- There continues to be a Marginal Risk (Level 1 of 5) for
  severe storms this evening into tonight for portions of
  eastern Iowa. Primary hazards will be heavy rainfall and
  isolated damaging winds.

- An elevated flash flooding risk may develop mid-week with repeating
  rounds of storms. There is a medium to high chance (50-70%)
  for portions of eastern Iowa to see over 3 inches of rainfall,
  with localized areas of 5+ inches possible (5-15%), leading
  to rises on area creeks and streams.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 239 PM CDT Mon Sep 14 2026

An active pattern will march on tonight throughout the week, with
repeated rounds of showers and storms. Synoptically, we will
continue to see a large upper-level anti-cyclone over the
southeastern CONUS through much of the week, with large-scale
troughing over the Pacific NW. This afternoon, an area of high
pressure over the central Great Lakes has helped to bring southerly
return flow/warm air advection over the area, with generally light
showers over northeastern Iowa. In time, these showers will lift
northward out of the area, leading to a brief respite from the
precipitation late this afternoon through the early evening.

Chances of showers and storms (70-90%) will increase across our
north late this evening and expand southward overnight tonight. This is
ahead of a cold front that will be our main forcing mechanism for
shower and storm activity for much of the week. Concurrently, a
southwesterly 45 to 55 knot low-level jet (LLJ) will also help to
enhance convergence and moisture transport ahead of the boundary,
with Pwat values progged to exceed 2 inches tonight. Pwat values
this high this time of the year is quite rare, placing above the
the percentile per the NAEFS ensemble. Instability will be
fairly modest, with MUCAPE values around 500-1000 J/kg and very
weak mid- level lapse rates. Deep-layer shear is a bit more
robust given the stronger kinematics, with 0-6 km shear around
40 to 50 knots. With all of this said, SPC continues to outline
a Marginal Risk (Level 1 of 5) for severe storms late this
evening through the overnight hours, mainly for a damaging wind
threat given the stronger shear. Additionally, rainfall amounts
will need to be watched closely overnight with the stronger LLJ
and extreme Pwat values that could support some flash flooding.
The 14.12z HREF ensemble PMM QPF values appear to range between
1-2 inches for a 6-hour period between 06-12z tonight, mainly
over east-central Iowa, with isolated 2-3" possible. FFG values
are right around these values, so some isolated flash flooding
remains possible. One area to watch for is around the Cedar
Rapids metro, which could support enhanced runoff.

As the cold front continues to dive southward Tuesday, and the
nocturnal LLJ waning by sunrise Tuesday, the latest high-res
guidance suggests a brief lull in the activity before things ramp up
again during peak heating Tuesday afternoon across our south. The
convective parameter space ahead of the boundary still shows more
modest values, with SBCAPE values around 500-1000 J/kg per the HREF,
with deep-layer shear slightly more favorable for stronger
storms (around 30 to 40 knots). With a pretty weak low-level
shear environment, damaging winds continue to be the primary
threat, and SPC has maintained a Marginal Risk for areas along
and south of a Keosauqua, IA to Walnut, IL line.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 219 PM CDT Mon Sep 14 2026

By Tuesday night, the cold front will stall out across northern
Missouri and central Illinois and act as the focal point for
additional rounds of showers and storm to redevelop mid- to
late-week. A nearly stationary longwave trough over the western
CONUS and ridging over the Southeast will keep our upper-level
flow out of the southwest through Thursday as weak shortwaves
are pulled northeastward into the Midwest. This will keep PoPs
around Tuesday night into Thursday as scattered showers and
storms fire along and north of the stationary front. With Pwats
over 1.75 inches likely (70-90%) area-wide through Thursday, the
flooding threat will remain elevated, especially after the
heavy rainfall tonight and Tuesday. Per the latest NBM, there is
a medium to high chance (50-70%) of total rainfall of 3 inches
or more over much of eastern Iowa through Thursday with
localized areas exceeding 5 inches possible (5-15%). Rises on
area creeks and streams are likely.

Heading into Friday, a Front Range low in Colorado is forecast to
form due to forcing from a lobe of mid-level vorticity pulled
northward from the subtropics. This will introduce a more southerly
component to the low-level flow as the stationary front converts to
a warm front and moves northward into Iowa. The upper-level flow is
expected to become zonal and force the Front Range low eastward
Friday night into Saturday. The increased surface convergence will
support another round of storms before the same boundary is left
behind for Sunday, keeping PoPs in the area.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 616 PM CDT Mon Sep 14 2026

Southeast winds will be gusty this evening, at 12 to 22 kts, and
some gusts up to 25kts. Generally VFR weather will continue,
with mainly dry conditions through late evening, at which point,
an area of rain and thunderstorms will spread northeast across
Iowa, reaching the CID and DBQ areas between 04Z and 07Z. Heavy
downpours will be possible, along with gusty winds. Overnight,
this area of rain and thunderstorms will slowly progress south,
reaching MLI towards 10-14Z, and BRL after 12Z. Prior to arrival
of storms late this evening and overnight, a period of LLWS is
expected as winds aloft will be strong from the south, at 40 to
50kts. Once storms arrive, this LLWS is expected to drop south
and dissipate.

Tuesday morning, a cool front will arrive, with a period of
decreasing coverage of rain/storms, and winds switching to the
northwest. A period of MVFR cigs is now expected with the
arrival of the cool front, and that may last through much of
Tuesday morning.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Delaune/Schultz
AVIATION...Ervin