680
FXUS63 KARX 192353
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
653 PM CDT Sat Sep 19 2026

.KEY MESSAGES...

- Showers and storms likely (40-70%) this afternoon and evening
  across portions of northeast Iowa and southwest Wisconsin.
  Locally heavy rainfall amounts of 2-4" will be possible where
  storms frequent the same locations. Additional flooding may
  occur where locally heavy rain falls on already saturated
  ground.

- Additional light rain chances (30-60%) Monday and Monday
  night.

- Drier and cool conditions throughout much of the upcoming week
  with highs generally in the 60s.

&&

.DISCUSSION...
Issued at 157 PM CDT Sat Sep 19 2026

This Afternoon - Evening: Additional Heavy Rain Potential in
Southwest Wisconsin and Northeast Iowa

Heavy rain impacts shift this afternoon to portions of northeast
Iowa and southwest Wisconsin with additional convective development
possible as shown in several of the CAMs. The general conceptual
model as we head later into the day is for the front responsible for
much of our rainfall to sag south with some surface convergence
along it. As this occurs, some instability attempts to be advected
into the region as southerly low-level flow pushes the warm sector
to our south northward. The key question will be if this instability
can be advected northward enough in light of the convective debris
over the region to support robust convection and if the forcing will
be sufficient. Many of the CAMs show some degree of convection
during the afternoon/evening but disagree on how organize it would
be. There are some pretty notable differences between various CAMs
such as the HRRR which has shown some tendency to convect all the
way up to I-90 as opposed to solutions like the ARW which keeps
convection limited across the local area. Consequently, confidence
remains somewhat low as to how impactful any additional storms may
be but given that soils are very susceptible given several locations
seeing upwards of 5-8" of rain last night.

As far as additional rainfall amounts are concerned, overall the
25th to 75th percentile spread in the recent HREF would suggest more
widespread totals across portions of northeast Iowa and southwest
Wisconsin of around 0.5" to 2". However, given the 90th percentile
values in the HREF showing values of 2-4" would think underneath
heavier storms that this could be feasible, which in turn could
exacerbate any area flooding on rivers and low-lying areas. To see
additional details on ongoing flooding concerns, refer to the Hydro
section for more information. Otherwise, cannot completely rule out
a weak tornado in far southern Grant or Clayton counties given
fairly decent low-level hodograph curvature and some tendency to
wetbulb the warm nose and allow for convection to be surface based.
Given the lack of deep-layer shear any updrafts will be short-lived
but something to consider for the mid to late afternoon
timeframe.


Upcoming Week: Cool and Drier

The lower tropospheric baroclinic zone slides to the south of the
region by Sunday morning, taking the bulk of the rainfall risk with
it. Cannot fully rule out some stray elevated showers scraping parts
of east-central Iowa during the day, but most of the region will
stay dry with some sun poking out as we move through the afternoon.
The mean longwave trough/cutoff low currently over the Inter-
Mountain West slides eastward for Monday night into Tuesday,
bringing with it the next potential for wider coverage showers.
However, with the deeper moisture displaced well to the south of the
region, any impacts from this rain will be low. Eastern flow off a
Great Lakes/Ontario high will keep temperatures seasonably cool and
mostly dry for the remainder of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 654 PM CDT Sat Sep 19 2026

Ongoing scattered showers should largely begin to diminish over
the next few hours outside of transient areas of light drizzle.
However, portions of northeast Iowa and southwest Wisconsin,
primarily along and south of Highway 18, may see showers and
storms redevelop overnight into Sunday morning (30-60%). These
showers/storms move eastward Sunday morning with low potential
(10-20%) for transient light showers to continue into the
afternoon.

Outside of the precipitation, IFR/LIFR conditions will continue
areawide through at least Sunday morning. There is some
indication that a few hours of scattering/lifting of the low
ceilings may occur during the afternoon, mainly for those along
and north of I-90, although there is some indication additional
MVFR/IFR ceilings may develop towards the end of the of the TAF
period. East winds may also begin to gust to around 20KT Sunday
afternoon as stronger winds around 2-4kft attempt to mix to the
surface.

&&

.HYDROLOGY...
Issued at 157 PM CDT Sat Sep 19 2026

Numerous river sites continue to rise this afternoon in light of
overnight rainfall. The river basins with greatest impacts remain
along the Turkey, Upper Iowa, Root and Cedar River Basins where
rainfall amounts of 4-8" fell. Additional rainfall this
afternoon/evening may result in some additional rises, however the
heaviest amounts of 2-4" will likely be localized in nature.
Moderate flooding is already ongoing at the Cedar River in
Lansing, MN with the crest occurring shortly. This flow will
work its way downstream with additional rises expected at
Austin, MN into moderate flood stage and Charles City, IA into
minor flood stage this weekend and into Monday. Additional flash
flooding may occur this afternoon and evening if locally heavy
rainfall occurs over saturated soils as well.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch through Sunday morning for WIZ061.
MN...None.
IA...Flood Watch through Sunday morning for IAZ029-030.

&&

$$

DISCUSSION...Naylor/Skow
AVIATION...Falkinham
HYDROLOGY...Naylor