043
FXUS63 KARX 140540
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1240 AM CDT Fri Aug 14 2026

.KEY MESSAGES...

- Low potential for heavy rainfall across northeast Iowa and
  southwest Wisconsin this morning with only a 10-20% chance for
  amounts of 1 inch or more.

- Showers and storms are possible this afternoon (20-40%) before
  additional heavy rainfall potential moves into northeast Iowa
  and southwest Wisconsin this evening into Saturday.
  Probabilities for 1 inch or more sit around 30-60%.

- Briefly drier conditions to close out the weekend and start
  the new week before showers and storms return by the middle
  of next week.

&&

.DISCUSSION...
Issued at 1237 AM CDT Fri Aug 14 2026

This Morning: Heavy Rainfall Potential

A surface boundary remains situated across central Iowa into
northern Illinois early this morning as 850hPa warm advection and
moisture transport nose into it, providing a source of lift for
convective development through the morning hours. The environment
along this boundary remains favorable for heavy rainfall as PWATs
above the 90th percentile of climatology exist across the region,
warm cloud depths exceed 10kft, and storm motion vectors parallel
the boundary, favorable for training storms. While the heaviest rain
is expected across central Iowa and northern Illinois within the
vicinity of the boundary and in the region of higher instability,
CAM solutions to suggest precipitation makes its way northward
into our portions of northeast Iowa and southwest Wisconsin
through this morning. Probabilities of precipitation across
these regions sit around 40-60% though probabilities for 1 inch
or greater are far lower and have trended southward as compared
to 12 hours ago, generally 10-20% at most per the 14.00z HREF.
That said, there`s also remains some uncertainty in how far
north rainfall is actually able to make it given the current
position of the surface boundary and little in the way of
synoptic forcing to shift it northward.

This Afternoon - Saturday: Additional Heavy Rainfall Potential

Through this afternoon, there is some suggestion of scattered shower
activity across the area, primarily for those along and south of I-
90, as some areas of maximized 850hPa moisture transport nudge into
the Upper Mississippi River Valley. Many CAM solutions do highlight
this potential with the 14.00z HREF suggesting probabilities sit
around 10-30%. Amounts with any showers would be light, generally on
the order of 0.1 inches.

Heading into this evening and tonight, the upper level ridge axis
located over much of the United States builds northward slightly
while another 500hPa shortwave moves eastward across the Midwest.
The boundary associated with this morning`s rainfall also remains
somewhere across Iowa and Illinois throughout the day, though where
exactly it situates itself is somewhat uncertain. Regardless,
another round of heavy rainfall looks likely along the boundary as
the wave moves through given a very similar set-up to this morning.
With the northward trend of the upper ridge and 850hPa moisture
transport/warm advection by association, there is some potential for
this round of heavy rain to make its way into those areas mainly
along and south of Highway 18 (60-80%) and perhaps towards I-90 (30-
60%). That said, the 14.00z HRRR solution suggests that any activity
will largely remain south of our area, primarily along and south of
I-80. Curious if the majority of the model suites are somewhat too
far north with precipitation potential given the several rounds of
rain across the region over the last few days and a more HRRR-like
solution would be more likely, though given the consensus
regarding the northward trend, there is currently higher
confidence in this more northern solution regarding rainfall
potential tonight. Fortunately, amounts look to be far less
impressive than they have been for those across central Iowa
into Illinois. Probabilities for amounts of 1 inch or more sit
around 30-60% in the 14.00z HREF with some members suggesting a
few pockets around 2 inches could occur per the LPMM.

Rainfall largely shifts eastward through Saturday morning resulting
in primarily dry conditions through the afternoon. However, there is
some low potential for some scattered showers through the afternoon
hours as another shortwave moves through the region.

Sunday - Mid Week: Briefly Drier, Additional Shower/Storm Chances

The upper level ridge begins to break down and retrograde on Sunday
as a jet streak and associated trough along the US/Canada border
translate eastward. A weak surface front moves through the Upper
Midwest along with these upper level features while high pressure
sinks southward behind the front. Can`t completely rule out some
scattered showers south of I-90 Sunday afternoon as this boundary
moves through the region, though there`s quite a bit of discrepancy
within the ensemble suites as far as timing and location of
precipitation is concerned. Because of this, the 14.01z NBM suggests
probabilities for precipitation during this period are 20-30%.
Heading into Sunday night and Monday, a drier period looks to be in
store for the region as the high pressure takes a stronger hold over
the region, though this will be short-lived as deterministic models
suggest another shortwave trough and associated surface front move
through the region by the middle of next week bringing additional
showers and storms (50-70%).

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1237 AM CDT Fri Aug 14 2026

Mostly VFR conditions present across the region with some patchy fog
already building in. Some valley fog will be possible for the KLSE
terminal this morning but uncertainty in the depth of the light wind
layer north of the Minnesota state line has lead to varying guidance
on the intensity of valley fog. Have included some IFR visibilities
for now but will continue to monitor observations (upstream as well)
through the night to see if amendments may be needed. VFR conditions
should prevail from mid morning through the afternoon with
east/southeast winds gusting to between 15-20 kts for a few hours.
Areas of rain look to build north into the evening, bringing low
MVFR/IFR stratus with it. Actual rain chances look better
across Northeast Iowa and portions of Southeast Minnesota so
have gone prevailing at KRST with PROB30s for KLSE. Widespread
IFR to LIFR CIGs will be expected overnight tomorrow night just
beyond the end of the forecast period.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Falkinham
AVIATION...Barendse