053
FXUS63 KARX 150745
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
245 AM CDT Mon Sep 15 2025

.KEY MESSAGES...

- Heat and humidity linger through midweek, with a transition
  back to seasonable temperatures towards the end of the week.

- Low (10-20%) risk for an isolated storm west of the
  Mississippi River today.

- Confidence in widespread showers later this week is decreasing
  with the main rain axis shifting westward.

&&

.DISCUSSION...
Issued at 245 AM CDT Mon Sep 15 2025

Summertime Warmth through Midweek

A blocking weather pattern lingers across the central CONUS
through much of the week, resulting in little change in our
summertime airmass over the next few days. Highs should continue
to top out in the 80s with dewpoints in the 60s and 70s through
Wednesday, with only a gradual cooling trend for Thursday
through Saturday as a mid to upper level cutoff low gradually
builds into the region from the west. Local modulations in these
forecast highs owing to storms are possible--mainly west of the
Mississippi River--but confidence in these storms is low (see
section below) and therefore it is tough to deviate from the
current NBM forecast highs. Temperatures should wander closer to
average by the upcoming weekend.

Low Probability Storm Risks for the Week

A multitude of low probably storms chances dot the forecast for
the upcoming week. This risk area is mainly west of the
Mississippi River with subsidence off the downstream ridge/high
pressure cell limiting the eastward progression of these storms.

For this morning, a ribbon of 335-K 700-mb theta-e air is
generating sprinkles across central Iowa early this morning.
This feature lifts NNE over the next 6-9 hours and could clip
southeastern MN before waning by mid-morning.

A passing upper tropospheric wave lifting NNE through the
Dakotas and western MN lowers heights just enough that surface-
based convection is a possibility this afternoon. HRRR/RAP
forecast profiles show 1500 J/kg of MLCAPE and somewhat
elongated hodographs that would be supportive of organized
convective structures. The missing piece is a forcing mechanism.
The upper trough axis will be lifting north of the region in
the afternoon and there is little in the way of a surface
boundary to latch onto. If anything, there is a signal for
weakly confluent flow at the surface that could be enough to
overcome the MLCIN. The widely varying (but rather dry)
solutions from the 00Z HREF members is telling of the low
predictability of this forecast. Have kept broad low (20%) PoPs
west of the Mississippi River to account for this remote storm
possibility. With ample moisture in play (PWATS around 90% of
climatology), any slower moving cell could produce efficient
rainfall rates.

Glancing ahead to the middle to latter part of the week, the
medium range solutions are depicting a stronger blocking pattern
that rebuilds somewhat for the end of the week over the Great
Lakes, refusing to give way to a cutoff low over the Northern
High Plains. This has resulted in a westward shift in the
precipitation probabilities that previously encompasses much of
the forecast area, relegating them to mainly west of the
Mississippi River. It doesn`t look like the low pushes into the
region until Friday or Saturday, which might be when we see more
widespread rainfall.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1236 AM CDT Mon Sep 15 2025

VFR conditions are expected to prevail over the next 24 hours
across much of the area with the exception of the usual
nighttime fog trouble spots around BCK and along the Wisconsin
River Valley. There is some uncertainty surrounding potential
for TS along and west of the Mississippi River but latest
trends suggest this is increasingly doubtful (10-20% chance of
occurrence) so have removed the PROB30 groups from the RST/LSE
TAFs. Otherwise, winds out of the east-southeast at around 5-10
knots will continue with a good amount of upper level clouds in
the 10-15 kft layer.

&&

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

&&

$$

DISCUSSION...Skow
AVIATION...Ferguson