597
FXUS63 KARX 082300
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
600 PM CDT Tue Jul 8 2025

.KEY MESSAGES...

- Spotty shower/storms chances for the rest of the afternoon-into
early evening.

- Rain chances Wed-Sat, but focused on Friday (70-80%). Stronger
storms possible Fri with locally heavy rain.

&&

.DISCUSSION...
Issued at 140 PM CDT Tue Jul 8 2025

> REST OF THE AFTERNOON/EARLY EVENING:

Shortwave trough dropping southeast across MN/northern WI per latest
watervapor satellite imagery will continue to track southeast
through the rest of the time. Another shortwave/MCV was churning
just south of the local area and responsible for the early morning
convection over parts of IA (and still continues across northern
IL). RAP MLCAPE climb to 500-1000 J/kg across WI this afternoon,
although relatively skinny profile. The mix could be enough to pop a
few showers/isold storms from mid afternoon into early evening,
mostly across WI. However, latest RAP/HRRR showing mid level capping
- would allow for a few agitated cu but not much more than that. Not
much for shear to support any updraft that gets going. For now, will
hold with the small chances (20%) over WI and monitor trends.


> WED-SAT: rain chances with Friday harboring the highest
likelihood. Conditional strong (severe?) storm risk Fri. Locally
heavy rain possible.

GEFS and EPS continue to spin a shortwave trough from the southern
rockies eastward Thu, lifting it east/northeast across the upper
mississippi river valley Fri. Another shortwave follows quickly on
its heels, dropping southeast out of southern Canada and pushing
across northern reaches of the region Sat. The first shortwave may
eventually merge/be absorbed into the 2nd feature, but generally
favored after both swing back northeast into Canada (post the local
area). Latest GEFS is trending a bit faster with the overall speed
of both upper level features compared to the EPS.

Meanwhile,  medium/long range guidance is starting to suggest a
thunderstorm complex will spark over the central plains late Wed
night, taking the residual MCV east and potentially bringing a shot
for showers/storms to southern portion of the forecast area. Clouds,
boundaries etc will have some influence on how that first shortwave
moves - perhaps more importantly to any strong/severe risk - how far
north an associated warm front lifts. Not much clarity at a few days
out, and might not get a better idea on evolution until track of the
Wed night/Thu MCV is more evident.

Pool of soupy/unstable air pools ahead of the initial shortwave
(Fri). Again, how far northward the CAPE axis extends is uncertain
as positing of the relevant features/forcers isn`t super clear
(yet). Enough wind shear could/would overlap with the unstable
airmass, aiding storm organization and heightening a strong
(severe?) storm risk.

What appears more certain is the potential/likelihood of locally
heavy rain. PWs continue to push north of 2" with warm cloud depths
of 4 to 4.5k. Mostly north-south orientation of the convection will
limit repeat, time-resisdence enhanced accumulations, GEFS and EPS
25-75 percentiles sit roughly from 3/4 to 1 1/4". However, the high
end outliers climb above 3". Not a widespread flooding scenario but
certainly one that could impact urban areas (street flooding) if
realized.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 600 PM CDT Tue Jul 8 2025

Isolated to scattered showers/storms that have developed this
afternoon have largely begun to weaken and are expected to fully
dissipate with sunset. Some concern for fog/mist remains for
the overnight hours (< 30%), but thinking it should be confined
to the low lying areas and valley locations that are most prone
to fog/mist development. As such, still not confident enough to
add into the TAFs. Light northerly winds persist tonight into
Wednesday under clear to mostly clear skies with diurnal cumulus
developing Wednesday afternoon.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Falkinham