664
FXUS63 KARX 121733
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1233 PM CDT Sat Jul 12 2025

.KEY MESSAGES...

- Storm chances exit east through central Wisconsin through the
  afternoon.

- Mostly sunny, daytime highs in the low 80s, and low confidence
  in limited storm chances for Sunday.

- Increased storm potential Tuesday through Thursday.

&&

.DISCUSSION...
Issued at 337 AM CDT Sat Jul 12 2025

Slightly Cooler Today & Sunday:

The overly active pattern wanes through the weekend as the surface
frontal boundary advects precipitation east through the morning
hours. The Canadian Continental airmass in its wake provides
some meager low level cold air advection, steepening low level
lapse rates, and increasing west-northwest winds near 20 mph at
times. Limited off deck winds keep maximum wind gusts lower.
Otherwise the slightly colder airmass sticks around through
Sunday with daytime highs from the high 70s to low 80s.

Air Quality Advisory Through Monday Morning:

The Canadian Continental airmass brings PM 2.5 with it from
ongoing wildfires mostly in central Saskatchewan. Air Quality
headlines have been issued by respective State departments in
Minnesota and Wisconsin valid through Monday morning. PM 2.5
concentration expected to slowly increase through today,
strongest through Sunday night. While vertically integrated
smoke concentrations will be dense, question of amount of subsidence
sinking PM 2.5 to the surface.

Low Storm Chances Sunday Evening:

Some disagreement in progressivity of the global pattern
causing differences in long term model solutions for PoPs
through the start of the new week. Most (75%) LREF Time Lagged
Cluster members usher in northwest flow in the wake of the
departing trough and return flow through the Central Plains
penetrating a filament of increased low level theta e into the
Upper Mississippi River Valley through Sunday. LREF (and near
terminus hours of available high resolution models) show a
quickly progressing frontal boundary with conditional
instability and strong upper level shear from the passing
synoptic wave. Very low confidence due to questions on northern
extent of theta e as well as coincidental timing with peak
diurnal heating. While overall confidence is low (25%) primary
impacts at the current forecast hour expected along northwestern
periphery from southeast Minnesota into central Wisconsin where
time-lagged Clusters paint 50% probabilities for 0.01" QPF over
24 hours. Have increased PoPs as a result away from a dry NBM
forecast in collaboration with neighboring forecast offices.
Additional high resolution model ingest into subsequent NBM runs
will likely provide a wetter solution. Similarly have added a
few percent of PoPs for Monday.

Time-lagged cluster analysis also paints a bullseye of 50%
probabilities over Minnesota for >500 J/kg CAPE, >-25 J/kg CIN, and
>30kts 0-500mb bulk shear. Given an expected limited temporal
and spatial extent, machine learning model guidance for anything
severe is <5%. As the forecast hour nears expect more
convective allowing models to provide better resolution and
forecast confidence.

Storms Through Midweek:

Highest precipitation and storm potential reaches the Upper
Mississippi River Valley Tuesday as anomalous Gulf moisture
(1.75" PWATS, SPC Climatology & 2 Standardized Model Climatology
Anomalies NAEFS/ENS) protrudes into the Upper Mississippi River
Valley. A quasi zonal wave train seemingly results in the
moisture boundary to zonally bifurcate the southern part of the
forecast area through Thursday morning. Limited LREF confidence
(0-20%) for 0.1" over a 6 hour period suggest many unknowns but
with high confidence () for anomalous moisture, heavy rain
potential will be something to keep an eye on in coming
forecasts.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1224 PM CDT Sat Jul 12 2025

Primary concern in the TAFs is the presence of smoke due to
wildfires far to the northwest. At issuance, many locations
along and east of the Mississippi River have MVFR visibilities
but upstream obs suggest this initial round will give way to
VFR conditions this afternoon. Additionally, MVFR cumulus,
sometimes with enough coverage to constitute a ceiling, is
present along and east of the Mississippi River but expect this
deck to rise through the afternoon as frequently occurs.
Guidance and upstream obs point toward smoke returning
overnight so have included a return to MVFR at RST/LSE.
Otherwise, some fog is likely along the Wisconsin River tonight
but current indications are this is not favored along the
Mississippi River and LSE.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Ferguson