649
FXUS63 KARX 251030
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
530 AM CDT Fri Jul 25 2025

.KEY MESSAGES...

- Lower storm chances (10-40%) mostly limited to far southwest
  Wisconsin.

- Extreme heat possible Sunday and Monday with potential heat
  indices 100 degrees or more.

- Storm chances Sunday night into Monday. Low confidence in
  exact location and potential impacts.

&&

.DISCUSSION...
Issued at 308 AM CDT Fri Jul 25 2025

Morning Observations & Overall Forecast Confidence:

A messy synoptic-alpha setup seen on satellite imagery early this
morning exemplifies the many factors that foreshadow a lack of overall
confidence in impacts through the period. In order of timing, precipitation
chances tonight into Saturday morning surround contention between
an open wave sagging southeast through the Upper Midwest, a ridge
driving return flow through the Southern Plains, and its
appendage over Wyoming with a meridionally- oriented upper
level jet streak driving return flow into the Dakotas. Anomalous
warmth and storm potential for the start of the new week will
be determined by confluence between an anomalously (RAOBs & SPC
climatology) strong anticyclone off the Gulf Coast early this
morning and an upper level jet streak over southern California
abetting energy to the trough over the southern Gulf of Alaska.

Drier Forecast Today, Limited Storms In Far SW Wisconsin:

A split in higher precipitation chances, north and south of the
forecast area, has widened in most recent forecasts due to the
aforementioned ridge appendage ridge advecting higher moisture
north while also slightly strengthening local high pressure. The
combination of diurnally induced instability contending with
the lingering high pressure and return flow not taking shape
until later Saturday morning, any storms shifting north expected
to degrade. Have trended to a drier forecast with a southern
shift in previous PoP forecast, keeping chances (40%) in far
southwest Wisconsin.

Although, the lag in return flow will also be tied to cyclogenesis
in the Central Plains which may require PoP amendments for Saturday
night into Sunday, albeit a very limited area, should accompanying
deformation band break this far north.

Extreme Heat Possible Sunday & Monday:

Behavior of upstream synoptic confluence this weekend will
drive extent of warm, moist air across the Upper Mississippi
River Valley Sunday through Monday. The EPS exhibits the coolest
solution, with apparent temperatures from the low to mid 90s,
compared to the GEFS and GEPS. Warmth in the GEPS can be
attributed to the strongest (weakest) solution to the ridge
(trough); limiting any flattening of isoheights. As a result the
GEPS grazes the 90 degree isodrosotherm Sunday bringing near
100 degree apparent surface temperatures. The GEFS does exhibit
some flattening to the ridge, keeping surface temperatures a few
degrees colder than the GEPS, although ushering in 80 degree
isodrosotherm on Sunday also brings 100 degree apparent
temperatures for Sunday.

Storm Potential Sunday & Monday:

Storm potential Sunday into Monday mostly tied to strength of the trough along
northwest flow. The EPS exhibits a corridor of 100% PoPs tied to the strongest
trough solution while both the GEFS and GEPS show a smattering, from the lack
of forcing, of 20-50% primarily north of Interstate 94. Given the warm, moist
airmass all LREF members exhibit copious amounts of instability with CAPE
values of 2500 J/kg+. Current confidence in overnight timing may limit severe
potential with CIN quickly taking shape upon loss of diurnal heating. Available
shear will be dependent on ridge location, evident in inter-model differences
in all member hodograph plumes.

Severe weather machine learning models (Fengu/Pangu) have
trended a wide area of 15-30% probabilities for a severe report
within 40km of a point. Will remain a forecast detail to remain
cognizant of as synoptic features take shape.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 522 AM CDT Fri Jul 25 2025

Patchy fog with MVFR to LIFR visibilities is ongoing as of
1030z, but thin cirrus over the southern half of the area has
tempered fog development somewhat. Expect sporadic reductions to
MVFR/IFR through 13z, primarily north of a AUM to BCK line.
Today, cumulus should return, mainly in the 3000-4000 foot layer
with occasional MVFR ceilings possible where cu is low and
plentiful enough. However, given low probability, have not
carried this in the RST/LSE TAFs. Some TS is possible late in
the period southeast of a CCY-82C line.

&&

.CLIMATE...
Issued at 430 AM CDT Fri Jul 25 2025

Record Warmth Potential Sunday & Monday (Record/Forecast):

                         Maximum              Warm Minimum
July 27:   -----    --------
Rochester, MN        100 (1931) / 88         76 (1919) / 71
La Crosse, WI        100 (1931) / 92         79 (1896) / 73

                         Maximum              Warm Minimum
July 28:   -----        --------
Rochester, MN        100 (1955) / 90         74 (1931) / 75
La Crosse, WI         98 (1955) / 92         75 (1949) / 78

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Ferguson
CLIMATE...JAR