431
FXUS63 KARX 200735
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
235 AM CDT Sat Jul 20 2024

.KEY MESSAGES...

- Slight precipitation and storm potential for some today,
  highest confidence along western and northern periphery.

- Similar conditions through new week: diurnally induced storm
  potential with a low possibility for anything severe.

&&

.DISCUSSION...
Issued at 230 AM CDT Sat Jul 20 2024

The dry conditions come to a close for some today, eventually. The
trough seen on WV imagery early this morning with weakening
energy struggle to eradicate and saturate the dry air in place.
Have gone with a slightly drier forecast as a result.

Rain & Storm Chances Today:

Initial saturation along our western periphery this morning is
associated with a surface low well to the southwest. With the trajectory
of this low, expect precipitation potential to remain along our
western periphery through this evening. Subsequent
precipitation chances early this afternoon sag south from
northern Wisconsin as the upper level trough traverses the Upper
Mississippi River Valley; dragging a back door cold front with
it. While mid to upper level lapse rates steepen from the upper
level low, a low to mid level temperature inversion and lack of
forcing limits overall confidence and coverage in precipitation
and storms. Southwest extent of precipitation potential will be
main forecast challenge albeit overall limited impact. Any
storms that do form will remain isolated and short lived with
little to no shear to work with; pulsing up and down with heavy
rain as a primary hazard.

Through The New Week:

The upper level low lingers through the new week, sending
perturbations around its periphery, perpetuating daytime
precipitation and storm chances locally. Long range ensembles
(GEFS/EPS/GEPS) all exhibit associated waves of 0.01"+ 100%
probabilities through the week. Coincidental timing of these
meager perturbations and peak diurnal heating will dictate best
storm potential. Investigating individual members, most contain
some semblance of SBCABE during the first half of the week
concurrent with diurnal heating before eroding it for the second
half. Long term (ECMWF/GFS) soundings show minimal concurrent
shear, limiting any confidence for severe potential.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1101 PM CDT Fri Jul 19 2024

MVFR to low-VFR cigs are likely across the region during the late
morning and early afternoon hours as the 20.02z RAP shows fairly
robust low-level saturation. With mid-level cooling expected,
this should aid in marginally better instability profiles during
the day tomorrow which will in turn help develop more
aggravated cumulus and showers and isolated storms as well with
diurnal heating. Consequently. decided to hold a VCSH at KRST to
address these diurnal showers and isolated storms. Coverage in
showers and storms will diminish during the evening hours. Winds
will remain around 5 kts through the TAF period from the
south/southwest.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Naylor