048
FXUS63 KARX 201751
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1251 PM 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 /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1243 PM CDT Sat Jul 20 2024

Strong signal in both deterministic and probabilistic models
for fog - perhaps LIFR - continues. That said, still a
possiblity that high clouds help prevent fog from forming, so
have elected to keep things MVFR tonight into early Sunday
morning with this update. As for TS possibilities, this is
looking increasingly unlikely during this TAF period, so have
left out all mentions of precip.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Ferguson