717
FXUS63 KARX 201035
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
530 AM CDT Fri Sep 20 2024

.KEY MESSAGES...

- Above normal temperatures continue through Saturday before cooling
down to more seasonable temperatures lasting into the middle of next
week.

- Chances of rain return for Saturday and Sunday as next system
  moves into the region.

&&

.DISCUSSION...
Issued at 249 AM CDT Fri Sep 20 2024

More Storm Chances for the weekend and early next week:

A short break in the action as surface high pressure builds in for
Friday. Heading into Saturday evening, a low across the
US/Canada border moves eastward while a closed low across the
Intermountain West pushes northeastward towards the Central
Plains. Splitting these two systems is a shortwave that will
move through the Upper Midwest Saturday afternoon through
Sunday. This will bring the next chance of showers and
thunderstorms to the area. Compared to early next week, there
seems to be a good agreement on precipitation occurring. As this
wave moves through, most of the precipitation will be focused
south of our CWA but northeast Iowa and southwest Wisconsin will
have the best chance (50 to 70%) for rain to occur. When
looking at ensemble guidance, the 25th to 75th percentiles for
24 hour precipitation totals ending Sunday evening are between
0.25 and 0.75" for the GEFS and 0.02 to roughly 0.25" for the
EPS. This difference is because the EPS and ECMWF keep the
majority of the precipitation to our south.

By Monday, the remnants of the closed low move into the area.
Current ensemble and deterministic guidance have some differences.
The GFS has the low further south than the ECMWF. This is
represented in the ensembles with most of the GEFS having fewer
precipitation than the EPS through Tuesday. Some members
(around 25%) of the EPS do have drier solutions, so there is
still uncertainty around the exact trajectory this closed low
takes. Depending on the path it takes, will determine how far
north the the precipitation goes. With both of these storms, we
will continue to monitor to see how precipitation trends go.

Warm temperatures through Saturday then cooler for next week:

Above normal temperatures (10 to 15 degrees above normal with some
locations approaching 20 degrees above normal) across the forecast
area with highs in the upper 70s to mid 80s through Saturday. After
Saturday, more seasonable temperatures for the beginning of next
week. High temperatures are expected to be in the mid 60s to near 70
for Sunday and Monday and then gradually warming up to the low to
mid 70s for the middle of next week.

&&

.AVIATION /12z TAFS THROUGH 12Z SATURDAY/...
Issued at 530 AM CDT Fri Sep 20 2024

CIGS: low clouds are quickly exiting east and should clear KLSE by
12-13z. SKC conditions expected for the rest of today into the
evening. High/mid level VFR clouds look to return from the west
overnight.

WX/vsby: with an increase in high level clouds expected overnight,
drier air spreading in from the west and limited depth to the light
wind layer, the threat for valley fog impacts at KLSE tonight are
low (at this time). Will continue to  monitor trends and adjust
forecast if trends show differently.

Rain chances return Saturday, moreso late afternoon/night per
latest short term guidance.

WINDS: swinging west with the passage of a sfc front early this
morning, then light and back to the south/southeast tonight.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION.....Rieck