729
FXUS63 KARX 101147
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
647 AM CDT Fri May 10 2024

.KEY MESSAGES...

- Showers and storms develop across the region this afternoon
  and evening. A few strong storms are possible with small hail
  and gusty winds the primary threat.

- Periodic rain/storm chances persist Sunday into next week.

&&

.DISCUSSION...
Issued at 301 AM CDT Fri May 10 2024

Today into Sunday

Latest 07z surface analysis shows surface ridge over western
Wisconsin/southern Minnesota. With subsidence underneath surface
ridge...clear skies and light winds has allowed fog to develop
mainly in low lying areas and river valleys this morning. Fog should
erode this morning due to daytime heating and skies will become
mostly sunny.

Then focus turns to vigorous shortwave trough over southern Canada
tracking over the Upper Great Lakes region this afternoon and
evening. With daytime heating and vertical motion/forcing associated
with shortwave trough...showers/storms will develop along/ahead of
shortwave trough/surface front. Latest 10.12z GFS/NAM suggest 0-3km
shear of 20 to 30 knots...however instability is limited with up to
500 j/kg of surface base CAPE by 21z today. Bufkit soundings
indicate inverted V soundings and straight hodographs across
forecast area this afternoon evening. Given limited instability and
marginal shear...expect a few thunderstorms to be strong with
gusty winds and hail.

Subsidence behind shortwave trough and under shortwave ridge
building in over the forecast area should provide dry weather across
much of the forecast area Saturday.

A weaker shortwave trough is expected to move over the Great Lakes
Region Sunday. The better lift/moisture convergence associated with
this shortwave trough will be over northern and eastern half of
Wisconsin. With daytime heating/weak moisture convergence near the
surface will provide scattered showers/storms across central
Wisconsin with lesser chances along/west of the Mississippi River
Sunday afternoon/evening.

Monday through Thursday

Main forecast concerns Monday through Thursday are shower/storm
chances through much of the forecast period. The latest
deterministic models/ensembles indicate west to east zonal flow
pattern developing through next week with major differences
occurring late in the forecast period. Weak upper level closed low
slowly tracks over the Central Plains states early next week.
Forecast area remains on the northern periphery of this feature.
Main axis of lift/moisture convergence is expected to be south of
the forecast area...however there is enough vertical motion/forcing
to produce showers and the possibility of a few storms...mainly
across the southern parts of the forecast area. Then...west to east
zonal flow pattern develops. Couple of pieces energy embedded in the
west to east zonal flow will allow showers/storms develop over the
forecast area Wednesday into Thursday. By Thursday...major
differences occur between deterministic/ensemble members in upper
level trough deepening over the Northern Plain states or flow
pattern remains nearly west to east across the northern tier states.
This will have impacts on much showers/storms linger across the
Upper Great Lakes into Thursday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 637 AM CDT Fri May 10 2024

Overnight river valley fog impacted KLSE temporarily, spreading
from the south. Typical fog impacted airports the Wisconsin
River Valley and southern Mississippi River Valley drainages to
1/4SM for most of the early morning hours. Satellite imagery and
METARs have been indicating these fog impacts lifting quickly
given the May sun angle. Therefore, have opted and left out
restrictions at KLSE at 10.12Z TAF issuance. Otherwise, limited,
if any, precipitation and associated flight impacts move from
northwest to southeast along a quick wave this evening. Higher
confidence for any impacts and precipitation lie in central
Wisconsin, northeast of both TAF sites. Therefore, have opted
VCSH at both TAF sites. Confidence for thunder is very low,
higher potential again in central Wisconsin.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory until 8 AM CDT this morning for WIZ017-029-033-
     034.
MN...None.
IA...None.

&&

$$

DISCUSSION...DTJ
AVIATION...JAR