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264
FXUS63 KARX 171959
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
259 PM CDT Fri May 17 2024

.KEY MESSAGES...

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- Saturday afternoon and early evening brings potential for showers
and thunderstorms to mainly west central Wisconsin. If thunderstorms
do develop, a severe storm cannot be ruled out.

- While it remains difficult to narrow down timing, next week
  looks to feature multiple rounds of showers and thunderstorms.
  Additionally, next Tuesday may feature the ingredients for
  severe thunderstorms but these are currently favored to
  develop south of the forecast area. Please keep up to the date
  with the forecast for next week.
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&&

.DISCUSSION...
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Issued at 425 AM CDT Fri May 17 2024

Saturday thunderstorms:

A shortwave looks to eject northeastward over ND to western Ontario.
An associated cold front will sweep eastward through MN toward the
CWA. Plume of moist advection ahead of this front should lead to an
axis of around 1000 J/kg of MLCAPE by the afternoon hours. As the
front arrives, a few showers and thunderstorms may develop. Model
soundings suggest warm temperatures at 750mb will likely limit the
ability for deep convection to develop, especially in southern parts
of the CWA. Additionally, with better winds aloft remaining to our
north, deep shear of only around 20 knots suggests convective
organization will be lacking. Thus, severe risk appears limited to a
stray severe hail or wind event.

Sunday night through Friday precip:

Next week brings an extended period with west-southwesterly to
southwesterly flow aloft with a series of shortwaves embedded in
this flow. With good 700/850mb moist advection seen ahead this
waves, multiple rounds of showers and thunderstorms will occur. PoPs
are once again spread across a much larger time period than will be
affecting, owing to low predictability in the timing of the
aforementioned shortwaves.

Of particular note is Tuesday, which looks to feature a rather
potent shortwave with most guidance bringing this northeastward during
the afternoon and evening hours. Ahead of this feature, moist
advection tracing back to the Gulf of Mexico could lead to large
amount of instability. With stronger winds aloft favored, this could
lead to a risk for severe thunderstorms. Primary uncertainties
surround the exact track of the system - if the system tracks just a
bit too far to the south, the forecast area would fail to
destabilize owing to ongoing rain during the morning hours. As of
this time, LREF joint probabilities suggest the best overlap of
shear, potential instability, and low convective inhibition is more
probable just to our south, but will need to keep a close eye on
this over the coming days.
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&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 650 AM CDT Fri May 17 2024

Main source of uncertainty in the upcoming TAF period is the
potential for a brief shower, mainly at RST soon after issuance
time. At this time, do not expect any kind of operational
impacts even if (10% chance) a shower briefly affects the
terminal. Otherwise, with winds a few knots stronger than last
night, do not expect a recurrence of the valley fog that plagued
LSE early the morning.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...Ferguson