859
FXUS63 KARX 032346
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
646 PM CDT Fri May 3 2024

.KEY MESSAGES...

- Showers and scattered storms are expected mainly Saturday.
  Rainfall amounts of up to a half of an inch from the showers
  or storms.

- Active pattern develops next week with periodic showers and
  storms through much of next week. Timing of convection into
  region remains an issue and will have impacts on the severe
  potential across the forecast area.

&&

.DISCUSSION...
Issued at 226 PM CDT Fri May 3 2024

Today through Saturday:

While quiet weather is in store for the rest of the day, guidance
continues to support a shortwave moving through the area on
Saturday. Accompanying this wave will be a 30 to 40kt 850mb jet
that will help to increase the moisture transport. PWATs will
increase into the 1 to 1.3 inch range. Recent guidance continues
to show some instability moving further north, as shown by
general consensus of 250 to 500J/kg of SBCAPE. The highest
instability continues to be in southern Wisconsin. Despite this
instability, it is not enough to promote any severe weather,
even with the high amounts of shear, 30 to 50kts of 0-6km bulk
shear. This means that thunderstorms will be possible as the
band of precipitation moves through the morning and early
afternoon on Saturday.

Sunday into Monday

Shortwave ridge builds into the Upper Great Lakes Region Sunday into
Monday. Subsidence underneath ridge will allow for mainly dry
weather across the forecast area both days. With light winds near
the surface...clear skies and an inversion developing over the
forecast area Saturday night/Sunday morning. There is the
possibility of fog formation across parts of the area...mainly in
low lying areas/river valleys. However...if northwest winds stay up
enough...fog may not form. At this time...have left mention of fog
out of the forecast.

Warmer airmass advects into the region Sunday into Monday...as 925mb
temperatures warm from around plus 10 degrees celsius Sunday to near
plus 14 degrees celsius by 00z Tuesday. High temperatures will be
mainly in the 60s Sunday and warming into the upper 60s to middle
70s Monday.

Monday night through Friday

Main forecast concerns from Monday night through Friday continues to
be shower/storm chances through much of the forecast period. Upper
level closed low slowly moves over the Northern Plains States and
weakens during the forecast period. Latest ensembles/deterministic
models continue to show differences in timing of the upper level
closed low/impulses rotating around the closed upper level low into
the Upper Mississippi River Valley. Confidence in timing of
convection and any severe potential with the storms remains low. The
latest GFS/ECMWF continue to indicate vertical motion/moisture
convergence with the closed upper level low/impulses. This will
produce periodic showers/storms through much of the forecast
period...Monday night into Friday. Temperatures will remain near or
slightly above normal with highs generally in the lower 60s to
middle 70s through the forecast period.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 646 PM CDT Fri May 3 2024

VFR conditions are expected overnight ahead of a band of
showers/embedded thunder that should approach KRST by sunrise
and KLSE by 12-15Z Saturday. With thunder chances only around
15-25%, did not include in the TAFs at this time. Trended a bit
more optimistic with ceilings, although a period of MVFR is
still favored, with the higher probabilities west towards KRST
(60-90%), decreasing to 50-70% at KLSE. Some potential for IFR
ceilings exists for a time as low levels saturate with the
showers, especially at KRST (20-40% chance), but have held with
MVFR for this update. Southerly winds up to 10 kts will shift
northwesterly by Saturday afternoon.

&&

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

&&

$$

DISCUSSION...DTJ
AVIATION...JM