265
FXUS63 KARX 161933
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
233 PM CDT Fri Aug 16 2024

.KEY MESSAGES...

- Showers and isolated storms continue for the rest of this afternoon
  and into the evening hours. Additional chances (20-40%) for
  showers persist for Saturday afternoon.

- Temperatures through next week will likely trend near to
  slightly below average for this time of year with relatively
  minimal precipitation chances.

&&

.DISCUSSION...
Issued at 233 PM CDT Fri Aug 16 2024

Today - Saturday: Seasonably Mild with Showers and Isolated Storms

The overall synoptic setup this afternoon revolves around a
vertically stacked upper-level to surface low centered across north-
central Wisconsin. Pivoting around this feature are several subtle
shortwaves aiding in instigating showers and storms with the overall
mesoscale environment featuring two distinct modes across the local
area this afternoon. Where low-level moisture has maintained with
dewpoints in the upper 60s to around 70, MUCAPE values remain
elevated enough (1000-2000 J/kg) to support more vigorous convection
as seen late this morning in Clark and Jackson counties. West of the
Mississippi River, increasing cloud cover and lower dewpoints have
minimized the amount of instability present. Consequently, would
expect the predominant mode of precipitation to be showers with a
low-end chance for a rumble of thunder or two west of the
Mississippi River. The potential for funnels throughout the
afternoon generally has trended less likely with guidance lacking a
surface feature to really latch onto as a subtle boundary pushes
east of the local area. As a result, have noted fairly low values in
the non-supercell tornado parameter in the 16.15z RAP for the local
area. Regardless, as cloud cover pushes east with the cyclonic flow,
instability will begin to wane favoring a more showery environment
into the evening hours for much of the local area with showers
gradually dispersing by sunset.

As we head into Saturday, the upper-level low continues to push
southeast through the Great Lakes. With a more northwesterly flow
regime and cloud cover overhead, temperatures will trend on the
milder side with highs in the middle to upper 70s across the region.
With additional weak pieces of upper-level energy behind the upper-
low, much of the CAMs still paint some shower coverage for the
afternoon on Saturday. A rumble of thunder or two cannot be ruled
out with MLCAPE values of up to around 500 J/kg in the 16.15z RAP.
Similar trend for Saturday as today with showers waning in coverage
later into the evening hours as well.

Sunday - Friday: Continued Slightly Below Average Temperatures

Looking into next week, our region is situated between two broad
synoptic features with a large upper-level ridge to the west and a
trough to the east. Consequently, our region is once again stuck in
northwesterly flow which will aid in keep our temperatures slightly
below normal through next week with median high temperatures of
middle 70s to lower 80s in the 16.00z grand ensemble (GEFS/EC
ens/Canadian ens) with little inter-quartile spread amongst
ensemble members. Precipitation chances appear minimal into next
week with any shortwaves riding over the aforementioned ridge
being the main source of any precipitation potential which long-
range guidance currently does not reflect. Regardless, with the
16.00z grand ensemble (GEFS/EC ens/Canadian ens) having very low
joint CAPE (over 500 J/kg) and shear (over 30 kts)
probabilities of under 20% through the middle of the week, any
organized severe weather appears unlikely at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1235 PM CDT Fri Aug 16 2024

Numerous showers move through the region early this afternoon,
becoming more isolated towards the late afternoon with the
risk for isolated showers continuing into Saturday. The threat
for thunder with these showers is very low and not mentioned in
the TAFs. Periods of MVFR to IFR visibilities are possible under
any of the heavier showers. Widespread MVFR to IFR ceilings
move in this afternoon and persist into Saturday with the lowest
ceilings overnight along with lower visibilities due to fog.
Winds veer from the WSW to the NW today around 10 kts, gusting
to around 20 kts this afternoon west of the Mississippi River.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Skow