312
FXUS63 KARX 100359
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1059 PM CDT Fri Aug 9 2024

.KEY MESSAGES...

- Daytime cumulus and showers/sprinkles continue through today.

- Cooler pattern on tap through the next few days.

- Low precipitation chances Sunday night into Monday along our
  southwest. Subsequent precipitation chances from Wednesday
  into next weekend.

&&

.DISCUSSION...
Issued at 106 PM CDT Fri Aug 9 2024

Today:

Upper level low on GOES water vapor imagery shows the
continually churning upper level low over the Great Lakes early
this afternoon, placing the Upper Mississippi River Valley in
the upstream Cold Air Advection (CAA) regime. The resultant
steepened low level lapse rates have quickened winds near 20
knots in spots and provided a widespread cumulus deck with
sprinkles/showers.

Temperatures Tonight & This Weekend:

With loss of diurnal heating and weakening CAA, expect clearing
skies tonight to provide surface temperatures cooling into the
mid 40s to low 50s. Increased winds from a tightening
pressure/height gradient will keep overnight valley fog concerns
at bay while potentially keeping temperatures slightly warmer
from increased low level mixing. Therefore, haven`t dropped
temperatures in typical cold spots as much, only a couple of
degrees. A passing surface high to our south through the weekend
will attempt to usher in return flow and warmer temperatures,
but will remain shunted by the lingering upper level low and
northwest flow. Regardless, slightly more diurnal heating
influence will bring temperatures above 70 area wide for the
weekend.

A persistent pattern expected for the new week as a lifting
Central Plains low ushers in weak warm air advection through
Monday, keeping temperatures in the 70s to low 80s through the
work week.

Precipitation Chances Through The Week:

Initial precipitation chances reach the local forecast Sunday
night into Monday on the cusp of weakening low and accompanying
warm sector lifting east northeast through the Central Plains.
The local dry airmass with displaced synoptic forcing limit
confidence and higher chances to our southwestern peripheral
counties in northeast Iowa.

Subsequent precipitation chances frequent midweek as long term
global ensemble confidence suggests a low bifurcating the long
wave ridge. There is some difficulty resolving the behavior of
the low potentially rejoining the parent trough over the Upper
Mississippi River Valley though so model spread is quite vast
with 20-90% for greater than 0.01" in 24 hours. Have kept with
National Blend which has 20-50% into the weekend. Will be
subsequent details to iron out in coming forecasts.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1058 PM CDT Fri Aug 9 2024

VFR conditions expected through the TAF period. Clearing skies
and lighter winds expected overnight. As a seasonably cool
airmass remains overhead, boundary layer is not expected to
completely decouple, so expecting some winds to remain
overnight. On Saturday, expect additional diurnal cumulus to
develop as WNW to NW winds remain in the 10 to 20kt range.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...JAW