627
FXUS63 KARX 101133
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
633 AM CDT Sat Aug 10 2024

.KEY MESSAGES...

- Seasonably cool temps will continue through the weekend with
  gradually warming expected heading into next week.

- Little rainfall potential through the weekend, with
  shower/storm chances increasing at times next week, but
  confidence in details (timing, impacts...) is low for now.

&&

.DISCUSSION...
Issued at 257 AM CDT Sat Aug 10 2024

This Weekend: Dry, cool

Seasonably cool, tranquil weather will be the rule through the
weekend. A few weak ripples in the flow will slide southeast on the
periphery of the closed upper low over Ontario that will slowly move
east through the weekend. However, with some warming of mid-level
temps today and minimal instability, the risk for any showers
is much less than Friday, although a diurnal cumulus field
likely will develop as boundary layer warming occurs beneath
seasonably cool air aloft. Low level thermal profiles will
slowly moderate through the weekend as the flow trends more
zonal and the upper low across Canada pulls east. As a result,
highs today in the mid 60s to mid 70s will increase into the
70s to near 80 on Sunday with lows tonight mainly in the 50s,
except for typically cooler locales which could fall into the
mid 40s.

Monday-Friday: Increasing shower/storm chances, warming

Overall, modest mid-level height rises are expected heading through
the week as broad ridging tries to work eastward from the
Rockies/plains. This generally supports a return to milder,
more seasonable temps through the week. However, global model
guidance indicates a series of embedded shortwave troughs
within the fairly zonal flow regime that could not only impact
rain chances and clouds, but also daily temps. One such wave is
forecast to pass east from the northern plains to the Upper
Mississippi Valley Sunday night into Monday. However, with
modest forcing and a drier airmass locally, organized rain
chances should dwindle with eastward/northward extent. Right now
low to medium (20-40%) chances are focused south of I-90 Sunday
night into Monday (highest over northeast Iowa). Either way,
instability looks quite limited with this system as the low
level jet/deeper moisture remain off to the south and west.

Moisture return should increase through the mid/latter portion of
the week as low-level flow becomes southerly amid the ridging
spreading east aloft. An uptick in shower/storm chances is expected
in conjunction with the moisture increase, although predictability
in details of the pattern evolution, especially with the timing and
amplitude of shortwaves, lowers with time. Accordingly, stuck close
to the broad-brushed blended (NBM) rain chances (20-40%) through the
mid to late week period. Overall, it does look to be a more active
period, though, and higher rain chances will likely be needed in
time for some of these periods as forecast confidence increases.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 633 AM CDT Sat Aug 10 2024

VFR conditions are expected through the TAF period with sct to bkn
cumulus expected during the afternoon. Winds will increase during
the afternoon to around 10-15 kts with diurnal mixing aiding
increasing wind gusts of up to around 20 kts. Winds will diminish
closer to sunset to around 5 kts. As we head into the overnight,
skies clear and winds lessen however, with the 10.09z RAP
showing fairly strong winds off the deck to around 15-20 kts,
valley fog formation at KLSE appears unlikely at this time.

&&

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

&&

$$

DISCUSSION...JM
AVIATION...Naylor