Area Forecast Discussion
Issued by NWS La Crosse, WI

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478
FXUS63 KARX 222347
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
647 PM CDT Mon Jul 22 2024

.KEY MESSAGES...

- Scattered to areas of showers/storm tonight into Tue. Severe
weather not anticipated.

- Trending drier Wed through Sat with warming temps for the weekend.
Sunday could hold the next rain chances after tonight/Tue.

&&

.DISCUSSION...
Issued at 200 PM CDT Mon Jul 22 2024

* TONIGHT/TUE - scattered to areas of showers and storms. Severe
  weather not anticipated.

A bit of west-east running shortwave energy currently dropping
across northern MN (per watervapor imagery) at early afternoon,
slated by the short term guidance to continue dropping
south/southeast through tonight. The RAP paints as much as 1500 J/kg
of MUCAPE to work on ahead of the shortwave tonight while also
showing some weak moisture transport. Not much/if any wind shear to
play with. The CAMS spark an area of scattered-broken convection in
response to the lift/instability, with some decrease in areal
coverage/punchiness as we move later into tonight (and lose daytime
heating). The short term guidance does hold at least small rain
chances through the overnight into Tue morning, shifting the
shortwave energy southeast early Tue morning.

However, another bit of shortwave energy is on the heels of the
first feature (also evidenced on watervapor imagery) and is progged
to quickly slide southeast across the region Tue afternoon. Short
term guidance suggesting enough break in cloud cover to re-establish
a pool of instability (2500+ J/kg SBCAPE) for this next shortwave
and accompanying sfc boundary to work on. Shear remains fairly weak
while 850 mb moisture transport runs parallel to the main forcing
mechanisms. CAMS spark more showers/storms for the afternoon/early
evening hours, with a southeastward push. While not looking like a
severe weather setup, instability suggests some perkier storms with
small hail and enhanced wind gusts.

Of note - when there is a break in the clouds, expect smokey skies.
Smoke from fires across Canada progged to work southeast through the
day Tue, per the HRRR. This should stay well a loft and (currently)
not expecting any surface impacts.


* REST OF THE WEEK - trending warmer, drier

Long range guidance is in good agreement with gradually shifting an
upper level ridge east from the west coast, moving the axis across
the upper mississippi river by 00z Sat. All 4 of the WPC clusters
concur with only minor differences in strength/location. High
pressure at the sfc precedes the ridge, sauntering in for the end of
the work week, easing east over the weekend.

The upshot is a shift in the "storm track" eastward after Tue,
favoring a spate of dry days headed into Sat. With the pattern
continuing to advance east, the ridge axis is slated to move over
the eastern Great Lakes Sunday, with southerly fetch of warm/moist
air returning. Some bits of upper level energy could spin out of the
southern branch of the flow and bring rain chances.

Meanwhile, what looks like seasonable temps for the latter half of
the work week should see an uptick for the weekend. Not necessarily
"hot", but both the GEFS and EPS suggest highs back into the upper
80s/around 90 for Sunday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 647 PM CDT Mon Jul 22 2024

Showers/storms will move southeast across the area this
evening/overnight, although confidence in the intensity and
coverage of precipitation becomes lower during this time due to
some expected nocturnal weakening. Did include a mention of
thunder at KRST for a time this evening with somewhat more
organized storms along the MN/WI border, although given the
marginal environment, confidence in storm evolution even beyond
a few hours is lacking. Additional storms are likely into
Tuesday, particularly during the afternoon as a weak front moves
through, but confidence in timing is too low to introduce any
rain/thunder. Otherwise, patchy fog could develop early tomorrow
morning. Have not included fog at KRST/KLSE, but cloud/rain
trends through the evening/overnight will need to be watched.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION...JM