Area Forecast Discussion
Issued by NWS La Crosse, WI

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310
FXUS63 KARX 241816
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
115 PM CDT Wed Jul 24 2024

.KEY MESSAGES...

- Drier and seasonable through Friday.

- Increasing heat and humidity starting this weekend, persisting
through much of next week. Rain chances also return, more favorable
Sunday night through Monday.

&&

.DISCUSSION...
Issued at 115 PM CDT Wed Jul 24 2024

OVERVIEW: change in the upper level flow as a well agreed upon,
both within and between the models, swing from troughing to ridging
progged for the rest of the week. The ridge over the west coast will
make steady progress east, still looking to shift its axis across
the upper mississippi river valley by 00z Sat. Not a blocking
pattern this go around as the ridge is favored to continue to ease
east over the weekend. The GFS and EC then shift to broad upper
level ridging. Some differences between the models` ensemble members
with placement, strength of the ridging (per latest WPC cluster
analysis)...but the overall picture paints the same: moving into a
warmer and more humid (hot) stretch of days. In addition, the flow
would support the potential for shortwave troughing to swing near or
across the region - and thus pcpn chances return to the forecast
starting Sunday.

TEMPS: after a seasonable stretch of days to finish out the work
week, high pressure at the surface shifts east for the weekend with
the ridge building overhead. A southerly fetch will start to pool
warmer and more humid air northward - and our temps will be on the
rise. The EPS is the warmer of the models with 75% of its members
pushing highs into the upper 80s to the lower 90s. Its upper 10%
flirts with mid 90s+ for a few locations. The GEFS is cooler, and
has held that trend. Still, its only a few degrees cooler than the
EPS and still warming above the late July/early Aug normals. With
dewpoints looking to climb back into the upper 60s to around 70 at
times, the humidity will tack on 5+ degrees for heat indices to
those high temps.

RAIN CHANCES; the region will get a break for a few days as the high
pressure asserts itself. Looks to stay dry into Saturday with the
pattern shift allowing for ripples a loft to have a better path to
bring shower/storm chances to the region for the new week.
Currently, both the EPS and GEFS suite of members favors Sunday
night through Monday for the higher rain chances...with a mixed bag
of lower end chances after that.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1228 PM CDT Wed Jul 24 2024

Surface high pressure is building in over the area, however patchy
low level moisture remains in place over parts of the area through
Thursday.  With heating today, the patchy MVFR ceilings should
continue to lift with a mix of sct-bkn020-050 conditions. A couple
of concerns into the forecast through Thursday.  With light winds
overnight and 1-3 deg dewpoint depressions, fog will be possible.
Some concern that with low level moisture lingering over parts of
MN/IA patchy stratus could hinder fog.  The 24.12Z gfslamp data and
prior runs have been very aggressive with widespread fog across the
rest of southeast MN/northeast IA into WI by 12Z Thu. Meanwhile, the
NAM/RAP/HRRR are only hinting at patchy fog.  Surface dewpoints will
generally be on the decline, however with the weak flow through 2km
and recent rains/evapotranspiration, dense valley fog should develop
where skies are clear with additional patchy fog possible. In
addition, the HRRR/RAP show vertically integrated smoke over the
southwest third to half of the forecast area shifting west, then
returning east Thursday with an increase in surface smoke near RST.
Hazy daytime visibility restrictions could occur at RST, but appear
to be after the end of this TAF forecast.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION...Zapotocny