Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180402
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1102 PM CDT Tue May 17 2022

.DISCUSSION...(Tonight through Tuesday)
Issued at 228 PM CDT Tue May 17 2022

Key Messages:

 - Strong to severe storms possible Thursday night into Friday

 - Cooler this weekend

A few short wave troughs to work with in the near term, including
one that has well established frontogenetic forcing brushing our
southern counties today. This is coinciding with southerly moisture
transport. The increased moisture and lift will continue to produce
showers for the area tonight into tomorrow morning. The highest
precipitation amounts /0.3-0.6"/ will be along and south of the I-94
corridor. Elsewhere, 0.1-0.3" are expected. RAP and HRRR model
soundings suggest little to no CAPE in the area overnight, so can
expect primarily rain showers.

More favorable conditions for strong storms stays to the southwest
of the area, though a rumble or two of thunder in far SW Wisconsin,
SE Minnesota, or NE Iowa is not out of the question if whatever CAPE
is available can be tapped into. The precipitation is expected to
move out of the area Wednesday evening/night.

Storm chances Thursday night into Friday:

Focus shifts to convective threat going into Thursday night.

While Thursday morning should start off quiet and pleasant, a
digging short wave trough dropping out of Canada will lead to a
changing pattern as the day progresses. Response from this wave will
lead to a fairly narrow but rapid return of low level moisture
northward along an approaching cold front. This is seen well in
moisture transport fields and model mixed layer CAPE fields
streaming northeast ahead of boundary reaching in excess of 1500
J/kg. Confidence is lower in how far north higher dewpoints may get
attributing to these values. Could be a hint of a warm front in
there as well, likely advecting northeast as the day goes on.

Based on the strength of the wave certainly see the possibility of
strong to severe storms as front comes in Thursday night. Timing
seems a bit more delayed than previous forecasts so this may work
against the overall threat. But given dynamics of stronger wind
field, convection could still be potent with a wind or hail threat
from late evening into the overnight hours. See Day 3 Storm
Prediction Center for other details on risk.

Convection will work east early Friday morning as front clears the
area. Medium range guidance a bit varied in how far north any
precipitation may form along this so will keep in small chances but
gut tells me this will likely remain south of the immediate area.

Weekend and early next week / Cooler weather:

The big story will be the cool down in temperatures for the weekend
as longwave troughing builds into the northcentral CONUS. Highs will
be in the 50s with some freeze possibilities Sunday and Monday
morning at least in the central Wisconsin cold spots.

Saturday could still bring some rain chances it appears. There are a
group of model solutions that stripe a post-frontal frontogenetic
rain band through southern WI...so 30-40% rain chances remain there.
Otherwise, a few instability showers may be around, or at least
diurnal stratocumulus.

A general warming trend begins on Monday in a fairly swift
progressive zonal flow as a series of shortwave troughs shift
through. On and off shower chances into midweek look reasonable with
storm chances returning later Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1102 PM CDT Tue May 17 2022

Rain showers will continue through most of the overnight hours.
However, MVFR ceilings have been slow to develop this evening.
As rainfall continues to moisten the surface and temperatures
slightly decrease overnight, MVFR ceilings are still likely, but
just closer to early morning by 12z. A heavier and more intense
shower passing directly over a TAF site could temporarily reduce
visibilities to MVFR conditions.

Winds will be on the lighter side of less than 10 knots, but
several wind shifts will occur over this forecast period. Easterly
winds will prevail through a majority of the period, but late
morning/early afternoon is when winds will rotate from the west
to then even southwesterly by the evening.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

DISCUSSION...Dahl / Shea / Baumgardt
AVIATION...Peters


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