Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 202320

Area Forecast Discussion
National Weather Service La Crosse WI
620 PM CDT Sun May 20 2018

.SHORT TERM...(This evening through Monday night)
Issued at 326 PM CDT Sun May 20 2018

At 3 PM, extensive clouds were found along and south of the
Interstate 94 corridor. These clouds and rain-cooled air kept
temperatures in the 50s. Meanwhile, north of the Interstate 94,
skies were primarily sunny with temperatures in the 60s.

The 20.00z are in good agreement that a trough will move out of
Kansas tonight and then transition northeast across the Mid
Mississippi River Valley on Monday morning. Another trough will
move out of Nebraska on Monday morning and then move northeast
through the Upper Mississippi River Valley on Monday afternoon and
night. Both of these system will bring periodic showers to the
area. Rainfall amounts will be up to a half inch. With extensive
clouds and rain, high temperatures will range from the mid 50s to
lower 60s.

.LONG TERM...(Tuesday through Sunday)
Issued at 326 PM CDT Sun May 20 2018

From Tuesday night through Thursday night, a warm front will
slowly transition northeast through the region. Like the past
couple of days, the models continue to struggle with the timing
and placement of this front. Along and south of the front, mixed-
layer CAPES will climb in the 1500 to 2500 J/kg range. This will
be more enough instability for some thunderstorms along and north
of the front. With weak shear, no organized severe weather is
expected. However, could not rule out a pulse-severe storm. One
thing that will have to be watch is a heavy rain potential. This
is due to a slow storm motion (10 to 20 knots) and precipitable
water values up to 1.5 inches.

From Friday into Saturday morning, an upper level trough will move
east through the region. This bring another round of showers and
storms to the area. Like earlier in the week, the shear is very
weak, so not anticipating any severe weather.

In the wake of this system, high pressure will build across the
region for the remainder of the holiday weekend. While there is
agreement with this, the models do differ on the high
temperatures. The GFS has its high temperatures mainly in the
lower and mid-70s. Meanwhile, the ECMWF has its high temperatures
around 80.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 620 PM CDT Sun May 20 2018

Took seemingly forever, but the lower stratus has finally slipped
just south of LSE and RST and will stay there into the evening.
However, do expect to see said lower MVFR clouds move back
northward tonight, arriving first at RST roughly 06-08Z per
current trends but holding off in LSE until sometime during the
morning hours of Monday. Can`t rule out a few showers at LSE or
RST either, though the most widespread rainfall into Monday looks
to slide south of the area across southwest Wisconsin and
northeast Iowa. Winds will remain light the next 24 hours, and if
we can maintain enough clearing this evening for either LSE or
RST, won`t be shocked if we see a little light fog develop.
However, per current forecast expectations, it appears enough mid
and high level clouds will be around to prevent that from
occurring. Will keep a close eye on trends the next few hours.




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