Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 210450

Area Forecast Discussion
National Weather Service La Crosse WI
1150 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 06Z TAFS through 06Z Monday night)
Issued at 1150 PM CDT Sun May 20 2018

The northern edge of MVFR ceilings has recently nudged just a hair
farther north back into RST, and per current satellite trends, it
appears this may hang tight the rest of the night, though some
periods of VFR could also return. Lower stratus should then spread
north late tonight through Monday morning along with perhaps some
showers at both LSE and RST (best chance LSE). Even lower stratus
then looks to develop across much of the area later Monday
afternoon into Monday night within light flow, with increasing
potential for IFR to even LIFR conditions along with some drizzle
and visibility reductions. It is even possible that some dense fog
could develop in some areas, but confidence not quite high enough
just yet to include that mention.




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