Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 111729

Area Forecast Discussion
National Weather Service La Crosse WI
1229 PM CDT Fri Aug 11 2017

.SHORT TERM...(Today through Sunday)
Issued at 250 AM CDT Fri Aug 10 2017

The low stratus will gradually shift east and south of the local
area this afternoon as the responsible low pressure system treks
eastward. High pressure then builds in for tonight and looks to be
the main weather feature for the region into Sunday.

One other note for today...a few of the meso models suggest an
isolated shower/storm threat over southern MN in the afternoon - in
a pocket of instability, and perhaps a small chance for rain for
eastern WI on the backside of the departing low, along a sfc trough.
Chances are small, and outside of the local forecast area - will
keep it dry.

The GFS and NAM have been persistent with scooting a 500 mb
shortwave trough across southern parts of the region later in the
day Sunday (EC and Canadian for that matter too). The shortwave will
have to battle the sfc high, still hanging out across the region,
along with relatively dry sfc/near sfc air. Instability is lacking,
as is wind shear. Poor setup for shower/storm chances. That said,
the shortwave likely has enough lift to work on the sparse
saturation to warrant continued small rain chances for Sun/Sun

.LONG TERM...(Monday through Thursday)
Issued at 250 AM CDT Fri Aug 11 2017

Models pointing to a bit more active pattern for the later half of
next week. Both the GFS and the EC take a pac nw shortwave trough
due east, sliding it across southern Canada/northern portions of the
local area Wed/Wed night. Surface front accompanies the upper level
forcing - pushed east by the EC on Thu, with the GFS suggesting the
tail end could linger west-east across parts of the region into Fri.
This boundary would then get worked on by another shortwave that
both models bring in for Fri/Fri night. A little instability to play
with later in the day Wed as this first shortwave moves in, but the
bulk of the deeper shear lies west, in the colder air. Some pcpn
chances for mid week as a result, although how far south those
extend (away from the parent shortwave) is not certain. Friday night
currently trending the most likely for a widespread/shower storm
threat - albeit well far out in time to be too confident.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1229 PM CDT Fri Aug 11 2017

Latest visible satellite imagery shows stratocumulus clouds
rotating around low pressure over the Great Lakes Region into
eastern Wisconsin. Latest 17z surface analysis indicates surface
ridge over western Minnesota. Surface ridge will build into
western Wisconsin and eastern Minnesota through taf period and
continue to erode stratocumulus clouds over central Wisconsin this
afternoon. The combination of light northerly winds at the
surface filtering in a drier airmass and winds above the surface
over 10 knots will inhibit widespread fog development in the
Mississippi River tonight. This will allow for VFR conditions to
prevail through the taf period at LSE taf site. With surface ridge
in control of the area VFR conditions are expected to prevail
through the taf period at RST taf site.




LONG TERM....Rieck
AVIATION...DTJ is the U.S. government's official web portal to all federal, state and local government web resources and services.