Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 121651

Area Forecast Discussion
National Weather Service La Crosse WI
1151 AM CDT Tue Sep 12 2017

.SHORT TERM...(Today and tonight)
Issued at 230 AM CDT Tue Sep 12 2017

Latest 08z surface analysis shows surface ridge extending from
Michigan into southern Minnesota/Iowa. Mostly clear skies were
seen across the forecast area per latest infrared satellite
imagery. Latest 07z metars over north central Wisconsin and in
the Wisconsin River valley indicate visibilities reduced to less
than a mile due to fog.

Surface ridge will remain in control of the area today into
tonight and provide mostly sunny/mostly clear skies across the
forecast area. High temperatures today are expected to be above
normal with highs in the upper 70s to lower 80s.

Tonight...the combination of light winds and clear skies...will
allow fog to form...especially in river valleys and the favored
areas of central Wisconsin. Have introduce patchy to areas of fog
in these areas...however with the lack of rainfall the past
week...fog may not be as widespread/dense in certain river

.LONG TERM...(Wednesday through Monday)
Issued at 230 AM CDT Tue Sep 12 2017

Upper level/surface ridge remains the dominant weather feature
Wednesday into Wednesday night and provide dry weather across the
forecast area. Then the focus turns to the upper level/surface
ridge building into the eastern Great Lakes Region and southerly
moisture flow returns into the Upper Midwest while a surface warm
front lifts north into central Minnesota and northern Wisconsin
Thursday into Thursday night. The 12.00z GFS/NAM/ECMWF suggest
first impulse to eject out of a upper level trough over the Rocky
Mountains and track along the surface warm front Thursday night.
Main moisture axis per 925-850mb moisture transport will be west
of the forecast area. Small chance of shower/thunderstorm at this
time look to be warranted for western most portion of the forecast
area Thursday night.

Main forecast concerns Friday into Monday are periodic
shower/thunderstorms Friday into Sunday. The 12.00z GFS/ECMWF are in
good agreement in ejecting pieces of energy embedded in the
southwesterly flow aloft into the Upper Midwest and Great Lakes
region through the period. With the 12.00z GFS/ECMWF indicating
increasing moisture convergence/lift over much of the forecast
area...confidence is increasing the forecast area will see periodic
scattered shower/thunderstorms Friday night into Sunday. Timing of
the shower/thunderstorm activity at this time appears to be an models differ on strength and placement of the pieces
of energy moving into the Upper Midwest/Great Lakes region.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1151 AM CDT Tue Sep 12 2017

High pressure will remain in control through the period. VFR
conditions expected at KRST but KLSE will likely have to contend
with some early morning river valley fog and stratus again in the 11-
13Z time frame. Plan on visibilities and/or ceilings temporarily
reduced into LIFR range from 11-14Z.




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