Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 311955

Area Forecast Discussion
National Weather Service La Crosse WI
255 PM CDT WED AUG 31 2016

.SHORT TERM...(This evening through Thursday)
Issued at 255 PM CDT Wed Aug 31 2016

At 2 PM, a short wave trough was moving southeast Minnesota and
central Wisconsin. With the model soundings showing very little
moisture across the region, this front was producing very few clouds
across western Wisconsin, Minnesota, and northern Iowa. Meanwhile
further east across eastern Wisconsin and the northern half of
Michigan, there was enough moisture below 800 mb for a 3 to 5K
deck of broken deck of clouds to develop. Temperatures were in the
lower 70s north of Interstate 94 and and in the mid and upper 70s
across the remainder of the Upper Mississippi River Valley.

For tonight and Thursday morning, the 31.12z models are in general
agreement that the 3 to 5K deck of clouds over eastern Wisconsin will
be transported west on the southern periphery of the Canadian
high. At this time, it looks like these clouds will mainly affect
southwest Wisconsin. These clouds will then dissipate as diurnal
mixing allows for drier air from aloft to mix toward the surface.

As far as valley fog tonight, soundings suggest that there will be
only a shallow layer of winds near the surface. As a result, kept
the patchy to areas of fog primarily confined to the Mississippi
River tributaries and the Wisconsin River valley.

.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM CDT Wed Aug 31 2016

On Thursday night and Friday morning, the 1028 mb surface high
will move southeast into northwest Wisconsin and Upper Michigan.
With this high not moving overhead, there are some questions on
how deep the light winds will be over the area. Both the NAM and
GFS show that this light wind layer will be very shallow, so
limited the areas of valley fog to the Mississippi River
tributaries and the Wisconsin River valley.

The timing of the showers and storms for the Labor Day weekend
are still in question. This is due to the uncertainty of the
strength and western periphery of the Upper Level ridge northwest
and west of Tropical Storm Hermine. This is ultimately slowing the
eastward progress of the cold front. With the 31.12z models
continuing to slow the front, the shower and thunderstorm chances
were taken out for Saturday night and Sunday morning.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1230 PM CDT Wed Aug 31 2016

Main taf concern is fog formation in river valleys tonight. High
pressure over the Upper Midwest and Great Lakes Region will remain
in control of the area this afternoon into Thursday. The latest
31.12z GFS/NAM/RAP Bufkit soundings show inversion developing
tonight and the combination of light winds...will result in the
formation of fog in river valleys after 06z Thursday. At this
time...VFR conditions will prevail at both RST/LSE taf sites.
However...a few or scattered deck of clouds with heights at or
around 200-300 feet could form at LSE taf site after 10z
Thursday...due to fog formation over the Mississippi River.


.ARX Watches/Warnings/Advisories...


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