Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 010338

Area Forecast Discussion
National Weather Service La Crosse WI
1038 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 06Z TAFS through 06Z Thursday night)
Issued at 1038 PM CDT Wed Aug 31 2016

While light surface winds and low dew point depressions are
favorable for valley fog at KLSE overnight into Thursday morning,
the radar wind profile and forecast soundings show northerly
winds around 20 kts atop the nocturnal boundary layer. These
stronger winds, combined with the possibility of some mid cloud
moving southward across the TAF airfield precludes mention of
IFR/LIFR conditions in fog at this time. Will keep some scattered
low stratus and BCFG from 01.10Z until 01.14Z and monitor
conditions for possible amendments. Otherwise, expect VFR
conditions at both TAF sites through the period with perhaps some
scattered afternoon cumulus. Light northerly winds will gradually
turn to the east through the day on Thursday.


.ARX Watches/Warnings/Advisories...


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