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Area forecast discussion
National Weather Service La Crosse WI
629 PM CDT Mon Oct 23 2017

Short term...(this evening through tuesday)
issued at 225 PM CDT Mon Oct 23 2017

Main impactful weather concerns are on strong northwest winds
tonight through Tuesday. These strong winds will create driving
difficulties for lightweight and high profile vehicles. Also,
unsecured lightweight objects may be blown around.

Strong northwest winds of 25 to 30 mph with gusts to 45 mph will
develop this evening across the open areas of southeast Minnesota
and northeast Iowa. These strong winds will then spread eastward
into western and central Wisconsin early Tuesday morning as low
pressure tracks into eastern Upper Michigan and rapidly
intensifies/deepens. A Wind Advisory is in effect for all of
southeast Minnesota and northeast Iowa starting at 7 PM tonight and
continuing through 6 PM Tuesday. A Wind Advisory will also be in
effect for all of western into central Wisconsin from 7 am Tuesday
through 7 PM Tuesday. The strongest winds in Wisconsin will be
confined to open areas and ridge top locations. A band of light rain
showers will track east across the area late this afternoon into
this evening thanks to frontogenesis in the 900-700 mb layer. This
band of showers is expected to increase in coverage and intensify
slightly across portions of western and central Wisconsin as the low
deepens. The low then retrogrades west as a trough digs into the
upper Mississippi River valley. Rain showers will then gradually
spread back to the west with light to perhaps moderate rain across
much of Wisconsin and periods of showers expected across northeast
Iowa and southeast Minnesota. It will be rather chilly on Tuesday
too with highs only making it into the lower to mid 40s. Winds will
subside Tuesday evening as the low heads east into Ontario.

Long term...(tuesday night through monday)
issued at 225 PM CDT Mon Oct 23 2017

After the windy day Tuesday, conditions will settle down Tuesday
night as the surface low moves off into southern Ontario. This
will allow the winds to quickly diminish and be under 10 mph from
about late evening through the overnight. Any lingering showers
late Tuesday afternoon will also quickly dissipate/move east of
the area and right now do not plan to carry any precipitation
chance into Tuesday evening.

The 23.12z models continue to show a period of short wave ridging
building in over the upper Midwest for Wednesday and Wednesday
night before the next system comes south out of Canada on the
northwest flow aloft. The general trend is for this short wave
trough to help form an upper level low over the upper Midwest
Thursday and Thursday night. Some differences start to show on how
long this system will remain over the region. Heading into the
weekend, the 23.12z GFS is forming a large cut off low over
hudsons Bay which swings the trough out of the upper Midwest and
into the eastern Great Lakes. The 23.12z European model (ecmwf) is much weaker with
the system over hudsons Bay allowing the upper level low and
troughing to remain over the upper Midwest and Great Lakes through
much of the weekend. These differences are also seen at the
surface where the GFS would take the precipitation out of the area
late on Friday while the European model (ecmwf) holds onto some light precipitation
into Saturday night. For now, will go with the faster evolution of
the GFS but may need to adjust this with later forecasts to hold
onto the precipitation chances a bit longer. This system will also
usher in the coolest air of the season. Overnight lows will dip
into the 20s and lower 30s from Thursday night through Sunday
night with 20s for almost the entire area Friday and Saturday
nights. Daytime highs during this period will primarily be in the
40s but some spots Friday could be stuck in the 30s the entire
day. With these cool temperatures, the precipitation types will
change between rain in the day to some light snow at night. At
this point, it does not look the snow should amount to much.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 629 PM CDT Mon Oct 23 2017

Rapid low pressure deepening is underway across Michigan this
evening and will continue tonight, resulting in rain showers
expanding in coverage back westward toward the Mississippi River
through the night. Similarly, lower clouds will also overspread
the area, with ceilings mainly MVFR for all areas by late evening,
continuing through much of Tuesday but eroding from the west
during the afternoon. Winds will be the bigger story, with
increasingly gusty conditions expected tonight into Tuesday. Peak
wind gusts of 35 to perhaps 40 knots are possible in many areas,
with sustained speeds of 20-25 knots likely, slowly subsiding
through late Tuesday and Tuesday evening.

&&

Arx watches/warnings/advisories...
WI...Wind Advisory from 7 am to 7 PM CDT Tuesday for wiz017-029-
032>034-041>044-053>055-061.

Minnesota...Wind Advisory until 6 PM CDT Tuesday for mnz079-086>088-094>096.

Iowa...Wind Advisory until 6 PM CDT Tuesday for iaz008>011-018-019-029-
030.

&&

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