Area Forecast Discussion
Issued by NWS La Crosse, WI

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922
FXUS63 KARX 250829
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
229 AM CST Sat Feb 25 2017

.SHORT TERM...(Today through Monday)
Issued at 229 AM CST Sat Feb 25 2017

Radar and surface observations continue to indicate some lingering
light snow was falling across mainly Wisconsin early this morning.
This activity was moving to the east and by 12Z expecting it to be
confined to the eastern sections of the forecast area with this
then moving out of the area by about 15Z.

A couple of short wave troughs currently over western Canada, will
zip across the Upper Midwest tonight and Sunday morning. These
waves are only expected to produce some weak pv advection in the
500-300 mb layer with this primarily staying north of the
forecast area. A weak area of low pressure at the surface will
come out of North Dakota today and move across northern Minnesota
and Wisconsin with these short wave troughs. The warm air
advection ahead of this low is expected to produce between 2 and 4
ubar/s of up glide on the 280K isentropic surface for late
tonight into Sunday morning, with some of this over the northern
portions of the forecast area. The northern portions of the
forecast area could also be influenced by some weak frontogenesis
in the 1000-850 mb layer. This forcing could be enough to generate
a little bit of light snow for areas generally along and north of
Interstate 94 and will continue to show some low end snow chances
across this area.

.LONG TERM...(Monday night through Friday)
Issued at 229 AM CST Sat Feb 25 2017

The next system to impact the area looks like it will come in
Monday night and Tuesday. This should be a combination of the
remains of the upper level low off the coast of northern
California and the short wave trough over Alberta. These are
expected to phase and come across the Midwest as a weakening
positive tilt system. The forcing does not look all that
impressive with this system with just some weak pv advection in
the 500-300 mb layer coming across late Monday night into Tuesday
morning along with the some weak frontogenesis in the 700-500 mb
layer. The isentropic up glide looks to be between 2 and 4 ubar/s
on the 285K surface. The potential problem with this system looks
to be the warm air aloft that it will bring in and the resulting
precipitation types. Enough warm air aloft should already be in
place by the time the precipitation starts for a mix of snow,
sleet and freezing rain with just rain across the south where
surface temperatures should be in the middle 30s. This wintry mix
will work north late Monday night into Tuesday morning before
transitioning over to all rain as the surface temperatures warm
into the upper 30s and 40s. Before this transition occurs though,
there could be some ice accumulations up to a tenth of an inch and
currently looking at the possible need for an advisory with this
event.

After this system exits the region, there will then be on and off
chances for some additional light precipitation for the remainder
of the week. The northern edge of the precipitation shield from a
system going through the Ohio River Valley could brush the area
Wednesday. A system could potentially drop into the Upper Midwest
on the northwest flow aloft to produce some more light
precipitation Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1136 PM CST Fri Feb 24 2017

Accumulating snowfall has moved east of TAF airfields allowing for
improved visibility. KLSE could still see an hour or two of MVFR
ceilings, but otherwise VFR clouds will be the rule overnight and
through the rest of the period. Breezy north-northwest wind
overnight will gradually diminish through the period and turn to
the west-southwest by Saturday afternoon.


&&

.HYDROLOGY...
Issued at 229 AM CST Sat Feb 25 2017

Water levels along the Black and Yellow Rivers appear to have
peaked with the Black River River steadily falling near
Galesville and the same happening on the Yellow River in Necedah.
Flows remain high on the Wisconsin River through Castle Rock Dam.
For specific information on these forecast points, see the latest
river flood statements.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 AM CST early this morning for
     WIZ017-029-034-041>044-053>055-061.

MN...None.
IA...None.
&&

$$

SHORT TERM...04
LONG TERM...04
AVIATION...Rogers
HYDROLOGY...04



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