Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 302129

Area Forecast Discussion
National Weather Service La Crosse WI
329 PM CST Wed Nov 30 2016

.SHORT TERM...(This evening through Thursday)
Issued at 329 PM CST Wed Nov 30 2016

At 3 PM, a low pressure area was centered over west-central
Wisconsin. With cyclonic flow aloft and surface to 850 mb lapse
rates greater than 8 C/km, numerous rain and snow showers have
developed across the Upper Mississippi River Valley. With the loss
of diurnal heating, the surface to 850 mb lapse rates will
gradually decrease into the 6-7 C/km range. As this occurs, the
areal coverage of these showers will decrease. Any snow amounts
from late this afternoon into tonight will be mainly confined to
southeast Minnesota, northeast Iowa, and the higher terrain in
western Wisconsin. Snow amounts in these areas will range from a
trace to a half inch.

With extensive cloudiness and neutral temperature advection at
both the surface and aloft tonight, did not deviate much from the
low temperatures that occurred this morning.

For Thursday, the surface and upper level low will slowly move
east northeast across central Wisconsin during the morning and
upper Michigan during the afternoon. With the steepest surface to
850 mb lapse rates being off to our east, not anticipating as
widespread rain and snow showers...thus...precipitation chances
are less than 30 percent.

.LONG TERM...(Thursday night through Wednesday)
Issued at 329 PM CST Wed Nov 30 2016

From late Saturday night into Sunday evening, a short wave trough
will move east through the region. Soundings show that the
precipitation will be initially start as snow and then transition
to rain or a mix of rain and snow as the boundary layer warms on
Sunday.  Little is any snow accumulation is anticipated.

From Tuesday afternoon through Wednesday, both the 30.12z GFS and
ECMWF have shifted this low further west with its surface low
track. This allows the strong warm air advection ahead of this
system to move into the region. With 925 mb temperatures climbing
up to 6C across much of the area, any precipitation that falls
with this system will likely be mainly rain. With that said, the
30.12z ECMWF has a 6 standard deviation with their high
temperatures (ranging from a low of 17F to a high of 43F). Some of
this difference is a result to differing timing on the speed of
this system. Meanwhile, the GFS only has a spread of 3 standard
deviations. With high standard deviations showing up in the
temperatures, the uncertainty on any forecast during this time
frame is far from certain.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1128 AM CST Wed Nov 30 2016

Upper low over southeast MN will continue to move east across the
area through the period. This will result in light rain and/or
snow continuing this afternoon into this evening, diminishing
after midnight. Otherwise, plan on MVFR/IFR stratus to linger
through the period along with occasional reductions in vsby to
3sm through this evening in precipitation.




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