Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 121714

Area Forecast Discussion
National Weather Service La Crosse WI
1114 AM CST Tue Dec 12 2017

.SHORT TERM...(Today and Wednesday)
Issued at 346 AM CST Tue Dec 12 2017

At 3 AM, lake effect clouds were streaming over central and
north-central Wisconsin. These clouds were also producing a few
flurries at times. Elsewhere, skies were clear. Temperatures early
this morning ranged from 10 to 20.

For tonight and Wednesday morning, a strong short wave trough,
currently located over British Columbia, will move through the
region. Unlike the system which came through the region on Monday,
this system will be bringing much more moisture with it. This is
a result of this system having a tie with an atmospheric river
prior to making its landfall. The models are in fairly good
agreement that this system could potentially produce anywhere from
a quarter to half inch liquid in the strong warm air advection
and frontogenetic region ahead of this wave. While the
deterministic runs favor a 3 to 5 inch (possibly more) snow band
north of Interstate 94, the ARW, NMM, and experimental HRRR
suggest that this band may be much further southwest. In addition
to track issues, there are also some timing differences due to
differences in saturation.

With the loss of ice just southwest of the snow band, there will a
band of freezing drizzle or drizzle. This band may produce some
light icing. Like the snow band, there is uncertainty on where
this may occur.

A Winter Weather Advisory will likely be needed, but with
uncertainties in the timing and track of system, opted not to do
one at this time.

On Wednesday afternoon and evening, there will be strong cold air
advection behind the departing short wave trough. This will result
in northwest wind gusts up to 40 mph across southeast Minnesota
and northeast Iowa.

.LONG TERM...(Wednesday night through Monday)
Issued at 346 AM CST Tue Dec 12 2017

The 12.00z models continued to have quite a bit of differences
in their timing and placement of precipitation moving through the
region. They were not only inconsistent with each other, but also
among their own families. Due to this, made little to no change
to the model blends.

The only thing that was consistent in the models was that the
upper flow will eventually become more off of the Pacific than
the Arctic; thus, temperatures should warm above normal by this
weekend and continue into early next week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday noon)
Issued at 1114 AM CST Tue Dec 12 2017

Generally good VFR this afternoon will give way to some MVFR or near
MVFR clouds this evening as lower moisture ahead of the next
approaching wave/low spreads in from the NW. This looking to rather
transient across the area this evening, as drier low level air SW of
the approaching low spreads across the area. Once the low passes
between roughly 12-14z Wed and a strong cold front pushes across the
area, MVFR clouds to return, along with brisk/gusty NW winds and
some -SHSN. Confidence pretty good on the winds and MVFR clouds
behind the front Wed morning, but not so much on the -SHSN.
Considerable variability among models/ensembles for -SN chances Wed
morning. Some keep the area dry or just flurries, while others
producing some snow accumulations at both KRST/LSE. Left precip
mentions Wed morning to VCSH for now, pending a tighter model
consensus or better signal which of the models may be more correct.




LONG TERM....Boyne
AVIATION.....RRS is the U.S. government's official web portal to all federal, state and local government web resources and services.