Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 121141

Area Forecast Discussion
National Weather Service La Crosse WI
541 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 12Z TAFS through 12Z Wednesday morning)
Issued at 541 AM CST Tue Dec 12 2017

Clear skies currently will give way to thickening mid level clouds
through the morning and early afternoon (first at RST by 14Z or
so), followed by a several hour window of lower stratus into the
evening hours. Conditions will largely remain VFR, but a few hour
period of MVFR ceilings does appear probable for RST this
afternoon and early evening before those clouds depart to the
east. Winds from the northwest 8-13 knots will become light this
evening before shifting back to the south 10-15 knots later
tonight, in advance of approaching low pressure. That feature will
eventually bring with it a round of IFR ceilings and potentially
some wintry precipitation by Wednesday.




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