Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 130942
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
342 AM CST Wed Dec 13 2017

.SHORT TERM...(Today and tonight)
Issued at 342 AM CST Wed Dec 13 2017

At 3 AM, a light snow band, associated with 700 to 500 mb
frontogenesis, was quickly moving east through Clark and Taylor
counties. The models show that this band will move east of these
counties by 5 AM and then pivots back into these counties toward
sunrise this morning. This showed up in many of the meso models
and the forecast was trended toward this. This would result in a
total of 2 to 5 inches of snow across Taylor and northern Clark
counties and up to 2 inches across southern Clark County. One
concern with this forecast is the latest HRRR and 13.06z NAM Nest
is suggesting that this heavy snow band may end up further north.

Along the Interstate 94 corridor, the main concern is a wintry
mix of snow and freezing rain. Snow total will be up to an inch
with some light icing possible. At this time, the largest concern
looks to be in northeast Jackson County. As a result, they are
the only one in the Winter Weather Advisory. We will continue to
monitor Buffalo, Trempealeau, Adams, and Juneau counties to see
whether they will be needed to be added or not. However, like
Clark and Taylor counties, there is concern that this band may be
further north and they get nothing.

For the remainder of the area this morning, the largest concern
will be whether the showers along the cold front will hold
together long enough to move through the area. If they did,
soundings suggest that any precipitation would be in the form of
rain. With the temperatures near freezing, these showers could
produce some light freezing rain which would result in some icy
roads. However, the models continue to show that this convection
will weaken as it approaches and the radar is starting to trend
that way too.

From late this morning, strong subsidence in the wake of the cold
front will produce wind gusts up to 40 mph across southeast
Minnesota and northeast Iowa from mid morning through mid
afternoon.

.LONG TERM...(Thursday through Tuesday)
Issued at 342 AM CST Wed Dec 13 2017

The 13.00z 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. With the area being located so close
to the baroclinic zone, the temperature forecast is tricky,
because we will be going back and forth between maritime Pacific
and continental polar air masses.  Due to this, made little to no
change from the model blends.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1105 PM CST Tue Dec 12 2017

Cigs: generally looking at VFR bkn cigs through the night, with a
lowering into MVFR post a sfc front Wed morning. The mvfr should
hang around through Wed night.

WX/vsby: variety of pcpn possible from tonight through Wed
afternoon. Warm air advection, frontogenetic forcing and an upper
level shortwave trough will all play roles - as will sfc temps, ice
in cloud, and cig heights/thickness of cloud layer. As it looks now,
a narrow snow band capable of several inches will setup northeast of
the TAF sites, closer to KLSE. Elsewhere, showery-mostly light
intensity pcpn is expected - mostly snow overnight/Wed morning, with
some loss of ice in cloud bringing a freezing drizzle potential late
morning/early afternoon - then back to snow. Snow or ice accums look
minimal at this time, but obvious impacts if icing is realized. What
falls, when and how much is not clear cut at this time and will
continue to monitor and adjust forecast as needed. Going to hang
onto the vcsh mention for now.

Winds: south will swing northwest and increase with the passage of
the sfc front Wed morning. Despite expected low clouds, bufkit
soundings suggesting gusts of 30-35 kts for KRST. Tight pressure
gradient won`t start to relax Wed evening.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST this evening for WIZ017-
     029-034-043-044.

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

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION.....RIECK



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