Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 131752
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1152 AM CST Wed Dec 13 2017

.UPDATE...
Issued at 721 AM CST Wed Dec 13 2017

Quickly changing situation for the event, with the heaviest snow
band pivoting a bit farther north than earlier thought. Have
dropped Jackson, Juneau, and Adams Counties from the winter
weather advisory given current trends, as there likely won`t be
much (if any) snow across those areas, with maybe just a touch of
light freezing drizzle in the post-frontal environment later
today. Also watching a band of enhanced precip wrapping around the
upper wave crossing toward southeast Minnesota, with some reports
of snow and also liquid precip with temps spiking right ahead of
said precip, just as the warm front is briefly arriving. All in
all, can`t rule out some brief snow surviving east, but we`ll also
be fighting the expanding warm sector toward the Mississippi
River through late morning, with temps perhaps jumping toward 40
degrees briefly in some areas.

With that in mind and given trends, have reworked the forecast
quite a bit to lower snowfall totals for all but northern Clark
and much of Taylor Counties in Wisconsin, while also still have
some risk for freezing drizzle right behind the cold front from
late morning into the afternoon given a deepening moist layer but
one lacking any ice for several hours. At this time, don`t
anticipate any huge problems travel- wise but of course will need
to watch trends closely.

&&

.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, Adams, and Juneau counties.
As a result, they are the only ones in the Winter Weather Advisory.
We will continue to monitor Buffalo and Trempealeau 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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1152 AM CST Wed Dec 13 2017

The main aviation concerns this forecast period are MVFR clouds
and strong northwest winds.

Current satellite and surface observations indicate a large deck
of stratus clouds with mostly MVFR ceilings extending from
northeast IA/southwest WI back northwest into southern Canada.
Confident that these ceilings will persist at least through the
afternoon. After 14.00Z, model guidance suggests there could be
breaks from the MVFR clouds. But given the upstream observations
and time of year, not confident enough to include a period of VFR
at this time.

Strong northwest winds of 15 to 25 kt with gusts to 25 to 35 kt
will continue through the afternoon. The winds should gradually
diminish after sunset and stay northwesterly around 5 to 10 kt
through Thursday.

&&

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

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

$$

UPDATE...Lawrence
SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Hollan



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