Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 111114

Area Forecast Discussion
National Weather Service La Crosse WI
513 AM CST Wed Jan 11 2017

.SHORT TERM...(Today and tonight)
Issued at 404 AM CST Wed Jan 11 2017

At 4 AM, a band of snow was moving rapidly east across northeast
Minnesota and northwest and central Wisconsin. This band was
associated with strong 600-500 frontogenesis and 850 to 500 mb
warm air advection ahead of a short wave moving out of the
Dakotas. In the wake of this system, an arctic cold front will
move southeast across the area today. The RAP is showing strong
700 to 500 mb frontogenesis across central Minnesota and northern
Wisconsin this morning. This will result in the development of a
narrow snow band across northern Clark and Taylor counties. With
the heaviest snow (2 to 4 inches) located across Taylor County,
decided to issue a Winter Weather Advisory for snow this morning.

Meanwhile further south another short wave trough moving out of
Nebraska will produce a strong band of 900 to 600 mb frontogenesis
across northeast Iowa and southwest Wisconsin from late this
morning into the afternoon. The NAM has the strongest 925 and 850
mb moisture transport into this boundary. As a result, its
precipitation totals are nearly double what shows up in the other
models. With the soundings showing that there will be a loss of
ice aloft and an elevated warm layer aloft, there will be a wintry
mix of snow, sleet, and freezing rain developing late this morning
and continuing into the afternoon across northeast Iowa and
southwest Wisconsin. With the strongest forcing, highest
precipitation totals, and highest consensus in the models, decided
to issue a Winter Weather Advisory for a wintry mix in Grant
County in southwest Wisconsin.

For tonight, a short wave trough will move quickly east across the
area. This will result in some light snow accumulations from late
this evening into Thursday morning. With limited moisture, expect
snow totals to range from a dusting to a half inch.

.LONG TERM...(Thursday through Tuesday)
Issued at 404 AM CST Wed Jan 11 2017

On Thursday night, a strong arctic high pressure area will move
across the area. With the fresh snow cover, initially thought
about going colder with the temperatures. However with the
soundings suggesting that the boundary layer may remain mixed,
opted not to do this for now.

On Friday afternoon and night, a short wave trough will move
across the region. Like its predecessor, this system does not have
a lot of moisture to work with. As a result, only expecting a
dusting to half inch of snow.

For early next week, there looks like another potential for a
wintry mix. The time frame is still a bit uncertain due to some
questions on how fast the upper level low will eject out of the
southwest United States. Typically in these situations, the models
have a tendency to move these system out of the southwest too
fast. However felt there was enough of a consensus in the GFS and
ECMWF to include a wintry mix from Monday into Monday night.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 513 AM CST Wed Jan 11 2017

Somewhat complicated aviation forecast as zonal flow keeps these
subtle weather systems moving through at a pretty good clip.

Mainly dealing with MVFR conditions this morning as new
frontogenesis area is establishing itself from northwest Iowa into
north central Wisconsin. Given proximty of this area to TAF sites,
expecting MVFR conditions to possibly give way to IFR for a time as
saturation near boundary continues. Thinking any precipitation will
be north and south of TAF sites.

Later today, as next wave passes through, could see some mixing that
would allow ceilings to rise back to MVFR, but confidence not great
past 12 hours in this weather pattern. Will also hold MVFR ceilings
in given amount of flow and boundary proximity in this flow. Might
not be until northern wave scours out conditions later in the week
to return to more widespread VFR.


WI...Winter Weather Advisory until noon CST today for WIZ017.

     Winter Weather Advisory from 1 PM this afternoon to 6 PM CST
     this evening for WIZ061.



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