Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 260542

Area Forecast Discussion
National Weather Service La Crosse WI
1142 PM CST Sat Feb 25 2017

.SHORT TERM...(This evening through Sunday)
Issued at 318 PM CST Sat Feb 25 2017

At 3 PM, a ridge of high pressure produced mostly to partly sunny
across the area. Temperatures were in the 20s. The coldest
temperatures (lower 20s) were found across the deep snow pack
which extended northeast from south-central Minnesota northeast
into northeast Wisconsin.

A low pressure system will move quickly east across northern
Minnesota and northern Wisconsin tonight. This system will provide
a slight chance of light snow north of Interstate 94. The
greatest chance will be from Taylor County north.

On Sunday, cooled the maximum temperatures over the deep snow
pack over southeast Minnesota, and west-central and north-central

.LONG TERM...(Sunday night through Saturday)
Issued at 318 PM CST Sat Feb 25 2017

Still plenty of questions on a couple of systems that will be
moving through the region from Monday night into Wednesday.
Like their predecessors, the 25.12z models continue to struggle
with when the warm air advection will move into the region ahead
of a short wave trough and surface low ejecting out of the
Southern Plains. The ECMWF and GEM are the fastest and move the
precipitation into the area by Monday evening. The NAM moves its
precipitation into the area early Tuesday morning. Finally, the
GFS keeps this system far enough southeast that the most of the
area will remain dry. While there are timing differences, they are
in fairly good agreement that the temperatures aloft will be warm
enough that the precipitation will be mainly liquid. While they
agree with this, they differ on the surface temperatures. The NAM
would be cold enough that a majority of the precipitation will be
in the form of freezing rain. Meanwhile, the ECMWF, SREF, and GEM
are warm enough that the precipitation would be mainly rain.
Overall felt the NAM was a cold outlier, so trended the surface
temperatures toward the warmer solutions. We will have to watch
this trend closely over the next several days.

On Tuesday afternoon and night, cold air advection builds across
the region in the wake of a northern stream short wave trough.
This cools the atmospheric column sufficiently that by the time
the next low moves out of the Central Plains (late Tuesday night
and Wednesday) that the precipitation would likely be mainly in
the form of snow. The GFS is by far the deepest and furthest west
with its surface low. It would produce 3 to 6 inches of snow
across northeast Iowa and southwest and central Wisconsin.
Meanwhile, the ECMWF track has slipped far enough to the
southeast that we would remain dry. The GEM is between these two
solutions and fit well with the model consensus forecast.

Like Sunday, cooled the temperatures over the deep snow pack over
southeast Minnesota, and west-central and north-central
Wisconsin for both Monday and Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1142 PM CST Sat Feb 25 2017

VFR conditions will be the rule through 27.06Z with periods of
clouds in the 6000 to 7000 ft agl layer through the night. Thicker
cloud cover is then expected to dissipate late Sunday morning
into the afternoon with mainly cirrus thereafter. Southerly winds
will remain elevated at KRST overnight in the 12 to 18KT range,
but then diminish and shift to the southwest later in the period.
At KLSE, winds will be light from the south-southwest.




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