Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 230532

Area Forecast Discussion
National Weather Service La Crosse WI
1132 PM CST Wed Feb 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 345 PM CST Wed Feb 22 2017

At 3 PM, a short wave trough was moving across northern
Minnesota. This system produced showers mainly north of our area.
However there were a few sprinkles reported along the Interstate
90 corridor. Temperatures north of Interstate 94 were in the 50s.
Meanwhile the remainder of the area saw temperatures ranging from
the upper 50s to lower 70s. Janesville and Boscobel (RAWS site)
Wisconsin both climbed to 72F. These are the warmest temperature
ever recorded in the state of Wisconsin during the month February.
The previous record was 69F at Kenosha on February 11, 1999 and
Beloit, Afton, and Brodhead on February 26, 2000.

.LONG TERM...(Thursday night through Wednesday)
Issued at 345 PM CST Wed Feb 22 2017

On Thursday evening, the models are still in good agreement that
as moisture over runs the stationary front to our south that
precipitation will continue to fall across the area. Soundings
continue to suggest that this precipitation will be mainly in the
form of rain during the evening and as the atmospheric column
cools after midnight that this precipitation will change to a
wintry mix of snow, rain, and freezing rain. Areas north of
Interstate 90 will likely see 1 to 3 inches of snow with some
light icing. Meanwhile areas along and south of Interstate 90 may
see some light icing. With mean layer CAPES climbing up to
250 J/kg ahead of a dry slot, there will also be the potential for
some scattered thunderstorms.

On Friday morning, there is a general consensus that a dry slot
will quickly spread across the area. With the the loss of ice
aloft, the snow will come to an end for much of the area from mid
morning through early afternoon. During this time, expect periods
of rain and freezing rain. However, looking at the temperatures
and dew points in the 22.15z SREF members, there is still a
possibility that the precipitation could be mainly in the form of
rain. With the model soundings showing a shallowing moisture
profile, there is concern that the precipitation amounts may be
too dry.

On Friday afternoon as the dry slot moves slowly east away from
the area, a deformation band will move east into northeast Iowa
and southeast Minnesota. With the addition of ice aloft and below
freezing temperatures aloft, this deformation band should contain
mainly snow. Additional snow totals north of a Charles City Iowa
to Medford Wisconsin line will likely range from 1 to 2 inches.

On Friday night, the deformation band of snow will move east
across the area. Additional snowfall amounts 2 to 4 inches are
expected west of Oelwein Iowa to Owen Wisconsin line and 1 to 2
inches east of this aforementioned line.

At this time, it continues to look like a total of 4 to 10 inches
of snow may fall north of a Charles City Iowa to Black River
Falls line. Elsewhere total snowfall looks to be in the 1 to 4
inch range. While there was not much change in the forecast
snowfall today, confidence on the location of this heavy snow band
remains low. For example, the operational ECMWF has this track on
the southeast periphery of its family members. There is a 4 to 7
standard deviation difference on its temperatures across the area.
The ECMWF ensemble has high temperatures on Friday ranging the
mid 20s to upper 20s with its coldest solution and mid 30s to mid
50s with its warmest solution. In addition, as stated I am seeing
similar things showing up in the 22.15z SREF members. In
addition, the potential of dry slot shutting off much of the
precipitation on Friday. Due to all of this uncertainty, left the
Winter Storm Watch as is for now.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1132 PM CST Wed Feb 22 2017

Surface cold front now along a line from KEAU to KLSE to KOLZ and
will continue to push eastward overnight. Behind the front, winds
increase from the northwest with some gusts into the lower 20 kt
range. MVFR/IFR cloud deck also on the move behind the front and
will impact TAF airfields for much of night. Some slight
improvement to VFR at KLSE and MVFR at KRST expected by mid
Thursday morning into the afternoon before conditions drop again
Thursday evening in response to the strong winter storm taking aim
on the region Thursday night through Friday. Could see a rain/snow
mix or even all snow at KRST prior to 24.06Z, but for simplicity
will keep it all rain for now with some reduction in visibility
into the MVFR range. Gusty northwest wind overnight will gradually
turn to the northeast by late Thursday morning into the afternoon.


WI...Winter Storm Watch from Thursday evening through Friday evening
     for WIZ017-029-032>034.

MN...Winter Storm Watch from Thursday evening through Friday evening
     for MNZ079-086>088-094.



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