Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 122134

Area Forecast Discussion
National Weather Service La Crosse WI
334 PM CST Mon Feb 12 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 333 PM CST Mon Feb 12 2018

At 3 PM, a 1043 mb surface high was centered over the Twin
Cities. This high was producing partly to mostly sunny skies
across the Upper Mississippi River Valley. Temperatures ranged
from 9F at Dodge Center MN to 21F in Boscobel WI.

The 12.12z models are in agreement that a weak short wave trough
will move east through the area. While the deterministic models
are dry across the area, the ARW, NAMNest, and NMM are producing
precipitation across much of the area tonight. Looking at the
soundings, much of the lift associated with this wave is above
650 mb and it is very dry in the sub cloud layer. Due to this,
kept the forecast dry. With more clouds across the area tonight,
temperatures will not be quite as cold as they were this morning.
Temperatures north of Wisconsin 29 will be around 0F and in the
single digits above zero elsewhere.

On Tuesday morning, the models are in general agreement that the
air mass will saturate down to 800 mb. However, they differ on
where the lift will be located. The NAM has its lift located in
this moisture north of Interstate 94. There is even a small
portion (about 25 to 50 mb) in the favored dendritic growth zone.
Meanwhile, the GFS has all of its located in the dry sub cloud
layer. Even if snow did happen to fall, it would be light and
would not last for too long. With this uncertainty, just kept the
forecast dry for now.

.LONG TERM...(Tuesday night through Monday)
Issued at 333 PM CST Mon Feb 12 2018

On Wednesday, 925 mb temperatures warm to around 1.5C ahead of an
approaching short wave trough. The clouds will be increasing
during the afternoon, so that may limit warming. However,
increasing winds aloft may result in enough mechanical mixing
to overcome these clouds. Due to this uncertainty, just stayed
with MOS temperatures for this time period.

On Thursday and Thursday night, a cold front will move southeast
through the region and another system that will be moving through
the Mid Mississippi River Valley and Lower Great Lakes.
Temperatures continue to look like it will be warm enough along
and south of Interstate 90 for a mix of rain and snow. Meanwhile,
the remainder of the area will be see some light snow. Any
accumulations look to be minor (maybe up to a half inch).

From Sunday into Monday, the models are differing on the timing of
a cold front moving through the region. The GFS moves this front
through on Sunday. Meanwhile, the ECMWF has another wave
developing along this front and this keeps the front from moving
through the area until Monday night. Due to these difference,
there is anywhere from 4 to 7 standard deviation difference with
the high and low temperatures in the GFS and ECMWF ensembles.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1114 AM CST Mon Feb 12 2018

VFR conditions expected through the TAF period. Northwesterly
winds this afternoon will become light and variable this evening,
before becoming southerly during the overnight hours. RST could
then see some gusts near 20 kts on Tuesday. Otherwise, scattered
high clouds will be seen this afternoon, with a broken deck around
10 kft agl moving in overnight.




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