Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 191735

Area Forecast Discussion
National Weather Service La Crosse WI
1135 AM CST Sun Nov 19 2017

.SHORT TERM...(Today and tonight)
Issued at 252 AM CST Sun Nov 19 2017

At 2 AM, a band of MVFR clouds associated with a short wave trough
was moving southeast through western Wisconsin. The 19.00z models
are in good agreement that these clouds will quickly exit region
prior to sunrise.

For this afternoon and early evening, the mid and high clouds
currently located over North Dakota will move quickly southeast
into areas along along and north of Interstate 94. These clouds
are associated with the left exit region of a 110 knot 250 mb jet

For tonight, additional mid and high clouds will move into parts
of northeast Iowa, southeast Minnesota, and southwest Wisconsin.
These clouds are associated with the right entrance region of the
aforementioned jet.

.LONG TERM...(Monday through Saturday)
Issued at 252 AM CST Sun Nov 19 2017

On Monday, southwest winds aloft will bring 5 to 9C 925 mb
temperatures into the region. With abundant sunshine, high
temperatures will range from the mid 40s to lower 50s.

From late Monday night into Tuesday morning, a strong Canadian
cold front will move quickly southeast through the region. The NAM
briefly generates some small CAPEs, steep 950-850 mb lapse rates,
and about 100 mb of moisture centered around 875 mb. This may
result in a brief snow shower. However, with other models, showing
limited moisture behind this front. Just opted to keep the
forecast dry for now. With 925 mb temperatures cooling into the -6
to -9C by Tuesday afternoon, high temperatures will only range
from the upper 20s to mid 30s.

On Wednesday afternoon and night, a short wave trough will move
quickly southeast through the region. Much of the synoptic lift
associated with this wave goes into saturation. The GFS soundings
show that much of this saturation occurs above 700 mb and there is
very dry air below this. This air is dry enough that the snow
could sublimate before reaching the ground. This trend shows up in
both the ECMWF and GFS. Meanwhile, the Canadian generates some
light snow across the area. For the time being, just left the 20
percent chance in the forecast.

On Friday and Friday night, the models are continuing to struggle
on the track of a short wave through the Great Lakes and Upper
Mississippi River Valley. This has resulted in huge spreads in the
temperature guidance. For example, the ECMWF ensemble has
temperature spreads of 9 to 11 standard deviations. In addition,
there has been little run to run consistency. The 12z ECMWF and
GFS guidance have continued to be much colder than their 00z
runs. As a result, very little changes were made to this time


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1135 AM CST Sun Nov 19 2017

VFR conditions are likely through the TAF period. There may be a
few patches of high cirrus streaming across the area at times, but
otherwise expect westerly winds around 10 kts to gradually shift
southwest to south this evening through Monday.




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