Area Forecast Discussion
Issued by NWS La Crosse, WI

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694
FXUS63 KARX 171735
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1135 AM CST Fri Nov 17 2017

.SHORT TERM...(Today and tonight)
Issued at 340 AM CST Fri Nov 17 2017

At 3 AM, gusty southeast winds were keeping temperatures steady
early this morning. They were ranging from 29F at Medford
Wisconsin to 36F at La Crosse Wisconsin.

The 17.00z models are in agreement that the 925 and 850 mb
moisture transport will gradually increase across the area this
morning. As this occurs, the low level moisture will steadily
increase. This will result in the development of drizzle south of
Interstate 94 and drizzle and freezing drizzle north of this
interstate. This precipitation should start to develop between 7
AM and 10 AM. There may be some light icing on untreated roads and
walk ways north of Interstate 94. Due to the patchy nature, we
will issue a Special Weather Statement to cover this and then
monitor it closely to see whether a Winter Weather Advisory for
freezing drizzle may be needed later.

For this afternoon and early evening, deep moisture and omega
will be found across the area. This will result in rain. Rainfall
amounts will range from a tenth to 2 tenths of an inch.

.LONG TERM...(Saturday through Thanksgiving)
Issued at 340 AM CST Fri Nov 17 2017

On Saturday, the cold front will move quickly southeast away from
the region. As a result, went with the highest rain chances
during the early morning and then quickly took them out by mid to
late morning. Strong cold air advection in the wake of this front
will cause temperatures to slowly fall during the day. Afternoon
temperatures will range from the upper 20s to upper 30s with wind
chills ranging from the teens to upper 20s. Currently have skies
clearing out during the afternoon. However, with the soundings
showing 925 mb moisture trapped underneath the subsidence
inversion and steep 950-900 mb lapse rates, concerned that this
might be too optimistic. It may not clear out until the Saturday
night.

On Monday, 925 mb temperatures will warm into the 6 to 9C range.
With the soundings showing plenty sunshine, temperatures will warm
into the 40s. There may be even some lower 50s south of
Interstate 94.

On Monday night, a Canadian cold front will move quickly southeast
across the region. With the airmass parched ahead of this front,
only expecting some clouds with its passage. In the wake of this
front, strong cold air advection will cause the 925 mb
temperatures to fall into the -6 to -9C range on Tuesday
afternoon. This will result in surface temperatures falling
during much of the morning and then they will either remain steady
or slowly rise during the afternoon. Afternoon temperatures will
range from the upper 20s to mid-30s and wind chills will range
from the teens to mid-20s.

On Thanksgiving, warm air advection will develop across the region
ahead of a short wave trough dropping southeast out of the
Canadian prairie provinces. The ECMWF is the fastest with this
warm advection with 925 mb temperatures ranging from 3 to 9C by
late afternoon. Meanwhile, the GFS is only 0 to 3C at this time.
With the air mass rather dry below 750 mb, only anticipating some
mid and high clouds. The ECMWF has high temperatures warming into
the mid and upper 40s with maybe some low 50s near and west of
Interstate 35 corridor. Meanwhile, the GFS has its high
temperatures ranging from the mid 30s to lower 40s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1135 AM CST Fri Nov 17 2017

Generally LIFR to MVFR conditions expected through much of the
period. Low-level moisture is increasing ahead of a trough of low
pressure and cold front this afternoon, with widespread LIFR to
MVFR ceilings, and some MVFR/IFR visibilities, in addition to
periodic -RA/-DZ. There is lower confidence in timing/coverage of
precip tonight, but some snow could possibly mix in with any
rain. Southerly winds will gradually decrease through the
afternoon with the approach of the surface trough. Will have to
monitor for potential LIFR visibilities, especially at KRST, with
slackening winds and a moist boundary layer late this afternoon
into tonight. Gradually improving conditions are expected late
tonight into Saturday as northerly winds usher in drier air. VFR
conditions should return to KRST sometime Saturday morning, and
near the end of this TAF period at KLSE.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...JM



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