Area Forecast Discussion
Issued by NWS La Crosse, WI

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483
FXUS63 KARX 061717
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1116 AM CST Tue Dec 6 2016

.SHORT TERM...(Today and tonight)
Issued at 330 AM CST Tue Dec 6 2016

Forecast concerns include morning precip today followed by coldest
air of the season so far.

A focused band of precip near the frontal zone is making slow
eastward progress across the area early this morning. Observations
have shown much of the precipitation to be falling as snow, with
some light rain/drizzle/freezing drizzle along the leading edge
of the precip. The precip should continue to lift northeastward,
likely weakening through the morning, with southwest Wisconsin
likely missing out on much of the precip. Visibilities have been
reduced at times to 1-3 miles in the snow southeast Minnesota,
northeast Iowa, and west-central Wisconsin leading to some
slushy/snowy roads that could make for slick travel for the
morning commute. There may be some fog as well out ahead of the
front/precip this morning.

Winds will become gusty from the west following the cold frontal
passage with daytime highs likely to be this morning. There is some
clearing this morning into eastern SD, and NAM soundings indicate
some drying working into the area through the day. However, it
remains to be seen how much clearing will be realized with low-
level moisture remaining trapped beneath a steep inversion. Temps
falling into the teens to near 20 by tonight and blustery west
winds will knock wind chill values down towards the single digits
by later today or tonight, quite the change from early this
morning.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CST Tue Dec 6 2016

The cold weather following our prolonged period of mild weather
will be the weather headline through late week. Model guidance has
been consistent in keeping the coldest airmass over the area
Wednesday-Friday with 850 mb temps bottoming out around -14 to
-15C by Friday. With a pretty tight pressure gradient in place
between the departing low across eastern Canada and strong high
pressure nosing into the plains, winds will remain breezy into
Thursday. The wind combined with temps in the teens and 20s will
keep wind chills in the single digits in many places even during
the daytime hours with below zero wind chills possible, especially
at night as temps fall into the teens. Winds will at least lighten
by Friday under the surface high, although air temps may be
coldest on Friday.

Cyclonic flow aloft and the passage of a surface trough may help to
produce some light snow/flurries under a low stratus deck
Wednesday Night/Thursday, but with little accumulation.

Heading into the weekend, the main forecast concern remains the
potential for snow with an upper trough forecast to eject out of the
Rockies within relatively zonal flow. Global 06.00Z model runs
continue to support this scenario, but differ somewhat on strength,
location, and timing. The ECMWF remains weaker and is also farther
north with the bulk of the precip compared with the GFS/GEM.
Ensemble guidance also indicates substantial variability among
solutions. Thus, it is too early to have confidence in any specifics
yet, but there remains the potential for accumulating snow this
weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1116 AM CST Tue Dec 6 2016

Main aviation concerns are extent of low clouds on back side of
large upper low slowing working across far northern Minnesota late
this morning. Initial cold front has moved through and moved bulk of
precipitation off to the east. This has allowed some VFR conditions
to return for a time, but in cold air advection zone, starting to
see mainly MVFR ceilings wrap back into the area.

Looks like ceilings will likely sit about Interstate 90 and points
north into Wednesday, with some gradual improvement in the MVFR to
VFR range. Held clouds in longer than guidance given pace that upper
low will progress east, and also bumped up winds somewhat.

Speaking of winds, with fresh snow cover and peak winds exceeding 30
kts at KRST, introduced some minor restrictions to visibility, but
this shouldn`t last too long.

&&

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

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Shea



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