Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 122329
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
529 PM CST Fri Jan 12 2018

.SHORT TERM...(This evening through Saturday)
Issued at 305 PM CST Fri Jan 12 2018

Surface high pressure across the Dakotas and western MN this
afternoon will gradually build across the Upper Mississippi River
Valley tonight into Saturday morning. This will result in clear
skies, allowing air temperatures to fall into the single digits
below zero to teens below zero. At the same time, there will be
enough of a pressure gradient to keep northerly winds elevated in
the 5 to 10 mph range, resulting in wind chills dropping to between
15 and 30 below zero. Will issue a Wind Chill Advisory for all but
Grant County. Northern and western areas will begin at 9 PM and all
other areas at midnight. Expect conditions to gradually improve by
mid Saturday morning.

Under the influence of surface high pressure, expect a mostly
sunny and cold Saturday with highs mainly in the single digits.

.LONG TERM...(Saturday night through Friday)
Issued at 305 PM CST Fri Jan 12 2018

Saturday night will be another cold night under the surface ridge
axis with some mid to high clouds beginning to increase later on as
mid-level warm advection develops. Despite lows in the single digits
to teens below zero, light winds are expected, mitigating some of
the wind chill impacts.

The next snow system is still on target for later Sunday and Sunday
night. Mid and upper level forcing will increase ahead of an upper
trough with some contribution from an upper jet streak passing south
of the area. Expect snow to develop during the afternoon from the
northwest and continue into Sunday night as surface trough/cold
front swings through with another blast of Arctic air in its wake.
Despite having very limited moisture to work with (precip water
values around 0.20 inches), there continues to be good consensus
with about 0.1 to 0.2 inches of QPF. NAM/GFS soundings show a 100 to
200 mb deep dendritic growth zone based near the surface. Overall, 2
to 3 inches of snow looks reasonable, locally up to 4, given the
fluffy, high snow ratio nature of the snow.

Some light snow/flurries will persist Monday within a stratus deck
under deep cyclonic flow aloft as the upper trough rotates into the
western Great Lakes region. Winds will be gusty behind the frontal
passage later Sunday night and Monday with cold advection and a
strong gradient between the departing surface cyclone and a 1050 mb
high dropping across the northern plains. This could lead to some
blowing/drifting of snow that falls across open areas/ridge tops.
The combination of the winds and a very cold airmass will lead to
more wind chill concerns Sunday night through Tuesday. With the
coldest 850 mb temps west of the Mississippi, -20 to -22C, highs may
remain near or below zero over parts of SE MN/NE IA, and in the
single digits to low teens farther east Mon/Tue.

Gradual moderation of the airmass will occur by Wednesday as the
surface ridge axis begins to slide east. By late next week, the
upper flow is expected to transition to southwesterly with much
milder air working back into the area. There`s pretty good agreement
that 850 mb temps will climb back above 0C by late next week, with
highs back near or above freezing by Friday. Precip chances through
mid to late week look to be on the low side at this point.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 529 PM CST Fri Jan 12 2018

VFR conditions are expected through the TAF period as high
pressure dominates the local weather pattern. Skies will remain
clear to mostly clear with the potential for a few cirrus at
times. Cannot rule out a few mid level clouds impacting KRST this
evening into the overnight with cloud bases around 11,000 ft.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Chill Advisory from 9 PM this evening to 9 AM CST Saturday
     for WIZ017-029-032>034.

     Wind Chill Advisory from midnight tonight to 9 AM CST Saturday
     for WIZ041>044-053>055.

MN...Wind Chill Advisory from 9 PM this evening to 9 AM CST Saturday
     for MNZ079-086>088-094-095.

     Wind Chill Advisory from midnight tonight to 9 AM CST Saturday
     for MNZ096.

IA...Wind Chill Advisory from 9 PM this evening to 9 AM CST Saturday
     for IAZ008-009-018-019.

     Wind Chill Advisory from midnight tonight to 9 AM CST Saturday
     for IAZ010-011-029-030.

&&

$$

SHORT TERM...Rogers
LONG TERM...JM
AVIATION...Wetenkamp



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