Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 152100

Area Forecast Discussion
National Weather Service La Crosse WI
300 PM CST Thu Feb 15 2018

.SHORT TERM...(This evening through Friday)
Issued at 300 PM CST Thu Feb 15 2018

It`s been another mild day with temps climbing into the mid 30s to
low 40s as of 2 pm. The warmer air will be fleeting with steady low-
level cold advection tonight behind a cold front working southward.
Upstream stratocumulus deck from northwest Wisconsin southwestward
across Minnesota will advance southeastward through the evening.
A bit of light snow is possible this evening as the upper trough
axis swings through, although lift isn`t very impressive, so
maintained 20-30 pops for now.

High pressure will build southward from the northern plains later
tonight with sunny skies expected on Friday. Lows tonight
will be much colder with most areas bottoming out in the single
digits to low teens. Below normal highs in the upper teens to mid
20s are on tap for Friday.

.LONG TERM...(Friday night through Thursday)
Issued at 300 PM CST Thu Feb 15 2018

Warm advection will kick in as the surface high slides east Friday
night and Saturday with temps climbing back into the upper 20s to
mid 30s for Saturday. An upper level trough and associated weak cold
front will move across the area on Saturday with a chance for light
snow. Accumulations up to around an inch are possible.

The upper flow will begin to become west to southwesterly on Sunday
as a longwave trough digs across the Pacific Northwest. A lead
shortwave trough will eject from the northern plains spreading a
band of warm advection snow across northern Minnesota and northern
Wisconsin, with the best chances looking north of I-94 at this time.
To the south, the 15.12Z GFS/ECMWF indicate 925 mb temps as high
as 6-8C by Sunday afternoon before the baroclinic zone sinks
southward. Thus, would not be surprised to see some fairly mild
temps possibly up into the 40s in some areas, but widespread
mid/high clouds and timing of the system could impact highs.

Models are in good agreement with a longwave trough moving from the
Pacific Northwest towards Ontario late Sunday into late Tuesday,
with some differences in timing, amplitude, and placement of the
trough axis. In response to the trough, a series of surface lows are
forecast to track from eastern CO/western KS northeast towards
southern Lake Michigan during the aforementioned time period. This
will lead to a prolonged period of chance to likely probabilities of
precipitation across the local area. Precipitation types are looking
to be challenging for this system. While northern parts of our area
could just see snow, central and southern portions could see all
types of wintry precipitation. This system will need to be monitored
closely, as it poses a threat for accumulating snow and ice. After
the system departs to the east, strong surface high pressure will
set up over the Upper Midwest, bringing cooler, but not bitterly
cold Arctic air to the region.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1126 AM CST Thu Feb 15 2018

Variety of conditions across the area this morning will lead to
changeable flight rules as we head into tonight. Bulk of area is
experiencing VFR conditions now that fog is clearing in far south,
but still watching area of cold advection stratus come in from the
northwest with mainly MVFR ceilings. Have timed this in later this
afternoon with idea that it will persist until later tonight when
weak short wave passes through and helps clear skies. How quickly
that occurs a bit in question but after period of MVFR conditions
tonight, expect return to VFR Friday.




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