Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 101132
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
532 AM CST Mon Dec 10 2018

.UPDATE...
Issued at 422 AM CST Mon Dec 10 2018

A Dense Fog Advisory has been issued for portions of southeast
Minnesota and northeast Iowa where the visibility has fallen to
1/4 mile or less. The fog may deposit a thin layer of ice leading
to slippery travel. The worst conditions are expected along ridge
top locations. The Dense Fog Advisory is in effect through 10 AM.

&&

.SHORT TERM...(Today and Tonight)
Issued at 215 AM CST Mon Dec 10 2018

Main forecast concerns for today are on fog early this morning, then
focus turns to cloud cover/stratus through much of the day.

Areas of fog and stratus have developed across the area early
this morning, and some of the fog has been locally dense. Slick
travel is possible in spots early this morning due to the fog
possibly creating a layer of frost/ice on roadways. Drive with
extra caution this morning.

The stratus will linger across the area through much of the day
leading to cloudy skies for many areas. The stratus looks to edge
east of the Mississippi River by early evening as winds just above
the surface start to increase ahead of an approaching weak trough.
Forecast models suggest the stratus could linger through much of the
night across central Wisconsin so will have to monitor cloud trends
closely. The weak trough then pushes into the eastern Great Lakes by
early Tuesday morning. The pressure gradient then becomes rather
weak across the region once again so will have to keep an eye on the
potential for more fog and possibly low stratus development.

.LONG TERM...(Tuesday through Sunday)
Issued at 215 AM CST Mon Dec 10 2018

Main forecast concerns in the long term are on freezing drizzle
and light snow potential on Wednesday, which may lead to slippery
travel.

After mainly quiet weather on Tuesday, outside of some early morning
fog potential, we are keeping an eye on a fast moving moving system
expected to impact the area during the day on Wednesday with the
potential for light snow and freezing drizzle.  Precipitation is
expected to start across northeast Iowa and southern Wisconsin early
Wednesday morning, likely before sunrise, and could fall in the form
of freezing drizzle. NAM forecast soundings show a lack of ice
aloft early in the day then as saturation increases as the low
deepens, the precipitation looks to switch over to light snow and
overspreads much of the area. Then during the afternoon as the low
exits, ice aloft could be lost again, and the precipitation may
switch back over to freezing drizzle over western into central
Wisconsin. Lift looks to be lost west of the Mississippi River by
Wednesday afternoon so precipitation will taper off, but weak lift
is expected to continue over western and central Wisconsin into
early Wednesday evening. So, overall expected impact from the
freezing drizzle is the potential for a glaze of ice during the
Wednesday morning commute on untreated road surfaces. Temperatures
then look to warm to or just above freezing by Wednesday
afternoon with the freezing drizzle switching over to drizzle, or
light snow if ice is introduced aloft.

A weak trough moves through the region Thursday into Thursday night
and may bring some light snow or rain to the region, but forecast
models are trending drier and we may not see any precipitation out
of this feature. Low pressure then deepens across the southern
Plains and lower Mississippi River Valley Thursday into Friday and
heads toward the east coast. This system will stay south east of the
area with dry weather and seasonably warmer temperatures expected
Friday into Saturday with highs climbing into the lower to mid 30s.
Precipitation chances return Saturday night into Sunday, but
forecast confidence is low during this timeframe.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 533 AM CST Mon Dec 10 2018

Areas of dense fog in southeast Minnesota and northeast Iowa will
gradually dissipate this morning as stratus advects into the area.
Currently thinking this should occur at KRST through 10.14z.
This fog and ceilings will likely remain MVFR at both TAF sites
into afternoon before dissipating in the wake of a trough.

Soundings once again suggest some MVFR fog after 11.08z tonight.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Dense Fog Advisory until 10 AM CST this morning for MNZ086-087-
     094-095.

IA...Dense Fog Advisory until 10 AM CST this morning for IAZ008>010-
     018-019.

&&

$$

UPDATE...Wetenkamp
SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...Boyne


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