Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 110920

Area Forecast Discussion
National Weather Service La Crosse WI
320 AM CST Mon Dec 11 2017

.SHORT TERM...(Today and tonight)
Issued at 320 AM CST Mon Dec 11 2017

At 3 AM, a band of snow was moving east through western Wisconsin.
This was associated with warm air advection ahead of a rather
vigorous vorticity maximum moving through eastern North Dakota.
The 11.00z models are in good agreement that this system will move
southeast through southwest Minnesota and Iowa this morning and
through northern Illinois this afternoon. This system will bring
with it elevated CAPES (up to 100 J/kg above 700 mb) and steep
700-500 mb lapse rates. These will be mainly located south of
Interstate 94. As a result, expect scattered rain and snow showers
to move into the area during the mid to late morning and then
exit the area by mid to late afternoon. A few locations could even
see up to 1 inch of snow under a heavy snow shower. May also have
to watch out for the potential of some light freezing rain, sleet
and a rogue lightning strike.

Strong northwest winds will develop across the area this afternoon
and then continue into the evening. Wind gusts will be in the 30
to 40 mph. This may make travel difficult for high profile

.LONG TERM...(Tuesday through Sunday)
Issued at 320 AM CST Mon Dec 11 2017

On Tuesday, strong cold air advection will cause 925 mb
temperatures to fall into the -9 to -15C. This will result in high
temperatures ranging from the teens to mid 20s. The coldest
temperatures will be in central and north-central Wisconsin.

From Wednesday through Friday night, the pattern will remain
rather active with several short wave troughs moving across
northern Minnesota and northern Wisconsin. The models continue to
struggle on the timing and the southern extent of the snow with
these systems. At this time, it looks like the best chance of snow
will be found along and north of Interstate 94. Confidence was not
high enough in any time period to go more than a small chance.

In addition to this, the upper air pattern will flatten some.
This will result in more Pacific air masses than arctic
intrusions; thus, temperatures are expected to become warmer-
than-normal as we head toward the weekend.

As we head toward Saturday night and Sunday, the models continue
to struggle on the track and strength of a low pressure system
moving through the region. Both the ECMWF and GEM have a band of
snow in the forecast area. Meanwhile, the GFS has this system well
south of the area.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1109 PM CST Sun Dec 10 2017

Brief IFR conditions are expected late tonight as a band of snow
pushes across the TAF sites. Plan on the snow moving through KRST
in the 8-9Z timeframe and across KLSE in the 9 to 11Z timeframe.
At this time it appears KLSE will see the lowest conditions with
visibility falling to around 1 SM and ceilings possibly lowering
to around 800ft. The snow will exit the TAF sites by sunrise then
scattered snow showers or light sprinkles are possible during the
day. Plan on a wind shift to the northwest late this afternoon
with sustained winds increasing 14 to 20 kts with gusts to around
30 kts possible.




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