Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 171635
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1135 AM CDT Fri Mar 17 2017

.SHORT TERM...(Today and tonight)
Issued at 251 AM CDT Fri Mar 17 2017

Main impactful weather concerns are on a wintry mix early this
morning potentially creating some light icing and slippery travel
across central into north central Wisconsin.

The light wintry mixed continued early this morning over central and
north-central Wisconsin, while areas further to the west along the
Mississippi River were mainly seeing rain. With the recent cold
temperatures across the area we have developed a shallow layer of
frost in the ground. So, some road and sidewalk surface, especially
those in shaded/sheltered areas, will experience some light icing
this morning. Areas along and northeast of Interstate 94 will be
cold enough for a little more icing. Untreated roads and sidewalks
will be slick this morning so be sure to allow for extra travel
time.

A shortwave trough will continue pushing across the area this
morning. Isentropic upglide on the 280-295 K surfaces pushes east of
the forecast area quickly after 12Z this morning so we should see
precipitation end in the 12-15Z timeframe. A secondary, stronger,
upper trough will sweep through late this afternoon into tonight.
This feature drives a cold front through the area with gusty
northwest winds developing. Scattered rain or snow showers are
expected too as colder air moves in with the trough. The big
question will be how for southwest does saturation occur. At this
point it appears central into north-central Wisconsin will be the
main area that sees this activity, but rain/snow shower chances may
need to be expanded southwest. Look for northwest winds to
increase this evening as cold air advection kicks in with speeds
of 15 to 20 mph and gusts around 30 mph at times. Low temperatures
tonight will fall into the upper 20s to around 30.

.LONG TERM...(Saturday through Thursday)
Issued at 251 AM CDT Fri Mar 17 2017

Cool high pressure then settles into the region on Saturday with
decreasing clouds expected. Highs on Saturday will range from the
upper 30s to lower 40s. Sunday looks to be the warmest day of the
weekend as upper ridging slides through the region. It will be
rather windy on Sunday thanks to a tight pressure gradient over the
area. Have leaned toward a model consensus blend for winds on
Sunday but if trends continue, the wind speeds and gusts may need
to be increased.

A cold front then slides through the region late Sunday
into Sunday night. The GFS indicates 0-4 KM MUCAPE of 250 to 850
J/kg attempts to edge into northeast Iowa and far southwest
Wisconsin and this would support a few thunderstorms. The ECMWF is
a little weaker and doesn`t generate any precipitation so
confidence is low that we will see showers or any storms during
this timeframe. Will keep thunderstorms out of the forecast but if
it appears the GFS has better handle on the situation
thunderstorms will have to be added to the forecast.

High pressure then looks to dominate the forecast from Monday
afternoon through Wednesday morning. Plan on more seasonable
temperatures for Tuesday through Wednesday with highs mainly in the
upper 30s to lower 40s and lows in the teens to 20s. Precipitation
chances return on Wednesday afternoon and continue all the way
into the weekend. A warm front pushes into the upper Mississippi
River Valley Wednesday into Thursday and this appears to be the
timeframe where we could have a better shot at seeing a wintry
mix. Forecast confidence is pretty low on precipitation type from
Thursday into the weekend since the ECMWF, GFS, and Canadian are
all showing differing low tracks. At this point it appears low
pressure will develop in the southwest CONUS but then the big
question is how does this low evolve. Will have to keep a close
eye on the next several model runs.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1135 AM CDT Fri Mar 17 2017

Cigs: band of low cigs moving in ahead of the main mass of mostly
mvfr clouds associated with an area of low pressure headed southeast
into the eastern Great Lakes. Expect approx 2 hour period of
IFR/MVFR with this band, but the main cloud shield quickly moves in
as this slides through. Probably done for sun until Sat. Expect the
stratus to hold into Sat morning, scattering out as the region comes
under the influence of high pressure.

WX/vsby: some fog accompanies this thin band of lower stratus for
early afternoon...roughly 2-5sm for a couple hours. Should improve
back to P6sm as this band exits east.

Wind: on the increase from the west northwest through the afternoon,
with bufkit soundings holding onto gusty conditions through the
night. Pressure gradient does/t start to slacken until later Sat
morning as that high approaches from the west.

&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...Rieck



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