Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 241148

Area Forecast Discussion
National Weather Service La Crosse WI
548 AM CST Sat Feb 24 2018

.SHORT TERM...(Today and tonight)
Issued at 334 AM CST Sat Feb 24 2018

A quick moving negatively tilted short-wave will lift across the
region today and tonight, providing ample lift for precipitation.
Still some lingering questions on exact surface low track and this
will have implications on thermal profiles and subsequent snow
amounts. GEFS/SREF mean shows the low rapidly moving northward
from northeast MO into central WI this evening, but individual
24.00Z operational runs show it anywhere from Milwaukee to Wausau
by 06Z tonight. For this forecast, will continue to follow a
blended model consensus.

Warm boundary layer temperatures and lack of cloud ice aloft will
keep the precipitation type as rain through the afternoon and
early evening roughly along and east of a line from Oelwein to La
Crosse to Black River Falls. To the west, thermal profiles and
sufficient cloud ice support all snow. The exception being
portions of northeast IA into far southeast MN where an initial
lack of cloud ice and colder surface temperatures could result in
a light glaze of ice this afternoon. While icing does not appear
to be a significant threat elsewhere, there could be periods of a
wintry mix in the narrow transition zone between snow and rain.
This evening into the overnight, the snow/rain line will move
north and east.

Precipitation first moves into southeast MN/northeast IA by mid-
afternoon and lifts quickly northeastward into this evening. With
the exception of areas northeast of I-94, precipitation should end
by midnight tonight. For areas that see mainly snow across the
northwest forecast area, expect 3-6 inches of snow. Amounts will
quickly taper off to the south and east. A few individual model
runs show portions of northern Dodge, Olmsted, Wabasha, and Taylor
Counties in the 6-7 inch range, but given persistent model
differences in storm track and total liquid QPF along with the
rapid progression of the overall system, will cap amounts at 6
inches and maintain the Winter Weather Advisory for all areas. As
the storm approaches later today, the day shift can re-evaluate
12Z model guidance and latest observations to see if an upgrade
to a warning is warranted.

Whether it`s 3, 5, or 7 inches, the overall impacts will be the
same. Within the advisory area, roads will quickly become snow
covered and slick. Snowfall rates as high as an inch or more per
hour are possible this evening, resulting in significant
reductions in visibility. While winds will generally be light
during the heaviest snowfall, stronger westerly winds will move
into the area after midnight and this could cause areas of blowing
and drifting snow, especially across southeast Minnesota and
northeast Iowa. If planning on traveling later this afternoon and
evening, be prepared for rapidly worsening conditions.

.LONG TERM...(Sunday through Friday)
Issued at 334 AM CST Sat Feb 24 2018

Sunday through Tuesday look dry with a noticeable warming trend as
high pressure dominates the regional weather pattern. Highs in
the upper 20s into the 30s on Sunday will warm into the upper 30s
and 40s by Tuesday. Some parts of southern WI, especially those
with little to no snow cover could top 50 degrees.

Next best chance for precipitation will be late Wednesday through
Thursday as another strong short-wave moves somewhere across the
Upper Midwest. Overall poor agreement between models right now,
so consensus POPs seem reasonable with the highest values across
the southern forecast area. Thermal profiles are highly dependent
on storm track, but warmer conditions could result in more of a
wintry mix or all rain for many areas. Dry conditions return to
end the work week with temperatures above normal.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 548 AM CST Sat Feb 24 2018

Dense fog will continue to impact KRST through roughly 24.15Z, but
then lift/dissipate through late morning. At KLSE, IFR visibility
reductions in mist/fog also possible through mid-morning.
Confidence not as high that it will drop below 2SM, but something
to watch through sunrise.

After the fog, primary impact to aviation operations will be snow
at KRST and a rain to rain/snow mix at KLSE later this afternoon
and into this evening.

Expect snow to reach KRST by 24.21Z with rapid reductions in
ceiling and visibility. The heaviest snow is expected this evening
with visibility dropping to 1/2SM. The snow should then end
quickly around midnight, but westerly winds will then strengthen
with frequent gusts into the mid-upper 20 kt range. This is
expected to create some additional reductions in visibility
overnight due to blowing/drifting snow.

Rain will reach KLSE by 24.22Z and should be accompanied by MVFR
ceilings and visibility. Colder temperatures into the evening
should allow precipitation to change over to a rain/snow mix and
perhaps eventually all snow. As precipitation changes phases,
expect a further lowering of ceilings and visibility into the IFR
range. As with KRST, precipitation will abruptly end around
midnight with winds then switching to the west, gusting at times
into the mid 20 kt range overnight.


Issued at 334 AM CST Sat Feb 24 2018

Right now, total liquid precipitation through tonight is a half
inch or less. For those areas that see mostly rain east of a line
from Oelwein to La Crosse to Black River Falls, some rises on area
rivers and streams are possible, especially if heavier showers
develop. Widespread flooding is not expected at this time,
although frozen ground will result in rapid run-off and some
ponding of water.


WI...Winter Weather Advisory from 3 PM this afternoon to 6 AM CST
     Sunday for WIZ032>034.

     Dense Fog Advisory until 9 AM CST this morning for WIZ017-029-

     Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Sunday for WIZ017-029.

MN...Winter Weather Advisory from 3 PM this afternoon to 6 AM CST
     Sunday for MNZ079-086>088-094-095.

     Dense Fog Advisory until 9 AM CST this morning for MNZ079-086-

IA...Winter Weather Advisory from 3 PM this afternoon to 6 AM CST
     Sunday for IAZ008-009-018-019.



LONG TERM...Rogers
HYDROLOGY...Rogers is the U.S. government's official web portal to all federal, state and local government web resources and services.