Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 170838

Area Forecast Discussion
National Weather Service La Crosse WI
238 AM CST Wed Jan 17 2018

.SHORT TERM...(Today through Thursday Night)
Issued at 238 AM CST Wed Jan 17 2018

Data analysis early this morning has a ridge of high pressure moving
slowly east across the region while low pressure tracks across
southern Canada. A few altocumulus/patches of cirrus associated with
the low were passing across areas north of I-94, otherwise it was
mostly clear and very cold across the area. Temperatures as of 2 AM
were in the single digits below zero. Wind were light/calm across
the area keeping wind chills in the single digits to 20 below zero.

Some warm air advection kicks in today on breezy southwest winds
with 925mb temperatures rising some 5 to 10C from Tuesday. Will have
to watch for some increase in mid/high cloudiness, but some warming
nonetheless anticipated with highs expected to top off in the
lower/middle 20s. However, southwest winds of 10-20 mph, gusting 25
mph will put a damper on the warming, producing wind chills in the
single digits/teens above zero.

Relatively quiet tonight through Thursday night. A mid-level wave
moves out of the central Canada provinces and across Lake Superior
Thursday morning. Any precipitation with this wave stays north of us
with just a general increase in mid/high clouds anticipated mainly
north of I-94. Plan on highs lows tonight and Thursday night in the
teens to near 20, with highs Thursday in the 30s.

.LONG TERM...(Friday through Tuesday)
Issued at 238 AM CST Wed Jan 17 2018

Milder weather is on tap for Friday and Saturday as we slip into the
warm sector of low pressure passing through Canada. We will probably
be in and out of clouds Friday with a general increase in clouds
expected Saturday as a cold front sinks south toward the area.
Otherwise, plan on highs in the middle 30s to the lower 40s.

Attention then shifts to a storm system impacting the area Saturday
night through Monday Night. 17.00z GFS/ECMWF/GEM coming into better
consensus this go around with track of the low favorable for more
snow output for our area. There may be some warmer air initially
ahead of the low which could bring a wintry mix in as early as
Saturday night and through the day Sunday. But as dynamic cooling
takes place in the deformation zone later Sunday night into Monday,
a transition to snow is expected. If the track remains the same or
slightly more south, our area would be in the center hairs for a
significant snowfall. However, this system is still 3-4 days out and
a lot of change/shift in track can still happen in the models. Will
continue to monitor at this point.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1050 PM CST Tue Jan 16 2018

Cigs/WX/vsby: A weak upper level disturbance will bring a sct-bkn
deck of 15-25 kft clouds overnight into Wed morning, but overall,
looking at VFR conditions through Wed into Thu. No wx or vsby
impacts anticipated.

Winds: high pressure slides south of the region tonight, with
tightening pressure gradient for Wed morning. Winds will increase
from the southwest, around 20kts sustained at KRST. Bufkit soundings
not supporting much in the way of gusts, and will leave out of the
forecast. RAP/NAM soundings suggesting LLWS by 00z Thu - moreso KLSE
than KRST - with winds by 2 kft ranging from 45 to near 50 kts for
the evening hours. Will add to the forecast for KLSE, monitor need
for KRST.




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