Winter Weather in Wisconsin, February 11 to 12, 2021

Area Forecast Discussion
National Weather Service La Crosse WI
1138 AM CST Thu Feb 11 2021

.SHORT TERM...(Today through Friday Night)
Issued at 351 AM CST Thu Feb 11 2021

Forecast concerns in the short term will be light snow moving
across the forecast area this afternoon and this evening and
continued bitter cold temperatures.

The 00Z sounding at MPX had a precipitable water of 0.07 inches with
fairly dry conditions below 500mb and 60 to 70 percent RH from
400 to 500mb. The GOES nighttime microphysics satellite imagery
showed mostly clear skies locally with a few mid and high level
clouds. 3am temperatures ranged from 4 below zero to 25 below zero
with wind chills 10 below to 30 below zero. Farther to the west
across parts of Iowa, Nebraska, and South Dakota, the mid clouds
are more substantial with light snow across parts of these states.

A strong upper level 145kt jet will dive southeast this afternoon in
combination with the exiting jet across Ohio.  Upper level
divergence will increase in combination with increasing warm air
advection, isentropic lift and frontogenesis. A very cold 1044mb
surface high pressure system is building into the Dakotas during
the day. With the cold dry airmass in place it will take a little
time for the saturation to occur. There seems to be good
agreement between the latest RAP/HRRR that light snow spreading
into the west noon to 2pm...and reach the Mississippi River 3-5pm
and into the rest of Wisconsin through the evening. The HREF
probabilities are similar through the mid to late afternoon,
spreading into WI during the evening. We'll need to watch this as
the isentropic lift appears to get going this morning. We mostly
have a trace to .05 of an inch of liquid or a trace to 1 inch of
snow as the positive vorticity advection/lift rotates through. The
temperatures are cold enough that we should see more plate versus
seeing the larger dendrites.  Additional light snow develops
Friday night ahead of a surge of cold air with trace to 1 inch
snow amounts. Higher amount should be across the southern part of
the forecast area.

Bitter cold wind chills continue this morning of 20 to 30 below
zero. A wind chill advisory remains in effect until 10am.

As the clouds increase this morning, this should help mitigate
the colder wind chills. Tonight, expect the clouds to decrease
with wind chills once again drop to 20 below zero or colder.
These conditions should develop during the evening for our western
county warning area counties, spreading east overnight into
Friday. Highs today should range from a few degrees below zero to
5 to 10 above. With the colder temperatures Friday, are looking
for highs from 5 below to 5 above zero. In coordination with
neighboring offices held off on new wind chill headlines until
the current one ends later this morning.

.LONG TERM...(Saturday through Wednesday)
Issued at 345 AM CST Thu Feb 11 2021

850mb temperatures drop to 16 to 24 below zero, so continue
bitter cold through the weekend and early next week. NAEFS
standardized anomalies are 3 to 4 standard deviations with 30 year
return intervals. The Weather in Context WPC prototype shows
several low maximum temperatures forecast for the central part of
the country Friday, Saturday and Sunday as well as record lows
Sunday and Monday morning. 30 to 35 below wind chills become more
prevalent Saturday night into Sunday/Sunday night and early
Monday. Expect wind chill headlines to continue through early next
week before week start to see moderating temperatures Tuesday
through Thu. Light snow lingers Saturday with snow chances
returning Monday night into tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1135 AM CST Thu Feb 11 2021

Light snow is spreading into the area faster than guidance had
been suggesting, just now getting underway at RST. Have therefore
introduced it at the beginning of the TAF period. MVFR to IFR
visibilities are expected with the snow this afternoon and
evening, along with MVFR ceilings. The snow looks to taper off
from west to east late this evening, between 03-05Z at the TAF
sites. Expecting up to 1" of accumulation at both RST/LSE. MVFR
ceilings will persist into early Friday morning, but clouds will
diminish quickly by daybreak. VFR conditions are expected through
the remainder of the period. Winds will remain out of the north to
northwest, generally 10 knots or less.

&&

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

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Kurz

Hazardous Weather Outlook
National Weather Service La Crosse WI
1124 CST Thu Feb 11 2021

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-121100-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-
Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau-
Adams-Vernon-Crawford-Richland-Grant-
1124 AM CST Thu Feb 11 2021

This Hazardous Weather Outlook is for portions of southeast
Minnesota...northeast Iowa and southwest into central Wisconsin.

.DAY ONE...Today and Tonight

Light snow will spread across the area this afternoon and tonight
with a trace to 1 inch of snow accumulation. This could produce some
slippery stretches on roadways.

Bitter cold wind chills again tonight with lowest wind chills from
20 to 35 below zero.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Very cold conditions will persist into early next week. Nighttime
and morning wind chills will range from around 15 to 35 below
zero through Monday. Additional wind chill advisories or warnings
are expected.

Light snow is again possible Friday night into Saturday.

.SPOTTER INFORMATION STATEMENT...

Snowfall reports are appreciated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

NOFWD