669
FXUS63 KARX 200000
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
600 PM CST Sun Jan 19 2025

.KEY MESSAGES...

- Bitter cold continues into Monday with nighttime temperatures
  turning a bit colder tonight. Wind chills will again drop into
  the -25 to -35 range tonight through Monday morning.

- Turning dangerously cold Monday night into Tuesday morning
  with wind chills as cold as -30 to -40 areawide. Extreme Cold
  Warning issued for Taylor and Clark counties, may need to be
  expanded into southeast Minnesota as well.

- Small chances (20-30%) for light snow mid to late week.

&&

.DISCUSSION...
Issued at 156 PM CST Sun Jan 19 2025

Cold and Blustery This Afternoon:

Bitter cold will remain the focus through Tuesday with a lobe of
850mb -25 to -30C temperatures this morning digging into the Upper
Mississippi Valley. Regional 12Z RAOB 850mb temps ranged from -21C
at DVN to -30C at INL. Last night`s low temperatures ranged from
about -5 to -10F in the south, with -10 to -17F further north
(coldest in Taylor County). Brisk northwest winds overnight
contributed to wind chills as cold as -25 to -35. Despite winds not
really backing down much today, a slight uptick in temperatures has
improved wind chills enough across northeast Iowa and far southwest
Wisconsin to allow the Cold Weather Advisory there to temporarily
drop off until later tonight. Temperatures aren`t climbing
dramatically this afternoon but have managed to scrape past the zero
mark in a few lucky southern locations.

With this cold airmass, satellite has shown some cloud streets over
the region since last night, with scattered reports of occasional
snowflakes reaching the surface earlier. RAP/HRRR soundings show
this shallow saturated layer between 950-850mb diminishing somewhat
this afternoon before redeveloping again tonight into Monday. Also
some reports of haze this morning.

Turning A Bit Colder Tonight:

Several factors to take into account for how cold it will get
tonight. Slightly colder 850mb temperatures will continue to settle
overhead into tonight. In fact, we`re keeping an eye on central
Canada where guidance has consistently showed an incoming shortwave
dropping south from western Manitoba this evening with a developing
core of even colder 850mb air. Can already start to see this
developing shortwave on water vapor imagery. This will prime our
area for a colder night ahead compared to last night. Cloud cover
should be similar to last night with a high likelihood (>80%) of
cloud streets redeveloping. This shouldn`t have too much of an
impact on cooling given the very cold airmass in place. Finally,
with the pressure gradient gradually relaxing overhead heading into
tonight, northwest winds won`t be as strong as last night. All in
all, these factors should favor temperatures dropping a few more
degrees tonight, ranging from around -5 to -10 south of I-90 to
around -10 to -20 further north, coldest in Taylor County. Wind
chills will again range from -25 to -35 into Monday morning,
potentially locally colder over portions of Taylor County.

Turning Dangerously Cold Monday Night into Tuesday:

Some afternoon wind chill improvement again expected across
northeast Iowa and far southwest Wisconsin on Monday, but the
coldest period will be Monday night into Tuesday as the 850mb core
of Arctic air drifts overhead. HREF probability for 850mb
temperatures colder than -30 is 100%, as it is with GEFS, ENS, and
GEPS ensemble data. Right now temperatures look to bottom out around
-10 to -20 area-wide, aided by light winds and clearing skies. Wind
chills are likely to bottom out between -30 to -40, coldest across
Taylor and Clark counties.

Cold Weather Headline Updates and Reasoning:

The only headline changes made were to upgrade Taylor and Clark
counties to an Extreme Cold Warning late Monday night into Tuesday
morning. Confidence is highest there for meeting warning criteria.
Will continue to monitor trends for southeast Minnesota, as that
would be the other area of concern for possibly needing an upgrade
to warning Monday night, but confidence isn`t quite up to 80% yet
for that area. Otherwise the current advisories remain untouched.
Will eventually need at least an advisory Monday night across
northeast Iowa and far southwest Wisconsin, but after collaborating
with neighboring offices will let midnight shift dig into those
details.

Small Chances for Light Snow Mid to Late Week:

Not much of concern weather-wise beyond this cold snap. Temperatures
slowly moderate through the second half of the week, and an incoming
shortwave is likely to bring some light snow chances heading into
Wednesday. Have continued with manual small precip chances (20-30%)
as NBM is running too low for the likelihood of seeing at least some
light snow. Slight chances could linger into Thursday but confidence
is rather low at this time. Another wave looks to cross the region
heading into the weekend with potential for light precip.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 553 PM CST Sun Jan 19 2025

Variable VFR/MVFR conditions through the period. A broad ridge
of high pressure covers the region. Reinforcing cold air moves
in for Monday with continued northwest winds. Most recent
satellite imagery has mostly clear skies, however a few metars
around Preston and Decorah are reporting MVFR ceilings. The HREF
shows patchy MVFR conditions tonight becoming more widespread
later tonight into Monday, lifting to VFR. Northwest winds 6 to
12kts tonight increase 10 to 15kts with some gusts in open areas
Monday. Cannot rule out some haze or ice crystals falling out
of the clouds with the very cold -25 to -30 deg. air Monday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Cold Weather Advisory from 3 AM to 11 AM CST Monday for WIZ054-
     061.
     Cold Weather Advisory until noon CST Tuesday for WIZ032>034-
     041>044-053-055.
     Cold Weather Advisory until midnight CST Monday night for
     WIZ017-029.
     Extreme Cold Warning from midnight Monday night to noon CST
     Tuesday for WIZ017-029.
MN...Cold Weather Advisory until noon CST Tuesday for MNZ079-
     086>088-094>096.
IA...Cold Weather Advisory from 3 AM to 11 AM CST Monday for
     IAZ008>011-018-019-029-030.

&&

$$

DISCUSSION...Kurz
AVIATION...Zapotocny

NWS ARX Office Area Forecast Discussion