Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 211707
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1207 PM CDT Thu Mar 21 2024

.KEY MESSAGES...

- Accumulating snow is likely tonight through Friday morning.
  Widespread 2" to 4" locally higher amounts possible,
  especially in southern Wisconsin. There is a 30% chance that
  wintry mix results in light icing for areas in NE Iowa and SW
  Wisconsin. Friday morning commute will be impacted with snow
  covered, slippery roads.

- Potential continues for another impactful storm to end the
  weekend into early next week. This storm will bring rain,
  snow, and wintry mix to the area however details remain
  uncertain due to the track/strength differences.

&&

.DISCUSSION...
Issued at 330 AM CDT Thu Mar 21 2024

Today through Friday:

An embedded shortwave trough will move through during the day today.
This will help to produce some light snow showers across western
portions of the forecast area. These lighter snow showers could
continue on until the main band of snow moves into the area. Not
much is expected in the way of amounts as the lower levels of the
atmosphere are relatively dry. As the next wave moves into the
Dakotas, it will strengthen as jet dynamics from the right entrance
region interact with it. Associated with this wave are a couple
areas of moderate to strong frontogenesis. The first band has
moderate frontogenesis with it and will either dissipate or shift
southward. The second band of frontogenesis forms when the low-level
jet moves into the area and provides an enhancement of lift.
Compared to the last couple of days, this stronger band of
frontogenesis has shifted southward. There is still some
disagreement between short range models about where these
frontogenesis bands set up. Depending on exactly where this
stronger band sets up will determine which areas receive higher
amounts of snow. Even though the strongest lift may not be over
the entire forecast area, light snow will continue into the
afternoon, however the focus shifts to where the low-level jet
interacts with the frontogenesis.

Much of the area currently has 3" to 5" of snow forecasted with a
30% chance that 6"+ could occur in southern Wisconsin. These snow
amounts may fluctuate depending on which scenario plays out
regarding the different frontogenesis bands. There is also a 10% to
30% of a glaze of ice in portions of northeast Iowa and southern
Wisconsin. Given these amounts, have coordinated with
neighboring offices to issue Winter Weather Advisories across
southeastern Minnesota, western Wisconsin, and northeast Iowa
for this evening through Friday morning.

Saturday through early next week:

Quieter weather is expected for Friday night through Saturday as
warm air advection returns to the area by Saturday evening. Heading
into Saturday night, a low will begin to move off the Rockies and
start heading into the upper Midwest region. There continues to be
differences in the exact track this low will take. Depending on what
track the low takes will determine several features, such as:how far
north the warm air goes as this will effect rain/snow totals, where
the highest precipitation totals occur, and how much snow we will
get. A shift to the west would indicate more rain than snow for the
area, whereas a shift eastward would mean more snow than rain.
Regardless of the track of the storm, there will be plenty of
moisture with this storm. Looking at NAEFS PWAT anomaly data, there
are values of 1 across the area suggesting that this event has above
normal precipitation potential than a normal storm for this time of
year. Another form of guidance to look at is the EFI Shift of Tails
which shows shift of tails of 1 and 2 for snow over Minnesota and
into western Wisconsin. This indicates that this storm could produce
significant snowfall. Overall, this storm will produce precipitation
across the forecast area and accumulating snow. The highest snow
totals continue to be northwest of the forecast area. There are a
lot of moving parts with this system so expect changes to this
forecast as we get closer to this storm occurring.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1151 AM CDT Thu Mar 21 2024

VFR conditions will continue through this afternoon into the
evening across the region with light winds prevailing. May see
some flurries or light snow this afternoon west of the
Mississippi River (including RST), but impacts to aviation would
be brief. Conditions deteriorate tonight with IFR ceilings and
visibilities expected (80-90% chance) after midnight.
Visibility reduction will be tied directly to the snowfall;
however, IFR ceilings are favored to prevail (50 to 80% chance)
through the morning hours Friday, before VFR conditions return
Friday afternoon.

&&

.FIRE WEATHER...
Issued at 330 AM CDT Thu Mar 21 2024

Dry conditions, especially east of the Mississippi River on
Thursday.

Thursday remains to be the driest day in the forecast period with
low relative humidities with values between 20% and 30% through most
of the forecast area with some relative humidities getting up into
the mid to upper 30 percents, especially west of the Mississippi.
Winds will be relatively light today with gusts between 5mph and
15mph. Drought areas with dry grasses will be susceptible to the
spread of fires, thus use caution if burning.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 1 AM to 1 PM CDT Friday for
     WIZ043-044-053>055-061.
     Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Friday for WIZ017-029-032>034-041-042.
MN...Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Friday for MNZ079-086>088-094>096.
IA...Winter Weather Advisory from 1 AM to 10 AM CDT Friday for
     IAZ008>010-018-019.
     Winter Weather Advisory from 1 AM to 1 PM CDT Friday for
     IAZ011-029-030.

&&

$$

DISCUSSION...Cecava
AVIATION...JAW
FIRE WEATHER...Cecava


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