Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 182337
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Elevated Fire Weather Conditions through Wednesday; still quite
  dry east of the Mississippi River Thursday.

- Warmer and windy for Tuesday

- Accumulating snow continues to look likely from Thursday night into
  Friday (70-100%). Snow amounts at this time look to be 1 to 4
  inches with the lesser amounts north of I94 and toward
  central IA.

- From this weekend into early next week, still a lot of
  uncertainty related to storm track, temperatures,
  precipitation types, and amounts, but could be an impactful
  storm.

&&

.DISCUSSION...
Issued at 255 PM CDT Mon Mar 18 2024

Today - Tuesday:

Current satellite imagery this afternoon shows clouds continuing to
diminish across the forecast area leading to sunny skies and
temperatures that are slowly beginning to rise into the 30s. A
system is set to track down into the Great Lakes tonight into
Tuesday. Ahead of it winds turn southwesterly with broad low level
WAA. Model soundings still suggest fairly limited moisture (mainly
mid/upper levels) to work on over the local forecast area, but will
not rule out the possibility for some flurries north/east of I-94.
With the passage of an attendant frontal boundary Tuesday morning,
winds turn back to the northwest with winds increasing 15 to 20 kts
and wind gusts 25 to 35 kts possible into Tuesday afternoon. Though
windy, the current forecast looks to put Tuesday as the warmest day
of the week with highs in the upper 40s to low 50s.

Cooler again Wednesday and Thursday with elevated fire weather
conditions:

We remain under northwest flow aloft Wednesday with cold air
advection and continued dry conditions. Temperatures drop to
below normal with highs in the 20s and 30. Northwest winds
continue 15 to 25 mph with lowest relative humidities 15 to 25
percent. Surface high pressure builds in for Thursday with
relative humidities remaining low; 15 to 25% east of the
Mississippi River, winds will not be as strong. See FIRE
WEATHER section for details.

Moisture advection returns Thursday across parts of Minnesota
and Iowa. At this time dry air remains in place, so have lowered
pops for Thursday afternoon and delayed the onset of
precipitation.

Thursday night into the weekend and early next week:

An active weather pattern develops late this week into the
weekend. A trough will rotate across Canada and this will tap
into moisture from the Pacific Northwest. An upper level jet
will be over the U.P. with upper level divergence in the right
rear entrance region over Minnesota. Initial area of warm air
advection develops over the Plains. The thermal profiles are
cold enough for snow, thus snow over the Plains with spread east
across Minnesota into Wisconsin with a potential mix for parts
of northeast Iowa. Based on snow ratios of 12-17:1 and the 25th
percentile is around 0.10-30" and the 75th percentile is 0.30"
to 0.50". This gives still a broad range of 1 to 2" to 7".
Temperatures will initially be warm and the dry air may limit
accumulations at onset. The bulk of the accumulations are
expected Thursday night and will linger into Friday morning.
Impacts would be due to the accumulating snow, the potential for
snow-covered roads, and icy spots for the Friday morning
commute.

Temperatures remain below normal Friday with highs in the 30s.

There are still a variety of solutions for the weekend storm
system into early next week as the northwest aloft pattern
changes to a southwest flow aloft. We initially start off cold
with light snow after the region Sunday, however the models
differ on the track of the storm features and how far north the
warm air will make it and even the potential for mixed
precipitation and thunderstorms. It very well could be an
impactful storm. The EC means are in the 2-4 inch range, however
the breadth and range had several 4-8" plus amounts. The GFS
ensembles have even larger ranges with several 9 to 15 inch snow
amounts at KLSE. The storm system continue to affect the area
into early next week with various precipitation types over the
area.  Stay tuned over the next few days as we continue to
utilize more of the high resolution data and hone in on the
track.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 630 PM CDT Mon Mar 18 2024

VFR conditions are forecast for the TAF period, though low VFR
ceilings creep into southeast Minnesota and central Wisconsin
early Tuesday morning before lifting. Southwesterly winds
increase overnight, with the biggest uncertainty being whether
lower elevations will mix out. Given that these valley sites
have already decoupled and the warm air advection aloft may aid
to strengthen the low-level inversion, odds look to be better
that these sites will see LLWS. A front sweeps through early in
the morning and causes winds to shift to the northwest for the
day and increase to 15-20G20-30kts by the afternoon.

&&

.FIRE WEATHER...
Issued at 245 PM CDT Mon Mar 18 2024

Elevated Fire Weather Conditions through Wednesday and through
Thursday east of the Mississippi River

Gusty winds 25 to 35mph+ Tuesday with above normal temperatures and
30-40% relative humidities of 30 to 40 percent. Drier for
Wednesday and still breezy with cooler temperatures, but lower
relative humidity values as low as 15%. The dry conditions
continue through Thursday east of the Mississippi Valley with
relative humidities as low as 15 to 25%.

Drought areas with dry grasses will be susceptible to the
spread of fires due to the winds each day.

&&

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

&&

$$

DISCUSSION...EMS/Zapotocny
AVIATION...Skow
FIRE WEATHER...Zapotocny


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