Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 121933
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
230 PM CDT Fri Apr 12 2024

.KEY MESSAGES...

- Weekend: Mild weekend but with breezy conditions, especially
  Saturday, and drier air, could see some elevated fire weather
  concerns.

- An active weather pattern early next week with showers and storm
  threats increasing Monday night. Rain certain Tuesday (90-100%)
  with a possibility of severe storms. Will need to watch trends.

&&

.DISCUSSION...
Issued at 230 PM CDT Fri Apr 12 2024

Weekend Weather

Relatively quiet and benign weekend ahead in northwest flow between
large upper trough to the east and building ridge to the west. Only
passing feature will be a short wave trough that drops through the
western Great Lakes Saturday night. Some hints this could lead to
some high based showers but trends appear to be limiting this just
northeast of area. This pattern is typically more of a drying one so
could limit the small rain chances left in our northeast and eastern
areas to mainly passing mid level clouds or virga.  In any event,
should not amount to much at all.

Perhaps the bigger story for the weekend will be the aforementioned
drying pattern and fire weather concerns. That will likely be main
impact to monitor with models likely overdoing dew points. Minimum
relative humidity fields will likely be in the 20s and even with
recent rains, could see adequate drying. Perhaps limiting factor
will be winds which are expected to remain below critical values.
Winds will likely be strongest Saturday afternoon in open areas
across southern Minnesota and northern Iowa so likely need some
messaging regarding elevated risk. Fire Weather related watches will
likely be out west of Interstate 35.

Active Weather Pattern Early Next Week

Weather pattern shift will certainly make for active start to the
week. Large amplifying trough will eject out of southwest bringing
dynamic changes to the Midwest, at least for Monday and Tuesday.
Rapid low level moisture advection north and broad lift ahead of
increasing wind fields will bring a near certain rain and storm
threat by Tuesday. Short term ridging and better moisture advection
west could allow us to warm nicely for Monday before clouds and rain
threats increase by that night.

Tuesdays forecast has one given and many other potential outcomes
based on surface low track and boundaries. Still far enough out
where ensemble data provides best forecast but it also shows the
spectrum of possibilites given how close the surface low could be to
our area. One given is the rain, especially when model blends load
with 95-100 percent this far out. As low approaches, should see
widespread showers and embedded thunderstorms. A bulk of plumes of
possible rainfall totals are in the 1.00 to 2.50 inch total
suggesting widespread, soaking rains are a given. So where does that
leave us for any severe risk?

Again, a lot depends on track of low and how far instability /CAPE/
fields can get north. Various ensembles suggest most outcomes keep
our CAPE relatively limited, 500 J/kg or less, with probabilities
showing a climb in values just to our southwest and then being
shunted to our south going into peak heating on Tuesday. This could
happen given amount of widespread shower activity expected at the
time. Overall pattern would hold stronger storm threat to the south
of our area but given how dynamic this system will be, including
stronger mid layer wind fields, still have to watch how things
progress. Storm Prediction Center Day 5 is up to Interstate 90 with
15 percent outline. Last couple deterministic ECMWF runs have held
surface low to our south which would keep warm sector just south of
the area too.

Behind this system cooler air to return as ridge flattens in the
west. Should also be a drier regime, but could be looking at some
frost or freeze potential so we will see how it pans out.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1130 AM CDT Fri Apr 12 2024

CIGS: spotty clouds here and there, but mostly SKC through the
period. The next chance for lower, impactful cigs could hold off
until Tue morning when a strong low pressure system approaches from
the southwest.

WX/vsby: no impacts expected through the weekend. Widespread showers
and a few storms are likely late Monday night into Wed with related
vsby impacts.

WINDS: gusty northwest winds (25-30kts) this afternoon, decreasing
quickly after sundown. Swings southerly Sat and picks back up,
although a bit less than this afternoon. Winds will decrease further
Sunday but the start of the new work week looks very windy with a
strong low pressure system slated to impact the region (Tue
windiest).

&&

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

&&

$$

DISCUSSION...Shea
AVIATION...Rieck


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