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257
FXUS63 KARX 281151
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
651 AM CDT Tue May 28 2024

.KEY MESSAGES...

- Rain & Storm Chances Continue Today, Becoming Drier Through
  Midweek

- Below Normal Temperatures Today & Tonight Quickly Warm Back
  Up Through Wednesday.

- Low Confidence In Timing Of Precipitation Chances At The End
  Of The Week.

&&

.DISCUSSION...
Issued at 244 AM CDT Tue May 28 2024

Rain Expectations Today:

After a another round of rain and storms through today, a drier
forecast is on tap through much of the work week. A phasing
negatively tilted trough on GOES Water Vapor imagery over the
North Dakota-Minnesota border early this morning is the
culprit for these precipitation chances through today. Near
mean PWATs of 0.5" to 0.75" in 18.00Z RAOBs with the quick-
hitting nature of the wave and best forcing east of the local
forecast area will limit overall impacts and rainfall under
0.25", primarily in central Wisconsin. HREF mean, maximum, and
probability matched mean are 0.1", 0.5", and <0.1" primarily in
central Wisconsin, respectively.

Storm Expectations Today:

Initial rainfall early this morning remains quite scattered,
losing stream quickly before the main show reaches southeast
Minnesota near 12Z on the cusp of the surface lows attendant
cold front draped to the southwest through the Dakotas early
this morning. The cold front and attendant temperature gradient
weakens as it approaches the area, decreasing storm extent
locally. Although, meager CAA throughout the day will result in
persistent scattered precipitation and storms. Steepening lapse
rates will result in scattered areas of weak instability near
500 J/kg in spots. Again, higher precipitation chances and
subsequent storm chances lie in central Wisconsin and points
east. Little to no shear suggests storms pulsing up and down.
Irregardless, some could produce small hail from low freezing
levels and thick hail growth zones.

Cooler Tonight:

Higher long term impact from the passing trough will be ushering
in a colder, drier Canadian airmass. This colder airmass seen
on overnight observations in the Dakotas, antecedent of the cold
front, as one would expect. Diurnal timing with the high May
sun angle will abate coolest temperatures locally during the
day, keeping daytime highs in the mid to upper 60s. As we lose
diurnal influence overnight, a drop into the 40s is expected.

Warming Through Wednesday:

These colder temperatures are short lived however as an amplified
upper level ridge with an axis from the Great Salt Lake in northern
Utah into central Manitoba early this morning on upper level GOES
water vapor imagery traverses through the central U.S. into
Wednesday morning. Similar to previous forecasts, long term
global deterministic and ensemble models disagree on location
of highest heights. Subsequently, Wednesday high temperatures
vary from the 60s in the GEFS to 80s in the GEPS. Have blended
into the 70s where highest confidence lies. Another impact will
be precipitation chances through the end of the work week.
Differences in resolving timing of the quasi- omega blocking
pattern is to blame. Therefore, with the weakest, quickest
ridge, the GEFS returns initial precipitation chances Thursday
night.While the GEPS staves off until Friday afternoon into the
early evening. Have gone with National Blend for now given the
longer forecast window but will be subsequent forecast detail,
other than high temperatures through midweek, to keep an eye
on.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
-- Changed Discussion --
Issued at 635 AM CDT Tue May 28 2024

Valley fog early this morning has brought 0 SM to KLSE and LIFR
at other smaller Mississippi River Valley airports. Showers
sagging southeast through Minnesota early this morning. VFR
ceilings have been observed but with cold air advection expect
some lowering. Therefore, have kept a pessimistic forecast.
Thunder possible with passing storms from northwest to southeast
later this morning through the afternoon. Storms linger east of
the Mississippi River into tonight. Low confidence for lifting
out of MVFR, so have kept it given the ongoing pattern. Forecast
models suggest another round of fog Wednesday morning but an
incoming dry airmass has its doubts. Will be subsequent forecast
detail after storm chances.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...JAR