Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 271132

Area Forecast Discussion
National Weather Service La Crosse WI
632 AM CDT Sun May 27 2018

.SHORT TERM...(Today through Tuesday)
Issued at 234 AM CDT Sun May 27 2018

The main concern will continue to be the above normal temperatures
for the remainder of the holiday weekend. The upper level ridge
will remain over the Mississippi River Valley through Monday which
will help to keep the warm air over the region as well.
Temperatures at 925 mb reached 27-28C Saturday and very little
change is expected today or Monday which should allow surface
temperatures to reach the lower to middle 90s with a few spots
climbing into the upper 90s. Fortunately, surface dew points will
not be oppressive with upper 60s to lower 60s today during the max
heating and lower to middle 60s Monday. This will help to keep
heat indices below advisory criteria for the most part, although
some spots could top 100 for a couple of hours Monday afternoon.

As for any rain, the chances look pretty slim. The upper level
ridge will remain over the area through Monday and will deflect
any short wave troughs well to the north of the area. A weak
surface boundary is expected to be stretched out from the Dakotas
across Minnesota into norhtern Wisconsin. Some convection will
form along and north of the front with the short wave troughs and
the question becomes how far south will it reach as it moves east
across Minnesota and Wisconsin. Forecast soundings only show a
weakly capped environment south of the boundary, so not entirely
out of the question that something elevated weak activity could
move across the area and will have a small chance generally north
of Interstate 90 for late tonight into Monday night for this. The
chances for some rain become a little bit better Tuesday as the
ridge axis starts to move east of the area allowing a short wave
trough running up the backside of the ridge to be closer to the
area. The best forcing and coverage of rain should remain over the
Missouri River Valley but some suggestions there may be a weak
boundary over the area to possibly help focus some development on
the eastern fringe of the low level moisture transport. Forecast
soundings still only show a weakly capped environment so not out
of the question for some development and will increase the rain
chances into the 20 to 30 percent range.

.LONG TERM...(Tuesday night through Saturday)
Issued at 234 AM CDT Sun May 27 2018

The models continue to advertise that the upper level ridge will
get pushed east to along the East Coast during this period, but
show differences on how the pattern evolves behind the ridge. The
upper level low currently over the Desert Southwest will open up
and lift northeast up the backside of the ridge as the remains of
Alberto moves north through the Mississippi River Valley. While
the models handle the remains of Alberto similarly, the 27.00Z GFS
continues to be stronger with the open wave from the upper level
low and still has it with a neutral to slightly negative tile
while the 27.00Z ECMWF is weaker and has a positive tilt. The GFS
is also farther south now with the track taking it across the
Dakotas and norhtern Minnesota which brings more forcing to the
local area than the ECMWF which takes it across the Dakotas into
southwest Ontario. The best chances for rain in this scenario
should be Wednesday when the forcing will be the strongest. It
then looks to dry out for the end of the week before another
system possibly starts to affect the area for the weekend.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 629 AM CDT Sun May 27 2018

High pressure will provide VFR conditions through the period.
High temperature for today will be in the 90s.




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