Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 281956

Area Forecast Discussion
National Weather Service La Crosse WI
256 PM CDT Tue Mar 28 2017

.SHORT TERM...(This evening through Thursday night)
Issued at 255 PM CDT Tue Mar 28 2017

Water vapor imagery this afternoon showed an upper level low over
New Mexico. This system is generally handled similarly by the
models as it lifts northeast. It is expected to remain a closed
low as it lifts into Kansas through Wednesday night and then
become an open wave and take a bit more of an easterly track as it
reaches the northern extent of the Ohio River Valley Friday. As
the system comes by the region, there should be periods of weak pv
advection in the 500-300 mb layer that come across the southern
sections of the forecast area from Wednesday afternoon through
Thursday morning. The surface low is expected to come out of
Kansas and track across northern Missouri into northern Indiana.
This will keep the local area on the cool north side of this
system and keep the best low level frontogenesis well to the
south. However, a band of weak mid level frontogenesis will set up
along and south of Interstate 90 starting Wednesday afternoon and
remain nearly stationary until late Wednesday night. Some warm air
advection will get wrapped around the northeast side of the
surface low which will result in 2 to 4 ubar/s of up glide on the
285K isentropic surface spreading across the southern sections of
the area from Wednesday afternoon through Thursday morning. All
this is expected to be ample forcing to produce mainly rain, with
the best chance along and south of Interstate 90. Will continue
to show the rain gradually spreading in during the day Wednesday
with the highest chances for rain (70 to 90 percent) Wednesday
night south of Interstate 90 and then across the southeast third
of the area Thursday morning. These rain chances will then start
to decrease Thursday afternoon with just some lingering chances
across the east Thursday evening.

There will be some precipitation type concerns at times Wednesday
night into Thursday morning for areas along and northeast of
Interstate 94. Temperatures are expected to cool into the lower to
middle 30s at the surface. This should allow some snow to mix in
with the rain at times. But there is also a concern as to whether
there will be always be ice in the clouds. The 28.12Z GFS shows
more ice in the clouds than the 28.12Z NAM or 28.12Z CMC and even
it suggests ice could be lost at times. If this is the case, there
could be a little bit of freezing rain at times where the surface
temperatures cool to about 33 or below.

.LONG TERM...(Friday through Tuesday)
Issued at 255 PM CDT Tue Mar 28 2017

As the storm system continues to move away from the area, ridging
will build over the Midwest to close out the work week and the
start of the weekend. Another system in the southwest flow will
come across the southern Rockies Sunday but is expected to take a
more east track and slip by well south of the area. As this is
occurring, a system will be taking shape in the northern stream
that will push a long wave trough down into the northern Rockies
Sunday night and then out into the Upper Midwest for Monday and
Tuesday. There is a small chance that some light precipitation
from the southern stream system could get into parts of the area
Saturday night and Sunday. Better chances for precipitation should
spread across the area Monday and Tuesday ahead of the advancing
northern stream system.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1151 AM CDT Tue Mar 28 2017

High pressure providing VFR conditions across the area this
afternoon. However, easterly airflow through the boundary layer
looks like it will draw MVFR stratocumulus back up into the
KLSE/KRST airports in the 12-13z timeframe.




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