Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 191108
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
608 AM CDT Mon Jun 19 2017

.SHORT TERM...(Today through Tuesday night)
Issued at 310 AM CDT Mon Jun 19 2017

Deep northwesterly flow across the Upper Midwest with upper troughing
over the Great Lakes will continue early this week bringing seasonably
cool high temps in the 60s and 70s through Tuesday with lows in the
50s. Scattered showers will develop again today with daytime heating
as 500 mb temps fall to around -18C and subtle weak upper waves
progressing through the flow. With the cold pool aloft more
favorably situated across the area today, coverage of showers
should be a bit higher than yesterday. A few storms are possible
with MUCAPE up to 1000 J/kg, but with weak forcing and deep layer
shear, do not expect organized storms.

A stronger upper shortwave trough and upper jet streak will dive
across the region overnight tonight bringing a continued chance of
showers. There is some variability among model solutions with the
exact track of the wave tonight, but as confidence increases, rain chances
may be increased over parts of the area, given the strength of
the wave. As this system passes to the east on Tuesday, weak
ridging will build into the region with drier weather expected for
later Tuesday. Lows Tuesday night may drop into 40s under the
ridge axis, especially across central Wisconsin.

.LONG TERM...(Wednesday through Sunday)
Issued at 310 AM CDT Mon Jun 19 2017

A fast zonal flow pattern aloft will develop on Wednesday over
the north central US. Low to mid level warm advection will begin
to increase ahead of an approaching cold front associated with a
shortwave trough expected to move across southern Canada. As a
result, temps should trend upward back into the 70s to low 80s.

Thunderstorm potential will be the primary concern Wednesday into
Thursday with this system. There has been a consistent signal for
convective activity to increase later Wednesday and Wednesday night
with the approach of a frontal system. With the strong mid-level
flow, deep layer shear will be more than adequate to support storm
organization. An elevated mixed layer advecting eastward from the
high plains will bring an axis of higher instability towards the
region on Wednesday, though the placement of the instability,
especially the eastward extent, varies among models. Would expect
convective development to occur in association with low/mid-level
warm advection with some support from a strengthening low-level
jet as the surface trough/front approaches. Currently the highest
chances locally for storms appears to be late Wednesday and
Wednesday night. The shear profiles would support the potential
for strong/severe storms, but confidence on the details of the
convective evolution is low at this stage.

With zonal flow persisting into late week, the frontal boundary may
be slow to completely clear the area until an upper shortwave trough
to the north helps push the front southward. Precip chances could
linger along the front on Thursday with additional rain chances
over the weekend as a stronger upper trough approaches. Cooler
temps are expected for next weekend as the flow aloft becomes
northwesterly again with highs in the 60s and 70s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 1108 AM CDT Mon Jun 19 2017

VFR conditions are expected to continue through the TAF period.
Scattered showers and isolated thunderstorms are expected to
develop and move toward the TAF sites by 16Z, but confidence is
low that a thunderstorm will directly impact either TAF site, so
have opted for a VCSH mention at this time. MVFR conditions would
be possible with any heavier shower/storm. Winds will increase
into the 10 to 13 kt range through the day today, with gusts to 20
kts possible. Additional showers and storms are possible at the
very end of the TAF period, around 11Z or so, but confidence in
timing and exact location is too low to include any mention with
this issuance.

&&

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

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION...CA



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