Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 230905

Area Forecast Discussion
National Weather Service La Crosse WI
405 AM CDT TUE AUG 23 2016

.SHORT TERM...(Today through Wednesday)
Issued at 405 AM CDT Tue Aug 23 2016

At 3 AM, the short wave trough that brought the scattered showers
and storms to northern Wisconsin on Tuesday afternoon and evening
was moving east across eastern Upper and northern Lower Michigan.
Further to the west, short waves were causing mesoscale convective
complexes across northwest Minnesota and central Nebraska.

Many of the meso models move the Nebraska mesoscale convective
complex northeast across eastern Nebraska and northwest Iowa this
morning and into southwest Minnesota this afternoon. It is from
here that the models begin to diverge with their solutions. The
ARW and NMM models bring this system due to east into northeast
Iowa and southeast Minnesota late this afternoon and evening.
This complex then moves off to the northeast as it moves into
western Wisconsin. This is due to this system being picked up by a
northern stream short wave trough. Meanwhile another mesoscale
convective complex develops across southern Iowa at the nose of
the 850 mb moisture transport ahead a low located over Kansas.
This system stays mainly south of northeast Iowa and southwest
Wisconsin late tonight and Wednesday.

Meanwhile the NMM and NSSL WRF, show that their mesoscale
convective complexes develop along the best areas of moisture
transport which is to our northwest and south. As a result, there
is only scattered convection along the trough as it moves through
the area.

The consensus was to follow the ARW and NMM solutions, so the
forecast was trended that way. While the 0-1 km mixed-layer CAPEs
will increase from less than 1000 J/kg tonight into the 1000 to
2000 J/kg range on Wednesday, both the 0-3 km and 0-6 km shear
remain very weak. Due to this, not seeing much support for any
organized severe. With precipitable water values approaching
1.8 inches and warm cloud layer depths close to 4 km, any showers
and storms will be efficient rain producers. However with the
system being rather progressive and weak moisture transport into
the area, not anticipating too many flooding concerns. With DCAPEs
on Wednesday afternoon climbing into 1000 to 1500 J/kg, we will
have to be on the lookout for the potential of wet microbursts.

.LONG TERM...(Wednesday night through Monday)
Issued at 405 AM CDT Tue Aug 23 2016

From late Wednesday night into Friday, high pressure will provide
dry weather and cooler-than-normal temperatures.

For the upcoming weekend, the models show that there will moderate
to strong moisture transport on the backside of the departing high
pressure area. This will result in the development of showers and
storms. On Saturday, both the 0-3 km and 0-6 km shear will be
favorable for the potential develop of super cells as a speed
maximum moves east through the area. However the 0-1 km
instability remains less than 500 J/kg, so the severe weather
threat at this time looks low.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1107 PM CDT Mon Aug 22 2016

Area VWPs show the winds above the surface have increased this
evening as expected and with the surface winds diminishing to
around 10 knots, it has set up a marginal low level wind shear
environment. The 23.00Z NAM forecast soundings continue to show
the winds aloft diminishing before sunrise so have not made any
adjustments to the end time of the wind shear. The gradient should
be tight enough and with mixing through the boundary layer to once
again produce afternoon gusts of 20 to 25 knots. A high VFR
ceiling is expected for Tuesday evening at both airports ahead of
the approaching short wave trough. The 23.00Z hi-res meso scale
models are all in agreement at this point that the showers and
storms with this short wave trough should hold off until after
this forecast period.


.ARX Watches/Warnings/Advisories...


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