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Area forecast discussion 
National Weather Service Green Bay WI
1243 PM CDT sun Aug 2 2015

Updated aviation portion for 18z taf issuance

Short Monday
issued at 254 am CDT sun Aug 2 2015

An area of thunderstorms that formed along an area of 1 to 3 km
moisture convergence will continue to track east through the early
morning hours. Another area of showers and
thunderstorms...associated with a shortwave and seen on water
vapor imagery over northern Minnesota...will track through the
northern County Warning Area later this morning. The main shortwave trough will
then track through later this afternoon and into this
evening...coincident with a surface cold front. These features
will bring several opportunities for precipitation across
northeast Wisconsin through tonight. Exact placement and timing of
these rounds is highly problematic...however the hi-res model runs
do offer some guidance in this regard as they have a good handle
on current activity tracking through the area. Once the main
shortwave tracks off to the north this morning there is a break in
the activity later this morning and into the early afternoon
before the main shortwave and cold front arrive. Therefore will
model the probability of precipitation after these runs and adjust as necessary as the day
GOES on.

Any convection that does fire stands a chance at being severe as
MUCAPES soar to 2000 to 4000 j/kg this afternoon with 0-6 km bulk
shear values of 40 to 50 knots...suggesting large hail and
damaging winds could be a threat. Closer inspection of low level
hodographs show significant wind shear...which means tornadoes are
also possible for any surface based storms. These factors have led
to an upgrade of the southern County Warning Area to the enhanced risk for severe
weather per the Storm Prediction Center day 1 outlook...which looks reasonable given
the factors in play this afternoon with better cape and shear
across that portion of the County Warning Area. Although the main convective Mode
appears to be an mesoscale convective system...supercells are possible this afternoon
before forming into a large mesoscale convective system.

Despite the abundant chances for rain...high temperatures today
could get to 90 degrees across the far southern County Warning Area as 850 mb
temperatures soar to around 20 degrees celsius. Any break in this
activity and temperatures this afternoon will soar. Further north
there appears less opportunity for an appreciable break in the
action. This when combined with lower 850 mb temperatures in the
middle teens should limit highs to around 80 degrees. Highs today
could go either way given the many complicating factors in
play...with breaks in the activity leading to higher temperatures and
more cloud cover and activity leading to lower high temperatures.

Temperatures will be much cooler on Monday behind the cold
front...with highs ranging from the upper 60s across far north
central the middle to upper 70s across central and
east central Wisconsin. Some showers are possible across the north
on a shortwave aids in the development of instability
showers. Chances for this look fairly low however...with probability of precipitation in
the slight chance category.

Long term...Monday night through Saturday
issued at 254 am CDT sun Aug 2 2015

The upper air pattern consisting of ridging over The Rockies and an
upper low from Hudson Bay to the Great Lakes will slowly translate
east during the upcoming work week. The medium range models are in
good agreement with the large scale through 00z Friday before
diverging. The European model (ecmwf) continues to better align with the ensemble
means...and will give more weight to its solution.

Monday night through Tuesday night...models are showing a deeper
trough over the Great Lakes than previously advertised during this
period. The cyclonic flow aloft will bring periods of clouds
overhead...with some enhancement during daytime heating Tuesday
afternoon. Prognosticated soundings continue to look capped during this
stretch...but both the European model (ecmwf) and GFS produce light quantitative precipitation forecast across far
northern Wisconsin. Will keep the small chance Tuesday afternoon in
this area...but it would not be surprising to see spotty showers
occur Monday or Tuesday nights. Highs on Tuesday will fall back
into the upper 60s north to middle 70s south.

Rest of the forecast...the upper low begins to lift off into Quebec
on Wednesday leading to a rebound of middle-level heights. But models
advertise weak shortwave impulses diving southeast across the
northern Mississippi Valley to the southern Great Lakes Wednesday
and Thursday. The GFS is most aggressive bringing low pressure into
the southern Great Lakes on Thursday...but this looks to be a
byproduct of convective feedback. With the front well south of the
region...think precipitation chances are too low to mention Wednesday night
through Thursday night. High pressure looks to build into the
region Friday and Saturday...potentially prolonging the dry
conditions. Perhaps the next chance of precipitation could occur by the
end of next weekend.

Aviation...for 18z taf issuance
issued at 1243 PM CDT sun Aug 2 2015

Scattered showers and thunderstorms are expected
during the afternoon and early evening as a cold front moves
across Wisconsin. The storms could produce strong wind gusts and
large hail. VFR conditions expected otherwise. Skies should clear
overnight and remain mostly clear through 15z Monday. An upper
level disturbance will produce scattered showers and clouds
between 3000 and 4000 feet Monday afternoon.

Grb watches/warnings/advisories...


Short term.....Kurimski
long term......mpc

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