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Area forecast discussion 
National Weather Service Green Bay WI
659 PM CDT Thursday Jul 30 2015

Updated aviation portion for 00z taf issuance

issued at 227 PM CDT Thursday Jul 30 2015

Seasonably warm temperatures expected through the weekend.

The main band of westerlies is currently across southern Canada and the
northern Continental U.S....has limited amplitude...and has a ridge over the west and
a trough over the Hudson Bay region. The main change during the forecast
period will be a slow and gradual increase in amplitude...with the
upper trough expanding southward. That will tilt the upper flow into the forecast
area more northwesterly with time.

Temperatures will start out warm...with daytime highs through the
weekend 4-8f degree above normal. By early next weak the upper flow should
tilt northwest enough to bring cooler air from Canada into the region...likely
dropping temperatures to a little below normal by late in the period. Precipitation
chances will be limited since the very humid air will remain to our
S...and the best dynamics with the upper trough will stay north. Although
all it takes at this time of year is one convective event to
supply a normal weeks Worth of seems likely that most
areas will end up receiving below normal precipitation for the period.

Short term...tonight and Friday
issued at 227 PM CDT Thursday Jul 30 2015

Mild temperatures and dewpoints in the lower 50s made for pleasant
conditions across northeast Wisconsin late this afternoon.
However...19z water vapor showed a shortwave tracking through NE
Minnesota and heading for northern Wisconsin. This feature has
already kicked off scattered storms that were moving through northwest
Wisconsin. With some instability in north central Wisconsin...and
lapse rates of 6-7k/km...these storms should maintain themselves
this afternoon as the shortwave swings through. Nothing severe is
expected as convective available potential energy are only 500j/kg at best...but with dry air
aloft and rap soundings showing inverted-v-like signatures...gusty
winds and brief heavy rain is possible through early this evening
to the north.

Any lingering showers and thunderstorms this evening should
quickly dissipate after sunset. Clear skies should prevail until
about midnight as a weak front pushes through and scattered cloud
cover develops...with broken clouds to the northas better qg
forcing gives some added lift.With very little change to the
overall weather pattern...stayed close to last nights low
temperatures with a hint of the best performing guidance thrown

Fridays set up looks a lot similar to what we had this afternoon.
Sunny and dry to start the day...with some fair weather cumulus in the
afternoon. Another weak shortwave will be dropping through the
mean flow which could kick off a few showers to the north. With NE
WI sitting on the anticyclonic side of a broad upper level...have
doubts showers will even develop. Fridays shortwave will not be as
defined todays with little to no added instability. However
high-res models continue to show isolated precipitation developing in
response to the lfq of a strong 300mb jetstreak brushing northern
Wisconsin. Kept slight chance probability of precipitation Friday afternoon...though confined
precipitation to only the far north. Highs tomorrow will be a degree or
two cooler than today...with continued breezy west winds through
not as high as we saw today.

Long term...Friday night through Thursday
issued at 227 PM CDT Thursday Jul 30 2015

Daytime temperatures will continue above normal for a few days...then eventually
cool as the upper flow tilts northwesterly. Stayed close to a blend of the
top performing guidance products.

Hard to get a handle on specifics of the precipitation forecast given the
pattern. Precipitation chances will be tied to small scale shortwaves rounding the
base of slowly strengthening lngwv trough. Current op model suite
not very encouraging for the precipitation we/ve been carrying for Sat
night...with many of the models now taking that through to the S of
the forecast area. Late sun/Sun night look better for precipitation at this
point. But then again in a pattern like this...things could look
totally different tomorrow. Stuck with chance probability of precipitation for most areas for
Sat night...and again on Sun night.

No sig changes made to the extended forecast initialization grids based
on a broad blend of guidance products.

Aviation...for 00z taf issuance
issued at 659 PM CDT Thursday Jul 30 2015

Scattered showers and isolated thunderstorms...associated with an
upper level short wave moving across northern Wisconsin...were
diminishing as sunset approached. Activity should die off or exit
the area by 01z to 02z. Winds will decrease with loss of daytime
heating and VFR conditions should prevail throughout the night.

BUFKIT overview of the 18z NAM and 18z GFS showed moisture in a
layer from about 4000ft to have some scattered to
broken clouds forecast in that height range during the day.
Showers cannot be completely ruled out but odds of them impacting
any particular taf site appear low at this time.

Grb watches/warnings/advisories...


short term.....Allen
long term......skowronski

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