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275
FXUS63 KGRB 231935
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
235 PM CDT Fri Jun 23 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 235 PM CDT Fri Jun 23 2017

Instability showers developed across northeast Minnesota and
northwest Wisconsin this afternoon. The showers were moving to
the southeast and will move into portions of the area during
the remainder of the afternoon into early evening, especially
north and west of the Fox Valley. An isolated thunderstorm
can not be ruled out north and west of the Fox Valley. If
any thunderstorm that does develop could produce gusty winds
to around 35 mph and small hail.

Cyclonic flow should leave some cloudiness through the night,
thus partly cloudy skies should suffice. Late tonight, next
shortwave energy could bring a chance of showers to the far
north late tonight. The more potent shortwave will move across
the region. Very cold air aloft at 500mb noted tomorrow with
temperatures approaching -25c. The combination of daytime
heating and cold air aloft would support scattered showers
and thunderstorms through the day. Total totals approaching 55,
and the 50 surface dewpoint and -20C at 500mb rule would also
support the possibility of an isolated severe hail report
Saturday afternoon. It will be very cool with highs around
60 north to around 70 across northeast and east-central
Wisconsin.

.LONG TERM...Saturday Night Through Friday
Issued at 235 PM CDT Fri Jun 23 2017

A similar pattern in the long term forecast as what models have
shown for the past few days. Focus is on timing of precipitation
and temperatures.

Showers and some thunderstorms are likely to be scattered across
the area at the start of the period. This will begin tapering off
through the late evening as instability is lost and the potent
mid-level short wave moves east.

A brief break in activity is expected Saturday night into Sunday
morning before another shortwave comes through late Sunday morning
and afternoon. Shear remains weak (less than 15 knots), with some
instability by mid- afternoon (MUCAPE 800-1200 J/kg). While these
parameters lead to low confidence in severe criteria thunderstorms,
low and mid- level lapse rates remain steep (7-8 C/km) with low
wet- bulb zero heights around 6500 ft. Some small hail and strong
gusty winds cannot be ruled out within any stronger storms that
develop.

There should once again be a quiet period late Sunday/early Monday
with another shortwave pushing through Monday morning.
Thunderstorms chances appear weaker on Monday as the strongest
shortwave energy may be east before peak heating. There will also
be high pressure building in at the surface. Will continue a
chance showers/slight chance thunderstorms through Monday
afternoon, but models seem to be trending towards ending this
activity earlier in the day.

Tuesday still looks dry as high pressure builds in at the surface.
Beyond Tuesday, models are in slightly more agreement that flow
will turn west/southwest by midweek with a surface warm front
pushing across the area and strong WAA to bring thunderstorm
chances to the area Wednesday and Thursday. Continued with the
blended model solution for this time period. It is too early to
determine the potential strength of these storms.

Temperatures will be below normal through the weekend and early
next week while the upper level trough remains over the Great
Lakes. Temperatures will moderate closer to seasonal normal by
midweek when the trough moves east.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1205 PM CDT Fri Jun 23 2017

Cumulus clouds will continue to develop across much of the area
this afternoon. Gusty west winds may gust to around 25 knots. Cool
air aloft combined with daytime heating will cause scattered
showers to form by early to mid afternoon and then continue into
the early evening hours. An isolated thunderstorm is also possible
that could produce some gusty winds to around 30 knots and small
hail. Some stratocumulus clouds will continue through the night.
Some showers may enter far northern Wisconsin towards 12z. On
Saturday, scattered showers and thunderstorms are expected after
15-16z and continue into early Saturday evening. Some gusty winds
and small hail are possible, especially Saturday afternoon.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......KLB
AVIATION.......Eckberg