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fxus63 kgrb 281936 
afdgrb

Area forecast discussion
National Weather Service Green Bay WI
236 PM CDT Fri Apr 28 2017

Forecast discussion for routine afternoon forecast issuance

Short term...tonight and Saturday
issued at 232 PM CDT Fri Apr 28 2017

What breaks in the cloud cover some locations will observe this
afternoon will be short lived as light rain with the next system
already in southern Wisconsin. Primary forecast challenge centers
on arrival, how far northward, and then departure of this area of
rain overnight. Rainfall appears to be mainly focused on the weak
850 trough which slides over the region this evening before
departing east of the area after midnight. NAM appears under done
with this system so used the European model (ecmwf) and GFS with timing of the
rainfall.

Surface high pressure then nudges into the Great Lakes region on
Saturday for a drier period with decreasing clouds for a period of time.
Winds turn northeast and blustery across the area with the
approach of the next system. Cooler readings along the Lakeshore
expected. Some progs begin to bring precipitation to far southern
areas later Saturday afternoon, so will start a ramp up period
late afternoon.

Long term...Saturday night through Friday
issued at 232 PM CDT Fri Apr 28 2017

A wet cool pattern is expected Saturday night through Tuesday
followed with a drier period and moderating temperatures for the
rest of next week.

A strong upper low system is progged to slowly move from the
Central Plains Saturday night into the western Great Lakes or
northern plains region by Monday. Gulf moisture with pwats of
1.00 to 1.50 inches work into the region ahead of this system with
the upper southwest flow. While not abnormally high pwats, the
duration provides the potential of a long duration soaking
rainfall. Start time over southern portions varies with the progs,
ranging from Saturday afternoon to Saturday evening, with
northern areas the latest. The later start for the north Saturday
night into Sunday morning will provide a potential of a light mix.

The brunt of the rainfall appears to be Sunday afternoon into
Sunday evening with the 850 warm front lifting northward into the
state. This would likely be the best chance of storms as well.
With the upper low system lifting northward over Minnesota, best
rainfalls after that will be northwest of the area with the
deformation area. But a continued soaking rainfall will continue
as the upper low drifts into the state.

Progs suggest the best instability and potential of stronger
storms remain south of the area for this storm system. Best
period of thunderstorms appear first with the warm surge later
Sunday and possibly with the upper low center Monday.

As the system pulls away Monday night into Tuesday the mix
potential returns, along with an instability shower variety on
Tuesday.

Later half of the week, northwest flow develops with a possible
short wave trough dropping over the area toward Thursday night.
Progs continue to divert next week with the building ridge over
the plains or another weak short wave trough and front dropping
over Friday night or next Saturday. Nevertheless the pattern
provides a period of drying and moderating temperatures.
&&

Aviation...for 18z taf issuance
issued at 1126 am CDT Fri Apr 28 2017

Cigs will continue to lift to VFR levels from south to north this
afternoon as the cyclonic flow with a low pressure system departs
further northeast of Lake Superior. A west to East Ridge of high
pressure will drift northward across the area this afternoon
into Saturday for an overall quiet weather regime. Another low
pressure region tracking over the mid Mississippi region this
afternoon into tonight may be close enough to produce a few light
showers south of Highway 10 this evening. Otherwise mainly VFR
conditions to prevail into Saturday.
&&

Marine...
issued at 232 PM CDT Fri Apr 28 2017

Persistent northeast winds along Lake Michigan this weekend may
produce high waves. Winds may approach gale levels late this
weekend into early next week as a strong storm system tracks into
the Great Lakes region.
&&

Hydrology...
issued at 232 PM CDT Fri Apr 28 2017

Above normal rainfall for April continues to keep river levels
and flows above normal. Recent rainfall this week have prompted
river flood warnings for part of the Wolf River south of Shawano.
Flows along the Menominee also remain above normal, with flood
advisories in effect for portions of the river and possible flood
warnings for minor flood stage this weekend. Another storm system
Sunday into Monday will be capable of producing another
widespread inch of rainfall over two days. Locally higher amounts
to 2 inches possible. This rainfall will continue to keep river
running above normal for the rest of April and into early may.
The above normal river levels and flows will likely begin to
affect recreational users and interests. Be current with any slow
no wake postings in your area.
&&

Grb watches/warnings/advisories...
none.
&&

$$

Short term.....Tdh

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