Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 241735
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1235 PM CDT SAT SEP 24 2016

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 349 AM CDT Sat Sep 24 2016

An 850 mb warm front will continue to bring slight chances for
showers to the northern cwa during the early morning hours.
However this activity is expected to end later this morning as mid
level ridging brings sinking motion and ends any lift required for
shower activity through the evening hours. Despite the mid level
ridging, abundant moisture will keep clouds in place across the
cwa today with high temperatures around normal for this time of
year.

Later tonight an occluded front tracks over the upper Mississippi
Valley, bringing the chance for showers and maybe a few
thunderstorms late in the period. The latest model trends have
been slower with the progression of this system, which will be
slowed by the aforementioned upper level ridge. Therefore will
push back POPs across the forecast area later tonight.

The best chance for rain from this system will be Sunday when the
occluded front tracks through the western Great Lakes. MUCAPEs
climb to 500 to 1000 J/kg Sunday afternoon, with the best
instability across the extreme southern portion of the cwa late in
the afternoon. Despite the decent instability, the area will be
plagued by abundant cloud cover and the nature of the instability
itself is very narrow and skinny. This would tend to lend itself
to heavy rain potential, which given PWATs up to 2 inches is very
possible, but only pulse severe at best. Given the low probability
of severe will leave out of the products such as the HWO, although
a chance in conditions could tilt the scales in the other
direction in future forecasts.

.LONG TERM...Sunday Night Through Friday
Issued at 349 AM CDT Sat Sep 24 2016

Main concern for this period will be 500mb trough closing off
across the western Great Lakes Monday, then meandering across
the Great Lakes region through the middle of next week.

Cold front will move across eastern Wisconsin Sunday evening. This
should bring a temporary end to the rain across much of the area
as the front moves east of the area. Thunderstorms are still
possible early Sunday evening across eastern Wisconsin, although
severe weather is not expected at this time. As the upper low
approaches from the west, chances of showers will increase again
with the highest chances of rain across north-central Wisconsin
after midnight. Some moderate changes to the forecast on Monday
into Tuesday. Increase rain chances considerably across the north
on Monday as upper low moves across the northern portion of the
state. The other change was to lower maximum temperatures by
several degrees. Monday may be the first real taste of fall with
highs in the 50s across the north. Did bump up winds Monday night
and Tuesday as the low meanders across Ontario/western Great Lakes
region. Could be some gusts Monday afternoon into Tuesday morning
to around 40 mph in some spots, especially over northern Door
County where better mixing will take place over the warmer waters
of the Bay of Green Bay.

The ECMWF has thrown a new wrinkle into the forecast for Tuesday
night and Wednesday which was not introduced into the forecast
just yet. The latest run is now showing the 500mb close low
meandering further west and would now support the chances of rain
during this period across eastern Wisconsin. If this trend holds
true today, the next few shifts may need to add a chance of
showers for this period. Otherwise, high pressure should dominate
the weather pattern Thursday into next weekend.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1234 PM CDT Sat Sep 24 2016

Combination of daytime mixing and dry easterly winds have chewed
away the clouds over eastern WI. Expect to see improvement across
central WI this afternoon with any lingering MVFR cigs giving way
to VFR cigs. The VFR conditions should continue through this
evening, but anticipate MVFR cigs to return overnight as southerly
boundary layer winds begin to pull gulf moisture into WI. A cold
front and trailing mid-level shortwave trough are forecast to
impact the Western Great Lakes on Sunday. Look for showers, with a
few thunderstorms, to move across northeast WI with cigs/vsbys
reduced to IFR/MVFR conditions overspreading central WI Sunday
morning and eastern WI late Sunday morning.
&&

.MARINE...
Issued at 349 AM CDT Sat Sep 24 2016

Gusty southerly winds will bring increasingly hazardous conditions
for small craft on Sunday. Behind the cold, gusty west to
northwest winds are expected Monday into Tuesday. Gale force gusts
are possible at times Monday afternoon into Tuesday morning across
the coastal waters of northern Door County. Winds should begin to
decrease later Tuesday afternoon and Tuesday night.
&&

.CLIMATE...
Issued at 349 AM CDT Sat Sep 24 2016

Temperatures so far this month are averaging 3 to 5 degrees above
normal this month. Looking at the next week, there are no real
indications of a hard freeze across the region, even the north.
So far this month, the lowest temperature at Rhinelander is 38
degrees. The last time Rhinelander failed to reach the freezing
mark in September occurred in 2008.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......Eckberg
AVIATION.......Kallas
MARINE.........Eckberg
CLIMATE........Eckberg


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