Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 230007
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
707 PM CDT Sat Sep 22 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Sunday
Issued at 232 PM CDT Sat Sep 22 2018

The latest RAP analysis and satellite/radar imagery show high
pressure centered over Lower Michigan and extending west over
Wisconsin. Mostly clear skies are prevailing over most of north-
central and northeast WI with only spotty cu forming, though a
more widespread cu field may rotate north from southeast WI into
east-central WI later on this afternoon. Meanwhile to the north,
a cold front extends from North Dakota to far northern Lake
Superior. Ample low clouds and spotty showers are present along
the front. As this front moves south and high pressure exits to
the east, cloud trends and temps are the main forecast concerns.

Tonight...High pressure will slide east to the eastern Great Lakes
while a Canadian cold front sags into the Upper Peninsula. Mid-
clouds will likely pass over northern WI ahead of the front, while
locations over central and east-central WI should largely enjoy a
mostly clear evening. As the front draws closer, models are
aggressive pushing in a low stratus deck into far northern WI
late. Backed off a little on cloud trends, since think models are
too aggressive based off the latest satellite imagery. As a
result, dropped temps a little, especially in some of the cold
spots over central WI, where some patchy fog is possible late. But
dont think temps will get cold enough for frost.

Sunday...The front will effectively stall over the Upper Peninsula
and far northern WI. Brought mostly cloudy skies south of
Rhinelander during the morning, but should see the stratus evolve
into a cu field in the afternoon, as winds back around to the
south at 850mb. Wouldnt be surprised to see a few sprinkles or
spits near the U.P. border during the morning. With partly cloudy
skies over central and east-central WI, temps will range from the
upper 50s in the far north to the upper 60s in the south.

.LONG TERM...Sunday Night Through Saturday
Issued at 232 PM CDT Sat Sep 22 2018

Dry weather will continue through Monday, with weak ridging at the
surface and aloft.

A cold front will move through the area Late Monday night into
Tuesday, bringing a chance of showers and isolated thunderstorms.
On Monday night, pops will be highest in the northwest (near the
cold front) and far southeast (WAA and a surge of tropical
moisture, with PWATs around 1.5 inches). On Tuesday, the main
focus should be over the southeast half of the forecast area,
where the frontal passage will still be occurring. Instability is
progged to be fairly weak during this event, with the greatest
instability (CAPE 500-750 j/kg) occurring in the Fox Valley region
midday Tuesday.

A mostly dry period is anticipated during the middle of the week
as the forecast area remains on the northern periphery of a
strong high pressure system.

Another cold front is forecast to arrive late Wednesday night into
Thursday, along with the next chance of showers. This system will
have even less instability to work with than the previous, so
will only mention a small chance of storms over north central WI
Thursday afternoon.

High pressure should bring another mainly dry period for the end
of the work week, but models disagree on the arrival time of
precipitation for the weekend.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 704 PM CDT Sat Sep 22 2018

VFR conditions are likely through Sunday, as high
pressure moves slowly east. Patchy ground fog is possible late
tonight across mainly the western TAF sites. It should quickly
dissipate early Sunday if it does form. Additionally, some MVFR
clouds may approach RHI late tonight into Sunday morning; however,
these should steadily lift into the day Sunday.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......Cooley



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