Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 182345

Area Forecast Discussion
National Weather Service Green Bay WI
645 PM CDT Wed Oct 18 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 249 PM CDT Wed Oct 18 2017

Dry conditions and warmer than normal temperatures will continue
in the short term with low amplitude upper flow across the
northern CONUS.

A cold front moved into western Wisconsin during the day but there
were only some middle and high clouds associated with it. Expect
the clouds to clear out relatively early tonight and winds will
weaken but should not die off completely. There should be just
enough wind to keep fog from becoming a problem and prevent
temperatures from tanking. Expect above normal lows tonight and
plenty of sunshine on Thursday, so another much warmer than normal
day is in store. Most locations will top out in the mid 60s to
around 70 degrees.

.LONG TERM...Thursday Night Through Wednesday
Issued at 249 PM CDT Wed Oct 18 2017

Quiet and seasonably warm during the start of the long term
forecast period, and then focus turns to precipitation chances
through the weekend and early next week along with cooling

Mid/upper ridge continues to dominate the flow over Wisconsin
through Friday. With 850mb temps around 16C daytime highs are
expected to be about 20 degrees above normal. Followed the trend
from previous shifts and boosted high temps a few degrees from

For Saturday/Sunday, models still show timing differences on
precipitation arrival ahead of a surface cold front. GFS remains
the quickest with some WAA showers as early as Saturday morning.
And now, the latest 12Z run of the Canadian has slowed the system
down quite a bit, with the area essentially staying dry until
Sunday morning, then developing a closed-off upper low just south
of Wisconsin through early next week. Will rule this solution as
an outlier for now, and focused more on the differences between
the NAM/GFS/ECMWF. Kept a blended solution which contains low
precip chances in south- central Wisconsin Saturday morning, then
slowly expanding east through the day. Right now, the most likely
timing for pcpn is Saturday evening through Sunday morning, with
any lingering showers moving east by midday. Models show some CAPE
(up to 800 J/kg) and bulk shear (25-30 kts) Saturday afternoon
and evening. If activity does arrive by Saturday afternoon some
thunderstorms are possible, but with the best dynamics still
further west no severe weather is anticipated.

Despite differences, with increased mid-level moisture/cloud
cover and 850mb temps falling to around 11C, expect high
temperatures Saturday to be a few degrees cooler than Friday.

Flow shifts northwest later Sunday through the rest of the
forecast period. There are a couple opportunities for rain showers
as shortwave energy passes through the flow, but with timing and
location difference there`s nothing significant to grab hold of at
this point. Temps will also be cooling off, with highs about 5 to
10 degrees above normal Sun/Mon and AOB normal Tues/Wed.

.AVIATION...for 00Z TAF Issuance
Issued at 642 PM CDT Wed Oct 18 2017

VFR conditions will continue through Thursday, with only high
level clouds anticipated. LLWS will affect GRB/ATW/MTW this
evening, then weaken as a cold front moves through. Gusty
southwest winds will redevelop late Thursday morning, but will
not be as strong as today.

Issued at 249 PM CDT Wed Oct 18 2017

Will stick with the SC.Y rather than upgrade to a GL.W. Gale
force gusts are possible, but it does not look as though they
will be widespread or persistent enough to warrant a Gale

Persistent strong southwest winds are likely to result in high
waves on Lake Michigan Friday into Sunday morning.



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