Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 280853

Area Forecast Discussion
National Weather Service Green Bay WI
353 AM CDT SUN AUG 28 2016

Forecast discussion for routine morning forecast issuance

Issued at 351 AM CDT Sun Aug 28 2016

Seasonably warm and rather humid the next few days, then turning
cooler and less humid.

The large scale pattern will deamplify a bit more in the next 24
hours, then a substantial upper trough is expected to deepen off
the West Coast. Amplification downstream from the deepening
trough will lead to a building ridge over the Rockies and western
Plains, and downstream troffing over eastern NOAM. The changes
will result in rising upper heights across the forecast area the
next few days, followed by a turn to northwesterly upper flow as
amplitude peaks midweek. The Rockies ridge is expected to begin
progressing east during the latter part of the forecast period,
reaching the western Great Lakes region by next weekend.

The air mass currently across the area is warm and rather humid,
so a few days of above normal temperatures are expected at the
start of the forecast period. Readings will drop back to AOB
normal as the upper flow tilts northwest during the middle to
latter part of the work week. But it appears the cool down will be
short-lived, as the approach of the western ridge will allow
temperatures to return to above normal by next weekend.
Precipitation opportunities will primarily be due to low-
predictability convective systems early in the period as the
pattern does not look favorable for precipitation once the upper
flow turns northwest.

.SHORT TERM...Today...Tonight...and Monday
Issued at 351 AM CDT Sun Aug 28 2016

Lingering moisture and light winds were allowing fog to form this
morning. Although some ob sites had visibilities AOB 1/4SM at
times, web cams suggest the visibility is still generally
sufficient for safe travel at highway speeds. There certainly must
be patches of dense fog out there, it just doesn`t look widespread
enough to justify an advisory. Will continue to monitor and handle
with SPSs unless conditions worsen significantly.

Otherwise, generally quiet weather is expected as high pressure
lingers across the area. Convection is likely to remain focused
west of the forecast area. The forecast issue is whether or not
any of that will be able to work into the northwest part of the
forecast area at some point. The support for precipitation today
seemed too low to keep the PoPs we had for north-central Wisconsin
in previous forecasts, so removed them. The LLJ remains focused to
our NW tonight, though it is possible that a WAA wing developing
east of an MCS likely to form over northern MN could affect north-
central Wisconsin. Modest westerly flow at upper levels could also
allow storms to spread east before dissipating, so kept PoPs for
that area. Not much changes on Monday, except the west flow may be
a bit stronger. Expanded PoPs east a bit, but nothing beyond
chance category.

.LONG TERM...Monday Night Through Saturday
Issued at 351 AM CDT Sun Aug 28 2016

The big change in the 500mb for next week is still on track which
will bring the first signs of fall to the area. Will have to wait
and see how potential tropical system in the Gulf of Mexico will
impact the large scale pattern.

For Monday night, confidence is high that storms will make it into
north-central Wisconsin Monday evening. Convective parameters
would support a few strong storms with gusty winds and locally
heavy rain. The big change for this period is to remove chances
for rain across east-central Wisconsin. The latest ECMWF model
supports this thinking. In matter of fact, if the slower ECMWF
solution is correct, will need to start thinking about the
possibility of stronger storms late Tuesday morning and afternoon.
Have left uncertainty wording in the Hazardous Weather Outlook
(HWO) for this possibility. A few showers may linger into the
early Tuesday evening near Manitowoc, otherwise tranquil
conditions will prevail.

The advertised cool down will arrive Wednesday with temperatures
at or slightly below normal along with lower humidity readings.
The latest run of the ECMWF is a little more pronounced with the
cool down, so nudged temperatures down a few degrees Wednesday
into Thursday. Will also need to watch Thursday as the ECMWF turns
low level winds to the northeast. Lake to 850mb temperatures
approaching 15C, thus is scenario would lead to more cloudiness
and the potential for lake effect showers near the Lake Michigan
shoreline. A lot of uncertainty in the wind forecast this far out,
thus did not add more cloud cover or showers to the forecast for
this period. High pressure will linger into early next weekend.
The next chance for widespread showers or storms would be later
Saturday into next Saturday night.

.AVIATION...for 12Z TAF Issuance
Issued at 351 AM CDT Sun Aug 28 2016

Breaks developing in the stratus deck across the area combined
with significant fluctuations in visibilities were resulting in
flight conditions varying considerably in time and space. That
will likely continue through daybreak, then improvement should
occur during the middle to late morning as mixing occurs. Light
winds again tonight may result in fog reforming, though a repeat
of the widespread stratus is not expected.



SHORT TERM.....Skowronski
LONG TERM......Eckberg
AVIATION.......Skowronski is the U.S. government's official web portal to all federal, state and local government web resources and services.