Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 230449

Area Forecast Discussion
National Weather Service Green Bay WI
1149 PM CDT Sun Oct 22 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 237 PM CDT Sun Oct 22 2017

The main forecast concerns will be timing the return of clouds
later tonight and extent of precipitation chances on Monday.

The 19z MSAS surface analysis showed the cold front responsible
for today`s rain extended from eastern Lake Superior to near
Chicago. Post-frontal rains still existed over most of northeast
WI, although drier air was working into central WI and the rain
was diminishing to sprinkles. A ridge of high pressure was located
from the central Plains into the Upper MS Valley with clear skies.
Farther upstream, visible satellite imagery was already picking up
the next batch of clouds over the Dakotas associated with our next
weather maker.

Scattered showers will exit far eastern WI early this evening as
the ridge of high pressure moves across WI and advects drier air
into the region. Skies will clear over the forecast area tonight,
however the next cold front/shortwave trough combination is
forecast to already be diving southeast across the Dakotas into
the Upper MS Valley after midnight. Mid/high clouds should also be
on the increase across north-central/parts of central WI during
the pre-dawn hours. Min temperatures are expected to range from
the middle to upper 30s north, upper 30s to lower 40s south.

As this shortwave trough continues to dig southeast into the
western Great Lakes/Midwest on Monday, the cold front will quickly
sweep across WI. Despite favorable dynamics aloft and lift from
the front, moisture is lacking as gulf moisture to be tied to a
system lifting northeast into the eastern Great Lakes. Look for
clouds to increase/thicken across northeast WI on Monday and will
continue to mention a small chance pop in the forecast due to the
strong mid-level forcing. Max temperatures to range from the
middle 50s north, upper 50s south.

.LONG TERM...Monday Night Through Sunday
Issued at 237 PM CDT Sun Oct 22 2017

A strong low pressure system will track through the central Great
Lakes region Monday and Monday night, then stall out over the
northern Great Lakes Tuesday and Tuesday night. Despite being
closer to the system affecting the area, NWP models are actually
in less agreement regarding the systems effects on the western
Great Lakes region. The main sticking point appears to be the
phasing of the southern stream system lifting north from the
southern Mississippi Valley and the northern stream system
tracking east through the western Great Lakes region. Despite the
model differences it appears the area is in for some rain and wind
as the pressure gradient tightens Tuesday and Tuesday night. How
these systems phase will make an impact on how much rain and how
windy conditions get across the region. At this point it appears
the highest wind gusts will be over Door County due to deeper
mixing over the warm waters of the Bay and Lake Michigan, where
gusts could get over 40 mph.

After a brief break in the action late Wednesday and Wednesday
night, two low pressure systems will track through the region
late in the week and into next weekend. These systems will bring a
continued chance for showers to the region. Given the cold air in
place they could also bring some accumulating snow to northern
Wisconsin during this period. However since these systems will be
quick moving and the warm ground in place, snowfall amounts are
expected to be fairly light. NWP models this far out continue to
show significant differences, so confidence in this part of the
forecast is fairly low.

.AVIATION...for 06Z TAF Issuance
Issued at 1149 PM CDT Sun Oct 22 2017

dense fog is expected across much of east central and
northeast Wisconsin tonight. Conditions below airport minima are
possible in some areas. Northcentral and central Wisconsin will
have enough surface winds and dry air to keep fog from being dense
in most places.

The fog should dissipate a few hours after sunrise. Then VFR
conditions are generally expected Monday, though an upper level
disturbance could produce bring some showers and MVFR conditions
to the area Monday night.

Issued at 237 PM CDT Sun Oct 22 2017

Gusty west winds and high waves are expected to continue across
the Lake Michigan nearshore waters during the early evening hours.
A small craft advisory is in effect for these areas this evening.

A strong low pressure system will track through the Great Lakes
early in the work week. A tightening pressure gradient across the
western Great Lakes region will cause gusty northwest winds
Tuesday and Tuesday night. Conditions hazardous to small craft are
expected during this period, with Gale Force winds possible.
Although no headlines are in effect for this system, they are
likely to be issued in subsequent forecasts.

Dense Fog Advisory until 9 AM CDT Monday for WIZ020>022-031-


SHORT TERM.....Kallas
LONG TERM......Kurimski
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