Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 181142
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
642 AM CDT Tue Apr 18 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 400 AM CDT Tue Apr 18 2017

Clouds continue to thicken ahead of an approaching low pressure
system seen on Water Vapor Imagery over the northern Plains. This
system will bring a warm front north through central and east-
central Wisconsin this morning, allowing highs to soar into the
lower to middle 60s, while highs north of the front stay in the
middle to upper 50s. The increased pressure gradient ahead of this
system will cause wind gusts to increase today to 30 to 40 mph.
Precipitation with this system looks to arrive later this morning
as Doppler Radar shows the precipitation already in Minnesota.
Upstream lightning data shows this system has thunderstorms with
it, which should increase given daytime heating as mid level lapse
rates increase increase in the warm sector. The cold front
associated with this system will track through late this afternoon
and this evening, ending the rain chances from west to east.

Despite the passage of a cold front, lingering clouds should keep
lows tonight relatively warm, ranging from the middle to upper 30s
across the north and in the lower to middle 40s across the south.
Dry weather will be short lives as the aforementioned cold front
stalls over northern Illinois and gets lifted back north as a warm
front on Wednesday. This will bring the chance for rain back to
the area Wednesday afternoon. Some thunder is also possible across
central Wisconsin where steep low level lapse rates will advect in
from the south.

.LONG TERM...Wednesday Night Through Monday
Issued at 400 AM CDT Tue Apr 18 2017

A system that will bring precipitation to the area Wednesday
night into Thursday evening is the main forecast concern.

00Z models showed a surface low moving across southern Wisconsin
late Wednesday night through Thursday morning and a significant
mid level trough moving through the state. Precipitation is
expected to spread across the entire area Wednesday night, and
there should be enough cold air over northern Wisconsin for snow
or a mix of rain and snow. Have an inch or two of wet snow
accumulating in parts of far northern Wisconsin 06Z-18Z Thursday.
Temperatures on Thursday will be well below normal for this time
of year, but it should still be warm enough to melt much of, or
all of, the snow during the day. Precipitation will start to wind
down Thursday afternoon, and be out of the area by 06Z Friday as
the system moves away from the state. Precipitation totals should
range from around 0.5 inch to a little more than an inch. This is
not expected to cause serious problems, but the runoff will act
to keep high flow on rivers and streams across the forecast area.

After the system departs generally dry weather will prevail for
the rest of this week into early next week with high pressure over
the state. After below normal temperatures on Thursday, near or
slightly above normal highs are expected for the rest of this
week into early next week.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 642 AM CDT Tue Apr 18 2017

Clouds will thicken this morning ahead of an approaching warm
front. An approaching cold front will bring showers and lowering
conditions to MVFR today through this evening. Thunder is also
possible, but should be isolated enough to leave out of the TAFs
with this issuance. Early morning LLWS will give way to gusty
surface winds later this morning with a strong pressure gradient
in place. The cold front will arrive late this afternoon and this
evening, turning winds to the northwest as the rain ends.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......MG
AVIATION.......Kurimski



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