Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 171147
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
547 AM CST Sat Nov 17 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 258 AM CST Sat Nov 17 2018

Fairly quiet weather expected in the short-term forecast; however,
there will be some light lake effect snow over Vilas County along
with continued below normal temperatures.

Today: The low pressure system that moved just to the south of the
area this morning will continue to shift off to the south and east
throughout the day. This will allow any light system snow to quickly
come to an end early in the day. Any impacts from the light snow
should be very limited. Otherwise, broad/strong high pressure will
begin slide eastward from the northern Plains this morning into the
Western Great Lakes region this afternoon. Ahead of the ridge and
behind the departing low pressure system northwest winds will slowly
shift westward as the high pressure center is expected to be
southwest of the area. The northwest winds, along with 850mb
temperatures around -15C, will lead to continued lake effect clouds
and snow showers across north central portions of Wisconsin. This
will be most notable across Vilas County; however, only an inch or
two is expected. Late in the afternoon, as the winds shift to the
west, any lingering lake effect snow will shift northward into the
U.P. and diminish as drier air moves into the area. It will be a
chilly day with highs in the 20s to low 30s with at least a light
breeze throughout the day.

Tonight into Sunday: The aforementioned high pressure system will
slide across the region through this time period, allowing for quiet
weather. Skies will be mostly clear through this time period, with
the only impactful weather expected to be the continued cold
temperatures. In fact, portions of north-central WI and the typical
cold spots may drop into the single digits above zero, while the
rest of the area drops into the low to mid teens above zero. Some of
the guidance is even colder; however, opted not to go with the
coldest guidance as there will likely be a light breeze through the
night as the high pressure center remains south of the area. Highs
Sunday will be in the 20s to low 30s, coldest over central and north-
central WI.

.LONG TERM...Sunday Night Through Friday
Issued at 258 AM CST Sat Nov 17 2018

The main concerns for this forecast period are the chances for
precipitation, especially early in the week. A low pressure
system, along a southward moving cold front, will pass through
Wisconsin late Sunday night/Monday. Models showed some
differences in location but the 00Z NAM, GFS, ECMWF and Canadian
all have the QPF focused across northern Wisconsin Sunday night.
Have mainly confined snow chances to the north Sunday night and
then increased PoPs across the rest of the area Monday morning.
Snow chances will be mainly in the Lake Superior snowbelt Monday
afternoon and early evening as the surface system departs. The
model blend only showed a slight chance for snow Tuesday night but
would not be surprised if the day shift needs to increase PoPs for
northeast Wisconsin Tuesday afternoon into Tuesday evening. Dry
weather is expected for Wednesday and Thanksgiving Day but models
diverge toward the end of the week and onset of the next round of
precipitation remains in question. Stuck with the blend and have
some light snow early on Friday changing to rain across the entire
area before noon.

Flow aloft will be out of the northwest early in the week with a
high amplitude ridge over western NOAM. The ridge should break
down as it makes its way east during the week. Flow is expected to
become southwest by Friday as the ridge axis passes east of
Wisconsin. The transition from northwest to southwest flow will
bring a warming trend. Near normal temperatures should return by
the middle of the week and readings should top out several degrees
above normal on Friday.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 547 AM CST Sat Nov 17 2018

Occasional MVFR conditions early this morning will steadily
improve to VFR conditions this afternoon through the rest of the
TAF period as high pressure builds across the area. There may be a
few snow showers this morning at RHI, but the chance is fairly
low. Winds will be relatively light throughout this TAF period.
&&

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

$$

SHORT TERM.....Cooley
LONG TERM......MG
AVIATION.......Cooley



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