Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 252343
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
643 PM CDT Sun Oct 25 2020

Updated aviation portion for 00Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 639 PM CDT Sun Oct 25 2020

Light snow continued across the area, probably mixed with a
little rain at times along the immediate lakeshore. The current
band of precipitation should shift east of the area in a few
hours, leaving just some occasional light snow and flurries for
the rest of the evening. The HRRR suggested another wave of light
precipitation would lift across about the SE 1/3 of the area
after midnight. There was little support for that on the other
model QPFs, but the radar mosaic did show increasing returns in
SW IA shifting NE, and the latest NAM/GFS runs had an area of FGEN
coming across the area at that time that would support some weak
ascent and light precipitation. Increased PoPs as little and
carried light precipitation later into the night to support this
possibility. Will continue to monitor, and if radar trends
continue to look favorable will increase PoPs further for E-C WI
for the late night period.
&&

.SHORT TERM...Tonight and Monday
Issued at 254 PM CDT Sun Oct 25 2020

Surface observations at 19Z indicated that light snow had started
across much of central and north- central WI. A little farther
south light rain was being reported in Wautoma. Will continue to
see light snow spread east across the area during the next couple
hours. Rain will likely mix with the snow across east- central WI
were sfc temperatures are warmer in the upper 30s to around 40
degrees. Temps cool off after sunset, with any mixed rain/snow
across the east transitioning to snow aside from right along
Lake Michigan. Precip is being driven by a coupled upper jet and
some weak fgen which will continue to influence the area through
tonight. While there remains plenty of moisture and saturation
through the DGZ, this forcing is weak. Therefore, very minor
changes made to the QPF/snowfall total forecast, with up to an
inch possible across central and northern Wisconsin, and a couple
tenths forecast across east- central WI where more rain will occur.
While amounts are minor, this will still be enough to create some
slick spots on roadways along with lower visibilities. Downstream
obs indicate visibility as low as 1 mile is possible as the snow
moves through.

Tonight...Precip comes to end for most locations between 06Z to
12Z as a sfc high pressure stretches into the area wiping out much
of the moisture, and the forcing shifts south. The exception is
northern Vilas County where northwest winds may create some lake
enhanced snow showers or flurries through mid- morning, and in
far eastern WI where light snow may not end until shortly after
sunrise. With overnight lows in the 20s to lower 30s, it`s
possible area roads remain slippery in spots for the morning
commute.

Monday...Clouds will stick around through the morning with some
breaks possible in the afternoon. As Wisconsin remains situated in
a broad upper trough, cooler temps continue, with highs ranging
from about 32 to 40 degrees tomorrow, which is 10 to 15 degrees
below normal for late October.

.LONG TERM...Monday Night Through Sunday
Issued at 254 PM CDT Sun Oct 25 2020

Main concerns in the extend forecast will be the colder than normal
temperatures through much of the work week.

Monday night through Tuesday night: Yet another trough is expected
to pass through the western Great Lakes Monday night into Tuesday.
At the same time, a stronger surface ridge is expected to build
across the area and linger through much of this time period. The
anticyclonic flow and dry air in place, will keep precipitation-free
conditions across the area. Expect gradual clearing conditions
Monday night into Tuesday. High temperatures are forecast to be
mainly in the 30s with overnight lows into the low teens to low 20s.
A few single digits are possible in the typical cold spots on Monday
night.

Wednesday into Wednesday night: The next/flatter trough axis is
expected to pass through the area during this time period. A cold
front is also forecast to pass through northeast Wisconsin Wednesday
afternoon into Wednesday evening, before shifting to the east
overnight. Moisture looks to be fairly limited, but it is possible
that some light rain/snow showers could develop across the area. If
any precipitation does develop, the best chances would be near the
Upper Peninsula border. At this point, have kept the ongoing dry
forecast. Highs are forecast to be in the upper 30s to mid 40s. Lows
are forecast to be in the low 20s to low 30s.

Rest of the extended: Much of the rest of the forecast period looks
to be fairly quiet overall. Moisture will be fairly limited, so
precipitation chances will be greatly reduced through much of the
extended. Below normal temperatures will linger through Thursday
before a gradual warming trend begins for the end of the work week.
This will be as a western ridge begins to shift east and flatten.
Will stick with a consensus of the models for that time period,
bringing mainly quiet conditions and temperatures warming closer to
normal.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 639 PM CDT Sun Oct 25 2020

Anticipate the current mix of MVFR and IFR conditions to settle in
at primarily MVFR during the evening. Need to see continued
support on radar before introducing another period of IFR
visibilities to E-C WI late tonight.
&&

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

$$

UPDATE.........Skowronski
SHORT TERM.....KLJ
LONG TERM......Cooley
AVIATION.......Skowronski


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