Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 221144
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
544 AM CST Wed Jan 22 2020

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 341 AM CST Wed Jan 22 2020

Gulf moisture was streaming northeast with the help of a 40 to 50
knot jet at 850 mb and 700 mb. This moisture will move into
north-central Wisconsin this morning and into central and far
northeast Wisconsin during the afternoon. At the same time the
right entrance region of an upper jet will produce vertical motion
across central through northeast Wisconsin. This combination
should result in light snow, possibly mixed with freezing drizzle
or sleet at the start. The snow will probably not arrive in east
central Wisconsin until late this afternoon or evening due to
remaining dry air in the mid levels.

Snow is expected across the entire area tonight and Thursday, though
weak low level warm advection and only modest upper support will keep
snow accumulations down from what they could be. Two to three inches
are possible in the twenty four hour period from this morning through
Thursday morning over most of the area. East-central Wisconsin
should be the exception with only an inch or so. Roads and
sidewalks will become slick later today through Thursday.

Temperatures will be mild, averaging 5 to 10 degrees above normal
during the daytime and about 20 degrees above normal at night.

.LONG TERM...Thursday Night Through Tuesday
Issued at 341 AM CST Wed Jan 22 2020

The main concern for the extended forecast is the continuation of
the unsettled pattern bringing snow and a mix of rain and snow to
the region through Saturday.

Thursday night through Friday night...An upper-level trough, with
a cut- off low, will meet up with a surface low pressure system
over the Middle Mississippi Valley Thursday night. Wisconsin will
have already seen some precipitation, mainly in the form of snow
on Thursday, due to the southerly flow pulling Gulf moisture into
the region ahead of the trough. With the moisture and mean flow
remaining nearly stationary into Thursday night, the light snow is
expected to continue across the forecast area. Throughout Friday,
both the upper-level cut-off low and the surface low will move
into the Ohio River Valley. The combination of the Gulf moisture
continuing to swirl over the Midwest and the systems staying to
the south of the region will keep periods of light snow across the
forecast area into Friday night. Since the southerly flow will
allow daytime temperatures to rise above freezing, it is possible
for a rain/snow mix at times as well on Friday, mainly across
central and east-central Wisconsin. By Saturday morning, it is
possible for some light snow or flurries to linger across eastern
Wisconsin before the low pressure systems move over the Northeast
U.S. Most locations will see additional snow accumulations of 1 to
2 inches between Thursday night and early Saturday morning.

Rest of the extended...With the cut-off low over the Northeastern
U.S., a broad upper-level ridge will build over the Upper
Mississippi Valley as a surface high slides across the Middle
Mississippi Valley Saturday into Sunday. This will keep quiet
conditions and above normal temperatures in the forecast for the
weekend. Model guidance shows some indications of a weak upper-
level disturbance moving over the western Great Lakes sometime
between Sunday night and Monday. Since the models do not have a
good handle on this upper-level disturbance, kept dry conditions
in the forecast for now. For Tuesday, there are some signs of
upper-level ridging building over the Upper Mississippi Valley
ahead of more significant system. However, models are not in
agreement with the timing or track of this system.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 544 AM CST Wed Jan 22 2020

Moisture moving northward from the Plains states will cause ceilings
to lower from west to east today and tonight. Along with the lower
ceilings will come light snow, possibly mixed with a little freezing
drizzle. IFR conditions are likely west of a STE to IMT line by afternoon,
with MVFR or VFR conditions further east. IFR conditions are expected
across the entire area tonight and Thursday with light snow.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......Hykin
AVIATION.......RDM


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