Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 100455
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1055 PM CST Fri Dec 9 2022

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 925 PM CST Fri Dec 9 2022

Light snow and drizzle are redeveloping upstream from southeast
Minnesota to Sheboygan. As low level flow below 800mb gradually veers
around to the southeast through the night, think will see the
light precip gradually edge north into central and east-central WI
late this evening into overnight. Updated pops to reflect the
earlier return of the light precip. Surface dewpoint depressions
are much lower south and west of the area, and while they will
edge up some overnight, they might limit coverage and impacts
during the coldest point of the day. Also raised min temps over
north-central WI where temps should remain steady or rise a degree
or two through the night.
&&

.SHORT TERM...Tonight and Saturday
Issued at 356 PM CST Fri Dec 9 2022

Precipitation trends and types for Saturday are the main focus from
this forecast period. Slightly above normal temperatures are also
anticipated during this forecast period.

Late this afternoon, clouds prevailed across the region, with the
exception in far north-central WI, as a result of a low pressure
system moving across Illinois. While snow showers were reported to
the north of this system in southern WI, no precipitation was
reported across the forecast area due to the amount of dry air in
the low to mid-levels. Overnight, moisture will gradually increase
in these levels causing cloud cover to thicken. The clouds will keep
low temperatures above normal with readings ranging from the low 20s
to the low 30s.

An upper-level trough will move across the Upper Mississippi Valley
on Saturday and bring a mix of precipitation. Due to a lack in
moisture in the mid to upper-levels, a mix of freezing drizzle and
snow is expected across central, north-central, and far northeast
WI, with drizzle in east-central WI. A brief period of freezing
drizzle may mix in with the drizzle in east-central WI during the
morning as well. Light snow accumulations up to an inch are possible
in central and north-central WI through late Saturday afternoon. A
light glaze is also possible in these locations. Untreated roads and
surfaces may become slick at times. High temperatures on Saturday
will be in the low to middle 30s.

.LONG TERM...Saturday Night Through Friday
Issued at 356 PM CST Fri Dec 9 2022

A mix of freezing drizzle, drizzle, and light snow will continue
across the region Saturday night and end from west to east as the
mid level trough moves through the western Great Lakes region.
Model soundings continue to show mid level dry air in place, which
will limit ice nuclei at times hence the freezing drizzle and
drizzle. The setting of the sun will increase the impact of the
freezing drizzle as roads could become slick Saturday night. For
areas that receive more snow a few tenths of an inch could fall,
mainly across the north.

High pressure will then keep the forecast area dry from Sunday
through the early part of next week with temperatures a few
degrees warmer than normal for this time of year.

Attention then turns to the large wound up system taking aim for
the area during the middle of next week. While models have pretty
much been all over the place regarding the track of the low,
recent 12Z NWP models seem to be in a bit better agreement
regarding the low track. The current model suite takes the low
from the central Plains Monday night, slowly track it east
through Iowa Wednesday, south of the area on Thursday, and finally
off to the east on Friday. This slow moving system will bring a
prolonged period of wintry weather to the region during the middle
part of next week as it tracks to the south.

Despite the better model consensus, there are still several
questions regarding how this system will play out across the area
next week. The first is timing as the models indicate that Tuesday
will most likely be dry as the system tracks a bit slower than
previously forecast. The second will be how far north the warm
sector makes it into Wisconsin, which will make a huge difference
in snowfall amounts. At this point northern Wisconsin looks mostly
likely to receive the most amount of snow, with lesser amounts
across central and east-central Wisconsin where more mixed
precipitation will occur. However, a small shift in the track of
the low would still put this area in the bullseye of heavy snow.
Given the model trends of moving the track of this low around
quite a bit from run to run any scenario is not out of the
question quite yet. The main take home message is anyone with
travel plans during the middle part of next week will need to
monitor this system closely, as it has the potential to be
impactful for the upper Midwest region.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1055 PM CST Fri Dec 9 2022

Between systems, widespread MVFR cigs prevail across northeast
Wisconsin late this evening. It remains expected that MVFR cigs
will slowly lower to IFR by late tonight into Saturday morning
across the region.

Considerably more uncertainty revolves around timing the next
round of precip into northeast WI. Light snow and freezing
drizzle is developing quicker across Minnesota and southwest
Wisconsin than expected. So it remains possible that a very light
wintry mix could move into central WI and east-central as early
as early overnight and to far northeast WI by early afternoon.
Vsbys are expected to fall to IFR in the snow/drizzle or freezing
drizzle. Very minor snow and ice accumulations are possible on
Saturday morning before temps warm to near or above freezing on
Saturday afternoon. Pavement temps are expected to warm above
freezing by 10 am, which will mitigate impacts of frozen precip on
runways. The light precip should gradually end on Saturday
evening.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE.........MPC
SHORT TERM.....Kruk
LONG TERM......Kurimski
AVIATION.......MPC


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