Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 222021
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
321 PM CDT Fri Mar 22 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Snow showers, flurries and drizzle will come to an end late this
  afternoon and evening. Little to no impacts expected on roads.

- There is a 50 to 90% chance of at least 4 inches of snow
  accumulations across areas northwest of the Fox Valley.
  Confidence on these percentages is highest in north-central WI,
  but decreases as you approach the Fox Valley. In other words, a
  fairly sharp gradient in the highest snowfall amounts is
  possible and its location is not yet clear.

&&

.DISCUSSION...
Issued at 320 PM CDT Fri Mar 22 2024

Short Term...Tonight and Saturday

Very persistent FGEN band stretching from near Shawano to
Marinette has finally started to weaken early this afternoon. The
FGEN will continue slowly weaken through the evening, but will
combine with a weak trough/shortwave dropping across northeast WI,
keeping the flurry and snow shower activity going through the
evening hours. Some drizzle/freezing drizzle is also occurring on
the southern side of the FGEN band and better DGZ, where we lost
the mid-level moisture. Will add some drizzle for parts of east
central WI late this afternoon. This activity will end overnight
as these features exit the area. As winds turn NNW over Lake
Superior later tonight, lake effect clouds and possibly a flurry
could make it into far north central WI as well. Continued to lean
towards the colder guidance tonight as we have fresh snow cover
over most locations. Where clouds clear, a few spots could drop to
around 0. Most other spots will see lows in the single digits and
teens, with slightly warmer readings near Lake Michigan.

For Saturday...dry conditions are expected as weak high pressure
slides into the western Great Lakes. Expecting some sunshine to
start the day, then clouds look to increase in the later morning
and afternoon. Highs will range from the upper 20s and low 30s in
north central WI to the mid to possibly upper 30s in central and
eastern WI.

Long Term...Saturday Night Through Friday

The main focus in the extended period will be the next wintry
system Sunday through Monday, which will bring impactful snow to
the western Great Lakes.

Saturday night through Monday...

Ensemble forecasts have deviated little from previous forecasts
and remain in good agreement in bringing a strong cyclonic system
northeastwards into the western Great Lakes starting Saturday
night into Sunday. Strengthening winds and strong warm air
advection will bring light precipitation into the region as early
as Sunday morning, before increasing fgen and divergence aloft
work to intensify and expand ongoing precipitation across the
area Sunday evening and overnight. This overnight period will be
the main timeframe to watch for wintry impacts, as the strong
surge of warmer air will be accompanied by unseasonably high
moisture content. Probabilistic PWATs support at least 0.60 inches
of water content (60%+) for much of central to north-central
Wisconsin during the overnight period. Snow will be the dominant
precipitation type during this period as well, with most
soundings showing air temperatures through around 700mb holding
around -10 to 0 Celsius. Taken together, this supports the
continued high probability (60-80%) of 6 inches of snow or more
in north-central Wisconsin. Winds during this time will also be
problematic, with gusts up to 25 to 30 mph possible, which may
make for some blowing or drifting for any snowfall. Therefore,
confidence in the need for future winter headlines continues to
grow. The main question left for this period will be where the
gradient of snowfall sets up to the south of this area, as the
surge of warmer air and moisture will be mainly stretched across
the north with the better fgen, and ptype will see an earlier
transition to rain further south.

As we get into Monday afternoon, most of the area will switch over
to rain. There are also some hints of the dry slot wrapping in
from the southwest sometime late on Monday, which could make for a
drier period in the day.

Rest of the forecast...
The cyclone bringing all the above weather will transition off to
the north and east through the day Tuesday. The colder air coming
back in behind this system will make for a transition to snow
again, but any additional snow will be fairly light and lack the
forcing and moisture to produce significant impacts. Quieter
conditions then return to the region for the middle of next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1242 PM CDT Fri Mar 22 2024

A mix of high-end IFR and MVFR/VFR conditions will continue into
the early afternoon hours as light snow and flurries continue
across much of the area. Look for the snow activity to wane
during the late afternoon and evening, with skies clearing in the
evening and VFR conditions returning by Saturday morning. Winds
will be generally out of the north and remain on the light side.

&&

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

&&

$$

DISCUSSION.....Bersch/Uhlmann
AVIATION.......Bersch


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