NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 082125
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
325 PM CST Thu Jan 8 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Rain and snow are expected late this afternoon into early Friday
  morning. 2 to 4 inches of snow are expected across north-
  central Wisconsin. Locally higher amounts could occur if switch
  to snow occurs soon than expected. A Winter Weather Advisory has
  been issued tonight for far northern Wisconsin.

- Where rain falls on melting snow and frozen ground and frozen
  rivers there is a potential for minor flooding in low-lying and
  poor drainage areas and also along rivers. There is a potential
  for ice jams as well into the weekend.

- Another system will bring snow Saturday and Saturday night. The
  probabilities for 2 inches of snow is a little lower, ranging
  from 20-40% across central and north-central WI to 40-65% across
  northeast and east-central WI.

&&

.DISCUSSION...
Issued at 324 PM CST Thu Jan 8 2026

Short Term...Tonight and Friday

Surface analysis shows a deepening surface low is currently
lifting just north of the Kansas City metro this afternoon. As
this system continues to track across Iowa and souther Wisconsin
this evening and overnight it will bring periods of moderate to
heavy rain and snow to the forecast area. PWATs with this system
are expected to climb near 1" which would be above the
climatological max for early January. With that there are two
main areas of concern, one being a round of wet snow across far
northern WI. The other being heavy rainfall on a decent snowpack
and frozen ground leading to potential minor urban and low-land
flooding as well minor river flooding and possible ice jams.

Snow chances for northern Wisconsin...

Initial push of WAA will bring light rain the region this evening.
The current track of the low will then place north-central WI
under a strong deformation zone late this evening leading to
dynamic cooling and a transition to snow between about 10PM and
midnight. Low-level temperature profiles are expected to become
nearly isothermal up to about 850mb and hover right around 0C.
This leads to inherent uncertainty with snowfall amounts as a
quicker cooldown would lead to rain changing to snow sooner than
expected and thus increasing amounts. Once rain does change to
snow HREF probs show a 40-60% chance for snow rates to reach 1"
per hour at times through about 4AM. After 4AM snow should start
to end fairly quickly from west to east Friday morning as much
drier air moves into the region. Result is expected to be 2-4" of
wet snow across northern WI, with a few localized areas of 5-6"
possible if the transition to snow occurs earlier than expected.
Depending on how quickly road crews are able to clear the snow
there could be some impacts to the Friday morning commute north of
HWY 8. A Winter Weather Advisory has been posted for far northern
Wisconsin for night through 6AM Friday.

Heavy rain and flood risk for central to northeast WI...

Strong frontogenetic lift on the southern edge of the deformation
zone is expected to overspread a corridor from central WI to far
northeast WI as the low tracks across southern WI tonight. This
will lead to periods of moderate to heavy rainfall (0.25-0.5" per
hour) from about 7PM this evening through early Friday morning.
Along with the strong f-gen modest elevated instability MUCAPE
~100J/kg and steepening lapse rates along fringe of the dry slot
could lead to brief periods of convectively enhances rainfall
rates. Within this corridor total QPF of 0.75 to 1.5" with locally
higher amounts near 2" is expected. With much of this rain falling
on a decent snowpack and frozen ground areas of minor low-land and
urban flooding are expected. Runoff into frozen rivers and streams
may also lead to minor river flooding and possible ice jams as
ice starts to break up. A Flood Watch as been posted for central,
northeast, and east-central WI.

In addition to convectively enhances rain rates the modest
instability along with 45-50kts of deep layer shear a few weak
thunderstorms are possible east of I-41 between 8PM and midnight.
Small hail and a few lightning flashes would be the extend of the
thunderstorm threats.

As the low pulls off to the east Friday morning rain may briefly
transition to snow across central and east-central WI, however,
don't expect much in the way of accumulating snow in these areas.
Precipitation will should start to end from west to east mid
Friday morning.

Long Term...Friday Night Through Thursday

Models continue to vary with the extent of phasing between
northern stream and shortwaves for the Saturday and Saturday night
system. Aloft, the jet streak structure wasn't favorable as the
region was not in the favorable entrance/exit region of the jets
streaks. Also, models QPF are not as high previous runs, thus
expected snowfall amounts are a little lower compared to previous
runs. The latest NBM probabilities for 2 inches of snow are now
only 20-40% across central and north-central WI and 40-65% across
northeast and east- central WI. The probability of 4" was only
20-40% across northeast WI. Looking at the WPC guidance ensemble
guidance for Green Bay, there was two separate clusters for
snowfall amounts. The first cluster was between 2-4 inches while
the second cluster was between 1-2 inches. There were a few
outliers with over 6 inches of snow. Overall, the ensemble mean
was a little over 2 inches. Thus some differences in the final
snowfall totals still exist, and probably will exist up to the day
of the event due to model handling of the phasing of the upper
features.

Beyond the Saturday system, several clipper systems moving southeast
with the mean flow will bring chances of snow or possibly a wintry
mix at times next week. Low confidence in timing and location of
the axis of precipitation due to varying model solution placement
and timing of each feature. Temperatures next week start out
milder than normal, then transitions towards normal or below late
in the week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1208 PM CST Thu Jan 8 2026

Patchy IFR/MVFR fog continues to linger across much of the region
late this morning. Visibilities will continue to improve south of a AUW
to OCQ line, while areas north of that line will be slower to
improve. Flying conditions will deteriorate this evenings as a potent
low pressure system lifts across southern WI. Light rain will
initially spread across much of the region beginning around 21Z.
Periods of heavier rain are expected later this evening and
overnight across central and east-central WI which may cause periods
of MVFR/IFR vsbys. North and west of an RRL to IMT line rain is
expected to transition to snow late tonight into early Friday morning
which will also cause IFR/MVFR vsbys. For ground operations 2-4
inches of accumulations expected across north-central WI. Along with
the precipitation impacts on visibilities IFR/LIFR cigs are expected
this evening through early Friday morning.

As the low moves off the east Friday morning flying conditions should
start to gradually improve. Downsloping northwest winds should help
to scatter out the IFR cigs over east-central WI, however, IFR
conditions may linger through the morning at RHI.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 9 PM this evening to 6 AM CST
Friday for WIZ005-010>013-018.

Flood Watch through Friday morning for WIZ019>022-030-031-
035>039-045-048-049-073-074.
&&

$$

DISCUSSION.....GK/Eckberg
AVIATION.......GK