272
FXUS63 KGRB 140415
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1115 PM CDT Fri Mar 13 2026

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 929 PM CDT Fri Mar 13 2026

Winter Storm Warnings continue for the area from Saturday night
through Monday afternoon. The following changes were made to the
headlines.

- Our southern two tiers of counties were split off to deliniate
  the higher potential for a mixture of sleet, freezing rain or
  rain for a period from late Saturday night into Sunday evening.
  Given the potential for mixed precipitation, snowfall amounts
  will likely not be as high as locations farther north, though
  totals may still reach 12-18 inches. Most of the snow in these
  areas should occur Saturday evening into the early overnight,
  and late Sunday night into Monday.

- Tightened snowfall ranges up to 18 to 24 inches with locally
  higher amounts for areas north of Hwy 29. Highest amounts look
  to occur in far northeast WI, where totals could reach 30
  inches.

- Still not ready to pull the trigger on a Blizzard Warning, as
  conditions probably won`t warrant it in most areas until Sunday
  afternoon.

- Updated WSW has been issued.

&&

.KEY MESSAGES...

- A major winter storm will impact the region late Saturday
  through Monday with widespread snow/ice with significant
  travel impacts. Winds gusting 35 to 45 mph could lead to
  blizzard or near blizzard conditions late Sunday into Monday
  with power outages and some tree damage.

- Although widespread impacts are expected across the region,
  recent trends have supported a slightly farther north
  placement of the highest snow amounts, with increasing
  potential for some mixed precipitation in parts of the Fox
  Valley on Saturday night into Sunday. The exact track will
  impact where highest snow amounts occur.

- Colder conditions early in the week (wind chills below zero
  at times) will gradually moderate through the week.

&&

.DISCUSSION...
Issued at 240 PM CDT Fri Mar 13 2026

This afternoon-Tonight:

A strong surface low across northern Lake Michigan continues to pass
eastward this afternoon with some lingering light snow over
north-central WI. Low- level cold advection and strong 850 mb
wind core has resulted in gusty northwest winds, in excess of 45
mph gusts across parts of central into east-central WI. Winds
will gradually diminish through the evening.

Saturday-Monday: Major, Potentially Record-setting Winter Storm

Confidence remains high for a major, long duration winter storm to
impact the region late Saturday, persisting through Monday.
Synoptically, a trough mid-level trough will roll eastward across
the Midwest with a surface low lifting across the western Great
Lakes on Monday with a tight pressure gradient setting up
between the low and a 1030 mb high nosing into the plains.

This will be a long duration event with initial warm advection
precip developing on Saturday night into Sunday before the
deformation zone precip shield wraps across the area Sunday night
into Monday. Ultimately, given the long-duration event and
likelihood for 1 to 3 inch snow rates at times within the
heaviest snow, a band of high end record type snowfall remains
on the table. However, of note from recent model trends has
been a northward nudge of solutions with the low track, with
some ensemble members taking a track as far north as southern
Wisconsin. The effect of a more northern track would be for
increased rain/sleet/freezing rain potential across central
Wisconsin Saturday night into Sunday before colder air wraps in
behind the low. This also nudges the favored area for highest
into northern Wisconsin. Thus, confidence in snow amounts is
lowest in this transition area, pending the ultimate track of
the low.

However, all areas will transition back to snow by Sunday evening
into Monday as the low pulls east and colder air wraps in. Winds
will increase through the day Sunday, with gusts of 40+ mph likely
at times Sunday afternoon through Monday. As colder air moves in,
the wetter snow character will trend drier. The combination of
strong, gusty winds with the falling snow may lead to whiteout
conditions and potential blizzard conditions especially late
Sunday into Monday.

Probabilities remain quite high for a band of over 12 inches (60-
90%), right now highest across northern Wisconsin with even 60-80%
probabilities for over 18 inches across northern Wisconsin. The
intense rates at times will cause widespread travel impacts,
while snow load will likely result in some power outages/downed
tree limbs, in concert with the strong winds. Again, though,
small shifts in track will impact where band of highest amounts
occur.

For now, upgraded the Winter Storm Watch to a Winter Storm Warning
area-wide beginning Saturday night. Some adjustments likely will be
needed through the weekend, with a consideration that upgrades to
Blizzard Warnings could be needed for at least parts of the area as
winds begin to ramp up. It`s important to note that this winter
storm will bring widespread impacts over a longer duration, with
variable impacts throughout the period. Even areas that may receive
mixed precipitation or possibly some rain will transition back to
snow. These details will be refined through the start of the
weekend.

Tuesday-Friday:

Broad northwesterly flow will be in place through the remainder of
week with a trend towards moderating temperatures. However, Monday
night lows in the single digits combined with gusty winds may yield
wind chills as low as 10 to 20 below zero. The moderating trend may
be slowed a bit by the snow cover that likely will be in place.

A progressive shortwave trough may bring some light snow for mid-
week (40-60%), but overall impacts appear minor.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1104 PM CDT Fri Mar 13 2026

Expect low clouds to continue to erode over the forecast early in
the TAF period, with patchy high clouds anticipated into Saturday
morning. Clouds will thicken Saturday afternoon, with light snow
or flurries developing in the southwest part of the forecast area
by sunset, then spreading northeast during the evening. The snow
will become heavier during the mid to late evening, with vsbys
dropping to IFR/LIFR in most places.

Light northwest winds will become light and variable overnight
into Saturday morning, with SE-E winds gradually increasing to 5
to 15 kts in the afternoon and evening.

Attention turns to the major winter storm Saturday night through
Monday. Heavy snow and strong winds are expected regionwide. A
wintry mix will develop from late Saturday night into Sunday
across central and east-central WI before transitioning back to
snow Sunday night. Over a foot of snow is likely, with some
locations in northern WI receiving over 2 feet. A light glaze of
icing is possible across central and east-central WI, including
the Fox Valley and lakeshore region late Saturday night and
Sunday. Strong wind gusts over 35 knots are likely Sunday afternon
through Monday, with gusts up to 45 knots possible. This may
result in blizzard conditions in some areas. Air travel will be
severely impacted regionwide, with airport closures likely at
times.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 1 AM Sunday to 4 PM CDT Monday for
WIZ005-010>013-021-073.

Winter Storm Warning from 7 PM Saturday to 4 PM CDT Monday for
WIZ018>020-022-030-031-035>040-045-048>050-074.
&&

$$

UPDATE.........Kieckbusch
DISCUSSION.....JM
AVIATION.......Kieckbusch

NWS GRB Office Area Forecast Discussion