624
FXUS63 KGRB 200503
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1103 PM CST Fri Dec 19 2025

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 954 PM CST Fri Dec 19 2025

Snow that initially moved in this evening ahead of the clipper
over the northern Plains fell apart as it ran into very dry air.
Second batch of snow is developing ahead of the warm front tied to
the low. No big changes to the more steady snow that will move
into northern WI overnight into Saturday morning. This is where
the greatest chance of seeing a couple inches of fresh snow will
occur. Recent models still on board with that idea.

Farther south, though limited moisture and forcing will lead to
very light precip, the ptype could be a problem either due to warm
nose aloft and/or ice stripping out aloft, leading to light
freezing rain/drizzle. Overall, QPF will remain quite low except
over far northern WI. 00z HREF shows this with chances of seeing
over 0.01 over cntrl and southern areas (south of highway 29) only
20-40%. However chances of seeing trace amounts rise up to 60%. If
this precip falls as sleet or freezing rain, then given cleared
roads and temps in the low to mid 20s with pavement temps around
20, we could see icy conditions form. It is all very conditional,
and will be a near term forecast situation to see how it evolves
later tonight. Did have enough confidence to put mention in updated
HWO and we`ll also continue to carry a mention in our social media
messaging.

Most favored timing for wintry mix would be from 4 am to 8 am
with any lingering precip beyond that switching back to snow
through 10-11a before it comes to an end.

&&

.KEY MESSAGES...

- Light snow possible late tonight into Saturday morning.
  Accumulations will largely be focused towards north-central
  Wisconsin, with a dusting possible across central and east-
  central Wisconsin.

- Westerly gales are expected late Saturday afternoon into
  Saturday evening.

&&

.DISCUSSION...
Issued at 226 PM CST Fri Dec 19 2025

Another clipper system is set to track through the northern Great
Lakes tonight through Saturday. Winds aloft will be on the
increase again through the lower to mid levels as a push of warmer
air arrives, but only a few gusts should mix down through around
midnight. As the cold air swings through with the main portion of
the clipper, fairly decent frontogenetic forcing should bring snow
into north-central Wisconsin. This feature is mainly focused
across the border along the Upper Peninsula, but cold air
advection over the rest of the region will likely suffice for at
least some flurries or light snow. Still, snow amounts around a
couple inches will largely be focused towards Vilas County, with
amounts tapering to around an inch by the time you get to a line
from Rhinelander to Iron Mountain, and lesser amounts further
south. Probabilistic guidance indicates areas south of a line from
Merrill to Marinette to Sturgeon Bay have less than a 20% chance
of exceeding an inch of snowfall, with less than a 10% chance of
exceeding 2 inches across much of north-central Wisconsin, save
for far northern Vilas County.

Next round of precipitation is then in the forecast for late Sunday
night into Monday evening. Although again precipitation amounts
will be light, this may yet be another period that bears watching
for mixed precipitation or freezing drizzle as a warm layer will
be in the area which may hamper ice production to a relatively
colder surface. Where the warmer air lines up as we get closer
will drive the precipitation type for this feature and the
impacts.

Temperatures for the period will see a couple swings through the
first few days of the forecast, with highs mainly in the teens
today and Sunday, but in the upper 20s to lower 30s on Saturday.
Then highs steady out for much of the middle of next week, with
highs mainly lingering in the upper 20s to middle 30s.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1102 PM CST Fri Dec 19 2025

A few flurries may occur from the mid clouds over north-central
WI into the early overnight. Otherwise, a round of light snow is
expected to develop late tonight into Saturday morning as a cold
front crosses the region. Conditions could drop to MVFR with the
snow, especially across north-central Wisconsin. Snowfall amounts
should generally be light, with a dusting south of KRHI and an
inch or two over far northern WI. Patchy freezing drizzle or sleet
could occur south of highway 29. Not enough confidence to include
in ATW or MTW, but those are the sites that would have the greatest
risk.

LLWS is expected through Saturday at times as southwest winds
increase to 30-40 kts just above the lighter surface winds from
the south. Conditions rapidly improve behind the cold front
Saturday afternoon as clouds scatter out. LLWS will gradually end,
but west surface winds will gust to 25-30 kts at all TAF sites.

&&

.MARINE...
Issued at 226 PM CST Fri Dec 19 2025

Strong southerly winds will build across Lake Michigan tonight,
with a few gale force gusts possible; however, a long enough
period of gales is not expected to upgrade to a Gale Warning. Gale
force winds are expected across all areas late Saturday afternoon
into Saturday evening with cold air advection bringing gusty
winds to the surface. The Gale Watch has been upgraded to a Gale
Warning for the waters during this period.

&&

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

&&

$$

UPDATE.........JLA
DISCUSSION.....Kurimski
AVIATION.......JLA
MARINE.........Kurimski

NWS GRB Office Area Forecast Discussion