990
FXUS63 KGRB 051803
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1203 PM CST Thu Mar 5 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Patchy freezing drizzle possible in northern Wisconsin tonight.

- Widespread rain (80-100%) impacts the region Friday and Friday
  night, with probabilities of 1 inch or greater rainfall as high
  as 50-85% from central into northeast Wisconsin.

- Thunderstorms possible Friday afternoon and Friday night,
  especially south and east. Heavy rainfall and a few strong
  storms with hail and gusty winds. Localized flooding possible.

- Mild, with highs in the 40s and 50s most days. Temperatures may
  reach into the 60s Sunday into Monday.

- Warmer weather may lead to ice breakup on rivers, resulting in
  ice jam flooding. Ice floes could also be a concern, especially
  Friday into Friday night, and Sunday into Monday.

&&

.DISCUSSION...
Issued at 1202 PM CST Thu Mar 5 2026

Small Precipitation Chances Expected tonight:

A shortwave near the Wisconsin/Illinois border, evident on water
vapor satellite imagery, will lift northeast, bringing a chance
of light rain to our southeast counties this afternoon and early
evening. Increasing WAA/isentropic lift and deepening moisture may
also lead to patchy drizzle tonight, with freezing drizzle
possible over parts of far northern Wisconsin. Locally slippery
travel conditions may develop later tonight. Widespread low
stratus and fog is also expected.

Friday/Saturday System with Thunder/Heavy Rainfall Potential:

The main system of concern will impact the area Friday into
Saturday morning as a strong low pressure system moves from the
central Plains to the western Great Lakes. Rain is the main
concern in the mild air mass, with thunder expected as elevated
instability (MUCAPE of 500-1000 j/kg and 700-500 mb lapse rates
of 6.5-8.0 C/km) arrives Friday afternoon into Friday night.
Forcing for the initial surge of widespread moderate to heavy on
Friday will be provided by strong WAA/isentropic lift on the nose
of a 35-45 knot low-level jet, and the passage of an 850 mb warm
front. An additional period of significant rainfall should develop
as the surface low lifts northeast along the cold front Friday
night. PWATs surging to 1.0-1.3 inches across the southeast half
of the forecast area, combined with convective potential, will
lead to pockets of heavy rainfall. NBM probabilities for amounts
in excess of an inch are highest (50-80%) from central into
northeast Wisconsin. The area could see minor flooding impacts
due to runoff from frozen ground, especially in conjunction with
any ice jam flooding that may be ongoing by that time.

There is a marginal risk of severe weather across the southern
half of the forecast area; therefore, cannot rule out some hail or
brief gusty winds with any stronger storms, especially Friday
night. CIPS analogs support a severe risk as far north as the Fox
Valley, along with rainfall amounts of 0.75-1.25 inches. As a
reminder that we`re still in the winter season, it is possible
that we will get a minor snow accumulation over far north-central
Wisconsin Saturday morning. This will occur when a shortwave
trough moves through and colder air arrives. Probabilistic
forecasts only show a 10-20% chance of 1+ inch of snow in Vilas
County, though would not be surprised to see a bit higher amounts
than that.

A generally dry period is expected from Saturday afternoon
through Monday night. Breezy southwest winds on Sunday and Monday
will bring very mild temperatures, with readings in the 60s in
our typical warm spots.

Another low pressure system arrives Tuesday and Tuesday night,
but models have large differences in the track, which will
greatly impact temperatures and precipitation type. The
differences between 25th and 75th percentile max temps are quite
striking; showing highs potentially ranging from as cold as the
middle 30s north to as high as the lower to middle 70s south.
Once this system departs, colder air will return temperatures to
near normal by the middle of next week.

Fog potential increases later this week as rising dew points and
melting snow add low-level moisture. The greatest potential
should occur as much higher dew points arrive Friday into Friday
night. Fog development will be most favored over the northwest
half of the forecast area, especially NC and far NE WI, where a
deep snowpack remains.

Ice Jam/Ice Floe Potential:

In addition to the previously mentioned potential for runoff
flooding from heavy rainfall with the Friday/Friday night system,
there is a lesser threat of ice jam flooding. The ice jam threat
should gradually increase by the weekend as warmer temperatures
promote some ice break-up. The ice jam threat will be reduced a
bit due to low water levels, though this may change after the
expected heavy rainfall Friday and Friday night. An increased
threat of ice floes on Green Bay could also develop, especially
Friday into Friday night, and again Sunday into Monday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1202 PM CST Thu Mar 5 2026

Low clouds and stratus across north-central Wisconsin has moved
north and west of the region this morning. Meanwhile, MVFR stratus
across southern Wisconsin have advected northward across central
and east-central Wisconsin as a low pressure system tracks well to
our south. This stratus will continue to move north this afternoon
and into this evening. Some isolated (~20% chance) showers will
be possible near KMTW this afternoon. Some patchy drizzle or
freezing drizzle across the north this evening should form
regionwide tonight. Fog will accompany the low stratus, but it is
not clear how low VSBYs will get overnight. An area of showers
will advect in from the southwest Friday morning ahead of an
approaching warm front with a high chance (50 to 80%) of affecting
the TAF sites.

East to northeast winds around 10 knots this afternoon will veer
east to southeast this evening and become southeast 10 to 15
knots Friday morning.

&&

.FIRE WEATHER...
Issued at 1202 PM CST Thu Mar 5 2026

Dry and mild conditions are expected across the region Sunday and
Monday along with gusty winds could cause elevated fire weather
conditions. Temperatures are expected to rise into the 50s and 60s
both days, with the highest temperatures expected on Monday. Dry
dew points could cause relative humidities to fall to 30 percent
or lower during the afternoon on both days. In addition, southwest
winds will gust up to 30 mph on Sunday and 20 mph on Monday. The
combination of dry, mild, and windy conditions could lead to
elevated fire weather conditions across the area Sunday into
Monday. The mitigating factor will be fuels, as recent rainfall
will mean fuels should be fairly wet.

&&

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

&&

$$

DISCUSSION.....Kurimski
AVIATION.......Kurimski
FIRE WEATHER...Kurimski

NWS GRB Office Area Forecast Discussion