NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 050811
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
211 AM CST Thu Mar 5 2026

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Only very small precipitation chances through tonight, but this
  includes a possibility of patchy freezing drizzle in northern
  WI tonight.

- Widespread rain (80-100%) impacts the region Friday and Friday
  night, with probabilities of 1 inch or greater rainfall as high
  as 50-80% from central into northeast WI. 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. Cooler weather returns by
  the middle of next week. Warm air flowing across cold ground and
  lingering snowpack (mainly NC/far NE WI) could lead to fog
  development at times, but especially when higher dew points
  arrive Friday into Friday night.

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

&&

.DISCUSSION...
Issued at 211 AM CST Thu Mar 5 2026

Mostly clear skies and light northeast winds were observed across
the forecast area early this morning, with temperatures in the
middle 20s to middle 30s. A large expanse of dense fog and very
low stratus covered NW WI and much of the western Upper Peninsula,
and was slowly expanding toward Vilas County. Showers associated
with a short-wave trough were shifting east over Lower Michigan,
but another batch was approaching from SW IA.

Small Precipitation Chances Expected through Thursday night: The
short-wave over SW IA 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 WI. 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 300-700 j/kg and 700-500 mb lapse rates of 6.5-8.0
C/km) arrives Friday afternoon into Friday night. Forcing for the
inital 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 WI.
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. SPC has expanded the Marginal risk of
severe a bit farther north across the forecast area, so 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 looking more likely that we will get a minor snow
accumulation over far NC WI late Friday night into Saturday
morning. This will occur when a short-wave 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 06Z TAF Issuance
Issued at 1130 PM CST Wed Mar 4 2026

MVFR cigs have lifted into portions of east-central WI late this
evening, which was earlier than expected. As such, have adjusted
the east-central WI TAFs to account for the MVFR cigs through
Thursday evening. Despite the earlier arrival in east-central WI,
there still appears to be agreement with the MVFR cigs reaching
the central WI TAF sites around 12z Thu. Meanwhile, across the
north, an area of fog/very low stratus has struggled to move into
north-central WI this evening. Anticipate these low vsbys/cigs,
possibly as low as 1/4 mile, to still reach the RHI TAF site, but
will be more brief than previously forecast, lasting around 3-4
hours around 12z Thu. IFR cigs are then anticipated after 00z Fri
across all TAF sites.

Isolated light rain showers may move over the MTW site Thursday
morning through the afternoon. Given the isolated nature, included
PROB30s when confidence is greatest.

Winds will remain light and variable through the night, turning
east or northeast Thursday morning and continuing through the end
of this TAF period.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kruk