214
FXUS63 KGRB 091735
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1235 PM CDT Thu Apr 9 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Light rain and a brief wintry mix are possible late this evening
  and tonight.

- Periods of heavy rainfall and thunderstorms expected late this
  weekend through the middle of next week. There is a 60-80%
  chance of rainfall greater than 1 inch from Saturday night
  through Tuesday night.

- Strong or severe thunderstorms possible Monday afternoon and
  evening.

- Minor flooding continues along the Wolf River, though runoff from
  melting snow in the Upper Peninsula paired with heavy rain may
  result in more widespread and significant flooding late this
  weekend into next week.

&&

.DISCUSSION...
Issued at 1234 PM CDT Thu Apr 9 2026

The latest RAP analysis and satellite imagery show a cold front
draped across the central Plains to central Illinois early this
afternoon. Cold advection is occurring north of the front across
northern Wisconsin. Shallow stratocumulus clouds pushed as far
southeast as central WI late this morning, but these clouds are
expected to mix out and retreat north through the afternoon.
Meanwhile, mid and high clouds will increase from the west ahead
of the next shortwave trough currently moving across northeast
Montana. This system is poised to bring the next chance of
precipitation to the region late this evening into tonight.

Precipitation chances are the main forecast concern in the short
term. Flow aloft will back and push an elevated front into
southern Wisconsin this evening. While the heaviest precipitation
will occur south of the area, mid-level convergence and
frontogenesis will support sufficient lift for light precipitation
from mid-evening through late overnight. A light wintry mix may
occur on the back edge of the precip as temperatures fall into the
middle 30s. A dusting is possible on grassy surfaces, but little
to no accumulation is expected. Clouds will be slow to depart on
Friday morning, but expect drier air and mixing to gradually erode
the clouds on Friday afternoon. High pressure will be centered
across the region Friday night before sliding east, allowing for a
brief period of quiet weather.

An amplifying upper level pattern will drive a strong frontal
system across the Midwest late this weekend into early next week,
leading to widespread precipitation chances. Return flow and
strong moisture advection will bring rain into central WI by late
Saturday afternoon, spreading across the rest of the region
Saturday night. Precipitable water values are forecast to reach
the 99th percentile by Sunday morning as a 50 kt low level jet
impinges on the area. These ingredients favor widespread showers
and thunderstorms. But with instability only 200-400 j/kg on
Saturday night into Sunday morning, the chances of severe weather
looks low. A relatively lull in the precipitation looks possible
for the second half of Sunday through Monday morning.

The period from Monday afternoon into Monday night bears the most
watching for severe weather potential. A cold front will sag into
the state from the northwest on Monday, following a brief lull in
activity Sunday night. Instability is forecast to surge upwards
of 1000 J/kg combined with deep layer shear of 40-50 kts. Tuesday
also bears scrutiny as an instability reservoir remains in close
proximity to the region. While predictability regarding specific
details remains below normal at this range, the combination of
height falls and a passing surface wave should support organized
convection. Showers may linger into Wednesday as the system
eventually departs.

Given the high moisture content and multiple rounds of rain,
there is a 60-80 percent chance of rainfall greater than 1 inch,
and a 20-40 percent chance of greater than 2 inches from Saturday
night through Tuesday night. This potential for heavy rainfall
will lead to an increase in river flooding potential, especially
with ongoing elevated water levels on area rivers.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1234 PM CDT Thu Apr 9 2026

Low end VFR fair weather clouds remain present across the region
early this afternoon. With further daytime heating and mixing,
these ceilings should continue to rise and retreat north. Mid and
high clouds will increase toward sunset ahead of the next system.

A shortwave trough will bring a chance for light precipitation
from west to east late this evening through the overnight hours.
Light rain is expected for the Fox Valley and Lakeshore terminals,
while a light wintry mix of rain and snow is possible for AUW,
CWA, and RHI. Flight conditions are expected to deteriorate to
MVFR ceilings within the precipitation. Brief MVFR visibilities
(30-50% chance) as well as IFR ceilings are possible late tonight
at RHI.

MVFR ceilings will linger into Friday morning after the
precipitation ends. A gradual return to VFR is expected after the
TAF period ends Friday as dry air moves into the region. Winds
will remain out of the west to northwest through this afternoon,
with occasional gusts to 20 kts, subsiding tonight.

Confidence is high regarding the development of MVFR ceilings
tonight, but lower regarding the development of MVFR visibilities
and IFR ceilings.

Outlook...VFR Friday evening through Saturday morning. Widespread
rain and a few thunderstorms with MVFR/IFR conditions likely
Saturday night through Sunday.

&&

.HYDROLOGY...
Issued at 1234 PM CDT Thu Apr 9 2026

No significant changes to the previous forecasters thoughts. Minor
flooding continues on the Wolf River early this afternoon. A
mainly dry period is anticipated through Saturday, with the
exception of light rain over parts of central and east central WI
tonight. Periods of heavy rain and thunderstorms arrive later in
the weekend and continue through the middle of next week. During
this upcoming period, probabilities for rainfall in excess of 1
inch are 60-80%, with a 20-40% chance of amounts in excess of 2
inches and a 5-15% chance of 3 inches or more. Current forecasts
call for 1.5 to 2 inches in most areas. Runoff from this rainfall,
combined with rapid snowmelt in the Upper Peninsula and far
northern WI, is expected to bring potential for more widespread
and significant flooding heading into the early to middle part of
next week. Right now, it appears the most significant flooding
impacts may occur on the Menominee River and its tributaries.

&&

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

&&

$$

DISCUSSION.....MPC
AVIATION.......MPC
HYDROLOGY......MPC

NWS GRB Office Area Forecast Discussion