NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 161648
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1148 AM CDT Thu Apr 16 2026

.KEY MESSAGES...

-Minor to major flooding is ongoing or forecast to occur on
 several rivers. Expect many rivers to continue rising into this
 weekend, with the greatest impacts expected on the Menominee and
 Wolf Rivers where major or record breaking flooding has been
 observed.

-Severe thunderstorm risk is increasing for Friday evening.
 Strongest storms are expected across central and north-central WI
 with all severe hazards possible.

-Thunderstorms Friday will produce locally heavy rainfall. If this
 occurs over the flood sensitive areas of central and east-central
 WI flood concerns may be exacerbated.

-Beginning Sunday a prolonged period of mostly dry weather is
 expected through at least the middle of next week.

&&

.DISCUSSION...
Issued at 217 AM CDT Thu Apr 16 2026

Short Term...Today...Tonight...and Friday

Today...

Widespread dense fog this morning will begin to dissipate after 8-9
AM with most of the fog cleared out by 10 AM. A few scattered
showers may also develop across central and east-central WI early
this morning along a stalled boundary that is snaked from Green Bay
back toward southwest WI. There may be a few rumbles of thunder, but
no stronger storms are expected. Will need to watch precipitation
rates as these showers pass over the flood sensitive areas of
central and east-central WI, but based on upstream treads don't
expect this round of precipitation to exacerbate ongoing flooding.
Any lingering precipitation should clear out early this afternoon as
a ridge builds in. This will leave dry conditions across the region
for the remainder of the day.

Severe Thunderstorms and Heavy Rain Potential Friday...

Beneath a stout cap a highly unstable airmass will be building
during the day Friday. Southerly winds will usher in a tough of 60+
dew points as far north as HWY 8 along with temperatures well into
the 70s away from Lake Michigan. A plume of 7-8 C/km mid-level lapse
rates associated with an EML will also be overspreading the region
at this time. This will result in an increase of surface based
instability to around 2000 J/kg late Friday afternoon. Forecast
soundings from across central WI also show strong low and deep layer
shear across the warm sector with 40-45 kts in the 0-6km layer and
25-30kts in the 0-1km layer. As the cap erodes late in the afternoon
isolated discrete super cells  may be able to initiate across
central WI within an area of subtly convergent surface winds. Any
storms that do develop within the warm sector will pose a large hail
(1-2") and tornado risk. Stronger and more widespread forcing will
then arrive between about 5-6 PM as a sharp cold front and upper
level trough push in from the west. With the cloud layer shear
oriented nearly parallel to the cold front storms mode will likely
transition from discrete cells to a line of storms. As this occurs
the severe wind threat will increase as will the QLCS tornado risk.
One area of uncertainty is how far east surface based storms will
persist. Surface winds will be out of the southeast most of Friday
which will keep a stable marine boundary layer across our far
eastern counties.

Along with the severe threat thunderstorms will also bring a risk
for heavy rain. PWATs in increase to near 1" Friday afternoon which
in near the 99th percentile for this time of year. HREF 90th
percentile hourly precipitation values which should be a good proxy
for hourly rainfall rates within the strongest storms are around
0.75-1" per hour. With fast flow through the cloud layer (40-45kts)
storms should not sit over one location too long, however, any areas
that see multiple storms could see upwards of 1.5-2" of rain Friday
evening into early Saturday morning. As has been the case the last
few days the greatest risk for flooding will be where there is
ongoing river flooding or across parts of central and east-central
WI where soils will still be saturated. On the back side of this
system much cooler air may result in a brief chance over to snow,
mainly across northern WI Saturday morning. However, with the ground
thawed don't expect any accumulations.

Long Term...Friday Night Through Wednesday

Saturday night through Wednesday

High pressure will build in across the western Great Lakes region
Saturday night, then slowly track east through the central Great
Lakes during the early part of next week. The high will provide a
much needed reprieve from precipitation for the area. Another cold
front is slated to track through the region Monday night or
Tuesday as the parent low tracks through southern Canada. This
system is expected to track through the region mostly dry as the
best moisture and lift will be closer to the upper level support
across southern Canada. Therefore, impacts from this upcoming
system early next week are expected to be minimal. Mainly dry
weather is expected to last through at least the middle part of
next week.

&&

.AVIATION /18Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1148 AM CDT Thu Apr 16 2026

Skies will gradually clear from the north and west this
afternoon. However, there are medium to high chances (40-80%)
for additional fog development this evening and overnight across
eastern Wisconsin. The fog will persist into Friday morning.
LIFR visibilities may occur for a time.

Winds will become southeasterly tonight and become gusty from
the south during the day on Friday. Beyond this TAF period,
gusts may exceed 25 to 30+ kts during the afternoon. Before
surface winds increase, a period of LLWS may occur early
Friday.

Thunderstorm chances will increase on Friday afternoon beyond
this TAF period.

&&

.HYDROLOGY...
Issued at 217 AM CDT Thu Apr 16 2026

Multiple rivers, namely the Wolf, Menominee, and Wisconsin Rivers,
continue to read in minor to moderate flood stage, with the
Menominee River now in major flood stage due to the additional
influence of snow melt from the Upper Peninsula. Home evacuations
are ongoing along the Wolf River. High flows and rising water levels
have also resulted in several dams being compromised or overtopped.
If you live near a river or stream, continue to monitor the latest
hydro forecasts and Flood Warnings from the National Weather Service
in Green Bay.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...None.
MARINE...Dense Fog Advisory until 1 PM CDT this afternoon for LMZ521-
     522-541>543.

&&

$$

DISCUSSION...GK/Kurimski
AVIATION...JM
HYDROLOGY...GK