251
FXUS63 KGRB 101126
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 AM CDT Fri Apr 10 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Periods of heavy rainfall and thunderstorms expected late this
  weekend through the middle of next week. There is a 85-95%
  chance of rainfall greater than 1 inch, and a 35-60% chance of
  greater than 2 inches.

- A round or two of strong to severe thunderstorms are possible
  during the early to mid part of next week, with the best chance
  occurring Monday evening.

- Minor flooding continues along the Wolf River, though combined
  runoff from melting snow in the Upper Peninsula and heavy rain
  will likely result in more widespread and significant flooding
  next week.

&&

.DISCUSSION...
Issued at 221 AM CDT Fri Apr 10 2026

Light rain associated with strong mid-level FGEN was moving
through the southeast half of the forecast area early this
morning, and should be east of the region by around 12z/Fri.

High pressure brings dry weather and low relative humidity today.
The dry conditions persist into early Saturday afternoon, with a
chance of showers arriving in NC/C WI later in the day.

A prolonged period of active weather arrives Saturday night into
Sunday and continues through the middle of next week. Periodic
showers and thunderstorms, and potential for heavy rainfall, can
be expected through the period.

The first batch of heavy rainfall arrives Saturday night into
Sunday, as a warm front lifts north into the region and a 45 to
55 knot southerly low-level jet brings a surge of Gulf moisture
(PWATs 1-1.5 inches) and marginal instability. Not seeing much
potential for severe storms during this first episode. Models
support a lull in the precipitation later Sunday night into
Monday, as H8 flow turns westerly (parallel to the baroclinic
zone), PWATs drop to less than 1 inch and instability wanes.

The front sags south and stalls across the area Monday into
Tuesday, and potentially lifts back to the north as a strong low
pressure system approaches Tuesday night into Wednesday. This
front will interact with a persistent flow of Gulf moisture and
marginal to moderate instability. Instability peaks across the
southwest half of the forecast area Monday afternoon and evening,
as MUCAPE increases to 1-2k j/kg. This instability, combined with
the frontal boundary and deep layer shear of 45-55 knots, supports
potential for severe thunderstorms. Models are not very robust
with convection Monday afternoon, but ramp up storms quickly
during the evening. Additional strong to severe storms could
develop as the front starts to lift back to the north Tuesday
afternoon and evening. If the surface low tracks far enough west
on Wednesday, we could see a surge of instability across eastern
WI as the cold front moves through in the afternoon, so cannot
rule out additional severe potential (especially damaging winds)
then. See the Hydrology section for possible flooding impacts.

Milder temperatures are expected through the period, with highs
reaching into the 70s in parts of the area Sunday-Tuesday, and
possibly even on Wednesday.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 615 AM CDT Fri Apr 10 2026

Stratocumulus clouds covered the region early this morning, with
a mix of low-end VFR and MVFR ceilings being reported. Isolated
IFR ceilings were seen in the far southeast part of the forecast
area, where rain was steadier overnight.

MVFR ceilings will linger in some areas until late morning, then
rising ceilings and partial clearing lead to VFR conditions for
the rest of the day. NE-NW winds of 5 to 10 knots are anticipated.
Clear skies are expected tonight, along with light SE-S winds.
It is possible that patchy fog may develop overnight, but the
dryness of the incoming air mass and a lack of measurable
precipitation in our fog-prone areas argues against anything
significant. Will leave any mention of fog out of the TAFs for
now.

&&

.HYDROLOGY...
Issued at 221 AM CDT Fri Apr 10 2026

Minor flooding continues on the Wolf River early this morning. A
mainly dry period is anticipated through Saturday. 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 85-95%,
with a 35-60% chance of amounts in excess of 2 inches and a 5-20%
chance of 3 inches or more. Current forecasts call for 1.75 to
2.25 inches of rain 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 by the middle of next week. Right now,
it appears the most significant flooding impacts will occur on the
Menominee River and its tributaries.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kieckbusch
HYDROLOGY......Kieckbusch

NWS GRB Office Area Forecast Discussion