NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 101743
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1243 PM CDT Fri Apr 10 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Periods of heavy rainfall and thunderstorms expected from
  Saturday night through the middle of next week. There is a
  85-95% chance of rainfall greater than 1 inch, and a 40-60%
  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 night and Tuesday.

- Minor flooding continues along the Wolf River through the
  weekend.  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 1243 PM CDT Fri Apr 10 2026

The latest RAP analysis and satellite imagery show shortwave
energy traversing the western Great Lakes early this afternoon,
which is pushing a cold front through the eastern Lakes and into
central Illinois. Weak cold advection is noted between this
boundary and high pressure centered over the eastern Dakotas and
southern Minnesota. Cloud cover has been slowly eroding from west
to east across the state this morning as the high builds into the
region. Current observations across northwest Wisconsin show
clearing skies with temperatures in the 30s and 40s. Farther
west, a robust longwave trough is entering the West Coast, which
will act as the primary driver for an increasingly active and
amplified upper-level flow pattern across the central United
States late this weekend and into next week.

Dry weather and a clearing trend will continue this afternoon as
the high pressure system settles across the region. Relatively
light winds and clear skies will promote efficient radiational
cooling tonight, likely leading to minimum temperatures falling
below NBM guidance. Despite the cooling, the arrival of a dry low-
level airmass will limit the potential for fog development. High
pressure will gradually slide east on Saturday, allowing clouds to
increase from southwest to northeast throughout the day. While
the dry airmass should keep conditions dry through mid-afternoon,
saturation in the lowest 2 km will increase after 4 pm across
central Wisconsin. Rain chances rise to around 40 percent by early
Saturday evening as moisture advection strengthens.

An increasingly active weather pattern develops Saturday night as
strong return flow and moisture advection surge into the region.
Precipitable water values are projected to reach the 99th
percentile by early Sunday morning as a 50-55 kt low-level jet
impinges on central Wisconsin. While a strong low-level inversion
will likely keep convection elevated Saturday night into Sunday
morning, these ingredients favor a widespread round of showers and
thunderstorms. Most locations can expect 0.50 to 1.00 inch of
rain during this first round, though stronger convection could
lead to localized amounts up to 1.50 inches. The probability for
rainfall exceeding one inch during this initial period is 40-60%.

The focus for severe weather potential shifts to the Monday night
through Tuesday timeframe. While a cold front is expected to sag
into the region from the northwest on Monday, a temporary lull in
precipitation is possible Sunday night and early Monday as weak
shortwave ridging passes overhead and flow backs to the west.
However, additional height falls and the passage of a surface wave
will trigger renewed rounds of showers and storms. Instability is
forecast to surge during this period, with most unstable CAPE
values reaching 1000-1500 J/kg Monday night and up to 2000 J/kg by
Tuesday afternoon/evening. When combined with deep layer shear of
40-50 kts, conditions will be supportive for organized strong to
severe thunderstorms at times during this period. While the
ingredients are present for strong to severe storms in the
forecast, predictability is generally below normal due to
uncertainty in frontal positions and cloud cover. It's also
unclear if storms will be surfaced based or elevated in nature. SPC
has outlined areas from central to east- central WI in a 15% risk
outlook for severe weather on Tuesday.

Chances for precipitation will begin to wane on Wednesday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1243 PM CDT Fri Apr 10 2026

Mainly high confidence of VFR conditions through the TAF period.
Latest satellite imagery shows a stratocumulus deck with bases
between 3500-6000 ft AGL currently impacting the terminals. KMTW
and KATW show MVFR ceilings at issuance, but anticipate ceilings
will rise to VFR within an hour after the start of the TAF period. These
clouds will continue to erode from west to east this afternoon as
high pressure builds in from the Dakotas.

Clear skies and light winds are expected tonight as the high settles
over the region. Despite clear skies, dry air in the low levels will
prohibit fog formation. On Saturday, mid and high clouds will increase
from the southwest. Precipitation is expected to remain south and west
of the terminals through 21z Saturday, though rain chances increase
across central WI (KAUW/KCWA) toward the end of the period.

Winds will remain from the northwest to north this afternoon around
7-10 kts, becoming light and variable or shifting to the southeast
under 5 kts after 03z Saturday.

Outlook...Rain, thunderstorms, LLWS, and MVFR/IFR conditions
arrive Saturday night and persist through Sunday.

&&

.HYDROLOGY...
Issued at 1243 PM CDT Fri Apr 10 2026

The cumulative effect of multiple rain events will lead to
significant hydrological concerns by the middle of next week.
While minor flooding continues on the Wolf River today, the
upcoming period from Saturday night through Wednesday carries a
85-95 percent probability of rainfall exceeding one inch, and a
40-60 percent chance of exceeding two inches. Runoff from this
heavy rainfall, combined with rapid snowmelt in the Upper
Peninsula, will likely cause more widespread and significant
flooding. The most significant impacts are currently anticipated
on the Menominee River and its tributaries, where probabilistic
guidance suggests several points could approach moderate flood
stage by Tuesday, April 14. Showers may linger into Wednesday,
April 15, as the upper trough slowly exits the region.

&&

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

&&

$$

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