398
FXUS63 KGRB 191915
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
215 PM CDT Fri Jun 19 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Scattered showers and thunderstorms will bring a 50-75% chance
  of rain this evening and tonight. Any storms will be capable of
  producing hail. Strong, gusty winds are also possible.

- Scattered showers are expected Saturday afternoon, with a few
  storms possible across far northeast Wisconsin, including Door
  County.

- Near to below normal temperatures and comfortable humidity will
  prevail through next week.

&&

.DISCUSSION...
Issued at 215 PM CDT Fri Jun 19 2026

Precipitation Chances...This afternoon`s water vapor and radar
imagery showed a shortwave moving eastward over eastern ND and
northern MN, producing scattered showers and a few storms. As the
shortwave continues to track east, the forecast area will see these
scattered showers and isolated storms move across the area early
this evening through late tonight. When the precip reaches central
WI late this afternoon/early this evening, a corridor of SBCAPE of
500-900 J/kg, steep mid-level lapse rates of 6.5-7.5 C/km, and deep-
layer shear of 35-45 kts, will be present, leading to a marginal
risk for a few strong to severe storms. Given the present cooler
airmass, the freezing level will be lower, around 7000 ft, leading
to a hail threat. In addition, a few models indicate inverted-v
soundings, suggesting a marginal wind threat as well. As the storms
move eastward, the storms will become elevated, but the severe
threat will decrease as deep-layer shear and lapse rates lessen. Any
showers and storms will exit east after midnight.

Northwest/cyclonic flow will be in place following the departure of
the shortwave on Saturday. With low-level moisture in place and then
diurnally increasing during the afternoon, CAMs are indicating
isolated to scattered showers developing during the afternoon, and
dissipating in the evening as the sun sets. Cannot rule out a few
rumbles of thunder, mainly in far northeast WI, where a couple
hundred J/kg of CAPE will be focused during the afternoon.

On Sunday, a strong system will move across the Middle Mississippi
Valley. While models continue to show the system remaining south of
the forecast area, a few ensemble members indicate the far southern
portions of the forecast area may see some rain on the northern
periphery of the system; elsewhere should remain dry.

Quiet conditions look to prevail for the start of the work week with
the next chance for showers and storms arriving sometime midweek.

Temperatures...With a relatively unchanged northwest flow expected
through next week, very little variance in temperatures is forecast.
As such, both afternoon highs (mainly in the 70s) and overnight lows
(upper 40s to low 50s) will hover slightly below normal.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 101 PM CDT Fri Jun 19 2026

VFR cigs from a cu field prevailed across the region early this
afternoon ahead of a system expected to bring scattered showers
and a few thunderstorms to the region throughout the evening. The
scattered showers and a few storms will move from west to east
roughly between 22z Fri and 07z Sat. Confidence remains low-medium
on storms moving directly over a TAF site, so continued to include
PROB30 groups at the central and north-central WI TAF sites. Also,
decided to include PROB30 groups at GRB and ATW, as models
indicate a brief window of instability that would keep a chance
of thunder in these areas. If the thunderstorms move over any of
the TAF sites, they may produce gusty winds, hail, and brief heavy
rain with a reduction in visibility.

Following the rain, expect some lower stratus with MVFR to IFR
cigs overnight into Saturday morning. The greater potential for
IFR cigs will be at the central and north-central WI TAF sites.
Ceilings should lift towards the end of this TAF period with SCT
to BKN cloud cover and a few showers during the afternoon.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion