269
FXUS63 KGRB 181726
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1226 PM CDT Thu Jun 18 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Scattered pop up showers are possible this afternoon. Some
  rumbles of thunder are possible but no severe weather is
  expected.

- Another quick round of showers is possible Friday night. No
  severe weather is expected.

- Below normal temperatures and comfortable humidity will prevail
  through next week.

&&

.DISCUSSION...
Issued at 152 AM CDT Thu Jun 18 2026

Persistent northwesterly flow is expected for the forecast period
as a large upper trough remains stretched over eastern CONUS.

Today...
Low clouds will persist into the morning hours before gradually
scattering out by the afternoon. Clearing skies will allow
temperatures to get into the lower to middle 70s, which will be
right around convective temperature in the afternoon. Expect
scattered pop-up showers to develop in the afternoon and evening,
supported by the arrival of a weak upper shortwave. Some thunder
could mix in at times with any showers, but instability and shear
remain too meager to support organized storms, so no severe
weather is expected today. Any rain will be relatively short-lived
and most of the day will likely still be dry even at the areas
that do see rain. Probability for showers will sit around 30-40%
at any one location, which largely means that most of the day will
be dry Any precipitation should diminish quickly overnight.

Friday and Saturday...
Additional pop up showers  will develop both Friday night and
Saturday afternoon as additional weak upper shortwaves cross the
region. Friday will be the more widespread of the two, with rain
chances sitting around 50-70% for much of the area. That said,
with minimal instability and shear in the region, any rain will be
light and the timing doesn`t favor widespread thunder (10-15%
chance). Saturday showers will largely be limited to northern
Wisconsin, along the Upper Peninsula border.

Rest of the forecast...
Temperatures will not change much through the extended, with each
day expected to largely stay in the lower to middle 70s each day.
The system for Sunday mentioned in previous forecasts has trended
southwards, leaving the day dry. The next widespread chance for
precipitation is currently expected to hold off until sometime
around the middle of next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1226 PM CDT Thu Jun 18 2026

An unsettled weather pattern will continue for the rest of the
day, with cumulus clouds building through the afternoon. A weak
upper disturbance could generate a widely scattered showers and a
few storms between 3 and 8 PM roughly. Maintained the prob30 group
for showers at RHI and added a prob30 to GRB and ATW. Otherwise,
high end MVFR to low end VFR ceilings early this afternoon will
rise to 4-5 kft.

Clearing skies late this evening before clouds (VFR) build with
daytime heating late Friday morning.

Gusty northwest winds to 20 kts at midday will continue through
the afternoon before subsiding. Gusts to 15 kts are likely on
Friday.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion