537
FXUS63 KGRB 141700
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1200 PM CDT Sun Jun 14 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Below average temperatures over the next week with highs
  mainly in the 60s and 70s.

- Intermittent shower/storm chances through the work week with
  the highest chances (50-80%) Tuesday and Wednesday. Organized
  severe chances look fairly low at this time.

&&

.DISCUSSION...
Issued at 312 AM CDT Sun Jun 14 2026

Below average temps:

Water vapor imagery and RAP 500 mb heights show a deep trough across
Ontario with sharpening northwest flow aloft while the GOES
nighttime microphysics imagery showed clouds associated with
post-frontal cold advection advancing south from northern
Wisconsin early this morning. A much cooler day is in store
with breezy northwest winds. Clouds will gradually clear through
the afternoon from the west.

The upper low across Canada will remain in place for much of
the week resulting in broad northwesterly flow across the Great
Lakes during this time. Consequently, confidence is high for
below average temps through the week with highs mainly in the
60s and 70s. Daily highs may be impacted by clouds/showers,
especially during the middle of the week.

Intermittent precip chances this week:

A series of progressive shortwave troughs will rotate through the
southern periphery of the broader trough through the week, resulting
in occasional showers/storms.

The first wave arrives late Monday into Tuesday, with the
highest shower/storm chances (50-80%) on Tuesday beneath the
upper trough. Organized severe weather potential looks low with
this system given weak deep layer shear and modest boundary
layer moisture/instability within drier northwesterly flow.
However, given the low freezing levels and cool air aloft, any
storms may produce small hail.

On its heels, a stronger wave and associated surface low is forecast
to progress across the Midwest around Wednesday. Somewhat greater
return flow and northward moisture transport is forecast with this
system. While there is spread in the position of the surface
low, broad ensemble consensus keeps the low and greater instability
farther south. In this scenario, the greater severe weather risk
would be farther south, with showers and some thunder potential
across the area. The EPS indicates low (10-30%) probabilities
for at least an inch of rain with this system over the area,
with the higher chances farther south into the more unstable
environment.

For late week, northwest flow is likely to persist, although
predictability of embedded shortwave troughs is lower. As a result,
rain chances are mainly in the 20 to 40 percent range during this
time.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1155 AM CDT Sun Jun 14 2026

Any lingering MVFR CIGS across far northern WI will rise
into the VFR category by mid-afternoon. Otherwise, CIGS of
3,5000 to 4,5000 feet should rise to 5,000 to 6,000 feet
later this afternoon, although clouds will be on the decrease
towards sunset. Northwest winds of 10 to 20 knots with gusts
to 25 knots will subside late this afternoon into early this
evening, then back west to southwest 5 to 10 knots this
evening and overnight as skies become clear during the evening.
Fair weather cumulus and gusts around 15 knots from the west will
develop around 16z Monday.

&&

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

&&

$$

DISCUSSION.....JM
AVIATION.......Eckberg

NWS GRB Office Area Forecast Discussion