NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 151005
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
505 AM CDT Mon Jun 15 2026

.KEY MESSAGES...

- 30-50% chance for non-severe storms across northern Wisconsin
  late this afternoon and evening, but brief gusty winds are
  possible.

- Additional showers and storms (60-90% chance) Tuesday and
  again later Wednesday into Wednesday night. Chances for
  organized severe weather remain low, but a few strong storms
  with small hail, gusty winds and heavy rainfall may occur.

- Below average temperatures in the 60s and 70s through the
  week.

&&

.DISCUSSION...
Issued at 235 AM CDT Mon Jun 15 2026

Today-Tonight:

Isolated to scattered storms (30-50% chance) may develop across
northern Wisconsin within a modestly unstable and seasonably dry
environment this afternoon/evening. Overall, the environment is not
supportive of organized severe weather, but steepening low-level
lapse rates with diurnal heating within a dry boundary layer may
support gusty outflow winds with any storms before stabilization
occurs during the evening.


Tuesday-Wednesday:

Two prominent shortwave troughs will impact the area through mid-
week. The first will move through on Tuesday. Again, boundary layer
heating beneath seasonably cold (<10th percentile relative to climo)
500 mb temps will result in a diurnal uptick in showers/storms. Deep
layer shear will be quite weak, keeping storms primarily
pulsy/disorganized in nature. However, any stronger storms may
produce small hail given the cool temps aloft.

The stronger wave and associated surface low will quickly approach
around the southern periphery of the broad trough of low pressure to
the north over central Canada on Wednesday. Deep layer wind fields
are quite impressive, with the ensemble mean EPS/GEFS/CMC 500 mb
winds forecast near the top of climatology for this time of year
southward across Iowa and Illinois within the jet core south of the
wave. Although there is still some spread in the track of the
surface low, the greater moisture return/instability is more likely
to remain south of the area. Thus, at this time, the greater severe
weather risk looks to remain south of the area, but will have to
monitor trends with this very dynamic system. This system
likely will bring widespread rainfall (50-80% chance for greater
than 1/2 inch) with locally higher amounts likely to be
influenced by the strength and placement of convection.

High temperatures will be limited to the 60s and 70s during this
time, dependent somewhat on the extent of clouds/showers.


Thursday-Sunday:

Northwest flow aloft will continue through the rest of the week with
some indication for gradual deamplification of the flow by next
weekend. Gradual warming should occur, but overall, near to
below average temps remain favored through next weekend.

There is less signal for organized precipitation late in the week
into the start of the weekend with predictability of embedded
shortwave troughs decaying at this range. Consequently, rain chances
are on the low end (20-50%) through this time period right now.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 505 AM CDT Mon Jun 15 2026

Generally VFR conditions will prevail throughout the TAF
period. Westerly winds will diurnally increase with occasional
gusts of 15 to 20 kts, before diminishing around sunset this
evening. Some diurnal VFR cumulus and high clouds will impact
terminals today.

Far northern Wisconsin is most likely to be impacted by thunder
late this afternoon and evening. Included a PROB30 group for
thunder at KRHI centered on the most likely period this
evening, 15.23Z to 16.03Z. Brief gusty outflow winds may occur
with storms. Chances for showers farther south are too low
(<25%) to mention in the TAF at this time.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...None.
MARINE...None.

&&

$$

DISCUSSION...JM
AVIATION...JM