NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 152330
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 PM CDT Mon Jun 15 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

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

- 60-90% chance of showers and storms Tuesday afternoon with a
  80-100% chance Wednesday afternoon and evening. Chances for
  organized severe weather remain low, but a few strong storms
  with small hail, gusty winds and heavy rainfall may occur.

- Moderate to heavy rain Wednesday afternoon and night with a
  60-80% chance of exceeding 1 inch of rain.

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

&&

.DISCUSSION...
Issued at 1209 PM CDT Mon Jun 15 2026

This afternoon-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 as
probabilities for rainfall have increased this run. There is
currently a 60-80% chance for greater than 1 inch with a 10-25%
chance for greater than 2 inches of rain. 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 (20-40%) through this time period right now and
have ticked down from previous runs.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 311 PM CDT Mon Jun 15 2026

Cu field across northern Wisconsin will continue to erode
throughout the evening with the loss of daytime heating.
West/southwest winds will likewise subside overnight. Scattered
showers and storms remain possible through this evening, so have
opted to keep the PROB30 mention of -TSRA in the RHI TAF where
thunder seems most likely. Brief gusty outflow winds and drops in
vsbys will be possible if a storm were to move directly over a
terminal.

Cigs will continue to lower and thicken ahead of an approaching
cold front Tuesday morning, eventually bringing MVFR flying
conditions to the western sites by around 12 to 15Z. Another round
of scattered showers/storms will then be possible Tuesday
afternoon and evening.

&&

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

&&

$$

DISCUSSION.....Kurimski
AVIATION.......Goodin