162
FXUS63 KGRB 081130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Mon Jun 8 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Above normal temperatures persist for the next week. High
  temperatures in the 90s paired with increasing humidity will
  result in potential for moderate to major heat-related impacts.

- Record to near-record high temperatures will be possible
  Wednesday afternoon.

- Chance for widespread showers with embedded storms today and
  tonight. Periods of heavy rain possible.

- Strong to severe storms possible late Wednesday afternoon into
  Wednesday evening. The best chance for stronger storms will be
  west of the Fox Valley.

&&

.DISCUSSION...
Issued at 102 AM CDT Mon Jun 8 2026

Temperatures... Warming trend holds steady as heat ridge builds,
though gradually becoming less confident in seeing higher end
heat indices (100+) during the middle to end of week timeframe.
NBM seems to be coming in a few degrees hot with highs in the low
to mid 90s during this time, though LREF ensemble shows mean
temperatures in the mid to upper 80s with a fairly tight
interquartile spread. Current thinking is that shower and storm
chances in/around the area would hamper temps from rising to their
full potential, though predictability of storm placement/coverage
is low at this time. Have nevertheless opted to lower high temps
on Wednesday by a couple degrees. Regardless, can expect well
above average (5 to 10 degrees) highs as subsidence under mid-
level ridge brings 850 mb temps between 22 and 25C down to the
surface. Would venture to say that headlines will be necessary at
some point during the middle of the week given widespread moderate
(level 2) to major (level 3) risk for heat-related impacts.
Likewise, if current temperatures hold, record to near-record high
temperatures will be within reach Wednesday afternoon.

Today/Tuesday... Chances (60 to 90%) for widespread rain arrive
later this morning from the west as a fairly potent shortwave
migrates through prevailing southwesterly flow and up into the
Midwest. PWATs range between 1.75 and 2" during this time, nearing
the absolute max relative to climo, so safe to say that periods
of heavy rain can be expected. However, rain seems to have a more
stratiform appearance during this time since organized convection
appears unlikely due to absence of upper support and lack of
surface forcing mechanism. However, embedded thunder will be
possible as modest instability (~800 to 1,000 J/kg) pools near
central Wisconsin. Any convection would be efficient rain
producers in this moisture-rich environment, so will have to
monitor for higher-end rainfall (1+") in this scenario. Probabilistic
guidance now shows a 50 to 80% signal for receiving one inch of
rain over central Wisconsin. However, flooding concerns should be
held to a minimum given D0 drought status and dry soils.

Severe potential Wednesday... Confidence increasing for severe
weather threat Wednesday afternoon into Wednesday evening as
surface low spins up over the northern Plains and negatively-tilted
shortwave tracks over the upper Mississippi Valley. Cold FROPA
looks to occur over western Wisconsin Wednesday evening, which
would put portions of central to north-central Wisconsin under the
most favorable risk area for severe storms as the front interacts
with maximized instability (~2,500 to 3,000 J/kg) prior to
nightfall. In this scenario, combination of steep lapse rates (7
to 9 C/km), supportive deep layer shear (35 to 40 knots), thick
CAPE profile in the hail growth zone, and low-level turning of the
hodograph would put all severe weather threats in play. Timing of
the front will play a large role in how the severe threat
evolves as it progresses east, with earlier FROPA resulting in a
more favorable environment across the eastern CWA. Other sources
of forecast uncertainty revolve around how lingering
showers/storms behave on Tuesday, and whether or not cloud debris
will hinder destabilization occurring Wednesday afternoon. Also
worth mentioning will be the heavy rain potential that accompanies
the severe threat due to steady influx of Gulf moisture raising
PWATs to near 2" (~99th percentile) Wednesday evening.
Probabilistic guidance shows a widespread 30 to 50% signal for
receiving one inch of rain during this time, though locally higher
amounts associated with stronger convection will be possible.

Extended... Active pattern sets up through at least the end of
the week as upper flow re-amplifies and several shortwaves
propagate over the northern CONUS. It is hard to pinpoint any
additional severe potential beyond Wednesday, as there remains low
predictability with how convection will behave earlier in the
week. This being said, ensembles suggest that another round of
rain/storms will be possible on Thursday. Will bear watching in
the coming days.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 359 AM CDT Mon Jun 8 2026

Mid clouds continue to increase this morning, eventually lowering
to MVFR, and even IFR, as SCT showers/storms arrive from the west
late this morning into early this afternoon. Have included TEMPO
groups for -TSRA at all sites, and PROB30 mentions of -SHRA
across the east-central sites for a line of showers ongoing this
morning. Showers will continue to propagate east throughout the
evening, persisting into Tuesday. Brief periods of reduced vsbys
will be possible if heavier rain or a storm moves over a terminal.
Winds start out of the southeast, gusting between 15 and 20 knots
this afternoon. Winds then switch to northeasterly late tonight
into Tuesday morning.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion