NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 082346
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
646 PM CDT Mon Jun 8 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Scattered showers expected at times this afternoon and tonight.
  Thunder may mix in at times. Locally heavy rainfall totals are
  possible, especially with any storms.

- Storms return Tuesday evening into Tuesday night. A few strong
  storms will be possible across portions of central Wisconsin.

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

- Above normal temperatures persist for the next week. Moderate
  to major heat-related impacts possible.

&&

.DISCUSSION...
Issued at 243 PM CDT Mon Jun 8 2026

Rain Potential Tonight into Tuesday...
Scattered showers continue across the region this afternoon along
a push of warmer air. These initial showers have largely lacked
more convective elements due to a lack forcing, so initial
rainfall amounts have generally remained light. A break in the
precipitation will be possible in the late afternoon behind the
initial showers before an upper shortwave brings back showers and
possibly thunderstorms. Although severe weather is not expected
with this feature, very heavy rainfall could be supported at times
overnight as the most recent upper air sounding shows PWATs up to
1.92 inches, above the climatological max for early June. Models
are even more aggressive in some areas, advecting up to 2-2.25"
into the region. Effectively, any convection will be able to
produce a lot of rain very quickly, which will pose a flooding
concern to watch during the evening to early overnight period. The
CAMs therefore show some very high localized rainfall totals in
the range of several inches. Fortunately convection should be
relatively localized tonight, so any flooding effect should also
be relatively limited in areal coverage. The greatest potential
for heavy rainfall will be over central Wisconsin, which is
currently in a SLight Risk of Excessive Rainfall for this period.

Tuesday Storms...
A period of relative quiet will be possible on Tuesday after any
overnight showers and storms depart the region. Expect partial
clearing to take place during the late morning to afternoon as
high temperatures head into the middle 80s across the area.
Attention then turns to a fairly sharp warm front that will
stretch from central Minnesota southeastwards into northern
Illinois. This slow moving front will be the leading edge of a
very unstable airmass along which storms will develop Tuesday
afternoon into Tuesday evening. Although this also means the best
potential resides to our west and south, will need to monitor for
storms riding along the gradient of best instability into our
region, including portions of central Wisconsin and the central to
southern Fox Valley. These areas are currently in the Marginal
Risk category for severe weather, which makes sense as the
gradient of instability is quite sharp and storms should see some
weakening as they move north and east into our area. Any stronger
storms will pose primarily a wind threat.

Wednesday...
Some scattered showers and even a few storms may still be in the
area along the aforementioned warm front from Tuesday as it works
its way into the region. These initial storms will likely still be
elevated and be sub-severe, bringing just a period of rainfall to
the region. Late afternoon to early evening will be the period to
watch for severe weather as storms develop again along a cold
frontal passage and the passage of a strong trough. Instability
ahead of the frontal passage ranges around 2000-2500+ J/kg CAPE
and deep layer shear in the range of 35 to 40 knots will be
supportive of organized convection. Steep lapse rates both at the
surface and aloft will be supportive of hail growth, while early
looks at low level helicity and shear would support damaging wind
potential, supercells, and possibly tornadoes. Heavy rainfall will
return for this period as well, as PWATs once again surge to
around 1.75-2" for much of the region. Impacts of heavy rainfall
should be somewhat limited by the anticipated fast-moving nature
of any evening storms, but a widespread soaking over an inch will
still be possible (30-50% chance), with locally higher amounts.
The timing of all these parameters will be somewhat dependent
upon how quickly skies clear behind any morning convection, but
the most likely factor will remain with the trough itself. Where
convective initiation will likewise vary a little with the
details of prior convection but most mid- range guidance does
still suggest it will be at least a little to our west before
expanding into our area during the late afternoon to evening. This
means that those with outdoor plans will be able to monitor radar
for developing convection upstream before it arrives. Overall,
would expect initial storms to have a hail threat before
organizing lines, bows, and/or cold pools bring more of a wind and
embedded tornadic threat downstream from where the storms
started.

Temperatures...
Given all the active weather, the heat impacts for the early to
mid week have diminished from where they stood a few days ago.
Expect high temperatures in the upper 70s to middle 80s Tuesday
and mid to upper 80s on Wednesday. This bring heat indices into
the middle 90s. If skies clear very quickly Wednesday and the warm
front gets further northwards we may yet see a need for heat
related headlines, but this is not currently in the forecast.
Temperatures then see a slow falling trend behind the Wednesday
active weather, which will be an end of any heat mentions in the
current forecast.

Extended...
Thursday may see another round of active weather in the region
during the afternoon and evening, but this will largely depend on
where air masses end up behind the active weather on Wednesday. A
few mid to long range models eject another shortwave into the
region with enough strength to bring the warmth and moisture back
into central to east-central Wisconsin. If this occurs, we may yet
see another round of active weather, but many of the details will
depend heavily on what happens Wednesday.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 643 PM CDT Mon Jun 8 2026

A round of scattered showers and thunderstorms will move across
the area this evening, then exit northeast WI overnight into early
Tuesday morning. Main concern overnight will be for fog to form.
CIGS should fall into the IFR category across eastern WI by late
evening or a few hours after midnight. The low CIGS will be slow
to clear on Tuesday, but should become VFR during the afternoon.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Eckberg