651
FXUS63 KGRB 010406
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1106 PM CDT Mon Jun 30 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Rain and thunderstorms are possible throughout Friday and
  Saturday which may impact 4th of July celebrations.

- Temperatures will be above normal through the week.

&&

.DISCUSSION...
Issued at 346 PM CDT Mon Jun 30 2025

Short Term...Tonight and Tuesday

Scattered thunderstorms moved across portions of far northeast
Wisconsin this afternoon. This cluster of thunderstorms sent
an outflow boundary southward to near Green Bay. Scattered
thunderstorms were also noted across west-central and northwest
Wisconsin. Meanwhile, lower dewpoints were filtering into eastern
Wisconsin on westerly winds and deeper mixing.

For the rest of the afternoon into this evening, cyclonic flow
aloft and daytime heating triggered the scattered storms across
the western part of the state. Some of these storms are expected
to make it into north-central and central Wisconsin during the
late afternoon and evening. Most of the stronger storms will
be capable of producing wind gusts to 45 mph and small hail. Could
not rule out an isolated storm with wind gusts to 60 mph and large
hail to one inch in diameter. The storms should come to an end
later this evening as we lose the heating of the day. Later
tonight when winds diminish and skies become mostly clear, patchy
fog is expected to develop. Lows should drop into the middle 50s
to lower 60s.

On Tuesday, some fair weather cumulus will develop during the
late morning and continue through the afternoon. Highs should top
out in the upper 70s to middle 80s.

Long Term...Tuesday Night Through Monday

Expecting generally quiet weather from Tuesday night through
Thursday night with high pressure at the surface and rising upper
heights. There are some subtle features, including a upper jet
streak and weak surface cold front which could bring small precip
chances therefore maintained 15-30% PoPs at times, otherwise dry.
A few thunderstorms are possible, too, but severe weather
potential is low.

Still watching the potential for rain and thunderstorms Friday
through Saturday night. A number of factors at play, including the
timing of various features which make narrowing down the specifics
this far out challenging. Overall dynamics are modest, but an
approaching surface boundary and low-level WAA will be enough to
initiate at least some thunderstorms. Forecast instability Friday
afternoon gets as high as ~2000 J/kg, but deep shear is weaker,
ranging from 15-30 kts. Instability Friday night and Saturday is
lower and generally less than 1000 J/kg, aside from the southeast
wedge of the forecast area, which builds up to 1500 J/kg Saturday
afternoon. Timing and strength of thunderstorms will come down to
the timing of these features, which is trending more towards late
Friday night or Saturday at the moment. Continued with NBM PoPs
which generally show a consistent wet period, but it will be a mix
of scattered rain/storms and no-precip.

Temperatures will remain above normal through the week with highs
in the 80s, and nearing 90 degrees on Friday. Humidity will also
remain noticeable due to dew points in the 60s most days, and even
some low 70s in the mix Friday into Saturday.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1104 PM CDT Mon Jun 30 2025

Skies have become mostly clear in wake of the showers and storms
from earlier this evening. As temps cool overnight, some fog may
form, though it is not expected to be as dense as what occurred
last night. Only terminal that has a mention of IFR vsby is RHI.
Tuesday will feature northwest winds gusting to 15 kts and
scattered fair weather cumulus clouds with MVFR bases in the
morning, lifting to VFR in the afternoon. Skies will clear out
quickly on Tuesday evening.

&&

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

&&

$$

DISCUSSION.....Eckberg/KLJ
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion