Maribel, Wisconsin Weather Forecast Discussion

721
FXUS63 KGRB 190406
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1106 PM CDT Thu Sep 18 2025
Updated aviation portion for 06Z TAF issuance
.KEY MESSAGES...
- Periodic chances for showers and thunderstorms are expected
  Friday into early next week. The severe weather threat remains
  low.
- Conditions hazardous to small craft will be possible on Lake
  Michigan waters south of Two Rivers Friday night into Saturday
  morning. There will likewise be increased potential for rip
  currents on Lake Michigan beaches along this section of
  shoreline.
&&
.DISCUSSION...
Issued at 157 PM CDT Thu Sep 18 2025
Short Term...Tonight and Friday
This afternoon... Radar continues to show returns popping over
northern and east-central Wisconsin this afternoon where
instability has been allowed to build in the vicinity of a cold
front. Any rumbles of thunder were confined to the southern Fox
Valley. Low-level moisture likewise continues to stream north of
the frontal boundary as a deformation zone associated with low
pressure over South Dakota takes residence over western
Wisconsin. Broken stratus/stratocu deck has persisted over much of
northeast Wisconsin as a result.
Forecast over the course of the next 24 hours remains volatile,
with several chances for low impact rain/storms existing across
the forecast area. Thunder potential will be on the rise mainly over
northern Wisconsin later this afternoon and evening as MUCAPEs
approach 1,000 J/kg, though coverage will remain scattered at best
as stability increases from the east. Better chances for
rain/storms then arrive Friday afternoon as an upper trough
interacts with a moisture corridor of PWATs around 175 to 200% of
normal. Brief periods of moderate to heavy rain will thus be
possible Friday afternoon and evening as the cold front sinks
south, especially if/where showers train over the same area. Post-
frontal temperatures then drop into the mid 60s across the
Northwoods Friday afternoon, while remaining in the mid to upper
70s in/around the Fox Valley.
Fog... Patchy fog will be possible late tonight into early Friday
morning along/north of Highway 29 as a low-level inversion traps
remnant moisture from recent rainfall near the surface. Any fog
should then quickly scatter out by daybreak as winds pick up out
of the east. Another possibility is that this moisture could
manifest as low stratus instead.
Long Term...Friday Night Through Thursday
A slow moving upper  trough will be the main driver for the
active weather over much of the extended, bringing another push of
warmer, more moist air into the region.
Active Weather...
As the upper trough moves eastwards, a push of warmth and moisture
will move into the region Friday night, bringing with it a chance
for scattered rainfall. Elevated instability during this period
ranges around 200-500 J/kg, which would support some rumbles of
thunder at times, but any stronger storms seem unlikely at this
time. Some isolated to scattered shower activity may then stick
around on Saturday before the next surge of instability arrives on
Sunday, bringing another round of more widespread precipitation to
the region. Instability parameters for Sunday are a little better
than the day prior, but do largely depend upon clearing for some
surface heating earlier in the day. If this occurs, thunder will
be more likely once again, but given the long skinny soundings and
relatively weak shear, the threat of severe weather remains low.
Finally, a stacked low pressure system is expected to develop over
the Central Plains next week, but the path of this low continues
to change. Current trends would take the active weather south of
our area, which would reduce any active weather impacts.
Temperatures...
High temperatures will hold fairly steady over the weekend into
next week, with high temperatures remaining fairly solidly in the
upper 60s to lower 70s.
Marine...
The incoming active weather for Friday night will likely also
bring some increasing winds and waves for the Friday night period,
which may pose a concern for mariners and beach goers.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1105 PM CDT Thu Sep 18 2025
Variable conditions have developed this evening across the
region, with low stratus and light fog over southern portions of
the Fox Valley to the lakeshore (MTW) and IFR status also over
north-central WI (RHI). VFR conditions are present elsewhere.
Eventually, more of the area will see IFR to MVFR cigs overnight
through Friday morning. Conditions will improve for all but the
lakeshore on Friday afternoon as stratus and fog may linger much
of the day at MTW. Though an isolated shower could occur
overnight into Friday morning, greatest risk for showers and
storms will not occur until later Friday afternoon into Friday
evening, especially at CWA/AUW and RHI. Have introduced some
PROB30 groups late on Friday for these terminals, followed by
prevailing groups for showers or even thunder (CWA/AUW). VFR cigs
will eventually give way to lower cigs later Friday night, toward
tail end of TAF period.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Goodin/Uhlmann
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion