Morris, Wisconsin Weather Forecast Discussion

835
FXUS63 KGRB 132357
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
657 PM CDT Sat Sep 13 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Areas of fog late tonight into early Sunday morning. Fog may be
  dense at times, resulting in locally hazardous travel.
- Mainly dry with above normal temperatures through early this
  week. Chances of showers and thunderstorms during the mid to
  late part of the week, with a significant cool down possible
  Friday and Saturday.
&&
.DISCUSSION...
Issued at 317 PM CDT Sat Sep 13 2025
Pesky stratus that formed on north edge of outflow from morning
storms over southern Lake Michigan is lingering from the Fox
Valley to the lakeshore. These clouds will scatter out later this
afternoon. High pressure settling overhead along with mostly clear
skies and light east winds will lead to areas of fog overnight.
Greatest risk for dense fog per HREF probabilities is over
northern WI where temps are expected to fall into the lower 50s.
Farther south and east, may be just enough wind in the boundary
layer to lead to stratus with patchy fog instead of widespread
fog. Additionally a lot of guidance is showing marine fog re-
developing and moving onshore. Not enough confidence to issue
dense fog advisory, but at least for some areas, certainly could
be needed. Fog and stratus will diminish by mid morning Sunday,
though based on recent trends if marine fog does form, it would
probably take longer to dissipate.
Dry weather then should hold through Tuesday as sharp ridging builds
aloft. Temperatures Monday and Tuesday will be well above normal,
with readings in the low to mid 80s. Nighttime lows will also be
well above normal, with readings in the upper 50s to lower 60s.
Beyond Tuesday, a low pressure and stronger cold front will gradually
work across the plains, crossing the Great Lakes Thursday into Friday.
The upper trough is positively tilted throughout, so winds aloft are
not strong and thus shear ahead of the front remains weak at best.
MLCAPES up to around 1000J/kg are likely on Wednesday afternoon and
evening, so scattered thunderstorms are possible, but limited shear
ultimately lowers the severe threat. Additional chances for showers
and storms occurs on Thursday as the front moves through. After well
above normal temperatures early in the week, decent signal that readings
fall back to normal or at least slightly below normal by Friday on into
next weekend.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 657 PM CDT Sat Sep 13 2025
Daytime cumulus clouds will continue to fade as we pass sunset. A
pesky, oddly shaped area of stratus remains situated over east
central WI, on the edge of GRB, ATW and MTW. Expect this area to
slowly shift east this evening. It could mix out for a time, but
additional low clouds and fog will develop late this evening into
Sunday morning, bringing IFR/LIFR conditions in many areas.
SREF/HREF probabilities of under a 1/2SM VSBYs over 50% from the
Fox Valley north and westward. Some lake fog is also expected,
which could sneak into MTW. After the low clouds and fog burn off
Sunday morning (by ~15z), look for VFR conditions for the rest of
Sunday. Additional low clouds and fog will be possible again
Sunday night, but likely after 06z.
Light and variable winds are expected tonight, with southeast
winds up to ~10 kts on Sunday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....JLA
AVIATION.......Bersch

NWS GRB Office Area Forecast Discussion