Medina, Wisconsin Weather Forecast Discussion

413
FXUS63 KGRB 262303
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
603 PM CDT Fri Sep 26 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- An extended period of low-impact weather is forecast through
  next Friday. Above average temperatures are expected during this
  time, with the best chance of highs reaching or exceeding 80
  degrees occurring on Saturday and Monday.
- Patchy fog and low clouds expected late tonight into early
  Saturday.
- Patchy frost possible in north central WI late Saturday night
  into early Sunday.
&&
.DISCUSSION...
Issued at 318 PM CDT Fri Sep 26 2025
Low clouds associated with a weak cold front will continue to
erode over the southern part of the forecast area late this
afternoon, and most of the cloud cover should be gone by sunset.
There is potential for some fog development tonight. Model
visibility forecasts favor fog in our southwest counties, though
surface and boundary winds are lightest and most supportive of fog
in eastern WI. The western part of the forecast area (C/NC WI)
should be more prone to low stratus development, due to boundary
layer flow increasing to 15 to 25 knots overnight. Bottom line is
that patchy fog and low clouds are expected, but widespread dense
fog is not.
A cold front will move through the forecast area on Saturday,
accompanied by a narrow band of clouds, but no precipitation.
WAA and compressional heating ahead of the front will boost highs
into the 70s and lower 80s in most areas. Gusty SW-W winds will
also occur. High pressure builds into the region in the wake of
the front, with clear skies, light winds and a dry air mass
supportive of cool overnight temperatures Saturday night. Have
lowered the blended models Min temps into the middle 30s in parts
of north central WI, where patchy frost is possible overnight into
early Sunday.
Another cold front drops south across the region Monday night,
with Canadian high pressure ridging across the region through the
rest of the week. This will result in slightly cooler, but still
above normal temperatures mid-week, and continued dry conditions
through the end of the week. Winds will pick up a bit out of the
southeast Wednesday night into Thursday, leading to possible
marine concerns (Small Craft Advisories) on Lake Michigan,
especially south of Two Rivers.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 603 PM CDT Fri Sep 26 2025
Aviation forecast focus revolves around the potential for low
ceilings and fog tonight. A band of low clouds, currently
situated between 2000-4000 ft over central to east-central WI,
will linger this evening. This moisture will interact with a
stalled frontal boundary before returning northeastward overnight
as winds shift to the southwest.
THROUGH 12Z SATURDAY...
Predominantly VFR conditions are expected to prevail at the start
of the period for most terminals. However, as we head into the
overnight hours, there is a potential for IFR visibilities and
ceilings to develop. Dewpoints have not had a chance to mix out at
MTW/OSH/ISW/MFI/CWA unlike at GRB and to a lesser extent at
AUW/ATW. This could lead to the development of low stratus and
potentially fog, especially over some of the central and east-
central WI TAF sites, including KMTW and KCWA.
While ensemble guidance suggests a 60-70% chance of visibilities
dropping below 1/2 mile, confidence in occurrence is not as high.
Increasing southwest winds in the boundary layer may prevent
widespread dense fog, favoring the development of low stratus
instead, particularly over central WI (KAUW, KCWA, KRHI). A brief
period of IFR to LIFR conditions due to fog and low ceilings is
most probable at KMTW between 09Z and 12Z, where boundary layer
winds are expected to be lighter. Confidence in the extent of the
lowest conditions is low. CIGS of 300-500 ft could develop during
this time, with VIS potentially falling to 1/2-2SM. This will
impact IFR alternate planning. SFC WNDS will be light and variable
initially, becoming SW at 3-5 KT overnight.
AFTER 12Z SATURDAY...
Any fog or low stratus is expected to burn off between 13Z and
15Z (8-10 am local time), with conditions improving to VFR across
all terminals. As the cold front moves through the region during
the afternoon, a period of SCT to BKN low clouds between 2500-4000
ft AGL is possible, which may result in brief MVFR cigs. SFC WNDS
will become W/NW at 10-15 KT with some gusts possible behind the
frontal passage. No significant aviation hazards are expected
during the afternoon.
OUTLOOK...
No significant weather events impacting aviation are anticipated
for Sunday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Kieckbusch
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion