Oconto Falls, Wisconsin Weather Forecast Discussion

083
FXUS63 KGRB 110337
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1037 PM CDT Wed Sep 10 2025
Updated aviation portion for 06Z TAF issuance
.KEY MESSAGES...
- Light showers will continue over far northeast Wisconsin until
  early evening.
- Areas of fog, locally dense, are likely over north-central,
  central, and far northeast Wisconsin late tonight. Dense fog is
  also possible on Thursday night.
- Chances for showers and thunderstorms return for Friday night
  and Saturday but severe weather is not expected.
- Above normal temperatures are expected from Friday through next
  Wednesday.
&&
.DISCUSSION...
Issued at 219 PM CDT Wed Sep 10 2025
Short Term...Tonight and Thursday
The latest RAP analysis and satellite/radar imagery indicate a
weak cold front extending from Wood County to Marinette County
this afternoon. This boundary, coupled with shortwave energy
aloft, is producing light showers just north of the front. Cloud
bases vary, with LIFR/IFR/MVFR conditions persisting north of the
front, while south of the boundary, cloud bases are higher,
ranging from 5-7 kft. Widespread low stratus over northwest
Wisconsin, the Upper Peninsula, and Lake Superior is very slowly
eroding, a trend expected to continue through the afternoon.
Probabilities are low that there will be sufficient mixing to
completely erode this low stratus layer. Consequently, a chance of
light showers remains over far northeast Wisconsin until early
evening. As high pressure builds into the region from the north,
the primary forecast concern shifts to the potential for dense
fog.
The cold front will continue its slow southeastward progression
tonight, moving into central and east-central Wisconsin. However,
convergence along the front is expected to weaken as it advances.
Concurrently, high pressure will build in from the north. As the
shortwave energy responsible for current showers exits the region,
clouds above the boundary layer are anticipated to dissipate. Low
stratus, however, is expected to persist north of the front. The
main uncertainty for tonight revolves around whether this
persistent low stratus will inhibit the formation of dense fog
after midnight.
Despite the potential for low stratus, the combination of high
pressure, light winds, and low boundary layer dewpoint depressions
will create favorable conditions for widespread fog development
across much of north-central, central, and far northeast Wisconsin
late tonight. Think fog is a solid bet, either by a descending
stratus layer, or by radiational cooling.  Statistical guidance
and model time- height sections strongly suggest that fog will
redevelop after approximately 12-2 AM CDT and subsequently spread
southward overnight. This fog is likely to become dense in
localized areas, particularly over north-central and portions of
central Wisconsin, which may necessitate the issuance of a Dense
Fog Advisory. This could impact Thursday morning commute.
The fog is expected to persist through 9-10 AM CDT on Thursday
before lifting into a low stratus/stratocumulus field by midday.
Improved afternoon mixing should lead to warmer high temperatures
on Thursday, reaching the upper 60s to mid-70s across the forecast
area.
Long Term...Thursday Night Through Wednesday
A relatively stable upper-air pattern is forecast to persist
through the upcoming weekend and into early next week. This
pattern is characterized by trough positions over the eastern and
western Lower 48 states, effectively bookending a strengthening
central U.S. ridge. This ridge is anticipated to break down
somewhat by the middle of next week. As a result of this robust
ridge, temperatures are likely to be above normal for much of the
period.
The primary  forecast concerns in the long term revolve around:
1) the potential for dense fog on Thursday night, and 2)
thunderstorm chances on Friday night and Saturday.
Dense Fog Potential: A pure radiational fog setup is likely late
Thursday night. While better mixing is expected during Thursday
afternoon, cross-over temperatures are only forecast to fall into
the mid-50s. With forecast lows in the upper 40s to lower 50s,
conditions will be highly favorable for dense fog development,
particularly north and west of the Fox Valley. This could impact
Friday morning commute.
Thunderstorm Potential: As the ridge builds into the area, a warm
front will slowly lift northeast across the upper Mississippi
Valley and western Great Lakes. Weak shortwave impulses tracking
across the northern Great Lakes will contribute to the development
of a low-level jet into Wisconsin on Friday night. Convergence on
the nose of this low-level jet should support elevated showers
and thunderstorms. Forecast soundings indicate warm temperatures
aloft (+10C) and skinny CAPE profiles, which could result in
200-400 J/kg of instability. Clustered showers and storms appear
possible, with the highest chances over central Wisconsin. The
severe weather threat is anticipated to be low given the weak
instability. Showers and storms should gradually weaken Saturday
morning, mainly over central and east-central Wisconsin, as the
low-level jet veers and sharp ridging continues to build aloft.
The remainder of the weekend looks mild and dry under the
influence of this strengthening ridge.
As the central U.S. ridge begins to break down, shortwave energy
could bring a chance of rain to the area from Monday night into
Tuesday. However, forcing associated with this system does not
appear particularly strong at this juncture, resulting in low
confidence in the specific details of this precipitation event.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1036 PM CDT Wed Sep 10 2025
Patchy areas of dense fog have begun to develop across Vilas Co.
this evening. Expect flying conditions will continue to deteriorate
across parts of the region tonight as light winds, remnant low-level
moisture, and an arriving high pressure system make fog/low status
formation likely. Fog will be most widespread across north-central
WI where skies were able to clear out this evening. Was most
aggressive with fog at RHI with periods of IFR/LIFR conditions possible
much of the overnight and early morning hours.
Across central and north-east WI there is more uncertainty with
when/where fog/low status may develop as lingering mid-level clouds
may inhibit fog development. Included TEMPO groups with IFR/LIFR
cigs and vsbys at AUW and CWA to frame out the best timing for fog
impacts.
Light northeast winds off the relatively warm waters of Lake Michigan
and Green Bay will also make fog/low status possible along the
lakeshore overnight into Thursday morning. IFR conditions will be
possible at times at GRB, MTW, and ATW. However, with lingering mid-
level clouds over that region tonight confidence in prolonged
periods of LIFR is lower.
Fog and low stratus will begin lifting in the 14-15z timeframe.
Slow improvement of flight conditions is expected on Thursday
morning. By the afternoon cigs should start to scatter out returning
VFR conditions to the region.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CDT Thursday for WIZ005-010>012.
&&
$$
DISCUSSION.....MPC
AVIATION.......GK

NWS GRB Office Area Forecast Discussion