Tilleda, Wisconsin Weather Forecast Discussion

333
FXUS63 KGRB 111933
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
233 PM CDT Thu Sep 11 2025
Forecast discussion for routine afternoon forecast issuance
.KEY MESSAGES...
- Areas of fog, locally dense, will impact travel across parts of
  the region late tonight into early Friday.
- Chances for showers and thunderstorms return Friday night into
  Saturday morning, but severe weather is not expected.
- Above normal temperatures are expected from Friday through next
  Thursday, with rain chances returning by the middle of next
  week.
&&
.DISCUSSION...
Issued at 233 PM CDT Thu Sep 11 2025
Short Term...Tonight and Friday
The latest RAP analysis and satellite/radar imagery indicate a
robust high-pressure system extending from James Bay southwestward
into the central Great Lakes this afternoon. Low stratus has
persisted across much of north-central and northeast Wisconsin,
though recent satellite trends show gradual erosion occurring from
both the northern and southern edges of the cloud deck. Based on
these observations, confidence is higher for central and north-
central Wisconsin to experience clearer skies by late this
afternoon. However, the eastern portions of the forecast area,
particularly where persistent northeast winds are maintaining
onshore flow, are less likely to see significant clearing. The
continued presence of this steadfast high-pressure system across
the region suggests that dense fog remains the primary forecast
concern over the next 24 hours.
The high-pressure system currently influencing our weather will
gradually shift eastward tonight, but its influence will remain
significant across north-central and northeast Wisconsin. With
skies expected to partially clear and winds becoming light,
conditions will once again become favorable for the widespread
development of low stratus and fog. Over the past several nights,
stratus has been more prevalent than dense fog, leading to
relatively low confidence regarding the precise locations where
dense fog will form. Furthermore, it is not entirely certain that
eastern Wisconsin, excluding the immediate lakeshore, will
experience significant clearing this afternoon, as the erosion of
the cloud mass has been slow.
Guidance suggests the highest potential for dense fog development
will be concentrated from the Bayshore and Fox Valley eastward
towards Lake Michigan. In these areas, light onshore flow is
expected to augment boundary layer moisture, creating a more
favorable environment for fog. However, this scenario is dependent
upon the stratus eroding later this afternoon. If the stratus
layer remains stubbornly in place, it should largely inhibit the
development of dense fog, particularly inland from Lake Michigan
where the stratus has been most persistent. Where skies do manage
to clear, areas of fog could begin to blossom possibly as early as
late this evening. Based on an analysis of cross-over
temperatures, localized areas of dense fog could develop,
potentially necessitating a Dense Fog Advisory.
Current model guidance points towards fog lifting around 14-15Z
(9-10 AM CDT) Friday. However, based on recent trends over the
past few days, this seems somewhat aggressive, and a late morning
dissipation (closer to 11 AM - 12 PM CDT) appears more realistic.
Thereafter, any lingering fog or low stratus is expected to evolve
into a fair-weather cumulus field for the afternoon. High
temperatures on Friday should reach the mid to upper 70s across
most locations, with cooler readings expected closer to the Lake
Michigan shore due to the persistent onshore flow.
Long Term...Friday Night Through Thursday
The long-term forecast through the middle of next week is
characterized by a strong agreement among various models and their
ensemble members regarding the synoptic pattern. Troughing is
expected to be present over the western and far eastern United
States, with a robust ridge building over the central portion of
the continent for much of the medium-range period. This ridge will
result in above-normal temperatures across our forecast area.
Thunderstorms: The primary focus within this extended forecast
period revolves around a chance of thunderstorms on Friday night
and Saturday. As the strong ridge begins to build into the area, a
warm front will slowly lift northeastward across the upper
Mississippi Valley and western Great Lakes on Friday and Friday
night. 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, combined with forcing along the edge of an upper-level
thermal ridge, should support the development of elevated showers
and thunderstorms. Forecast soundings indicate relatively warm
temperatures aloft (around +10C) and skinny CAPE profiles,
suggesting that 200-500 J/kg of elevated instability could be
present. Clusters of showers and storms appear possible from late
Friday evening through early Saturday morning. Given the weak
instability, the severe weather threat associated with this
activity is expected to be low. The remainder of the weekend,
including Saturday afternoon and Sunday, looks to be mild and dry
as the sharp ridging continues to build aloft, promoting stable
conditions.
Rain Chances Mid-Week: As the dominant ridge begins to break down
by the middle of next week, shortwave energy originating from the
base of the western trough could bring another chance of rain to
the area on Monday and Monday night. However, precipitation
associated with this feature is expected to weaken as it
approaches our region due to the presence of the strong ridge
aloft. More significant shortwave energy from the mean western
trough looks to approach the area by next Wednesday and Thursday,
potentially bringing a more widespread chance of precipitation.
However, due to the continued influence of the strong ridge, even
as it breaks down, confidence in the specific details of the
forecast for the middle to latter half of next week remains low.
Temperatures will generally remain above normal throughout this
long-term period, a direct consequence of the persistent ridging.
No other significant impactful weather, such as excessive heat,
strong winds, or fire weather, is anticipated during this extended
period based on current model trends.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1206 PM CDT Thu Sep 11 2025
Low stratus (IFR/MVFR ceilings) continue to blanket the region
early this afternoon. The stratus is eroding from the north and
south, north of the U.P. border and also over central WI, and
expect this trend to accelerate early this afternoon. Expectations
are for this stratus to evolve into fair weather cloud field with
bases from about 2.5 to 4 kft by mid-afternoon. Some clearing is
anticipated late this afternoon or early this evening.
High pressure will remain over the region tonight, leading to
favorable conditions for low stratus and fog once again. Guidance
is hitting eastern Wisconsin harder with lower visibility and
ceilings (LIFR/IFR) thanks to light onshore flow off Lake Michigan
augmenting the low level moisture. Remained pessimistic with
ceilings and visibilities at GRB/ATW/MTW as a result, with
deteriorating flight conditions occurring after 05-07z.
Visibilities and ceilings will be slow to rise again on Friday
morning, but a return to VFR conditions is tentatively schedule at
most TAF sites by 16z.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....MPC
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion