Sobieski, Wisconsin Weather Forecast Discussion

023
FXUS63 KGRB 022354
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
654 PM CDT Thu Oct 2 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Temperatures warm through the weekend, peaking in the lower to
  upper 80s on Friday and Saturday afternoons. Several record
  highs will be in jeopardy both days.
- Conditions hazardous to small craft are expected from Saturday
  afternoon through early Monday morning.
- Gusty winds from 30 to 40 mph paired with near record
  temperatures may result in increased fire weather potential
  at times on Saturday and Sunday.
- Most locations stay dry until Sunday night with the arrival of a
  stronger cold front. Chances for isolated to scattered showers
  then last through Tuesday afternoon.
&&
.DISCUSSION...
Issued at 225 PM CDT Thu Oct 2 2025
Short Term...Tonight and Friday
The latest surface analysis reveals a tranquil and unseasonably
warm autumn day across north-central and northeast Wisconsin. Our
region is currently situated in a zone of southwesterly flow,
positioned between a dominant high-pressure system anchored over
the East Coast and an approaching cold front draped across
northwestern Minnesota. This frontal boundary is serving as the
focus for a plume of deep moisture, with precipitable water values
soaring to over 200% of normal from the southern Plains into
northern Minnesota. Despite the ample moisture, weak convergence
and a lack of significant instability are keeping shower activity
isolated along the front for now. As this front slowly progresses
eastward, our primary forecast challenges will revolve around the
potential for light showers and the potential for record-
breaking warmth.
Temperatures: An unseasonably warm airmass will continue to surge
into the region on persistent southerly winds tonight and Friday.
At the 925mb level, temperatures are forecast to reach 22 to 23
degrees Celsius, which will translate to surface high temperatures
climbing into the lower to middle 80s for much of the area on
Friday. This level of warmth is significant for early October and
will put some daily record high temperatures in jeopardy.
Lingering clouds, particularly across eastern Wisconsin, may
slightly temper the heating process, but a very warm day is
expected regardless.
Thunderstorms: The probability of thunderstorms remains very low,
but not zero. As the weakening cold front tracks into far
northern Wisconsin late tonight and Friday morning, a pocket of
elevated instability, on the order of 500 J/kg, could be
sufficient to trigger a few high-based showers. Confidence in this
activity is low due to minimal large-scale support and poor
convergence. A slightly better, though still low-confidence,
chance for isolated showers and thunderstorms (around 20%) will
emerge late Friday afternoon and evening over far northeast
Wisconsin. Here, the development of lake breeze boundaries could
create a localized zone of convergence, but a prevalent dry
airmass will be a significant limiting factor for any sustained
convection.
Dense Fog: There is a slight potential for some patchy fog to
develop late tonight, primarily over far northeastern Wisconsin.
However, widespread impacts are not anticipated.
Long Term...Friday Night Through Thursday
Temperatures: The weekend will feature a continuation of the
record-setting warmth. An upper-level ridge is expected to build
over the eastern half of the country, maintaining the flow of a
very warm airmass into Wisconsin. Saturday is shaping up to be the
peak of this warm spell, with 925mb temperatures near 23 degrees
Celsius supporting widespread highs in the middle 80s on Saturday.
Some of the typically warmer locations could even touch the upper
80s. Record high temperatures will once again be possible on
Saturday. Temperatures will begin to cool slightly aloft on
Sunday, but highs in the low to mid-80s are still likely,
especially across eastern Wisconsin. A significant pattern change
will bring an end to the anomalous warmth by the Monday-Tuesday
timeframe.
Strong Winds: As a trough deepens over the center of the
continent this weekend, the pressure gradient will tighten across
the region, leading to increasingly gusty winds. On Saturday,
southerly wind gusts of 30 to 35 mph are possible. The winds are
expected to become even stronger on Sunday, with gusts potentially
reaching 35 to 40 mph as the cold front approaches.
Elevated Fire Weather: The combination of unseasonably warm
temperatures, gusty winds, and forecast relative humidity values
between 35-45% will lead to elevated fire weather concerns this
weekend. Sunday appears to pose the greater threat due to the
stronger wind gusts. While the Wisconsin DNR currently assesses
the fire danger as low to moderate, and heavier fuels remain
relatively moist, the situation will require careful monitoring as
finer fuels like grasses and leaf litter will dry out quickly. The
increased leaf debris at this time of year combined with these
gusty winds may elevate the threat for power line fires.
Rain Chances: The extended period of dry weather will come to an
end as a cold front finally sweeps through the region. Light rain
showers will be possible along and ahead of this boundary from
Sunday night through Tuesday. However, overall moisture appears
limited, and rainfall amounts are expected to be light. The
probability of receiving more than a quarter-inch of rain is
currently only in the 20-40% range. Following the frontal passage,
high pressure is expected to build in for the middle of next
week, bringing cooler conditions.
Marine: South winds will increase this weekend into the 25 to 34
kt range, peaking on Sunday. Waves will likely peak on Sunday
evening at 3-5 feet on the Bay and 6 to 10 feet on the Lake. High
confidence that a Small Craft Advisory will be needed with a
preliminary timing from Saturday afternoon through early Monday
morning.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 640 PM CDT Thu Oct 2 2025
Higher dew points and a cooler marine layer in eastern WI may
allow patchy fog to develop in far NE WI, the lakeshore, bayshore
and Fox Valley areas as the surface pressure gradient weakens late
this evening and overnight. Suspect that MTW will be most
affected by this, so have hit the fog hardest there.
Aside from the overnight fog potential in eastern WI, expected
mainly VFR conditions, with a few showers accompanying a weakening
cold frontal boundary as it arrives later tonight into Friday.
Not convinced that the isolated/scattered weak convection in NE
MN will survive the trek into northern WI tonight, given a lack of
overnight instability. However, could envision potential for
scattered showers and isolated thunderstorms developing in
northern WI Friday afternoon, as weak daytime instability forms in
the vicinity of the stalled front. Have added a Prob30 for
showers at RHI.
Surface winds will be light from the south to southwest through
the period. Borderline LLWS is possible in NC WI during the late
evening and overnight hours tonight, as southwest winds increase
to around 30 knots. However, have not added this to the RHI TAF
site at this point.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....MPC
AVIATION.......Kieckbusch

NWS GRB Office Area Forecast Discussion