Isaar, Wisconsin Weather Forecast Discussion

854
FXUS63 KGRB 030715
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
215 AM CDT Fri Oct 3 2025
Forecast discussion for routine morning forecast issuance
.KEY MESSAGES...
- Temperatures warm through the weekend, peaking in the mid to
  upper 80s Friday and Saturday afternoons. Several record highs
  will be in jeopardy both days.
- Conditions hazardous to small craft are expected Saturday
  afternoon through early Monday morning.
- Gusty winds paired with near record temperatures will result in
  increased fire weather potential 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 205 AM CDT Fri Oct 3 2025
Persistence forecast more or less continues, with the main focus
being potential for record-breaking high temperatures this
afternoon and Saturday. Attention then turns to increasing winds
over the weekend, bringing with them elevated fire weather
concerns and hazardous marine conditions. Most recent suite of
medium/long-range model guidance remains pessimistic about rain
chances over the weekend.
Temperatures... At this point, pretty confident in saying that at
least a couple locations are likely to break record high
temperatures this afternoon, and again Saturday afternoon. 925 mb
temps are progged to read between 22 and 24C both days, which,
when paired with subsidence from thermal ridging, will likely
translate to surface temps reading in the mid to upper 80s for
many. Few to scattered cloud cover should also allow for
effective warming at the surface, further increasing forecast
confidence. Little to no recovery is expected Friday and Saturday
nights, with lows notably only making it into the low to mid 60s
in/around the Fox Valley (record high mins?). Post-frontal
temperatures then drop back into the 50s and 60s to start the
work week, with highs potentially falling into below average
territory by mid-week.
Winds/fire weather... Pressure gradient tightens up over Wisconsin
beginning Saturday afternoon, with coincident 40 to 50 knot LLJ
spelling out potential for deep mixing and increasing winds.
Widespread surface gusts of 30 to 35 knots look to be possible,
especially Sunday afternoon. When combined with little to no
precip and record high temperatures, elevated fire weather
concerns begin to come into play. RHs bottom out in the low to mid
30s Sunday afternoon, mainly in the sandy soil regions of far
northeast Wisconsin. These areas will be well within the
thresholds for power line fires during this time, especially as
leaf litter continues to fall and finer fuels start to dry out. As
it stands now, the DNR`s Fire Danger Rating sits at "High" to
"Very High" for most of northern Wisconsin both Saturday and
Sunday. As such, will continue to hit the messaging a little
harder for power line fires in subsequent products.
Marine... Pretty slam dunk for a prolonged period of marine
headlines this weekend as robust southerly winds build waves on
Lake Michigan to 4 to 6 ft on Saturday, and near 10 ft Sunday
afternoon. Less slam dunk on the Bay, though if trends hold, small
craft conditions will be possible at times. Winds may occasionally
gust to near gale force on Sunday, especially up by Death`s Door.
Maintain that preliminary headline timing would be Saturday
afternoon through early Monday morning.
Rain/storm chances... Decaying cold front is still progged to clip
northern Wisconsin this afternoon, bringing with it a slight
chance for an elevated shower or two. A modest pool of
instability (~500 to 600 J/kg MUCAPE) gathers ahead of this
boundary as weak low-level moisture transport makes its way into
far northeast Wisconsin, resulting in potential for isolated
thunder during this time. However, any shower that does go up will
have to contend with a massive reservoir of dry air as high
pressure sits and spins over the eastern CONUS. Blocking pattern
then breaks down late this weekend, as robust troughing over the
Intermountain West ejects a shortwave into the upper Mississippi
Valley as a cold front sweeps east. Deeper moisture behind the
front still looks to be an issue, with most AI models keeping the
main swath of precip off to our south. Suspect that any shower
activity will be sheared out regardless as 850 mb LLJ sits over
eastern Wisconsin. Probabilistic guidance now shows chances for
receiving 0.25" of rain at around 30 to 40% over east-central
Wisconsin through Monday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1033 PM CDT Thu Oct 2 2025
Higher dew points in eastern WI should allow patchy fog to
develop as the surface pressure gradient weakens 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 late tonight. The latest
regional radar mosaic suggests that most of the overnight
convection should remain north of WI. There is some potential for
scattered showers and isolated thunderstorms to develop in
northern WI Friday afternoon, as weak daytime instability forms in
the vicinity of the stalled front. Will keep a Prob30 for showers
at RHI mid to late afternoon.
Surface winds will be light from the south to southwest through
the period. Borderline LLWS is possible in NC WI overnight, as
southwest winds aloft increase to around 30 knots. However, given
the borderline wind speeds and brief duration, have not added
this to the RHI TAF.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Goodin
AVIATION.......Kieckbusch

NWS GRB Office Area Forecast Discussion