Marshfield, Wisconsin Weather Forecast Discussion

882
FXUS63 KGRB 021659
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1159 AM CDT Thu Oct 2 2025
Updated aviation portion for 18Z TAF 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 again this
  weekend.
- Gusty winds paired with near record temperatures may 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 Monday night.
&&
.DISCUSSION...
Issued at 207 AM CDT Thu Oct 2 2025
Temperatures... Trends solidly holding for record warmth Friday
and Saturday as southerly flow regime reigns. Afternoon highs are
likely to make it up into the mid to upper 80s for most, with NBM
interquartile range only showing a few degree spread.
Additionally, ECMWF Extreme Forecast Index (EFI) shows 90 to 95%
of ensemble members forecasting a record breaking event. All of
the above would lend to a high confidence forecast of record high
temperatures across northeast Wisconsin, especially if 18C 850 mb
temps are realized. Little recovery is expected Saturday night,
with lows only getting into the low to mid 60s (record high min?).
More seasonable temperatures are then on deck to start the work
week, with post-FROPA highs falling back into the 50s and 60s.
Winds/fire weather... Southerly winds begin to ramp up Saturday
and Sunday as the pressure gradient tightens up over northwest
Wisconsin. Coincident 50 knot LLJ will likewise open the tap for
deep mixing during this time, with the result being potential for
30 to 35 knot gusts at the surface. When paired with record
setting temperatures and little to no precip in the forecast, fire
weather concerns begin to enter the chat. RHs bottom out in the
low 30s Saturday afternoon, though fuel moisture remains a
question. However, with leaf debris beginning to come into play,
will definitely warrant monitoring in the coming days. Would not
be surprised to see the Fire Danger Rating come up heading into
the weekend.
Marine... Brief period of small craft conditions expected south of
Sturgeon Bay through this morning. Have backed off the current
headline to end at noon today instead of the original 4 PM due to
waves coming down sooner. Hazardous marine conditions then return
this weekend as southerly winds ramp up ahead of an approaching cold
front. Waves are progged to build to 2 to 4 ft on the Bay, and 5 to
8 ft on Lake Michigan, with a consistent signal leading to higher
confidence in additional small craft headlines.
Rain/storm chances... Have maintained a mostly dry forecast for
today and Friday even as a weak cold front skirts northern
Wisconsin. Main hindrance will be the lingering influence of dry
air from dominant high pressure situated over the eastern CONUS.
Thermal ridge then looks to break down late this weekend,
bringing about our next noteworthy rain chances late Sunday
through Monday. Robust trough over the Intermountain West will
eject a shortwave into the upper Mississippi Valley Sunday
afternoon as a cold front sweeps east over Wisconsin. However,
long-range guidance continues to be unimpressed with precip
amounts during this time, as deeper moisture looks to be confined
to a narrow corridor behind the front. As such, probabilistic
guidance only shows a meager 10% chance of receiving 0.25" of rain
Sunday into Monday.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1159 AM CDT Thu Oct 2 2025
Mainly VFR conditions are expected through the TAF period.
A weak cold front over northwest Minnesota will move eastward
across the region tonight into Friday morning. However, this
boundary is expected to weaken. Moisture and instability are
limited, resulting in a very low chance of mainly high-based
showers over far northern Wisconsin, with no impacts anticipated
at the TAF sites.
Expect scattered to broken mid/high clouds (bases generally above
8000 ft) to persist through the period. South to southwest winds
will generally be under 10 kts (with the exception of a few gusts
15-20 kts this afternoon).
Confidence in VFR conditions is high. No significant aviation
hazards are expected.
Outlook...Good flying weather will continue into Friday night.
Winds will increase on Saturday and Sunday and could pose some
aviation challenges at times.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Goodin
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion