Cato, Wisconsin Weather Forecast Discussion

892
FXUS63 KGRB 300720
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
220 AM CDT Tue Sep 30 2025
Forecast discussion for routine morning forecast issuance
.KEY MESSAGES...
- Areas of fog, locally dense, will impact the region this
  morning. The fog may result in locally hazardous travel
  conditions for the morning commute.
- Dry conditions prevail through at least Friday, with small
  chances of showers and isolated thunderstorms this weekend into
  early next week. Majority of time this weekend will be rain
  free.
- Above to much above normal temperatures through the weekend.
  Peak of warmth, with near record highs, Friday and Saturday.
&&
.DISCUSSION...
Issued at 217 AM CDT Tue Sep 30 2025
Fog this morning...As dewpoints increased late on Monday, the
mostly clear skies overnight and cooling temps (below the crossover
temps) have allowed for patchy fog thus far. Sfc observations are
showing some vsby less than 1 mile, but webcams show nothing too
widespread or dense yet. Areas of dense fog could occur between 4
am and 8 am, so may still need Special Weather Statement or even
Dense Fog Advisory this morning. Nothing imminent at this moment,
but will continue to monitor for this potential.
High pressure over Ontario will build south today, pushing a cold
front southward across the western Great Lakes. After the early
morning fog diminishes, not much impact from this front due to a
dearth of low-level moisture. Winds will shift to the northeast,
but this doesn`t appear to result in significant cooling over the
warm conditions experienced Monday. Highs this afternoon will
still reach the lower 80s inland and near 80 in the Fox Valley.
The onshore flow will keep temps in the lower 70s near the
lakeshore, but even these "cooler" readings are still well above
normal for the last day of September. High pressure stays in place
tonight into Wednesday. Mid and high clouds over the plains will
attempt to spread over the region, leading to partly to mostly
cloudy skies tonight into Wednesday morning. This should dampen
the fog chances tonight. Wednesday will be the coolest day of the
week with highs mainly in the lower to middle 70s.
Beyond Wednesday, chances for any showers or storms, small as they
appear to be, will not occur until this weekend as frontal boundary
shifts toward western Great Lakes. Upper forcing driving that
front starts out robust early this week over the Pacific Northwest,
but fades away as it encounters strong ridging centered over the
midwest to southeast United States. Main focus for nose of low-
level jet this weekend is well to the north, so would tend to
think that is where greatest chances of rain will set up as well.
Our far north could get clipped by some showers and storms though
this weekend though. Secondary upper low dives over the southwest
United States by this weekend. It is not until this wave ejects
out over the plains and midwest early *next* week that primary
front moves over the region, leading to greater chances of at
least scattered showers and some storms.
Main story for the longer range forecast beyond Wednesday will be
another surge of well above normal temps late this week into the
coming weekend. SW flow will boost 850mb temps to at least 16c by
Thu and this lasts through Sunday. The spread from the 25th to
75th percentile in resulting high temps is very small, leading to
higher confidence forecast that highs will reach well into the
80s again Friday, Saturday and probably Sunday too. NBM
probabilities show 70-100% of most area seeing at least 80 on
Friday with values at least 60% for the weekend. Cranking it up a
bit, probabilities for seeing highs of at least 85 have increased
over recent runs, peaking at 40-60% on Friday from far northeast
WI, to west of the Fox Valley and into portions of central WI.
Seems a few locations could be near records for Friday (10/3 and
Saturday 10/4, though nothing is a lock at this point. Keep in
mind, normal highs by late this week are in the low to mid 60s.
It is feasible that Friday night and/or Saturday night we will
see *low* temperatures that end up being that warm.
Other than the fog early this morning, only other impact weather
of note will be on Lake Michigan Wednesday night into Thursday as
increasing southeast winds and building waves may lead to possible
marine concerns (Small Craft Advisories), especially south of Two
Rivers.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1000 PM CDT Mon Sep 29 2025
Confidence is increasing for areas of IFR/LIFR conditions
developing overnight.
Most locations remain VFR late this evening, but a few locations
have seen ground fog develop already. Expectations remain that conditions
will deteriorate after 06Z as fog develops and spreads. Areas of
IFR/LIFR conditions for both visibility and ceilings are expected
through sunrise. Conditions will improve to VFR between 13Z and
14Z Tuesday as fog dissipates. VFR is expected for the remainder
of the afternoon with light E/NE winds.
Outlook...
VFR conditions are expected to continue into Tuesday night.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....JLA
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion