Underhill, Wisconsin Weather Forecast Discussion

173
FXUS63 KGRB 081943
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
243 PM CDT Mon Sep 8 2025
Forecast discussion for routine afternoon forecast issuance
.KEY MESSAGES...
- Temperatures climbing back to or slightly above seasonal norms
  this week, with some highs in the 80s in spots possible late in
  the week and/or next weekend.
- Chances (30-70%) for rain showers and a few storms return
  tonight into Tuesday night.
- Conditions hazardous to small craft, along with dangerous
  swimming conditions, expected on the bay and Lake Michigan late
  this afternoon into Tuesday afternoon/evening.
&&
.DISCUSSION...
Issued at 243 PM CDT Mon Sep 8 2025
Short term guidance has trended away from any mention of sprinkles
for the afternoon period, so kept a dry forecast running through
the afternoon and evening as warmer air fills in aloft. Light rain
will arrive across the far north tonight however as an approaching
upper shortwave and LLJ behind the warm front lead to precip
development. Some evidence of the shortwave is visible in
Minnesota already this afternoon. Some rumbles of thunder may also
mix in at times, as instability remains moderate. Still, by
Tuesday morning any rain activity will largely be limited to
north-central Wisconsin.
As we get further into Tuesday, the frontal boundary will sag
further southwards, which will bring some showers and rumbles
further into central and northeastern Wisconsin, but there still
remains some question on whether and precipitation will get as far
as the Fox Valley and eastwards, so kept pops to a minimum through
the afternoon. Another weak shortwave will cross the area in the
afternoon on Tuesday, which coupled with some tall skinny CAPE
could produce a few more rumbles of thunder. Rain totals from
Monday night through Tuesday will be heaviest in north-central
Wisconsin, which will see the longest period of potential
rainfall. Probability of exceeding an inch lingers around 20-30%,
so heavy rainfall potential remains limited. The slow arrival of
precipitation will bring a wide spread in temperatures on Tuesday,
with highs limited to the middle 60s in north-central Wisconsin to
the middle 70s near the Fox Valley and lakeshore.
Added some low pops to Wednesday as well, as diurnal heating will
again produce some surface based instability across the region. No
larger organized forcing will be present, but wouldn`t be
surprised to see some isolated shower activity develop during the
afternoon. Overall potential at any one location will likely
remain around 15-20%, but a few locations will likely see a brief
sprinkle. Current rain amounts should be light, with probability
of exceeding a tenth of an inch only getting to around 20-30%.
Finally, a quieter period will be around through the rest of the
work week but another round of precipitation will be possible over
the weekend as another cold front crosses the region. High
temperatures for the weekend remain uncertain, but if we stick in
the warmer sector we may see some highs get back into the low 80s
on Saturday.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 114 PM CDT Mon Sep 8 2025
Winds will be gusty across the region through the afternoon, with
periodic gusts up to 20 knots at times through the evening. As
winds drop off a bit overnight, some LLWS will develop across much
of central to east-central Wisconsin before deeper mixing returns
on Tuesday. Showers are likely to spread into northern Wisconsin
during the overnight period as well, but will primarily be limited
to impacting RHI during this TAF period. The rain coverage will
expand south and eastwards into the portions of central Wisconsin
Tuesday afternoon as well, beyond the current TAF. Thunder
potential before this afternoon period seems limited, so excluded
a mention for now.
&&
.MARINE...
Issued at 243 PM CDT Mon Sep 8 2025
Southwest/south wind gusts to around 25 kts continues this
afternoon, but will be limited due to the unfavorable warm air
over the warmer waters, limiting mixing. Wave model kept 4`+
waves, so no other changes were made to the Small Craft Advisory,
with the bay ending Tuesday morning as winds decrease and Lake
Michigan ending Tuesday afternoon/evening to allow for the wave
action to subside. The large waves will result in dangerous
swimming conditions at Lake Michigan beaches. Bumped up the start
time of the Beach Hazards Statement as well.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement through Tuesday evening for WIZ022.
Beach Hazards Statement through Tuesday evening for WIZ040-050.
&&
$$
DISCUSSION.....Uhlmann
AVIATION.......Uhlmann
MARINE.........Uhlmann

NWS GRB Office Area Forecast Discussion