438
FXUS63 KGRB 181145
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
645 AM CDT Mon Aug 18 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Active weather returns to the region today, with showers and
  thunderstorms expected in the afternoon and evening. A few
  strong or severe storms are possible in the afternoon and
  evening.

- Some rain today may be heavy, with around 40-60% of exceeding
  an inch of rainfall across portions central and east-central
  Wisconsin.

- A few isolated showers are possible along the lake breeze in
  east-central Wisconsin on Tuesday, but the rest of the week
  looks dry.

&&

.DISCUSSION...
Issued at 401 AM CDT Mon Aug 18 2025

The main period of impactful weather in the forecast period will
be today, mainly in the afternoon and evening.

An initial swath of precipitation is on its way across the area,
bringing predominantly light rain to portions of the region. This
initial round is expected to continue to overspread the region
through the morning hours and may see more moderate rain at times.
Isolated rumbles of thunder may briefly touch into central
Wisconsin at times, but relatively low impacts are expected
through the mid to late morning.

Attention then turns to afternoon period as an upstream MCV
arrives from the Dakotas. This thunderstorm complex is visible
currently on satellite and radar over northwestern Iowa and
southwestern Minnesota and will likely track along the 850 mb warm
front, following the northern edge of the instability gradient.
This track would bring it into portions of central Wisconsin by
around the late morning and cross Wisconsin during the early to
mid afternoon. As with previous forecast discussions, the northern
extent of this storm complex will largely be dictated by the warm
front, which at this time will likely stay south enough that the
northern edge of the storms will just touch into portions of
central and east-central Wisconsin, roughly along Highway 10 or
so. The afternoon period will be the one to watch for any isolated
severe potential, but with the more southerly track to the
incoming MCV, widespread severe weather is not expected. Still,
some isolated areas of damaging winds, small hail, and heavy
rainfall are still possible. The more southerly track will also
trap the better moisture south of the region, reducing the
rainfall potential slightly. Now the probability of exceeding an
inch of rainfall sits around 40-60%, mainly just for portions of
central Wisconsin. Behind this more organized wave, some
additional showers and rumbles will be possible but the area is
not expected to destabilize enough to produce any additional
severe weather in the evening before quieter conditions return.

Rest of the forecast...
Added a small chance for precipitation to the forecast on Tuesday,
to account for some convergence along the lake breeze boundary
along eastern Wisconsin in the afternoon. This could produce some
brief showers in portions of the area and possibly a rumble of
thunder but overall impacts should be low. The rest of the
forecast continues to appear dry through most of the work week,
but a weak cold front could still bring a few more showers into
the area on Friday.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 645 AM CDT Mon Aug 18 2025

Rain and thunderstorms will impact the region today and will bring
some MVFR to IFR ceilings at times throughout the daytime hours.
An initial round of thunderstorms is expected to move through in
the late morning to afternoon hours followed by some scattered
showers. Added a TEMPO group to time out this initial round of
storms. Some additional storms may develop in the late afternoon
or evening, but coverage is expected to be more isolated, so kept
this as a PROB30 group. Any storms will likely lower visibility
for a time in the afternoon.

By the evening, active weather is expected to depart the region,
but the recent rainfall and calming winds will allow for some fog
formation, especially across central Wisconsin. Expect another
period of IFR flying conditions overnight for fog before
improvement arrives again Tuesday morning.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 10 AM CDT this morning for WIZ022.

Beach Hazards Statement until 4 PM CDT this afternoon for WIZ040-
050.
&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Uhlmann