541
FXUS63 KGRB 162335
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
635 PM CDT Wed Jul 16 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Heavy rain across portions of central and east-central WI will
  taper off this evening. A Flood Watch is in effect for central
  WI until 7 pm and portions of east-central and northeast WI
  until 10 pm.

- Small risk of severe storms continues through late afternoon across
  central and east-central WI. Damaging winds would be the
  primary risk along with torrential rainfall and possible
  flooding.

- The warm and humid weather will come to an end tonight. Cooler
  and less humid on Thursday and Friday.

- Small craft should exercise caution on the bay of Green Bay through
  late this afternoon. A Small Craft Advisory is in effect for
  the bay and nearshore areas of Lake Michigan tonight into
  Thursday morning.

- An active pattern is expected Friday night through the middle
  of  next week with periodic chances of thunderstorms. Stronger
  storms and heavy rain are possible at times.

&&

.DISCUSSION...
Issued at 219 PM CDT Wed Jul 16 2025

A Mesoscale Convective Vortex continues to move across the region
this afternoon, bringing showers and scattered thunderstorms to
the region. Some of the strongest storms could produce strong
or damaging winds, an isolated tornado and torrential rainfall
across central and east-central WI. This feature will also bring
in additional moisture as precipitable water values at Green Bay
are expected to increase to 2.11 inches late this afternoon or
near the daily record supporting the likelihood of heavy rainfall.
The movement of the mesoscale convective vortex will support a
nearly west to east band of heavy rain across portions of central
into east-central Wisconsin. The greatest rainfall is expected to
fall in a corridor from Marshfield to Wisconsin Rapids to Waupaca
and Wautoma to Appleton and Oshkosh east to Kewaunee and
Manitowoc. For locations south of Highway 29, HREF probabilities
indicated a 50-90% chance of 1 inch of rain, 30-60% chance of 2
inches and a 10-30% chance of 3 inches. The greatest risk of heavy
rain and flooding will continue for the remainder of the
afternoon into early this evening. Rainfall rates in the heavier
showers and storms could be as high as 1 to 3 inches per hour,
resulting in urban street flooding and ponding of water on area
roads while creeks and ditches may rise rapidly. Fishermen and
boaters on rivers should anticipate river rises and faster flows
from runoff Thursday and Friday.

On the backside of the vortex, gusty northerly winds and building
waves will result in hazardous conditions for small craft into
Thursday morning. Also, low stratus is expected tonight, combined
with northerly winds should keep any dense fog away. The big
change will be the cooler weather and much less humid conditions.
Highs on Thursday will only be in the upper 60s to middle 70s. The
dewpoints will continue on Friday and then will increase again
over the weekend.

The westerlies will linger along the U.S./Canadian border through
the rest of the forecast period. This will result in an active
period with periodic chances of showers/storms next week. The
potential exists for stronger storms and heavy rainfall at times.
The first round of storms arrive Friday night into Saturday
morning with dry conditions expected Saturday night into Sunday
night. The chances of showers and storms return Tuesday and
Wednesday. Temperatures will be close to normal this weekend, then
rise above normal for much of next week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 629 PM CDT Wed Jul 16 2025

The risk of thunderstorms is diminishing early this evening
across northeast and east-central WI. Despite the lower risk
of thunderstorms, heavy rain is still possible at times
through 02z from KMTW/KATW/KGRB/KOSH through KOCQ and KSUE
as a large cluster of showers and a few storms exit the
area. Later tonight, MVFR to IFR CIGS expected with gusty
north/northeast winds near the bay and lake. Many questions
linger Thursday morning in how quick the low clouds clear
out. Based on the bufkit soundings, CIGS should rise in the
VFR category by late morning at most locations.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 7 PM CDT this evening for WIZ037-045.

Flood Watch until 10 PM CDT this evening for WIZ038>040-048>050.
&&

$$

DISCUSSION.....Eckberg
AVIATION.......Eckberg