883
FXUS63 KGRB 070256
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
956 PM CDT Thu Aug 6 2026

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 753 PM CDT Thu Aug 6 2026

Dewpoint depressions are already very low along the Lake Michigan
shoreline from Sturgeon Bay to Manitowoc. This area has the
greatest potential for dense fog later tonight. Dewpoints mixed
out somewhat over the Fox Valley late in the afternoon and
confidence of dense fog is lower here. Most guidance are not
excited about fog tonight, but will continue to monitor trends
for a possible dense fog advisory.

&&

.KEY MESSAGES...

- There is a marginal (1/5) risk for severe weather Friday
  afternoon through Friday evening.

- Several rounds of showers and storms are expected this weekend
  through early next week, though confidence in storm timing and
  severity remains low.

- Near normal high temperatures in the low to mid 80s through
  most of next week.

&&

.DISCUSSION...
Issued at 112 PM CDT Thu Aug 6 2026

Near term through Friday morning...High pressure will result in
mostly clear skies and light winds. Patchy fog may occur again
tonight, but it will not be as dense and widespread as it was this
morning.

Rain/storm chances...Leading chance of storms Friday afternoon
into Friday evening appears to carry the highest risk for severe
this weekend. Tail of very sharp shortwave seen over Saskatchewan
today swings across MN to Lake Superior Friday afternoon. Cold
front reaches western Lake Superior to northwest WI during peak
heating of the day, with MLCAPEs increasing to 1500-2000J/kg just
ahead of the front. Strongest effective shear is closer to
shortwave, near 40 kts, with 30+ knots from northern WI to central
WI by late afternoon. Shear tails off to less than 20 kts farther
east. A few strong storms with gusty winds the primary hazard are
expected over north-central and central WI, shifting east while
weakening through late evening until around midnight.

Beyond Friday, general idea remains on track. NW flow will bring
several weaker shortwaves across the area, but primary area of
higher instability and shear remains west and southwest of
northeast WI, Iowa into northern Illinois. Decent agreement that
after the front passes later Friday night, Saturday will be dry,
with another round of smaller pops late Saturday night. As low
pressure forms over the central Plains late in the weekend, front
will return north and bring the highest chances for showers and
storms Sunday night into Monday. Some time frame during this
broader window will feature widespread showers and embedded
storms as the low-level jet and elevated instability will be
aimed toward at least our southern forecast area. This is also
when ECMWF EFI still shows the closest approach of greater signal
for higher CAPE/shear, so this will have to be watched especially
given the front will be nearby. Given the front straddling the
area and PWATs over 1.5 (80-90th percentile), there is a marginal
risk (level 1 of 5) for excessive rainfall/flooding especially if
there are training storms.

Front settles south of WI next Tuesday, but weaker waves in
northwest flow could still allow for a few showers or storms
Tuesday into Wednesday. Pops for this time remain low, at 15-30%.

Temperatures/smoke...Temperatures will continue to be around normal
in the low to mid 80s through the weekend as upper flow flattens
out and weakens. Humidity levels will be comfortable, with
dewpoints reading in the upper 50s to mid 60s. There will be an
increase in dewpoints into the mid and upper 60s on Friday ahead
of the front. A plume of elevated wildfire smokes works its way
into Wisconsin through Friday. Another push of smoke occurs late
in the weekend into early next week. No significant impacts to
visibility or air quality are expected with the smoke.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 956 PM CDT Thu Aug 6 2026

Patchy ground fog remains expected overnight. Coverage should be
less than last night with the greatest potential along the
lakeshore from Sturgeon Bay to Manitowoc. Fog in the Fox Valley
is more questionable but patchy fog remains possible. Have
continued including the tempo for 1 1/2SM vsbys at GRB. The fog
should lift between 13-14Z Fri.

Fair weather clouds should again pop 15-16Z Fri and most
widespread over northeast WI. As a cold front approaches the
region from the northwest, there is a chance of showers and
thunderstorms over north-central and central WI after 21-22Z.
Have therefore added a prob30 at RHI/AUW/CWA. Prob30s have also
been added to GRB/ATW after 00Z Sat. Some storms could contain
gusty winds should they develop. The threat of showers and storms
will end by the end of the TAF period.

Lastly, southwest winds will become breezy on Friday with gusts up
to 20 kts. Otherwise, light winds under 10 kts are forecast.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE.........MPC
DISCUSSION.....JLA
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion