670
FXUS63 KGRB 132040
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
340 PM CDT Sun Jul 13 2025

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Near-surface Canadian wildfire smoke will continue to result in
  poor air quality and reduced visibilities into Monday. An Air
  Quality Advisory remains in effect until noon Monday.

- Next round of more widespread active weather arrives Tuesday
  afternoon into Thursday.

- Very warm and humid conditions to start the work week with heat
  index values in the upper 80s to low 90s.

&&

.DISCUSSION...
Issued at 340 PM CDT Sun Jul 13 2025

Rain / Thunderstorm Chances: Isolated showers and storms should
develop across northeast MN and far northwest WI later this
afternoon and evening as a weak frontal boundary interacts with
peak daytime heating/instability. As the boundary sags to the
south overnight, a stray shower or sprinkle may make it into
north central or central WI after midnight into Monday morning as
the activity wanes. Greatest chances for measurable rain (over
20%) remain just west of Vilas and Lincoln counties, so will hold
PoPs under 15. The boundary will linger in the area through the
day on Monday, along with a weak shortwave, so a stray shower
can`t be ruled out, but again, chances are under 15% so will keep
the afternoon dry.

Better chances for widespread showers and storms will arrive late
Tuesday into Wednesday, as a zonal upper flow will prevail over
the northern CONUS, with fast moving shortwaves riding this flow,
along with a quasi-stationary frontal boundary draped across the
Upper Midwest. This will be a decent set up for a bout or two with
a large complex and heavy rain, as an impressive pool of moisture
and instability will reside south of the boundary. Models still
trying to iron out where the best threat for heavy rain (along
with possible severe storms) will be, with the placement and
orientation of the LLJ and boundary will play a big role in where
any complex forms and how long we will be under the threat for
heavy rain/storms. Probs for an inch of rain in any one 24-hour
period are running at 20% or lower, but think these will increase
once the models latch on to a better consensus.

Smoke Trends: Satellite and surface observations continue to show
an area of Canadian wildfire smoke across the region. The first
thicker batch will move through this afternoon into early tonight,
with a break in the thicker smoke (currently in MN and northwest
WI) expected to work east across the area this evening into
tonight. HRRR/RAP/Canadian take the next thick batch of smoke,
currently over far northwest MN, into locations mainly north of
Hwy 29 on Monday. The smoke will bring poor air quality, a
burning smell, along with reduced visibilities to 3-6 miles at
times. An Air Quality Advisory remains in effect until noon on
Monday.

Temps / Humidity: A very warm couple of days are expected Monday
and Tuesday with highs climbing to the mid 80s to near 90.
Dewpoints on Monday will climb into the mid and upper 60s across
central and east central WI, producing heat index readings in the
upper 80s to around 90. The entire area should see dewpoints in
the mid 60s to near 70 Monday night, making for a very warm and
muggy night. Dewpoints in the mid 60s to around 70 will continue
on Tuesday, with heat index readings in the mid 80s to low 90s.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1247 PM CDT Sun Jul 13 2025

Smoke from Canadian wildfires will continue to move across the
region at times through the TAF period, bringing poor air quality
and mainly MVFR visibilities. The first batch will move through
this afternoon into tonight, with a break in the thicker smoke
(and the MVFR visibilities) expected to slowly work west to east
across the area later today into tonight. Another batch of thicker
smoke is forecast to move into northern WI Monday morning.
Otherwise, look for daytime cu to continue through the afternoon
then fade this evening. As a weak frontal boundary sags into and
across the area overnight into Monday morning, a stray shower will
be possible, but chances are under 20% and no impacts are
expected, so will not include. Some mid-clouds will also likely
accompany this boundary.

A period of LLWS is possible over northern WI (RHI) overnight
into early Monday as 2000 ft winds increase to 30-35 kts. It looks
marginal and short-lived, so have confined it to just a few hours
at RHI late tonight.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Bersch