758
FXUS63 KGRB 151116
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
616 AM CDT Wed Jul 15 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Another hot and humid day is expected across central and east-
  central Wisconsin with heat indices reaching 95 to 100 degrees
  south of HWY 29. Across northern Wisconsin the heat and humidity
  will start to abate today.

- There is a small ~10% chance for showers and storms this
  evening. Increasing shower and storm chances arrive Thursday and
  continue through Saturday. Predictability of any storms
  becoming severe is low.

- Air quality and visibility is expected to be impacted by smoke
  from wildfires burning across northern Minnesota and southwest
  Ontario today through at least Thursday.

&&

.DISCUSSION...
Issued at 239 AM CDT Wed Jul 15 2026

Heat and Humidity...A moisture boundary, currently snaking across
northern Upper Michigan westward into the Minnesota Arrowhead, will
sink south today leading to a noticeable decrease in dew points
across northern Wisconsin. Air temperatures north of HWY 29 will
still peak in the upper 80s to around 90 degrees, but with the
decreasing humidity heat indices are not expected to reach advisory
criteria. South of HWY 29 dew points will remain in the mid 60s to
low 70s through this afternoon which along with with temperatures
peaking in the low to mid 90s will result in one more day of heat
indices in the mid 90s to around 100 degrees. A Heat Advisory has
been extended through this evening for counties in and around the
Fox Valley and into parts of central Wisconsin.

As the upper ridge that has been driving this heat wave continues to
break down through the end of the week temperatures and humidity
will continue to gradually moderate. Temperatures on Thursday may also
be held down a few degrees as both surface and elevated smoke from
wildfires burning across northern Minnesota and southwest Ontario
filters over the forecast area.

Smoke Trends...As mentioned above, with surface winds taking on more
of a northerly component today into Thursday wildfire smoke will
filter over the region. With the anticipated impacts to air quality
the Wisconsin DNR has issued a statewide Air Quality Advisory that
currently runs through noon Thursday. In addition to the air quality
impacts, periods of reduced visibility due to smoke are expected
today and Thursday.

Precipitation Chances through this weekend...Today will again be
largely dry across the forecast area. As the aforementioned moisture
boundary sinks south some CAMs show it becoming a focus for a few
isolated showers and storms across central Wisconsin (west of an
Oshkosh to Stevens Point line) this evening. Given the moist air
mass in place strong instability levels will be present to promote
brief strong updrafts, however, weak deep layer shear will prevent
any storms from becoming well organized. If a storm does develop (5-
10% chance) main hazards would be cloud to ground lightning and
brief downpours.

Precipitation chances begin to increase Thursday evening and continue
into this weekend as the upper-level flow becomes northwesterly
allowing a series of short-waves to move across the western Great
Lakes. For now have broad PoPs of 40-70% during this periods,
however, it does not look this entire period will be a wash out.
Given the warm moist air mass that will be in place any short-waves
that pass over the region during peak heating may lead to a round of
stronger to possibly severe storms, but at this point no day stands
out has having a greater severe weather threat. Ridging is forecast
to redevelop over the region Sunday returning dry conditions to start
next week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 615 AM CDT Wed Jul 15 2026

Main impact to aviation through the TAF period will be the arrival
of wildfire smoke as winds become northerly behind a weak surface
boundary sinking south this morning. Surface observations from
northern WI and the UP are already showing reduced vsbys due to
smoke and expect that trend to spread to all terminals this morning.
The degree to which surface visibility will be impact is uncertain.
For now have generally VFR vsbys through much of the day with a drop
to MVFR possible this evening. Will need to monitor trends in
surface vsbys today and will likely need to make TAF amendments
based on there the pockets of the most dense smoke develop.

Other than the smoke high based cirrus is expected to stream across
northern WI through much of the TAF period. There is also a low end
5-10% chance for an isolated shower or thunderstorm to develop in
central WI this evening which could impact AUW and/or CWA, but given
the low confidence have left any mention of precipitation out of
those TAFs.

.KOSH...

VFR cigs are expected to continue through this TAF period. Light
west winds become northerly  this morning , before turning
northeast/east late this afternoon/early evening. Wildfire smoke
will slide south behind a weak front today likely causing vsbys to
drop this afternoon, potentially to MVFR by this evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM CDT this evening for WIZ035>039-045-
048>050.
&&

$$

DISCUSSION.....GK
AVIATION.......GK

NWS GRB Office Area Forecast Discussion