018
FXUS63 KGRB 181825
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
125 PM CDT Sat Jul 18 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Another plume of wildfire smoke is expected to spread over the
  region from north to south this afternoon. Smoke will then
  likely cycle around the region through the weekend. Degraded air
  quality and visibility are expected at times.

- A round of thunderstorms is likely (60-80%) to impact the region
  Monday into Monday night. There is a level 2 out of 5 severe
  thunderstorms risk Monday.

&&

.DISCUSSION...
Issued at 220 AM CDT Sat Jul 18 2026

Precip/Thunderstorm Chances...A cold front moving into far northwest
WI early this morning will continue to progress south east through the
morning. Along the front a few isolated showers or weak storms are
possible (20-30%) through about 7AM this morning. Once the front
clears the region upper riding will start to build in keeping this
weekend dry.

Monday remains the main focus for thunderstorm activity as an upper
level vorticity max and seasonally strong jet streak are progged to
move across the state. At the surface southerly winds will deliver a
plume of upper 60s to low 70s dew points which paired with steep
mid- level lapse rates associated with an elevated mix layer will
result in strong destabilization. The combination of favorable
thermodynamics and kinematics will create a parameter space
supportive of possible higher end severe storms Monday. However,
storm scale details such as timing, storm mode, and convective
evolution remain uncertain. A few key features to watch will be
how any morning convection modifies the environment and how much
instability is able to recover. There will also likely be some
elevated wildfire smoke over the region that may also hamper
instability to some extent. Lastly, the degree of capping
associated with the EML will be key in determining how much
instability can build through the day ahead of the surface front.
Think the high end scenario would be a round of elevated storms
during the early morning capable of producing marginally severe
hail and damaging winds followed by a lull in storm active through
the late morning and afternoon then a period of semi discrete
super cells with all severe hazards possible. Quick upscale growth
along the progressive front may then lead to the development of a
QLCS with bowing segments producing swaths of damaging winds
Monday evening. A lower end scenario is that morning convection
lingers into the afternoon shunting the stronger instability to
the south and increasing capping resulting is much less impressive
severe potential. As CAMs come into range over the next 24-48
hours some of these details will come more into focus, but how
exactly storms will play out may not be clear until Monday
morning.

Behind this front, drier weather is expected for mid-week as high
pressure builds in with gusty northerly winds on Tuesday.

Smoke Trends...Relief from the smoke will be rather short-lived as
winds shifting back to the northwest today allowing another plumb
of smoke to cycle over the region this afternoon through Sunday.
However, HRRR and RRFS surface smoke fields show this round of
smoke being less intense than this past Wednesday/Thursday. Still
impacts to air quality and visibility are expected today and
Sunday. With northwest flow aloft amplifying next week, additional
bouts of smoke may impact the area over the next week, dependent
on fire behavior to the north and wind direction.

Temperature Trends...Seasonably warm temperatures are expected this
weekend under surface high pressure, but with less humid conditions.
Stronger cold advection will occur behind the frontal passage early
next week, with near to below average temps then favored through
late next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 123 PM CDT Sat Jul 18 2026

A SCT/BKN cu field with cloud bases of 3000 to 5000 ft AGL
prevailed across the region early this afternoon. Meanwhile,
wildfire smoke dropping from the north was causing MVFR/IFR vsbys
across most TAF sites. Northerly winds this afternoon were gusting
to 15 to 20 kts.

Anticipate the cu field to dissipate into this evening, but the
smoke may keep cigs around 3500 ft AGL late this evening and
overnight. The northerly winds will decrease and turn
northeast/east into this evening and overnight. Winds then turn
south/southwesterly by the end of this TAF period. Additionally,
vsbys will remain in the MVFR/IFR category due to the smoke but
may lift to 6SM or above Sunday morning when guidance indicates
some relief, mainly for the east-central WI TAF sites.

.KOSH...

SCT clouds around 4500 to 5000 ft are anticipated this afternoon
with northerly winds gusting to around 16 kts. However, vsbys are
expected to decrease to MVFR due to smoke dropping south over the
area. Decided to have vsbys as low as 3SM starting at 22z today,
but this may have to be lowered to IFR depending on how thick the
smoke becomes upstream. Vsbys look to increase to at least 6SM
Sunday morning, but the smoke will still be around on Sunday. The
northerly winds will decrease and turn northeast/east this
evening, becoming southerly towards the end of this TAF period.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion