319
FXUS63 KGRB 141042
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
542 AM CDT Tue Jul 14 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Intense heat and high humidity will continue today. Maximum
  temperatures this afternoon will reach the middle to upper 90s with
  heat indices ranging from 95 to 105 degrees.

- Showers and storms are possible at times Wednesday evening
  through this weekend. Predictability of any of these storms
  becoming severe is low.

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

&&

.DISCUSSION...
Issued at 207 AM CDT Tue Jul 14 2026

Dangerous Heat/Humidity...Today is forecast to be the hottest day of
the year thus far with temperatures rising into the mid to upper 90s
across the forecast area. The warmest temperatures are expected
across eastern WI, including the Fox Valley, as model consensus
shows a localized maximum of 29-31C 925mb temperatures over this
region. In terms of heat indices most locations are forecast to
reach 95F to 105F. Downsloping winds and the sandy soils across
northern and far northeast WI may lead to slightly lower dew points
(low 60s) this afternoon, however, where dew points are lower air
temperatures will tend to be slightly warmer given the lower
moisture content in the air. In addition to impacts related just to
the heat and humidity, low temperatures this morning are not going
to offer much relief, especially across eastern WI where lows will
only fall into the low to middle 70s. This could lead to compounding
heat stress, particularly for vulnerable populations that may have
limited access to air conditioning.

While Wednesday won`t be quite as hot as today areas south of HWY 29
will still have a 70-90% chance for heat indices over 90 degrees and
high temperatures in the upper 80s to low 90s. As the upper ridge
breaks down and slides east temperatures do gradually start to
moderate Thursday through this weekend.

Heat Advisory remains in effect through 9PM tonight. Will need to
consider extending the Heat Advisory into Wednesday for counties
along and south of HWY 29 as heat indices are forecast in the upper
90s, where dew points will be in the mid to upper 60s.

Precipitation Chances...Today is expected to be largely dry across the
region, however, CAMs do hint at a weak boundary/area of middle
level confluence sinking across Upper Michigan and into northern WI
this afternoon and evening. This feature does provided the focus for
a low chance (~10%) of an isolated storm or two north of HWY 8.
Should a storm develop strong instability (MLCAPE 1500-2000 J/kg)
and marginal 25-30kt deep layer shear could support an isolated
strong storm. Again there is only a low end threat for a storm to
even develop given the weak forcing and expected capping. Additional
isolated showers and storms are possible (10-15%) Wednesday
afternoon/evening due to diurnal instability and upper-level
divergence in the right entrance region of a 500mb jet.

Beginning Thursday and continuing through this weekend upper-level
flow is expected to becoming primarily northwesterly. This will
allow for subtle short-waves to track across the region and spur on
periods of showers and storms. If any of these short-waves track
across the region during peak heating a round of strong to possibly
severe storms is possible given summer instability levels. However,
guidance does not point any specific day or time period as having a
greater risk for severe storms. This is in part due to a lack of
stronger shear over the region.

Smoke Impacts...As winds become more northerly Wednesday smoke from
wildfires across northern Minnesota and southwest Ontario will begin
to filter over the region. Per the Wisconsin DNR AQI values are
forecast to reach the moderate range Wednesday and possibly Thursday.
In addition to the impacts on air quality smoke may also reduce
visibility at times, especially across north-central WI.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 541 AM CDT Tue Jul 14 2026

VFR through the TAF period. Just a few high clouds at times this
morning and again this evening. A weak boundary sinking into far
northern WI could spark an isolated thunderstorm this evening north
of RHI. Very low confidence that a storm will develop and affect a
TAF side so keep all sites dry through the TAF period.

5 to 10 kt with gusts 15+ kt this morning and afternoon. Tonight
winds weaken and shift to the northwest.

Looking ahead, could be dealing with wildfire smoke (both aloft
and near surface) Wednesday and Thursday as winds shifting more
northerly bring smoke from fires over northern MN and southwest
Ontario into our area.

.KOSH...

VFR conditions will prevail at KOSH today with just a few high clouds
at times. Westerly winds will increase this morning to 8-10kts with
gusts up to 15kts. Winds then decrease this evening and turn
northwesterly for Wednesday.

Could be dealing with wildfire smoke (both aloft and near surface)
Wednesday and Thursday as winds shifting more northerly bring smoke
from fires over northern MN and southwest Ontario. It is too early
to tell if smoke will be dense enough at KOSH to lower vsbys
categories below VFR.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM CDT this evening for WIZ005-010>013-
018>022-030-031-035>040-045-048>050-073-074.
&&

$$

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

NWS GRB Office Area Forecast Discussion