908
FXUS63 KGRB 131931
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
231 PM CDT Mon Jul 13 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Intense heat is expected today and Tuesday with highs in the 90s
  with a few locations around 100 degrees. Heat indices both days
  to range from 95 to 105 degrees, resulting in heat related
  impacts. A Heat Advisory remains in effect until 9 PM Tuesday.

- Showers and storms are possible at times from Thursday night
  through the weekend. It is too early to determine their
  severity.

&&

.DISCUSSION...
Issued at 231 PM CDT Mon Jul 13 2026

Dangerous Heat/Temperatures...An upper-level ridge centered over the
Northern Plains/Upper Mississippi Valley will prevail over the area
through Tuesday before gradually sliding south into Wednesday and
losing its magnitude. But, its center will still be just to the
south Wednesday into Thursday. This results in the heat peaking
today and Tuesday, while still remaining above normal/very warm for
the remainder of the week through the weekend.

Air temperatures this afternoon and Tuesday afternoon will climb
into the 90s to near 100 degrees in some spots, mainly in far
northeast WI. The high heat (925mb temps around 30C) will be focused
more across far northern WI today, but will become focused across
eastern WI Tuesday, so the Fox Valley will be a few degrees higher
Tuesday than today, potentially in the upper 90s.

Dew points and the amount of dry air filtering into the area from
the west over the ridge remains the big question for how much we
will be able to mix. If we can mix higher during the afternoons, the
air temperature will increase, but dew points (and therefore heat
indices) will decrease. Generally, dew points this afternoon have
been in the upper 60s to low 70s across central and east-central WI,
with slightly lower dew points in the low to mid 60s across the
Northwoods. This will bring heat indices into the upper 90s to
around 105 degrees for this afternoon. A similar story is looking
likely for Tuesday`s dew points, but may be a few degrees lower than
today, but this still results in heat indices in the upper 90s to
around 105 degrees due to the air temperatures.

No changes were made to the Heat Advisory currently in effect until
9 PM Tuesday. However, it may need to be extended into Wednesday for
a few counties across central and east-central WI as heat indices
are forecast in the upper 90s, where dew points will be in the mid
to upper 60s.

Precipitation/Thunder Chances...With the prevailing ridge, dry
conditions are expected through at least Tuesday night before the
ridge begins to slowly move south and northwest flow resides
overhead. Some guidance is indicating a moisture starved boundary
dropping south over Lake Superior/Upper MI Tuesday night may bring
an isolated shower to the region early Wednesday, but confidence is
low in this occurring given the lack in support/moisture. There are
also signs of isolated diurnally driven showers/storms developing
over the area Wednesday afternoon. Otherwise, periodic chances for
showers and storms are anticipated from Thursday through the weekend
with the prevailing northwest flow allowing for any shortwave to
move overhead, however, there is low confidence on when/where storms
would occur.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1245 PM CDT Mon Jul 13 2026

VFR conditions are expected through this TAF period with only a
few high clouds passing overhead tonight. Westerly winds around
10 kts are expected through this TAF period with gusts to around
17 kts this afternoon. A period of LLWS is possible across far
northern WI after midnight through early Tuesday morning, mainly
impacting the RHI TAF site.

&&

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

$$

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

NWS GRB Office Area Forecast Discussion