697
FXUS63 KGRB 101116
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
616 AM CDT Mon Aug 10 2026

Updated aviation portion for 12Z TAF issuance

.UPDATE...
Issued at 519 AM CDT Mon Aug 10 2026

Mid clouds clearing out early this morning has allowed fog to
increase in coverage north and west of Wausau, extending to the
U.P. border. As temps have fallen below crossover temps (lowest
dewpoint during the peak of heating on Sunday), areas of dense fog
have formed with many obs reporting visibility less than one-half
mile. Webcams show some dense fog as well, suggesting this is not
just typical shallow ground fog. Have issued a Dense Fog Advisory
for portions of central and north-central WI until 10 AM. Some
fog expected away from these areas, but should stay more patchy.

&&

.KEY MESSAGES...

- Warmer today, with highs in the lower to middle 80s. Highs in
  the 80s through Wednesday, then slightly cooler late this week.

- Dry today, then potential for additional rounds of showers and
  storms late tonight through middle of the week. At this time,
  risk of severe storms is low.

&&

.DISCUSSION...
Issued at 1250 AM CDT Mon Aug 10 2026

Today into this evening...Scattered clouds and some fog (locally
dense) early will give way to mostly sunny skies in the afternoon
as we will be north of front that is moving through early this
morning. A couple CAMS hint that if some elevated showers form in
eastern SD this morning, they could drift over our southern areas
this afternoon. Something to watch, but most guidance keeps us
dry, so will ride with that idea. Dry weather and more sun than
Sunday will boost temps into the lower to middle 80s, though east
component winds will keep Lake Michigan shore/Door County cooler.
Dry weather holds for any evening activities, though patchy fog
may occur near Lake Michigan. Temperatures will be in the low to
mid 70s.

Shower and storm chances (15-30%) return late tonight through
Wednesday...Showers and storms developing this evening over
Dakotas forecast to produce shortwave/upper jet that shifts east
toward WI late tonight. Gradient of instability from MN to
southern WI, as is the stronger convergence with LLJ. Even so,
with the wave and elevated instability farther north, cannot rule
out some showers and storms on Tuesday morning, with perhaps
slight boost in coverage farther north during peak heating of
afternoon as MLCAPEs increase over 1000J/kg. Effective shear over
40 kts would support stronger storm if convection develops. SPC
does keep the marginal risk for severe farther south near the more
persistent frontal boundary/highest instability.

Rain chances (30-60%) then continue Tuesday night into Wednesday
as additional as another shortwave moves through the region and
the front remains close enough to our area. Similar to expectations
for late tonight and Tuesday, appears better signal for severe
remains south. However, late Tuesday night through Wednesday,
there is stronger forcing farther north and sufficient instability.
Seems like this time frame may hold the greatest chances for some
stronger storms over our area, especially if things slow a bit and
these factors catch up to at least the beginning of peak heating
on Wed. FWIW, ML progs show a weak "bump" in severe probs to 5-15%
for Wed after a relative minimum in severe potential Mon-Tue.

Dry and cooler late this week, then chances for rain (30-40%) return
for the weekend...High pressure builds in across the area Wednesday
night through Friday, pushing the front and lingering instability
south and generally keeping the area dry through the rest of the
week. Highs will settle into the 70s regionwide. Low temperatures
in the 40s north seem a certainty Thursday night with high overhead.
Low end from NBM (5th percentile) even points to potential for
upper 30s in typical cool spots near the U.P. border (e.g. KLNL).

The high eventually shifts east, allowing for the chance for showers
and thunderstorms to return to the area Friday night into next weekend.
On the early side, but does seem that Sunday would be the drier of the
two days.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 615 AM CDT Mon Aug 10 2026

Fog/mist that developed early this morning will persist through
13z-14z, before improving. Fog will be most widespread and dense
over north-central WI, including RHI. After fog diminishes,
scattered VFR fair wx cu with bases 040-060 will prevail through
the afternoon. VFR conditions continue tonight, though there could
be light fog over east-central WI late tonight, including at
GRB/ATW/MTW. Winds will be light through the TAF period.

Chances for showers and some storms occur on Tuesday morning,
though strongest storms look to remain to the south closer to
primary frontal boundary. Occasional MVFR conditions may occur
with the showers.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CDT this morning for WIZ005-
010>012-018-019-030.
&&

$$

UPDATE.........JLA
DISCUSSION.....JLA
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion