809
FXUS63 KGRB 141756
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1256 PM CDT Mon Jul 14 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Near-surface Canadian wildfire smoke will be most likely over
  northern WI this afternoon into early evening.

- A few isolated showers and thunderstorms are possible this
  afternoon in portion of central and east-central Wisconsin, but
  no severe weather is expected.

- Next round of more widespread active weather arrives Tuesday
  afternoon into Thursday. Isolated strong or severe storms are
  possible.

- Very warm and humid conditions to start the work week with heat
  index values in the upper 80s to low 90s.

&&

.DISCUSSION...
Issued at 258 AM CDT Mon Jul 14 2025

Smoke...
Near surface smoke is expected to progress eastwards out of the
region through the morning hours today, bringing back better
visibility and air quality to most of central and east-central
Wisconsin. However, another round of smoke may follow behind a
weak cold front in the north, touching into portions of far
north-central Wisconsin near the Upper Peninsula border in the
afternoon. Fortunately, a wind shift to the south should take this
smoke back out of the region by the end of the day today.

Precipitation...
The aforementioned weak cold front could bring a few showers to
far north-central Wisconsin this morning, but overall any
precipitation should be brief and light. No storms are expected.

Another chance for some isolated to scattered shower and thunder
activity will arrive this afternoon. Soundings support
destabilization at the surface and CAMs continue to suggest some
isolated activity across portions of central to northeastern
Wisconsin, roughly along a corridor from Wausau to Marinette.
Without better synoptic support, any storms that do form will
likely be brief pulse-like in nature and no severe is anticipated
at this time. Given how similar conditions provided little in the
way of convection across Minnesota yesterday, chose to keep
relatively low end pops for an isolated chance for the afternoon.

Finally, the next widespread round of active weather arrives
Tuesday and could last as long as Thursday. A quasi-stationary
front will lift into the Upper Great lakes region Tuesday,
bringing with it a fairly decent amount of warmth and moisture.
This will likely serve to bring at least a couple rounds of rain
and more organized weather into the region both Tuesday and
Wednesday. On Tuesday, the best axis of warmth and moisture will
be stretched from western to north-central Wisconsin, roughly from
Eau Claire to Land O Lakes, so these will be areas to watch for
the development of any stronger storms. Afternoon soundings show a
corridor of better instability along the aforementioned areas,
with MUCAPE around 1000-1500 J/kg in our neck of the woods ahead
of a cold front. Main question will be whether forcing along the
front and surface warming will be able to overcome some upper
capping that will also be present. Additionally, bulk shear
remains modest, around 20 to 30 knots. As a result, severe weather
potential remains isolated, but a few strong storms will be
possible on Tuesday. Damaging winds and hail will be the main
threats with any stronger or severe storms. Heavy rainfall will
also be possible, with PWATs around 1.5-1.75 across the northwoods
where the storms will be.

Wednesday will also see active weather, as any lingering
convection and rain from Tuesday continues to move through the
region as the stationary front shifts southwards. Instability will
be at a premium on Wednesday especially once the front is through
the area in the afternoon, so severe weather may struggle to
develop. That said, many of the details will still depend on how
convection on Tuesday evolves; frontal timing, any clearing (and
subsequent warming), or lingering thunderstorm outflow could all
change how any storms evolve on Wednesday. At this time, the best
potential remains to our south on Wednesday, with the instability
barely reaching portions of central Wisconsin. Heavy rainfall
will still be a concern however, as the strong surge of moisture
pushes PWATs towards 2 inches in the afternoon. Probabilistic
guidance brings the probability of exceeding half an inch to
around 50-70% for much of central to north- central Wisconsin on
Wednesday. The 90th percentile also shows around 1.50-1.75 inches,
which would suggest that some localized much higher amounts are
possible in areas that see any stronger thunderstorms or training
storms. Some lingering rain could last overnight before departing
the region on Thursday.

Temperatures...
As mentioned above, we are expecting a surge of warmth and
moisture into the region, which will bring much warmer weather for
both today and Tuesday. Expect highs in the upper 80s today, and
even a few low 90s on Tuesday. Dewpoints will also be in the upper
60s to lower 70s by tonight, so expect a warm and muggy night.
The rain and passing front will bring some cooler temperatures in
for Wednesday and highs will be back in the 70s by Thursday. From
there, temperatures will moderate some for the end of the week,
with highs generally in the upper 70s to lower 80s.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1255 PM CDT Mon Jul 14 2025

Smoke from Canadian wildfires will impact AUW/CWA/RHI the rest of
the afternoon. Scattered cu will occur, but will mainly be VFR. A
few showers and storms developing over northern WI may graze
central WI TAF sites, but coverage is very isolated so will leave
it out for now. Approaching front may lead to scattered low clouds
late tonight and around daybreak on Tuesday over northern WI,
including at RHI. Rest of Tuesday will feature scattered VFR cu.
Pop-up showers and storms are expected late Tuesday afternoon into
Tuesday evening over northwest WI. Some showers and storms may
eventually reach into northern WI Tuesday evening, including at
RHI.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......JLA