533
FXUS63 KGRB 091141
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
641 AM CDT Tue Jul 9 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Small chances (30% or less) for showers and storms will
  continue today through Thursday. The severe weather threat
  remains very low. Locally heavy rainfall will be possible.

- Some rivers, creeks, and streams across east-central Wisconsin
  will continue to run above bankfull due to recent rainfall.

- A warmer/drier period looks to be in store toward the end of the
  week and into the weekend. Heat index values in the 90s are
  expected for much of the area.

&&

.DISCUSSION...
Issued at 350 AM CDT Tue Jul 9 2024

Short Term...Today...Tonight...and Wednesday

The chances for showers/storms and fog chances/trends are the main
focus today into Wednesday.

Shower/Storm & Cloud Trends:

Dry conditions are expected this morning, then as daytime
instability builds, expect a few showers to develop across far
northeast WI, especially near the MI border where the greatest
surface convergence will exist (lake/bay breezes). Some weak
upper support thanks to a RRQ of an upper jet and weak shortwave,
but capping around 700mb, SBCAPEs of only 500-1000 J/kg and deep-
layer shear of 10 to 20 kts will hold back any storm that can
form. This activity could slowly meander south into the Fox Valley
later in the day, but any activity will wane this evening as
instability/convergence weakens. After the low clouds and fog burn
off, some sun is expected across central and northern WI this
morning, then look for daytime cu to develop in the later morning
and afternoon along with some higher clouds spreading in. Further
south/east, the cloud shield from the remnants of Beryl will
limit sunshine, especially this afternoon. This cloud shield looks
to stick around into Wednesday morning as well, especially over
eastern WI, with additional daytime cu expected later in the day.
Have increased cloud cover over much of the area on Wednesday.
While the majority of the precip from the remnants of Beryl will
stay to our east, parts of far east central WI could get clipped
by some light rain. In addition, a weak trough/shortwave will push
across the region, bringing the chance of a few pop-up
showers/storms in the late morning and afternoon, though the
better coverage looks to be to our southwest. Weak shear and
limited instability will again the storms in check, but heavy
downpours will be possible in any shower/storm.

Fog / Wind / Temps:

Light winds and clear skies, along with recent rainfall, has
allowed for fog to develop across parts of the area early this
morning. Nighttime microphysics satellite showing the most
widespread fog (locally dense) across north central WI. The fog
will continue early this morning, possibly expanding a little
south/east toward sunset, then will burn off/lift by mid-morning.
Fog potential tonight will be a little tricky as clouds associated
with the remnants of Beryl will likely limit fog potential. But
will include fog across north central WI, where skies are expected
to remain mostly clear for at least part of the night and enough
low level moisture from recent rains will remain in place.

Temps look to remain near or slightly above normal with highs
mainly between 75-85 degrees. Lows tonight will drop into the 50s
across north-central WI, and hold in the 60s across the Fox
Valley. A touch of humidity will remain in place across central
and eastern WI, with dewpoints mainly in the 60s. Some dewpoints
in the 50s will bring less humid conditions to much of the
Northwoods.

Long Term...Wednesday Night Through Monday

Dry conditions will end the work week before much hotter
conditions arrive for the weekend. The heat and humidity will
prime the area for a couple rounds of active weather starting over
the weekend into early next week.

The only interruption to a dry end of the work week will be a
brief chance for a few stray showers Thursday afternoon. Any
showers will rely heavily on weak surface instability (SBCAPE
around 500-1000 J/kg) as upper forcing will be lacking during this
time. Ultimately, would expect some developing afternoon cumulus
with a few showers possible if the better dewpoints and warmth do
build into the area, but even then would expect most of the area
to be dry. High pressure begins to build in Thursday night into
Friday, which will keep us dry until the weekend.

Southerly flow will ramp up Friday night, bringing a surge of very
warm and humid air into the region for the weekend through early
next week. High temperatures in the middle to upper 80s are
expected by Saturday, with a few 90s mixed in for both Sunday and
Monday. This will push heat indices into the middle 90s so make
sure to plan for the heat if you are outdoors this weekend.

While the surface flow brings in much warmer temperatures, upper
flow will bring a series of fast moving shortwaves Saturday
through Monday. This will make for several potential rounds of
active weather, with the best bet being during the afternoon when
diurnal instability is at its maximum.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 641 AM CDT Tue Jul 9 2024

Ground fog, thickest across north central WI, will lift and/or mix
out through ~13z. Otherwise, look for VFR conditions today. A
cloud shield associated with the remnants of Beryl will spread
high clouds across much of the area, thickest across the Fox
Valley and lake shore. Some daytime cu are also expected. An
isolated shower or storm will be possible this afternoon or early
evening, but chances too low (20% or lower) that it will impact a
TAF site. Any shower/storm will dissipate late this afternoon or
evening. Ground fog will be possible again late tonight and early
Wednesday morning across mainly north central WI (RHI). Some light
showers or sprinkles may approach MTW Wednesday morning as well.

&&

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

&&

$$

DISCUSSION.....Bersch/Uhlmann
AVIATION.......Bersch