201
FXUS63 KGRB 101938
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
238 PM CDT Wed Jul 10 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Small chances (30% or less) for showers and thunderstorms this
  afternoon/evening and over the southern portion of the CWA
  Thursday afternoon/early evening. The severe weather threat is
  very low, but storms could produce locally heavy downpours and
  gusty winds.

- Warmer and more humid conditions arrive this weekend through
  early next week. Heat index values in the 90s are expected over
  central, east central and parts of far NE WI Sunday into Monday.
  Heat indices could approach advisory criteria over the southern
  CWA on Sunday, unless thunderstorm development occurs.

- Increasing moisture and instability, combined with a couple
  short-waves and cold frontal passages, could lead to a few
  rounds of strong to severe storms this weekend into early next
  week.

&&

.DISCUSSION...
Issued at 237 PM CDT Wed Jul 10 2024

Fog potential tonight, and building heat, humidity and storm
chances for the weekend into early next week, are the main
forecast concerns.

Scattered showers and isolated thunderstorms developing near a
weak boundary over northern WI will drift south late this
afternoon and evening, but should mainly stay west of the Fox
Valley and lakeshore areas. Inverted-V soundings support gusty
winds with any storms, but severe weather is not anticipated.
Brief heavy downpours are also possible, but PWATs are not
excessively high.

Later tonight, clear skies, light winds and high pressure ridged
over the northwest part of the CWA will lead to favorable
conditions for fog development. The fog should be most extensive
in the Wisconsin River Valley (NC/C WI), and dense fog will be
most likely in NC WI. The fog should mix out early Thursday
morning.

A relatively quiet day is anticipated for the rest of Thursday,
with isolated showers and storms developing during peak heating,
especially over C/EC WI. Any lingering convection should quickly
wane after sunset.

Dry conditions expected for the rest of Thursday night and Friday,
with high pressure situated just to our east, and weak upper level
ridging and capping in place on Friday.

More interesting weather arrives for the weekend as southerly
winds bring an increasingly warm, humid and unstable air mass into
the region. The heat will likely get beat back by periodic bouts
of thunderstorms as short-waves track through Saturday afterno on/
evening and Sunday afternoon/evening, and a cold front moves
through later Monday and Monday night. Thus, confidence in
reaching heat advisory criteria is in doubt. The best bet would
appear to be over C/EC WI on Sunday, as stronger capping may hold
off storms during the day. Will likely see a couple periods of
strong to severe storms during this time frame, especially Sunday
into Monday, when CAPE will build to 2-3K j/kg (at least) and deep
layer shear and upper level wind fields will be increasing.
Details are sketchy at this time, so pops will remain in the
chance category through these periods until better spacial/time
resolution can be determined.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1231 PM CDT Wed Jul 10 2024

VFR conditions will prevail through midnight, with only isolated
showers and storms expected this afternoon and early evening.
Confidence in a storm hitting any particular TAF site is too low
to include a mention at this time.

Later tonight, conditions will become favorable for fog, most
notably over north central and parts of central WI. IFR/LIFR
conditions look like a good bet, and VSBYs may drop to 1/4SM
at times at the RHI TAF site, especially between 09z-12z/Thu.
The fog will quickly mix out by 13z-14z/Thu, with scattered
cumulus clouds developing later in the morning.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kieckbusch