553
FXUS63 KGRB 122347
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
647 PM CDT Mon Aug 12 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Isolated to scattered showers and storms (20% to 30% chance)
  will continue for the rest of the afternoon and early this
  evening, and then again Tuesday afternoon/early evening. Severe
  thunderstorms are not expected.

- Showers and some thunderstorms likely (50 to 80% chance)
  Thursday into Friday. Severe potential remains low, but locally
  heavy rain could occur. Small chances of rain (20-40 percent)
  this weekend.

- Conditions hazardous to small craft possible on Lake Michigan
  Thursday and Thursday night.

&&

.DISCUSSION...
Issued at 225 PM CDT Mon Aug 12 2024

Short Term...Tonight and Tuesday


As of 2 pm, isolated showers and perhaps a thunderstorms developed
across Shawano and Marathon counties. The showers/storms were
sagging slowly south-southeast at less than 10 mph. Under partly
sunny skies, temperatures warmed into the middle 70s to lower 80s.

Isolated showers and storms will continue for the rest of the
afternoon into early this evening. Some of the showers and storms
could produce a brief period of heavy rain. Severe storms are not
expected. The rain should end by mid evening, otherwise skies will
be clear to partly cloudy. Lows tonight should drop into the lower
to middle 50s north to around 60 south and along the bay and Lake
Michigan.

A repeat performance is expected Tuesday afternoon into the early
evening hours. The cumulus field is expected to develop during
the late morning into the early afternoon. Bufkit soundings
indicated 500 to 1,000 J/KG of CAPE to support the mention of
thunder. High temperatures should climb into the upper 70s to
middle 80s.

Long Term...Tuesday Night Through Monday

Some lingering instability showers will quickly want Tuesday
evening with the loss of daytime heating. Otherwise, high pressure
settling in across the central Great Lakes will keep the forecast
dry for the middle of the week as temperatures inch to a few
degrees above normal for this time of year.

A low pressure system will organize across the Plains during the
middle of the week and slowly make its way east towards the upper
Mississippi Valley Thursday and the western Great Lakes Thursday
night. The system itself will have strong dynamics and abundant
moisture, as evidenced by PWATs of 1.5 to 1.75 which is the 90th
percentile for this time of year, along with modest instability.
This should lend itself to steady rain during this period with
occasional heavy rain and isolated thunderstorms. QPF amounts
during this period will likely be 1 to 2 inches, with locally
higher amounts possible.

The low looks to linger across the region on Friday, then track
east of the region sometime this weekend. The key to how long the
low hangs around the region will be if it becomes cut-off across
the central Great Lakes or is more of an open wave. Even if the
low becomes cut-off, the heaviest rain should be over by the
weekend as the best instability and dynamics will have waned by
then.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 646 PM CDT Mon Aug 12 2024

A nearly stationary front from DLH to AUW to MTW was
producing scattered showers and thunderstorms again this afternoon.
They should gradually dissipate during the evening after sunset.
VFR conditions and mostly clear skies are expected elsewhere.
Patchy ground fog is likely again late tonight through 13z Tues.

Skies should start out clear Tuesday, but clouds with bases of
4000 to 6000 feet should form by midday. There could be scattered
showers or thunderstorms in the later afternoon and evening from
roughly RHI to GRB.

&&

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

&&

$$

DISCUSSION.....Eckberg/Kurimski
AVIATION.......RDM