967
FXUS63 KGRB 172325
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
625 PM CDT Tue Sep 17 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Near-record high temperatures expected to continue for Wednesday
and Thursday.

- Showers and non-severe thunderstorms are expected (60 to 80%
chance) in central WI on Thursday night/Friday morning.

- A pattern shift is expected Friday into this weekend, with highs
dropping down into the 70s, and increased rain chances every few
days.

&&

.DISCUSSION...
Issued at 251 PM CDT Tue Sep 17 2024

Confidence is high that the weather for tonight, tomorrow, and
Thursday will remain very similar to the past few days. Above-normal
temperatures are expected, with highs in the 80s and lows in the
60s. Dewpoint temperatures are forecast to be in the 50s, so no
hazardous heat index values are expected... though worth noting that
our forecast area remains in the "yellow" category for the
HeatRisk... which indicates a "Minor" level of heat-induced impacts.
A "Minor" HeatRisk level can especially impact those outdoors
without effective cooling and/or adequate hydration.

Heading into Thursday night and beyond, a change in our overall
weather pattern will occur...

For Thursday PM, we will be keeping an eye on a trough axis that
extends north-south from Canada through Minnesota and is expected to
help generate strong to potentially severe thunderstorms over
Minnesota during the peak heating hours on Thursday. This boundary
is expected to move eastward into Wisconsin, arriving near central
Wisconsin around the midnight hour. The key thing for our area is
that as the sun goes down, the intensity of this precipitation will
also diminish. At this time, severe weather is not forecast in our
area for Thursday/Thursday night, and lightning will be the primary
hazard. At this time, rainfall chances in central WI are around 80%
for Thursday night, and around 50% across the Fox Valley. With the
weakening system, forecast rainfall is in the 0.10" to 0.25" range.

For Friday PM, this system will generally be centered around the Fox
Valley region into Lake Michigan. As with this system on Thursday,
peak daytime heating hours are when this system will be its most
intense. Still time for the location/timing to change, but as of
now, it appears the key ingredients for strong/severe weather will
be located more over Lake Michigan. Aloft, the forecast wind profile
is not very strong, with 850mb winds slated to weaken to the 15kt
range. So along with a slight change of thunder (25%), we could see
a brief wind gust of around 20 to 25 mph mix down to the surface.

The passing of this boundary helps unveil the curtain for the
overall weather pattern change heading into next week. Long-range
forecast models are hinting at us transitioning into an overall
weather pattern of a quick-moving system to bring showers and a few
rumbles of thunder every few days. There is not yet any notable
"arctic" air embedded in this pattern, so am expecting above normal
temperatures to continue... however, with the clouds and showers, am
expecting the magnitude of the above normal temperatures to be much
lower than they have been the past few days. Instead of near-record
high in the mid to upper 80s, would expect temperatures to be closer
to the mid to upper 70s range... still above-normal, but 5 to 10
degrees above normal as opposed to 15 to 20 degrees above normal.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 624 PM CDT Tue Sep 17 2024

Good flying weather is expected tonight through at least Thursday
morning, with the possible exception of ground fog for around ten
miles inland from Lake Michigan and the bay (MTW, OCQ, and
possibly SUE and MNM)b etween 08z and 13z each morning. There
will be periods of high clouds, but otherwise skies will be
generally clear.

&&

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

&&

$$

DISCUSSION.....Kotenberg
AVIATION.......RDM