547
FXUS63 KGRB 261128
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
628 AM CDT Wed Jun 26 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

 - Cooler and less humid weather is expected today, along with a
   slight chance of showers and possibly a thunderstorm.

 - Showers and thunderstorms will bring periods of rain to the
   region Friday and Friday night. Probabilities for heavy rain
   greater than 1 inch over a 24 hour period are relatively low at
   less than 10% through 7 am Saturday. The severe weather threat
   is also low at this time.

 - Some rivers and streams will remain above bankfull and near
   flood stage into the middle of the week.

&&

.DISCUSSION...
Issued at 232 AM CDT Wed Jun 26 2024

Short Term...Today...Tonight...and Thursday

A mid level trough with an attendant shortwave, seen on water
vapor imagery over northern Minnesota, will track through northern
Wisconsin today. The shortwave will bring increasing clouds and
may produce some isolated showers and a rumble or two of thunder
with SBCAPE values around 500 J/kg. Temperatures will be cooler
today; ranging from around 70 across the north to the upper 70s
across central and east-central Wisconsin away from the lake.

High pressure building in across the western Great Lakes will keep
the weather dry tonight and Thursday. Cool weather will continue
as low fall into the upper 40s across the north tonight, with
lower 50s across central and east-central Wisconsin. Highs on
Thursday are only expected to rise into the lower to middle 70s.

Long Term...Thursday Night Through Tuesday

Focus of this forecast revolves around thunderstorm and severe
weather potential during the Friday and Friday night timeframe.

Friday and Friday night...Within low amplitude flow along the US-
Canadian border, shortwave energy traversing east will bring a surge
of deeper moisture to the region. Precipitable water (pwats) values
are forecast to climb to 160-180% of normal by Friday afternoon.  In
general, models point towards a low impulse shortwave pushing into
the region on Friday afternoon ahead of the main shortwave and cold
front which will still be positioned over the northern Plains and
northern Mississippi Valley respectively.  This shortwave will aid
in generating large scale ascent within the warm advection zone well
ahead of the front and prior to the instability moving into the
region.  In this environment, deep saturation with above normal
pwats will lead to a chance of widespread rain, but the severe
threat is low through Friday afternoon.

The cold front moves through on Friday night and models project a
ribbon of elevated instability up to 1000 j/kg will be present along
the boundary.  Deep layer shear will be increasing by this time to
around 30-40 kts.  Guidance is not ambitious with precip chances or
qpf along the front, which may have to due with precip earlier in
the day.  At this point, will pass along concerns to the next shift
but continue to downplay severe weather chances as low.

Probabilities for heavy rain greater than 1 inch over a 24 hour
period are also relatively low at less than 10% through 7 am
Saturday.

Rest of the forecast...Relatively quiet weather will prevail this
weekend with seasonable temperatures and humidity levels falling by
Sunday.  The next chance of thunderstorms will arrive by next
Tuesday.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 628 AM CDT Wed Jun 26 2024

VFR conditions are expected through the TAF period. A few mid and
high clouds will continue to stream in at times across the area
this morning. These mid and high clouds will exit later this
morning, with lower cumulus clouds developing through the morning
and continuing into the afternoon. There could be a few sprinkles
or showers from these clouds as a weak boundary drops through the
area, but it appears conditions will stay VFR. Gradual clearing
is expected this evening into the overnight hours.

&&

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

&&

$$

DISCUSSION.....Kurimski/MPC
AVIATION.......Kurimski