218
FXUS63 KGRB 302330
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 PM CDT Thu May 30 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- A more unsettled pattern is forecast to return this weekend
  through at least the middle of next week. Currently, Sunday
  night through Monday has the best chance for strong thunderstorms
  and heavier rainfall.

&&

.DISCUSSION...
Issued at 336 PM CDT Thu May 30 2024

Short Term...Tonight and Friday

Dry and quiet conditions are expected to continue through at least
early Friday morning before the next chances for rain return, mainly
in north-central WI. Main forecast challenges are timing out the
shower chances and how far east they will track throughout the day
on Friday.

This evening through tonight...Departing upper-level ridging and a
surface high will keep dry conditions across the forecast area
during this forecast period. However, high and mid-level clouds will
sneak into central and north-central WI overnight. As a result, have
low temperatures a couple degrees warmer in these areas, in the
middle 40s to low 50s, compared to east-central and far northeast WI
with values ranging from the low 40s to mid 40s.

Friday...A decaying line of showers associated with a weak shortwave
moving from the west will attempt to bring showers into north-
central WI Friday morning. The evolution of these showers and their
progression eastward throughout the rest of Friday is uncertain due
to the amount of lingering dry air from the departing high. CAMs
support the dry air factor as they show the showers becoming
scattered and even dissipating as they continue eastward. However,
by the afternoon, models suggest a low-level southerly jet
increasing across western WI ahead of an approaching cold front.
This may allow the scattered showers to redevelop during the
afternoon and move into central and north-central WI. A few rumbles
of thunder will also be possible during the afternoon as enough
instability will be present. Meanwhile, conditions in east-central
and far northeast WI will remain dry on Friday. Therefore, have
slightly cooler high temperatures in central and north-central WI,
in the upper 60s to mid 70s, with values ranging from the mid to
upper 70s in east-central and far northeast WI. Highs along the
lakeshore will be the coolest with values ranging from the mid 60s
to upper 60s.

Long Term...Friday Night Through Thursday

A transition back to a more unsettled is expected to begin the
extended period and will likely continue through at least the
middle of next week.

Friday night through Sunday morning...As a ridge continues to
push toward the eastern Great Lakes and out of the region Friday
night an axis of deeper moisture (PWATs of 1-1.2") will move over
central and north-central WI out ahead of an upper-level
shortwave. Isolated to scattered showers and weak storms are
expected to spread northwest to southeast Friday night through
Saturday afternoon. Weak instability during this period will
limit the potential for any stronger storms, but isolated weak
thunderstorms will be possible, mainly Saturday late morning and
afternoon across central and north- central WI. A weak low-level
ridge will bring a brief end to the precipitation chances
Saturday night through Sunday morning.

Sunday Afternoon through Monday night...A more widespread chance
for showers and thunderstorms is expected across the region
beginning Sunday afternoon with an initial northward surge of
warm moist air (PWATs 1.4-1.7") ahead of surface low developing
over the Northern Plains. Ensemble cluster analysis shows
considerable uncertainty with the timing and location of showers
and storm during this period , however, the better chance for
severe thunderstorms Sunday appears to be west of the region
where instability with be greater. The better chance for severe
weather in the CWA appears to come Monday late morning/afternoon
with the passage of the attendant cold front. Key factor in the
severe weather chances will be if and to what degree instability
recovers after the first wave of showers and storms Sunday
afternoon and evening. Still need to iron out the finer details
during this period, but if you have outdoor plans Sunday
afternoon and/or Monday you`ll want to keep an eye on the
forecast.

Rest of the Extended...Another brief lull in the precipitation is
expected for most of Tuesday before the next system pushes into
the region next Wednesday.

Temperatures...Near to or just slightly above normal temperatures
are expected across the area during the extended period. Highs
each day are forecast to range from the low 70s to around
80 degrees away from Lake Michigan, while locations on the
immediate shoreline will likely see highs in the mid to upper
60s.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 621 PM CDT Thu May 30 2024

VFR flight conditions are anticipated through the TAF period, with
a gradual increase in cloud cover in the northwest part of the
forecast area as a weakening front approaches on Friday. The
front may generate scattered light showers in NC WI Friday
afternoon, and these may reach the RHI TAF site late in the day.

Light SE-S winds are expected tonight, with moderate S-SW winds
expected on Friday. There is a chance of borderline LLWS in far NC
WI late tonight, but this is currently expected to remain NW of
the RHI TAF site.

&&

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

&&

$$

DISCUSSION.....Kruk/GK
AVIATION.......Kieckbusch