706
FXUS63 KGRB 301803
AFDGRB

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

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A Frost Advisory remains in effect through 9 AM for locations
  generally north of a Merrill to Antigo to Wausaukee line.

- Due to recent rainfall, a few rivers will remain at bankfull but
  below minor flood stage through the weekend.

- 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 thunderstorms and
  heavier rainfall.

&&

.DISCUSSION...
Issued at 323 AM CDT Thu May 30 2024

Short Term...Today...Tonight...and Friday

Arrival and extent of rain showers on Friday is the primary focus
as high pressure dominates the weather today and tonight.

Sharp ridging aloft is present from the central CONUS to Hudson
Bay. Similar at the sfc as high pressure ridge stretches from
northern Quebec across James Bay and into the western Great Lakes.
Other than a few mid clouds over southwest WI, skies are clear to
start the day over the region. Edge of high clouds ahead of cold
front and some showers and thunderstorms over the Dakotas is
drifting across Minnesota and Iowa. These clouds will be over
Wisconsin tonight. In the meantime, it is a chilly start over
northern WI where temperatures have fallen into the mid 30s and
Frost Advisory is in effect until 9 AM this morning generally
north of a Merrill to Antigo to Wausaukee line. Readings are in
the 40s elsewhere.

Moving forward today, other than some fair weather cumulus clouds
later this morning into the afternoon, skies will be mostly sunny.
Gradient east wind enhanced by lake breeze will keep the immediate
Lake Michigan shore cooler in the lower 60s this afternoon, but
readings just inland will reach the 71-74 range. Increasing mid
and high clouds will keep readings tonight warmer over north-
central WI. Portions of northeast to east-central WI that remain
clear longer tonight could see readings drop to near 40 where
winds go calm. Most locations will see lows tonight in the mid
40s.

Friday will feature increasing and thickening mid clouds from west
to east as upper trough over the northern Plains slowly smashes
down the sharp upper ridge over our region today. Surface cold
front over the northern Plains will shift across Minnesota through
the day and reach western Wisconsin by Friday evening. Increasing
theta-e advection ahead of the front will combine with weak
instability to result in small chances of showers and maybe a
rumble of thunder moving into especially central Wisconsin to
north-central Wisconsin in the afternoon. That said, forecast
soundings show a lot of dry air around in wake of the departing
ridge and the forcing is hardly robust. Thus, think showers on
Friday will be scattered at best and it is likely northeast and
east-central WI likely remain dry through the day. Highs on
Friday could reach the mid-upper 70s, but it will be cooler in
the upper 60s/around 70 from Wausau to Eagle River due to thicker
clouds and better chances of showers, and also near the immediate
Lake Michigan shore with a southerly flow.

Long Term...Friday Night Through Wednesday

The dry stretch will come to an end for the extended period as
active weather returns for the weekend and early next week.

Friday night and Saturday...
Upper ridging will slide into the eastern Great Lakes Friday
evening, allowing the axis of warmer air and active weather to
move into the region overnight through Saturday morning. Scattered
on and off showers are expected to be in the region but any
precipitation will likely remain light as the main moisture
remains blocked off with a more southerly system. A rumble of
thunder or two will also be possible by the afternoon, but overall
the storm chance will be relatively small.

Sunday into Monday...
The next period to watch for a more widespread rainfall event will
be Sunday and Monday. A strong shortwave will cross the Northern
Plains Sunday, helping in the development of a surface low that
will come towards the region sometime late Sunday through Monday.
The timing and path of this system remain uncertain at this time.
A more northerly track would likely keep our area out of the warm
sector for Sunday, keeping the area dry; but a more southerly
track would bring a round of showers and storms at least into
central Wisconsin already late Sunday evening. In either case,
the main event will likely be associated with the attendant cold
front that should come through the region sometime Monday.
Although its a bit early to assess severe potential, moisture will
be plentiful with PWATs pushing up to around 1.4-1.6 inches so
heavy rainfall will again be in the works. Depending on the track
and timing of the initial precipitation, some of the mid-range
models also bring some additional storm development Monday
evening, which may support some stronger storms if we can get
instability to increase across the region during this timeframe.

Rest of the forecast...
Finally, most long range models bring another fast moving
shortwave into the region around the middle of next week, which
would likely bring another round of showers and storms through
the region.

Temperatures...
High temperatures will warm over the weekend with highs in the
upper 70s to lower 80s by Sunday. From there, high temperatures
will remain fairly steadily in the upper 70s to lower 80s through
the middle of next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 103 PM CDT Thu May 30 2024

Good flying conditions are expected at all TAF sites through early
Friday morning. However, some models are showing signs of LLWS
developing in north-central WI overnight. But confidence is not
high enough at this time to include this at the RHI TAF site.
Conditions will begin to change in north-central WI at the end of
this TAF period with the arrival of light showers and possibly a
rumble of thunder. Anticipate the showers and possible rumbles of
thunder to pair with brief MVFR conditions around midday Friday in
north-central WI.

&&

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

&&

$$

DISCUSSION.....JLA/Uhlmann
AVIATION.......Kruk