984
FXUS63 KGRB 090300
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1000 PM CDT Wed May 8 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- An unsettled weather pattern will bring intermittent chances of
  showers and a few thunderstorms through the weekend. Severe
  weather is not expected with any of these thunderstorms.

- Low temperatures in the lower to middle 30s will be conducive
  for a frost or freeze over north-central and far northeast
  Wisconsin on Thursday night.

- Due to rainfall over the past week, river levels remain
  elevated. Some rivers may reach or surpass bankfull.

&&

.DISCUSSION...
Issued at 313 PM CDT Wed May 8 2024

Short Term...Tonight and Thursday

Precipitation trends and overnight temperatures will be the main
concerns in the short term forecast.

The dry conditions present in the region through the early
afternoon may be interrupted briefly late this afternoon and
evening across northern Wisconsin. Short term models continue to
show some isolated shower activity for the northwoods, with modest
instability around 100-400 SBCAPE j/kg. This trend is supported by
the gradual development of a cumulus field across this area on
satellite and a few weak radar echoes in development before 3PM on
the Michigan side of the border. Therefore kept a low
precipitation mention mainly north of a line from Wausau to Oconto
but expect the showers to be fairly light. Any showers that do
develop will quickly dissipate after sunset.

Tonight, a southern stream system will lift northwards to the area
through the overnight hours. Continued to trend the region drier
and push precipitation southwards, as increasing northeasterly
flow will likely keep most of the area. If showers do reach
portions of central to east-central Wisconsin, it likely won`t be
until after daybreak on Thursday. Low temperatures overnight will
drop into the middle 30s across the far north near Vilas County,
which may produce areas of patchy frost. The frost window will
still be quite short tonight, but anyone with sensitive plants
outdoors will need to monitor Thursday night as well, as the
overnight temperatures could be much lower, into the upper 20s to
lower 30s for much of northern Wisconsin.

Thursday, the rain associated with the system to our south will
largely struggle to reach our area, as northeasterly winds pull in
dry air to the region. The continued southerly track has promoted
confidence in continuing to reduce the pops for Thursday across
the area. The northeast flow will also bring some cooler
temperatures, with daytime highs on Thursday expected to be in the
upper 50s to lower 60s.

Long Term...Thursday Night Through Wednesday

At the start of the period, a longwave trough to stretch from
eastern Canada southwest through the Great Lakes into the central
Rockies. The eastern part of this trough will sweep east by the
end of the work week, to be followed by a mid-level shortwave
trough quickly dropping southeast into the Great Lakes Friday
afternoon into Saturday morning. This trough will be the first of
a series of troughs that will follow into the middle of next week.
Thus, precipitation chances to exist about every 24 to 36 hours.
At or slightly below normal temperatures are expected through
Saturday before temperatures moderate to at or above normal levels
for next week.

Thursday night and Friday...
High pressure will move into the western Great Lakes region
Thursday night, bringing mostly clear skies and light winds to
northeast WI. Near ideal radiational cooler conditions in place
will allow for temperatures to easily fall into the 30s to around
40 degrees with a few upper 20s possible in our colder locations.
Frost is a definite possibility over northern and parts of central
WI and will continue to highlight in the HWO. This high pressure
quickly exits to the east Friday morning, to be replaced by a
stout mid-level shortwave trough and surface low. Even though
instability is marginal at best, there is lift from both a weak
cold front and left exit region of the upper jet. Mid-level
forcing is also evident with a strong embedded shortwave within
the trough. Based on the latest model timing, expect shower
chances to reach northern and central WI Friday afternoon which
will include a slight chance for non-severe thunderstorms. Max
temperatures Friday to reach around 60 degrees near Lake MI,
mainly lower to middle 60s inland.

Friday night and Saturday...
While thunderstorm chances diminish early Friday evening with the
loss of daytime heating, the chance for showers will persist
through much of the night especially over eastern WI as the cold
front/shortwave trough move through the area. Still cannot rule
out a small chance for pop-up showers Saturday afternoon as a cool
air mass and daytime heating may provide enough instability to
kick off light precipitation. Max temperatures on Saturday to
range from the upper 50s far north/near Lake MI, lower to middle
60s elsewhere.

Saturday night and Sunday...
Any instability showers will end with the loss of daytime heating.
A ridge of high pressure just to our east will allow for skies to
become partly cloudy Saturday night with a west-southwest wind at
5 to 10 mph. A few colder spots may see patchy frost, but most
locations should stay frost-free. The next cold front/shortwave
trough tandem is forecast to move into the western Great Lakes by
Sunday afternoon with our next chance for showers/slight chance of
thunderstorms. Better instability to be to our west, thus severe
potential looks pretty low right now. Max temperatures on Sunday
to be in the lower to middle 60s lakeside, upper 60s to lower 70s
inland.

Sunday night through Wednesday...
The chance of showers/slight chance of storms will continue Sunday
night as the cold front/shortwave trough move across the region.
Forecast confidence is rather low for the first half of the new
work week as the models are having a hard time with the movement
of systems pushing across the northern tier of states. The CMC
favors Tuesday with the highest pops, the ECMWF favors Wednesday,
while the GFS has chance pops each day from Monday through
Wednesday. Blended model has kept the small pops in the forecast
each day, but anticipate more refining of these pops as we get
closer to this time frame. Temperatures do appear to go above
normal next week with inland locations getting into the 70s.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 947 PM CDT Wed May 8 2024

VFR conditions are expected across the TAF sites during the TAF
period. Showers will lift north over southern Wisconsin on
Thursday, but should stay out of the area and not impact the TAF
sites.

&&

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

&&

$$

DISCUSSION.....Uhlmann/Kallas
AVIATION.......Kurimski