003
FXUS63 KGRB 111932
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
232 PM CDT Tue Jun 11 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Periods of light rain are expected through this evening. A
  thunderstorm is possible, but no severe weather is anticipated.

- There is a Marginal Risk of severe thunderstorms late Wednesday
  afternoon and Wednesday evening when one or more complexes of
  storms could impact the region. The latest indications suggest
  locations over central Wisconsin have the highest chance of
  seeing strong storms, which may contain gusty winds and hail.
  Confidence is low where these thunderstorms will track.

- Well above normal temperatures are forecast from Sunday into the
  middle of next week. Heat indices may surpass 90 degrees at
  times.

&&

.DISCUSSION...
Issued at 232 PM CDT Tue Jun 11 2024

Short Term...Tonight and Wednesday

The latest RAP analysis and satellite/radar imagery show a cold
front moving across the northern Mississippi Valley with help from
a modestly potent shortwave trough. A broken band of rain along
the leading edge of a warm advection zone is proceeding east at
about 30 kts across central Wisconsin. This band of showers will
likely weaken somewhat, but not enough to dissipate before
reaching eastern WI. The trailing cold front has been inactive
so far today, but convective clouds are building along the
boundary. Between this system and the next system arriving on
Wednesday, precip and severe weather chances are the focus of this
forecast.

Precip Trends: Behind the light band of rain showers, the
convective allowing models indicate that additional showers may
redevelop later this afternoon.  No thunderstorms are expected.

Right along the front, a few thunderstorms could develop early
this evening along a narrow ribbon of 600-800 j/kg cape. If
thunderstorms develop, central WI will have the greatest chance.
Brief gusty winds will be possible through the evening if storms
develop.  Then quiet conditions return overnight.

Then within fast, zonal flow aloft, light showers could develop
over north-central and far northeast WI in the afternoon. But all
eyes will be on southeast Minnesota and northern Iowa for strong
thunderstorm development along the instability gradient in the
afternoon. Some storms could make a run at central Wisconsin after
5 pm.

Severe weather chances: Within a region of strong instability
(2000-3000 j/kg mixed layer cape), strong to severe thunderstorms
are forecast to develop over central Minnesota around 1-2 pm.
These thunderstorms are forecast to grow upscale into a complex
and track along the cape gradient on the nose of the 35-45 kt low
level jet to the southeast and into southwest Wisconsin by late
in the afternoon. While tracks and timings may still change, the
latest guidance suggest central WI will be on the northern edge of
any convective complex. Some guidance shows instability upwards of
1500 j/kg sneaking into Wood, Portage, and Waushara counties where
a severe wind/hail threat may develop by 22-23z. If it comes to
fruition, the strong to severe thunderstorm threat should end
relatively early on Wednesday night due to fast forward motion of
the complex, perhaps around the 10 to 11 pm time frame.

Chances appear lower than previous forecasts over north-central WI
where another complex could develop over the Arrowhead of
Minnesota before tracking east into Lake Superior.

Long Term...Wednesday Night Through Tuesday

The main focus of the extended forecast will be on the evolution
of the 500mb pattern through the end of the week, which may bring
both our next round of strong active weather and well above normal
high temperatures.

Active weather underway from late Wednesday afternoon will
rapidly push through the region during the evening hours,
departing by the early overnight hours. The strongest storms may
yet move through portions of central Wisconsin, but general
consensus still brings the strongest storms south of the area. See
the short term discussion for additional information.

The cold front that brought the active weather through on
Wednesday is expected to drop well south of the area Thursday,
bringing back quiet conditions for our area. Any redevelopment
along the cold front will stay south, impacting primarily
northern Illinois and southern Wisconsin.

As high pressure begins to depart Saturday, southerly return flow
will begin to ramp up. A strong push of warm moist air will cross
the region by late Saturday, bringing with it another chance for
some active weather. Instability parameters due suggest some
potential for stronger storms, so Saturday afternoon through
Sunday will be a time period to watch for severe potential.
Behind this, the area is expected to be well in to the warm
sector. Long range guidance still brings high temperatures well
into the 80s both Sunday and Monday, with a chance for low 90s.
These temperatures may still come down on Sunday depending on how
quickly any precipitation and cloud cover pushes through from
Saturday, but the warmup remains in the forecast.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1158 AM CDT Tue Jun 11 2024

Previous forecast appears on track. A cold front will bring a band
of light rain across the region this afternoon. Flight conditions
should generally remain VFR in eastern and central WI, but may
drop to MVFR in north central and far NE WI this afternoon for a
couple hours. There will be a very small chance of storms, but
confidence to add to the forecast. Showers will exit the region
from west to east this evening, followed by clearing and a return
to VFR conditions overnight.

Generally good flying weather is expected through Wednesday
afternoon. By late in the afternoon or early evening, shower and
thunderstorm chances will increase.

&&

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

&&

$$

DISCUSSION.....MPC/Uhlmann
AVIATION.......MPC