896
FXUS63 KGRB 021120
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
620 AM CDT Sun Jun 2 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Patchy/areas of fog through around daybreak this morning,
  especially central and north-central Wisconsin where it could
  be locally dense.

- Rain and some storms Monday. An isolated strong storm in the
  afternoon could produce gusty winds.

- More strong storms are possible Tuesday afternoon into Tuesday
  night. Gusty winds and heavy rain will be the primary hazards.

&&

.DISCUSSION...
Issued at 403 AM CDT Sun Jun 2 2024

Short Term...Today...Tonight...and Monday

Fog early today, then a mostly sunny and warm day. Showers and some
thunder spreading from west to east on Monday.

Fog as expected has become most dense over central Wisconsin where
a Dense Fog Advisory remains in effect through 9 AM. Based on
recent obs have expanded the advisory into Vilas, Oneida, Langlade
and Waupaca counties. Elsewhere fog has been much more patchy with
minimal fog thus far Green Bay into the Fox Cities. Fog will
quickly diminish all areas after daybreak. Lingering stratus will
transition to scattered cu in the aftn, but skies will be mostly
sunny overall. High temps near 80 away from the Lake Michigan
shoreline where readings will be limited to mid to upper 60s.

Tonight will stay dry until very late when low pressure system
and warm front begin to approach the western Great Lakes. A few
showers may make it into central to north-central zones, but much
better chances hold off til daytime on Monday. Expect swath of
showers and embedded thunder to work across region on Monday,
probably not arriving over northeast and east-central WI til
afternoon. There are details to be ironed out in terms of where
greater focus for storms will be with possible convective aided
shortwaves, MCVs working in from the central Plains. Even so,
stronger low-level jet, theta-e advection and jet entrance region
should result in widespread showers over our area. Better chance
for stronger storms will be in the afternoon southwest of AUW to
OSH line as MLCAPES rise toward 1000j/kg and there would be
increased effective shear from any convective shortwave. SPC has
marginal risk on our southern doorstep which agrees with the
expected pattern and majority of high-res CAMs. High temps will
depend on how quick the showers move into the area and how
widespread they are. Readings will range from around 70 north-
central to the mid 70s southwest closer to the warm sector in the
afternoon.

Long Term...Monday Night Through Saturday

An active pattern continues in the extended forecast as an upper
trough lodges itself across northern CONUS, bringing through
periodic rounds of active weather.

Monday night through Tuesday...
Although any strong storms are expected to depart the region by
the evening hours, continued isentropic ascent overnight will
sustain at least a few showers going overnight Monday into
Tuesday. Although this could also hamper instability development
later in the day on Tuesday, models do still develop fairly strong
surface instability, upwards of 1500+ SBCAPE, as dewpoints push
well into the 60s during the afternoon. Therefore, additional
surface based thunderstorms are possible in the afternoon. The
factors limiting severe weather however, are unimpressive mid-
level lapse rates, a lack of bulk shear for organizing storms,
and the delay in the cold front passage mentioned in previous
forecasts; which is now expected to remain out west during our
best diurnal instability and only make its way into northeast
Wisconsin well into the overnight hours. Taken together, would
expect pulse storms to be possible Tuesday afternoon and evening
with brief strong wind gusts. Heavy rainfall will be a concern
however, as these storms will be relatively slow moving and PWATS
remain impressive for the time period. Finally, the passage of the
cold front overnight will likely help sustain any ongoing rain and
storms, furthering the heavy rain concern, but will likely not lead
to widespread severe weather. Encapsulating all this, the marginal
risk category for severe remains off to our west Tuesday while we
are in the marginal risk for excessive rainfall, which makes
sense.

Rest of the forecast...
The upper pattern will for the rest of the extended appears to
slow down and stall out, favoring a continuation of periodic
active weather over our region. The broad upper low that brought
the cold front through the region appears to stall out over south-
central Canada and the northern CONUS, resulting northwest flow
and several rounds of relatively lighter active weather through
the rest of the work week and into early next weekend. The good
news here however is that this is not expected to be severe
weather at this time, as cooler temperatures and drier air will
limit any thunderstorm potential.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 617 AM CDT Sun Jun 2 2024

Fog and low stratus with localized VLIFR/LIFR conditions will
dissipate between 12z-14z. Worst conditions are found across
central to north-central Wisconsin. Beyond this, VFR conditions
for the rest of the TAF period with scattered fair weather cu late
this morning into the afternoon and thickening mid clouds from
west to east tonight. Spot shower could develop at CWA/AUW and RHI
late tonight. Low chance so have included prob30 groups to cover
the potential.

Conditions deteriorate to MVFR (local IFR) from west to east on
Monday as showers and some thunderstorms spread across the area.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CDT this morning for WIZ005-010-
018-019-030-035>037-045.
&&

$$

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