769
FXUS63 KGRB 010856
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
356 AM CDT Sat Jun 1 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Scattered showers into early this evening. Best chances for non-
  severe storms (30-40 percent) north-central to central WI this
  afternoon into early this evening.

- Rain and storms are possible Monday afternoon. While storms
  aren`t expected to be severe, an isolated strong gust up to 35
  to 40 mph with any storms is still possible.

- A better chance for strong storms arrives later in the day
  Tuesday. These storms may also be accompanied by heavy rainfall.

&&

.DISCUSSION...
Issued at 355 AM CDT Sat Jun 1 2024

Short Term...Today...Tonight...and Sunday

Coverage and location of shower and thunder chances today is the
main focus.

Shower chances today and fog potential tonight: Radar loop early
this morning shows showers have shifted north and west of even
north-central WI closer to narrow ribbon on higher PWATs and
close to weakening cold front/moisture boundary. This boundary
will shift slowly east today so some showers will spread back into
central and north-central WI this morning. Instability limited so
have scaled back on any thunder mention through mid morning.
Later this morning into the afternoon seems when most of cwa will
have the greatest chances for some showers, still very scattered
in nature though. This will be as the boundary upstream shifts
across in response to shortwave trough sliding east into northwest
Ontario and also as the southeast area is on fringe of southern
stream system lifting across the Ohio Valley. Best chance for
thunder is this afternoon from north-central to central WI with
weak instability pooling along what will mainly be low-level wind
shift, mainly noted at H85. Showers end early this evening.
Nighttime cooling and a moist boundary layer could lead to some
fog late evening and overnight. Capped this at patchy coverage
now, but some more widespread fog is possible where rain is more
persistent today. Once the fog diminishes after daybreak on
Sunday, other than some diurnal cu, conditions will remain dry
into Sunday afternoon as bubble of high pressure slides across the
area.

Temperatures: After a mild start early this morning, expect highs
today to reach at least the low 70s with greatest chance of mid
70s from southwest cwa into far northeast WI where rain is least
likely into the afternoon. High pressure across the area tonight
will promote temps falling back into the upper 40s north and in
the mid 50s elsewhere. Cu and a weak lake breeze will be the only
thing to put breaks on temps on Sunday. Mixing to H75 inland
supports highs eclipsing 80 most everywhere with even some lower
80s possible. Coolest readings around 70 will be right along the
Lake Michigan shore.

Long Term...Sunday Night Through Friday

The main focus for the extended forecast will be on Monday and
Tuesday, both of which could have a round of active weather and
storms.

Sunday night and Monday...
Ensemble guidance brings a surface low northwest of the region
overnight through Monday morning. A northward surge of warm air
will likely bring some rain into the region by the mid morning,
ahead of a strong upper shortwave that will help sustain and
spread eastwards a round of showers and storms. The timing of
this shortwave will not favor severe weather however, as
instability in the region will be fairly scarce without a chance
to warm up. Additionally, the cold front previous forecasts
focused on for redevelopment has become less defined due to the
more northerly track of the surface low. Therefore severe weather
later on Monday isn`t favored either. All that said, any isolated
storms that do form in the region could still bring a few stronger
gusts, mixing down some of the 30-40 knot winds around 925mb and
850mb.

Tuesday...
Attention then turns to the next system as another strong
shortwave crosses northern CONUS and southern Canada. This will be
a fairly strong and dynamic system, bringing a surge of warmth
and moisture into the region before the trailing cold front
arrives. With dewpoints pushing into the lower 60s, surface
instability will be fairly high for this event. Timing remains
uncertain, ranging from Tuesday evening to the overnight hours,
which in turn brings uncertainty into the overall severe potential
as instability will start to wane overnight. That said, the
dynamics of this system remain impressive so this time period will
bear watching going forward.

Rest of the forecast...
Guidance suggests that the low mentioned for Tuesday may occlude
north of the region around the middle of the week, separating from
the mean flow and bringing additional, lighter rounds of
precipitation in the region to round out the week. This will also
bring some milder temperatures back to the area, with highs
falling back into the middle 60s to lower 70s for the middle to
end of the work week.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1023 PM CDT Fri May 31 2024

A very slow moving cold front across northwest Wisconsin will
produce scattered showers and isolated thunderstorms north of a
SAW to RHI to EAU line tonight.

This front should move slowly east Saturday, probably producing
scattered showers and isolated thunderstorms west of a IMT to STE
line by early afternoon. There could also be scattered showers or
thunderstorms near the bay and Lake Michigan in the late afternoon
or early evening as an upper level disturbance moves across
southern Wisconsin. VFR conditions are likely Sunday.

&&

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

&&

$$

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