848
FXUS63 KGRB 070920
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
420 AM CDT Fri Jun 7 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Breezy west to northwest winds are expected today, with gusts to
  25-35 mph. Conditions hazardous to small craft are expected
  today due to the gusty winds.

- Showers are expected overnight into Saturday morning, with a
  slight chance of thunderstorms Saturday afternoon, mainly across
  northern Wisconsin.

&&

.DISCUSSION...
Issued at 420 AM CDT Fri Jun 7 2024

Short Term...Today...Tonight...and Saturday

We dry out today but remain on the breezy side. Light rain spreads
back across the region overnight into Saturday. Main forecast
concerns are timing precip chances, assessing thunder chances on
Saturday and how gusty winds will get today (especially near Lake
Michigan).

Shower/Thunder Chances & Clouds:

Other than a stray sprinkle early this morning, look for dry
conditions today. A mix of clear skies and clouds will start the
day, with most of the clouds in northern and eastern WI, with
some clearing in central WI. We will remain in cyclonic flow with
enough moisture remaining in the lower levels to get some daytime
cu, especially were it is sunny for a time in the morning. Clouds
will increase and thicken from the west tonight as a shortwave
trough and frontal boundary approaches from MN. These features,
along with an area of deep layer moisture, will spread an area of
mainly light rain across the area overnight (mainly central and
north-central WI) and into Saturday morning (area-wide). Most of
the rain will exit late Saturday morning or early afternoon. Rain
amounts look to be in the 0.10-0.40" range for most locations, so
there will be no flooding concerns. As for thunder chances, looks
like the clouds/rain arrive early enough to really limit
instability during most of the day (under 100 J/kg MUCAPE expected)
so will remove the thunder mention for most of the area.
Exception may be over the far north where models show a ribbon on
slightly higher instability (along with 30-50 kts of bulk shear)
that may be be enough to touch off a storm right along the
front. Better instability builds behind the boundary as some sun
is expected to provide surface heating. This could touch off a few
spotty showers (or storm?) late in the day, but some concerns how
much moisture would be left over to produce any significant
activity. Severe weather is not expected.

Winds:

Soundings look pretty similar to yesterday, showing 25-30 kt
winds around 2000 ft to mix down to the surface. This should
produce gusts to 30 mph across the area, with a few gusts to 35
mph possible. Winds will diminish later this afternoon as winds
aloft decrease and the better mixing fades. Less breezy conditions
arrive for Saturday with gusts mainly under 20 mph.

Temps:

With a similar set up to yesterday, followed the best performing
guidance (BCONSALL/BCCONSRAW/NBM) for this afternoon which has
highs climbing into the upper 60s to middle 70s. This is supported
by 925mb temps climbing to between 13-17C. Lows tonight will drop
into the upper 40s to middle 50s. Clouds and rain will hold temps
down for part of the day on Saturday, but as the precip exits in
the afternoon and winds downslope, still think we can get into the
mid and upper 60s to possibly near 70. Did lower temps near the
lake shore as they will be see the rain exit last and have an
onshore winds for part of the day.

Long Term...Saturday Night Through Thursday

Main focus from this forecast period revolves around precipitation
trends for Sunday and early next week. Temperatures will be slightly
below normal for Sunday through early next week, with potential
warming by midweek next week.

Saturday night through Sunday...Besides some lingering light
chances for showers and storms Saturday evening across the north
following a cold frontal passage from earlier in the day, dry
conditions are expected for Saturday night. A shortwave dropping
over the western Great Lakes and CAA may allow for light diurnally
driven showers to develop on Sunday. However, forecast soundings
indicate limited moisture in the column, leading to isolated
coverage. Thunder chances will be very low given a lack in
instability and steep mid-level lapse rates.

Rest of the extended...High pressure and upper-level ridging look
to build over the Upper Mississippi Valley for Monday, however,
there is a new wrench being thrown into the mix of solutions. Some
solutions indicate the ridge will not occur, rather a closed low
would drop southeast across the Northern Plains to the Midwest on
Monday. While this signal has been present in some ensemble
clusters over the past couple of runs, the spread was quite high.
The latest ensemble clusters still show a signal for the ridge to
occur, but there are now more members agreeing with the closed low
solution, in addition to the deterministic GFS and UKMET. If the
ridge occurs on Monday, the next chance for precip would be
sometime Tuesday/Tuesday night. But, if the ridge doesn`t occur,
portions of the forecast area may see precip on Monday and be dry
for Tuesday. Until details become clearer, forecast confidence is
not high for any period for the remainder of the long term.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 947 PM CDT Thu Jun 6 2024

A northwest flow of cool air aloft will produce mostly cloudy skies
across much of the area through midday Friday. MVFR ceilings are
possible late tonight through 15Z Friday northeast of a RHI to SUE
line, with VFR ceilings further south. Mostly clear skies are
expected Friday afternoon and evening across the region.

&&

.MARINE...
Issued at 420 AM CDT Fri Jun 7 2024

A similar synoptic set today as yesterday. Several sites had
gusts near/over small craft criteria yesterday, while others
struggled. There still is some uncertainly regarding how much
mixing will occur as you get near/in the cooler waters, especially
with no showers to help bring down the gustier winds. But with
soundings showing 25-30 kts of wind mixing down from 1000 ft,
would expect some gusts to around 25 kts, mainly near the shores
of the bay and Lake Michigan. A Small Craft Advisory has been
issued from 7am to 6pm. Less breezy conditions arrive this evening
into Saturday.

&&

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

&&

$$

DISCUSSION.....Bersch/Kruk
AVIATION.......RDM
MARINE.........Bersch