Area Forecast Discussion
Issued by NWS Green Bay, WI

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523
FXUS63 KGRB 170339
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1039 PM CDT Wed Jun 16 2021

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 238 PM CDT Wed Jun 16 2021

Quiet weather will start off the short term and last through at
least the evening before more active weather arrives overnight and
again Thursday afternoon/evening.

High pressure will continue to influence the region this afternoon
before sliding off to the east this evening and early overnight.
Moisture will be on the increase overnight, which bring a slight
chance of rain to portions of central and northern Wisconsin early
on Thursday, as the remnants of storms to our west arrive ahead of
a cold front. Return flow will also bring an increase in low
temperatures for the region compared to last night, with readings
in the middle to upper 50s across the area.

Weather becoming a bit more active in toward the end of the
short- term portion of the forecast. Warmer and more humid weather
will arrive for Thursday along with isolated to scattered
afternoon showers and thunderstorms.

Thursday will be a bit more active day for the region, although
thunderstorm activity in the morning and afternoon will be fairly
isolated. In the morning, decaying showers ahead of the cold front
will reach the region, stretching mainly from central to northern
Wisconsin. This early precipitation will be fairly limited in
coverage, mainly due to the large amount of dry air still
remaining across the lower levels in the area. As we get into the
afternoon, ample return flow and WAA ahead of the front will push
temperatures to the 80s near the surface, but also introduce a
fairly robust capping layer through at least the lower 2-3km of
the atmosphere. This should limit any surface based convection
through a good portion of the afternoon ahead of the main upper
trough. That said though, mid to upper level instability does
still reach around 1500-2500 J/kg of CAPE, as well as bulk shear
values around 45-55 kts. This does provide the potential to
organize a few elevated storms, if something does get going, with
the main threats being large hail and damaging winds from
thunderstorm outflow. Heavy localized rainfall will also be
possible, as fairly impressive PWATS around 1.5-2.0 are around,
mainly aloft. This threat may be reduced somewhat by the dry air
below, at least early on in the event. All in all, can`t
completely rule out severe potential through the early to late
afternoon, although coverage will, again, be spotty. Northeast
WIsconsin is in a Marginal severe risk by SPC for this timeframe,
and this is reasonable.

The better chance for severe weather will be later in the day on
Thursday, as the cold front finally arrives accompanied by the
upper shortwave. Although MCS activity will be focused to our
southwest, it may yet affect portions of central to east-central
WI as the exact track remains unclear. Please see the extended
discussion for further details.

.LONG TERM...Thursday Night Through Wednesday
Issued at 238 PM CDT Wed Jun 16 2021

A significant pattern change is expected this weekend into
early next week that will bring cooler than normal temperatures
to the area. There are several chances of showers and
thunderstorms during the period.

For Thursday night, a cold front will move across the area during
the evening into the overnight hours. The current Storm Prediction
Center Day 2 Outlook has the area in a marginal risk of severe
thunderstorms. Models continue to show 500 to 1,500 J/KG of CAPE
and 0-6km shear values of 35 to 45 knots to support severe
thunderstorm activity. There is plenty of warm air aloft that
may limit the coverage of storms across north-central and
northeast Wisconsin. In addition, a thunderstorm complex is
expected to develop south of the area with the northern edge
of this thunderstorm complex clipping portions of central and
northeast Wisconsin later Thursday evening into early Friday
morning. Will continue to highlight the risk of severe
thunderstorms in the Hazardous Weather Outlook. Any lingering
showers should exit far east-central WI around 12z Friday
morning.

On Friday afternoon, some instability showers and a few
thunderstorms may develop across far northern Wisconsin. Models
indicating 500 to 1,000 J/KG of CAPE on the Iron Mountain bufkit
soundings. Models show low wet bulb zero heights and inverted-V
soundings along with 850mb winds around 30 knots and 700mb winds
to near 40 knots. These parameters would support some of the
showers and storms could produce small hail and wind gusts to
around 40 mph. Most of the activity will end around 7 pm Friday
evening.

Dry conditions are expected on Saturday with next system arriving
late Saturday night, and more likely on Sunday. Showers and
thunderstorms will move across the region Sunday into Sunday night
as another cold front moves across the area. It is too early to
determine the risk of severe thunderstorms across the area. Much
cooler temperatures are expected early next week as 850mb
temperatures drop to +2C to +7C. This will result in high
temperatures on Monday ranging from around 60F north to around 70F
south along with a chance of rain. Highs on Tuesday will be in
the lower to middle 60s north and in the lower 70s south with dry
conditions expected. Temperatures return closer to normal next
Wednesday.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CDT Wed Jun 16 2021

Clear skies, light winds and excellent visibility
will continue through most of the night. Middle and high clouds
will move into northcentral Wisconsin later tonight, and increase
across the area Thursday as an upper level disturbance and
surface trough approach from the west.

There is a slight chance of a shower or thunderstorm northwest of
an Iron Mountain to Wausau line Thursday morning, and a chance of
thunderstorms across the entire area Thursday afternoon and evening.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from Thursday morning through late
Thursday night for WIZ022-040-050.
&&

$$

SHORT TERM.....Uhlmann
LONG TERM......Eckberg
AVIATION.......RDM



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