Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 270350
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1050 PM CDT Sat May 26 2018

Updated aviation portion for 06Z TAF issuance

.SYNOPSIS...
Issued at 247 PM CDT Sat May 26 2018

Scattered showers and thunderstorms tonight, mainly over the
north. Otherwise, very warm and rather humid for the rest of the
holiday weekend, with some fog over and near the lake and bay at
times.

The primary band of westerlies will remain across Canada
throughout the forecast period. A secondary band of westerlies was
across the CONUS, characterized by a deep trough near the West
Coast, sharp ridging over the western Plains, and a weak/diffuse
trough over the Mississippi Valley. The trough/ridge couplet out
west will weaken some during the first part of the forecast
period. At the same time, the remnants of subtropical storm
"Alberto" lift north through the eastern CONUS. The western trough
will re-energize by next weekend as energy heading east from the
Pacific peels out of the northern stream and digs down the West
Coast.

The large scale pattern favors very warm temperatures, at least
into the middle of the upcoming work week. Readings could be held
back a little by thunderstorm outflow and east winds at times, but
should remain well above normal for much of the period, then drop
back closer to normal late. There will be numerous opportunities
for rain, but most events will be comprised of scattered showers
and thunderstorms, likely making rainfall totals for the whole
period quite variable from place to place.
&&

.SHORT TERM...Tonight and Sunday
Issued at 247 PM CDT Sat May 26 2018

It was another warm to hot day away from the bay and lake this
afternoon. As of 2 pm, Rhinelander set a new record high for the
date at 91 and Green Bay at 90 which broke the old record of 88
set in 1914 and 1978.

Meanwhile, storm and fog are main concern for this period along
with another hot day expected on Sunday. Latest satellite images
indicated enhanced cumulus field across northern Wisconsin while
strong and at times severe thunderstorms were noted across Upper
Michigan. Showers and thunderstorms are expected build southward
into north-central and far northeast Wisconsin this afternoon
and move across far northeast Wisconsin early this evening.

The latest analysis indicated mixed layer capes of 1000 J/Kg,
0-6 km shear values of 25 to 30 knots to support strong or
severe thunderstorms for the remainder of the afternoon into
early this evening. Damaging wind gusts to 60 mph and hail
up to a half dollar are possible in the stronger storms.
The greatest risk of strong or severe storms will be across
Marinette, Oconto and Door Counties. The showers and thunderstorms
will end by late evening. Overnight, patchy or areas of fog
will develop across far northeast Wisconsin, especially where
it rains today.

On Sunday, another hot day is expected for most with highs
in the 90s. There is some concern about how warm it will get
across portions of northeast Wisconsin away from the bay and lake
as an expected outflow boundary may drop southward across the
area this evening. This outflow boundary could keep temperatures
down a few degrees in this portion of the state.

Meanwhile, satellite images indicated an expansive fog bank
offshore Manitowoc and Kewaunee Counties which was moving
northward into Door County. The back edge of the dense fog was
lifting northward, thus the dense fog advisory will expire at 7
pm. Also, showers and storms and outflow boundaries should also
help mix out the fog. The fog is expected to return at times
later tonight and especially into Sunday which could impact
drivers.

Only minor changes made to max temperatures across northeast
Wisconsin on Sunday due to potential outflow boundary tonight.

.LONG TERM...Sunday Night Through Saturday
Issued at 247 PM CDT Sat May 26 2018

A cluster of storms riding east atop the upper ridge to our west
may maintain itself long enough to turn back ESE into the northern
part of the forecast area late Sunday night or Monday morning.
Redevelopment is also possible later Monday on any lingering
outflow boundaries in the area. Temperatures Monday will be
tricky. Another very warm/hot day is possible, unless a boundary
gets shoved far enough south to produce easterly flow across the
area. Stuck close to the standard forecast initialization grid
generated from a broad-based blend of guidance, as that has been
performing very well for highs lately. The one change was to edge
readings down near the lake.

Precipitation chances later in the week are somewhat nebulous as
additional shortwave energy riding over the large scale ridge
could generate convection in the area. The area could also get
clipped by the remains of subtropical storm "Alberto" lift
northward over the eastern CONUS. The result was several forecast
periods with chance PoPs.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1050 PM CDT Sat May 26 2018

Isolated thunderstorms continue across northeast Wisconsin.
Although they are expected to mainly stay away from the main TAF
sites, a storm could impact GRB just before TAF issuance. The
remainder of the region will be clear to partly cloudy. Areas of
fog, which may be locally dense are expected across portions of
far northeast Wisconsin where rain fell this evening. Any fog and
low stratus across far northeast Wisconsin should dissipate
around 15z on Sunday. Hot conditions are expected on Sunday with
highs in the middle 80s to middle 90s with VFR skies.
&&

.MARINE...
Issued at 247 PM CDT Sat May 26 2018

Dense marine fog lifting northward across the area this
afternoon. The back edge was lifting northward and should
clear northern Door County by 7 pm. Maybe able to cancel
the southern portions of the dense marine fog advisory
south of Kewaunee with the afternoon package.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Eckberg
LONG TERM......Skowronski
AVIATION.......Kurimski
MARINE.........Eckberg


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