Special Weather Statement, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
900 PM CDT Sat Aug 8 2020

.UPDATE...
(Issued 900 PM CDT Sat Aug 8 2020)

Bulk of convection associated with weak mid-level wave moving ENE
and remaining just northwest of CWA this evening. Low level
convergence weakening with loss of insolation, but with passing
weak mid-level wave and remaining instability axis of 3-4K MUCape,
can not rule out scattered convection affecting northern CWA for a
time overnight.

Still looks like best chance for more widespread convection will
be later Sunday afternoon into the evening when southern extension
of stronger mid level short wave moves through the area. Once
again Cape will be in the 2-4K joule range, along with better bulk
shear of 25-30 kts.

MBK

&&

.SHORT TERM...
(Issued 323 PM CDT Sat Aug 8 2020)

Tonight through Monday:

The current round of showers and storms appear to be associated
with a departing LLJ, some mid-level convergence, and a weak wave
moving into northern MI. As we begin to lose forcing the impact of
the increasing WAA has become apparent with satellite imagery
showing somewhat suppressed CU to the S/SW of the area. Could see
an isolated storm develop along the WI/MN/IA border but confidence
in that is low. Tonight into Sunday models are fairly consistent
indicating brief ridging over southern WI, which should help to
keep dry weather in place. Then by the afternoon and evening, a
trough moves N/NE out of SD/NE and into MN. Dewpoints in the lower
70s coupled with steep lapse rates aloft will support CAPE of
3,000+ J/kg in northern WI and MN. This is where we expect an MCS
to initiate tomorrow afternoon and should track E/SE towards
southern WI. Both hires and global models are struggling with how
to handle this pattern. Most hires models had an MCS moving south
through the area today, which is yet to transpire. So, we have to
take those forecasts with a grain of salt and stick to the main
synoptic forcing for a look at what we can expect.

As mentioned above the WAA and CAP continue for Sunday and help to
limit activity during the day. The inversion aloft begins to break
down as the shortwave moves across northern WI to the point where
we could see convection dive south along any moisture/instability
axis. Can't disagree with the slight/marginal risks for strong to
severe storms due to the favorable environmental factors just
confidence in timing/location of storms is low. Damaging winds,
large hail, and very heavy rainfall will be the main impacts.
The next 24-36 hours will be driven by mesoscale factors
associated with ongoing convection.

Temperatures both Sunday and Monday top out close to 90 degrees
and with high humidity, the heat indices range from the low to mid
90s. A cold front either associated with the MCS or following not
too long behind will bring some relief as we head into next week.
Models vary on the timing of the front mainly due to the
differences in the handling of the convection. So stuck with a
blend of guidance for temps on Monday.

Stumpf

&&

.LONG TERM...
(Issued 323 PM CDT Sat Aug 8 2020)

Tuesday through Saturday:

Tuesday through Thursday should generally feature quiet weather
across southern WI due to surface high pressure over the Upper
Great Lakes. The upper level flow will remain zonal. An 850mb
baroclinic zone is expected to line up from southern MN to central
IL during this period. The GFS has this zone further east than the
ECMWF and thus brushes southern WI with thunderstorm chances
Wednesday and Thursday while the ECMWF keeps our area dry. Highs
will be in the lower 80s with dewpoints in the upper 50s and lower
to mid 60s, so this will be a nice stretch of summer weather.

By Friday, a compact, closed upper low is expected to slowly move
across the Midwest. This could bring a few showers and
thunderstorms to southern WI Friday into Saturday, but the main
area of storms should remain over IL.

Cronce

&&

.AVIATION...
(Issued 900 PM CDT Sat Aug 8 2020)

For the 06Z TAFs:

Can not rule out a few thunderstorms affecting the northern areas
overnight. Otherwise, VFR conditions are expected through much of
Sunday. Scattered thunderstorms are expected to develop Sunday
afternoon and affect portions of southern WI through the evening.

MBK

&&

.MARINE...
(Issued 900 PM CDT Sat Aug 8 2020)

Nearshore...Winds at the lakeshore and over the near shore waters
have been subsiding since early evening with the loss of
insolation. Waves are mostly below 4 feet south of North Point
Light, so cancelled Small Craft Advisory for southern marine
zones. Lingering higher waves of 3 to 6 feet north of North Point
Light will decrease late this evening, so wl allow Small Craft
Advisory in these areas to expire at 05Z.

Open Waters...Gusty south winds over the Lake Michigan open waters
have been gradually diminishing through the evening. This trend
should continue but remain mostly in the 10 to 20 kt range
overnight. A few thunderstorms will affect parts of the lake
overnight as well.

MBK

&&

.BEACHES...
(Issued 900 PM CDT Sat Aug 8 2020)

Wl let Beach Hazard Statement run its course at Lake Michigan
beaches in Ozaukee and Sheboygan counties, and let it expire at
midnight. South winds remain at 10 to 15 knots, so waves heights
at the beach will continue to gradually diminish.

MBK

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060 until midnight Sunday.

LM...Small Craft Advisory...LMZ643-LMZ644 until midnight Sunday.

&&

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Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
1006 PM CDT Sat Aug 8 2020

WIZ046-090345-
Marquette-

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN MARQUETTE COUNTY...

At 1005 PM CDT, a strong thunderstorm was located near Westfield, or
11 miles east of Friendship, moving east at 25 mph.

Winds of 30 to 40 mph and pea size hail are possible with this storm.

Locations impacted include...
Westfield, Lawrence, Neshkoro, Springfield Corners and Harrisville.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4384 8922 4385 8960 4398 8960 4398 8922
TIME...MOT...LOC 0305Z 271DEG 21KT 4394 8960

CMILLER