Special Weather Statement, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
916 PM CDT Wed Oct 3 2018

.UPDATE...Cold front into extreme SE MN and NE IA heading east.
Some storms have congealed a bit into far SW WI. Still feeding off
some fairly high CAPE values there. More stability further east.
So we'll be keeping an eye on those as they head deeper into srn
WI. Upstream post frontal wind gusts in MN and IA concerning
though isallobaric contributions to the wind regime appear to
easing but only slightly. Wind gusts reaching towards 40 mph into
sw/parts of sc WI seem reasonable. Increased winds a bit into
parts of the western cwa for now. That is a windier area of the
cwa and upstream terrain in MN/IA does tend to be windier, so some
decrease plausible into srn WI.

PC

&&

.MARINE...Increased winds a bit to account for slightly windier
regime than what we had going. No change to headlines though some
winds may be a bit stronger within gale range in the north and
push some gale values in the south. Cold front will work through
overnight with a switch in winds from southwest to northwest.

PC

&&

.PREV DISCUSSION... (Issued 617 PM CDT Wed Oct 3 2018)

UPDATE...Showers/thunderstorms continue to develop along and
ahead of frontal boundary cutting through srn MN into nrn IA. Also
seeing some development in SW WI. Expect this activity to continue
to move east into our area as the evening wears along. Good shear
in place though would expect some diurnal reduction in CAPE. Some
of this activity could become a bit on the hefty side given the
early evening instability in place, but overall meso models are
not showing this taking on much organization and best chance of
some stg/svr appears to be more across SC WI earlier in the evening.

PC

AVIATION(00Z TAFS)...VFR this period with thunderstorm potential
through about midnight. Gusty south and southwest winds ahead of
the front will shift to the northwest after thr front goes by
later in the evening. The northwest winds will become more
northerly Thursday and eventually northeast around high pressure
moving to our north.

PC

PREV DISCUSSION... (Issued 344 PM CDT Wed Oct 3 2018)

SHORT TERM...

Rest Of This Afternoon And Tonight...Forecast Confidence Is
Medium.

SPC meso charts shows instability building across southern WI
with unseasonable/near record warmth and summer-like dew points to
go along with it. MLCAPE values are 1500 J/kg plus with favorable
0-6km shear of 40 knots. Dew points climbing into the mid 60s to
near 70. Meanwhile, low pressure is shifting northeast from SW
MN. The 500 millibar shortwave and upper jet core is favoring nrn
and cntrl WI which is where SPC has the enhanced risk. Also
better thermal gradient there with no sun/sun considerations.

The low level flow does turn more to the southwest, as the
surface front arrives, which seems to be our primary source of
ascent. The meso progs show some convection riding into the
northwest CWA towards 00z, and continuing across the cwa exiting
around 05z or so in the southeast. If anything, these progs have
been backing off a bit on the timing of the convection into our
CWA. These progs are also highlight the likelihood of the most
active storms being north of our CWA, where better dynamics and
thermal discontinuities reside.

Later tonight, as the cold front passes, the winds turn northwest
and will become gusty, with colder 850/925 mb temps pushing in.
With the winds staying up and influence of lingering cloud cover,
this will likely keep temps from dropping off too drastically.

Thursday...Forecast Confidence Is Medium.

High pressure will slide across the northern part of the state
and off to our northeast in the afternoon. So, winds will bend
from the north to northeast. A much cooler day is in store, with
the invasion of the cooler 925/850 mb temps. The LLVL RH progs
are showing a fair amount of dry air, and MOS sky cover is pretty
optimistic as well.

Thursday Night Through Saturday...Forecast Confidence Is Medium.

Active weather pattern continues, with a shot at heavy rainfall
across the area Friday night.

A quasi-stationary front looks to set up southwest to northeast
into the forecast area later Thursday night into Friday night.
Low pressure should track northeast along it across the area
Friday night. Main feature for upward vertical motion will be the
low level jet nose, which will point into the area Thursday night,
and again Friday night. There is focused warm air advection across
the area Thursday night to help with upward vertical motion. There
will also be fairly robust upper divergence Friday night, with
the right rear quadrant of a 250 mb jet streak.

Thus, there looks to be two rounds of precipitation, one later
Thursday night into Friday morning, then a better shot Friday
night into Saturday morning. The first round does not have a lot
of elevated CAPE to work with, so rainfall amounts are expected to
be modest. The best shot at elevated convection and possible
training cells would be Friday night, when the low moves northeast
along the surface boundary across the area. Area forecast
soundings are showing a favorable heavy rainfall setup, with most
heavy rainfall parameters on the higher end of the spectrum.

A good 1 to 1.50 inches of rain may fall just Friday night, with
a total of 1.25 to 2 inches possible for Thursday night into
Saturday. Locally higher amounts are possible Friday night, given
the convective training possibility. May consider flooding
headlines in later forecasts for Friday night, as partners in
Madison and southwest of there have indicated that any appreciable
rainfall over the next several days may cause more widespread
flooding issues.

The showers and some storms may linger into Saturday, until cold
air advection behind the cold front starts to bring drier air
into the area from the northwest Saturday afternoon.

LONG TERM...

Saturday Night Through Wednesday...Forecast Confidence Is Medium.

Active weather pattern looks to persist during this period, as the
500 mb high over the Carolinas remains nearly stationary. This may
actually amplify the 500 mb flow to a more south to north
configuration over the central part of the country. This may help
steer the low pressure system tracks to the west Sunday night
into Monday night, versus over the area. However, there are quite
a bit of model differences with the low track and effects on the
area. Thus, there is uncertainty with where any heavy rainfall
areas will set up. Kept blended model PoPs for now, which bring
likely or greater PoPs for Sunday night into Monday.

Another strong low for the middle of next week may move northward
into the region, bringing another round of showers and storms.
Again, enough model uncertainty to keep blended model PoPs going
for now. This entire period may bring another 1 to 2 inches or
more of rainfall, which would have big impacts upon those areas
already having water issues. Keep up with the forecast for this
period.

AVIATION(21Z TAFS)...

VFR this period with main concern being gusty south/southwest
winds ahead of a cold front and tsra potential this evening. The
potential for stronger storms to enter northwest CWA around 00z
or so, and exit the southeast around 04z-05z. As cold front
passes, there will be a wind shift to the northwest, and then a
shift to the north or northeast for Thursday. LLVL RH progs are
looking pretty dry, and both NAM and GFS MOS showing little in
the way of cloud cover in the cooler pattern on Thursday. So, the
typical lower ceilings we often see in this regime may be absent.

MARINE...

Gale Warning has been under achieving with more clouds, but still
expecting things to amp up, so will leave things as is for now.
Further south, the Small Craft Advisory headlines look good.
Strong and gusty south/southwest winds have increased ahead of low
pressure. As the low tracks to our north and shifts to our east
overnight, it will sweep a cold front through our area. This will
switch winds to the northwest, and then to the north for Friday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 10 AM CDT Friday for LMZ643>646.

&&

Tonight/Thursday and Aviation/Marine...Collar
Thursday Night through Wednesday...Wood

Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
920 PM CDT Wed Oct 3 2018

WIZ046-047-051-052-056>060-062>072-050230-
Marquette-Green Lake-Fond Du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
920 PM CDT Wed Oct 3 2018

This Hazardous Weather Outlook is for portions of east central
Wisconsin, south central Wisconsin and southeast Wisconsin.

.DAY ONE...Tonight

There is a slight risk for severe thunderstorms this evening.
Thunderstorms are expected to move east through the area through
about midnight. An isolated severe storm is possible.

Wind gusts may approach 40 mph in the wake of a cold front
overnight.

.DAYS TWO THROUGH SEVEN...Thursday through Wednesday

There are chances for thunderstorms at times Thursday night into
next week. The best chances will be Friday night.

The biggest concern will be rounds of heavy rain and possible
flooding during this period, especially Friday night. There will
also be continued or new rounds of river flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation most likely will not be needed.

LMZ643>646-050230-
Sheboygan to Port Washington WI-
Port Washington to North Point Light WI-
North Point Light to Wind Point WI-
Wind Point WI to Winthrop Harbor IL-
920 PM CDT Wed Oct 3 2018

This Hazardous Weather Outlook is for portions of Lake Michigan.

.DAY ONE...Tonight

A Small Craft Advisory remains in effect, for gusty south winds
and building waves. Winds will shift to the northwest later
tonight and remain gusty.

There is a slight risk for severe thunderstorms, through midnight
or a bit after. Thunderstorms are expected to arrive between 10 pm
and linger through around midnight. An isolated severe storm is
possible.

.DAYS TWO THROUGH SEVEN...Thursday through Wednesday

The Small Craft Advisory is in effect until 10 AM Friday, though
it may eventually need to be extended until later Friday due to
lingering high waves.

There are chances for thunderstorms at times Thursday night into
next week. The best chances will be Friday night.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-050230-
Lake Michigan Michigan City IN to St. Joseph MI 5 NM offshore to
mid-line of lake.-
Lake Michigan from Seul Choix Point to Rock Island Passage 5NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and North of a line from Charlevoix MI to South
Fox Island 5NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5NM Offshore to
mid lake-
Lake Michigan from Point Betsie to Manistee MI 5NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI 5NM
offshore to mid lake-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5NM offshore to Mid
Lake-
Lake Michigan from Sheboygan to Port Washington WI 5NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor to Michigan City in 5NM
offshore to Mid Lake-
Lake Michigan from Pentwater to Manistee MI 5NM offshore to Mid
Lake-
Lake Michigan from Whitehall to Pentwater MI 5NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5NM offshore to Mid
lake-
Lake Michigan from St Joseph to South Haven MI 5NM offshore to
Mid Lake-
920 PM CDT Wed Oct 3 2018

This Hazardous Weather Outlook is for the open waters of Lake
Michigan.

.DAY ONE...Tonight

A Gale Warning is in effect through tonight for the north half of
the open waters of Lake Michigan. Southerly gales will shift west
to northwest during this time. Very high waves are expected.

There is an enhanced risk for severe storms over the north half
of Lake Michigan tonight, with a slight risk to the south.
Thunderstorms are expected to move southeast through the area
during this time. Some of the storms may become severe, with
damaging winds, large hail, and a waterspout or two possible
especially over the northern portion of the lake.

.DAYS TWO THROUGH SEVEN...Thursday through Wednesday

There are chances of thunderstorms at times from Thursday night
into next week.

Collar
www.weather.gov/mkx

Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
929 PM CDT WED OCT 3 2018

WIZ056-062-063-067-068-040315-
Green-Lafayette-Iowa-Sauk-Dane-
929 PM CDT WED OCT 3 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHERN LAFAYETTE...
NORTHWESTERN GREEN...IOWA...SOUTHEASTERN SAUK AND WESTERN DANE
COUNTIES...

At 928 PM CDT, radar indicated strong thunderstorms were located
along a line extending from 7 miles northeast of Spring Green to 7
miles west of Platteville. Movement was east at 55 mph.

Winds in excess of 40 mph are possible with these storms.

Locations impacted include...
Western Madison, Middleton, Waunakee, Verona, Mount Horeb,
Dodgeville, Sauk City, Mineral Point, Deforest, Cross Plains,
Mazomanie, Spring Green, Shorewood Hills, Black Earth, Belmont,
Blanchardville, Barneveld, Dane, Blue Mounds and Arena.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 4294 9043 4327 8996 4327 8933 4285 8960
      4270 9014 4271 9043
TIME...MOT...LOC 0228Z 261DEG 47KT 4324 8995 4274 9062

BOXELL