Flooding in Wisconsin, September 1 to 30, 2018

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1141 PM CDT Fri Aug 31 2018

.UPDATE...

No major changes at this point. Thunderstorms should move into
the region after 2 AM, with peak activity between about 3/4 AM and
8/9 AM.

&&

.AVIATION(06Z TAFS)...

Thunderstorms are expected to move into the region overnight,
affecting the terminals late tonight into Saturday morning.
Precipitation should end for a time later Saturday morning into
the mid day hours, before additional thunderstorms develop
Saturday evening and night.

Flight conditions should be VFR for the first part of tonight,
before dropping to MVFR and IFR as thunderstorms move into the
region. A brief improvement is possible Saturday afternoon, before
thunderstorms arrive Saturday evening and night.

&&

.PREV DISCUSSION... (Issued 931 PM CDT Fri Aug 31 2018)

UPDATE...

A few thunderstorms developed across the Chicago area earlier this
evening, and have mostly pushed off shore into Lake Michigan. A
few showers will be possible for another hour or so across Kenosha
and Racine Counties, but most places should remain dry through at
least midnight.

Between midnight and 2-3 AM, thunderstorms are expected to develop
across the southwestern portions of the forecast area, and push to
the east through sunrise. Marginally severe hail is possible with
the strongest storms, but as discussed earlier, rain remains the
greatest concern. Overall no major changes at this point, with a
general 1 to 1.5 inches of rain expected through mid morning
tomorrow, with locally higher amounts.

MARINE...

A few thunderstorms will be possible across the southern portion
of the lake this evening. Additional rounds of thunderstorms are
expected late tonight toward daybreak on Saturday, and again
Saturday night and Sunday through at least the middle of the week.

Outside of thunderstorms, winds and waves should remain below
Small Craft Advisory levels.

PREV DISCUSSION... (Issued 646 PM CDT Fri Aug 31 2018)

UPDATE...

Still some uncertainty with how things will evolve overnight
tonight, but there is growing consensus that the area should be
mostly dry through midnight. After midnight, thunderstorms will
begin to blossom as the low level jet is able to tap into a solid
1500-2000 J/Kg of elevated CAPE. With sufficient bulk shear, a few
stronger storms will be possible. Given the elevated nature to the
thunderstorms, the severe weather threat should be limited to
large hail.

Of greater concern is the potential for heavy rain. PWATs will
increase to 2"+ overnight, with slow storm motions. There may also
be some potential for backbuilding, as Corfidi vectors fall to
less than 10 knots by the pre-dawn hours. All of this suggests
that some locations will likely see periods of very heavy rain,
but with little in the way of surface features to organize
convection, it's tough to pinpoint any specific area that has the
highest potential at this time. The Flash Flood Watch is well-
placed with those areas that have the least tolerance for
additional rainfall, and these areas will certainly be of
greatest concern for impacts should they see the rain overnight.

AVIATION(00Z TAFS)...

Thunderstorms will begin to affect the terminals overnight into
the morning hours on Saturday. Expect VFR ahead of the
rain/thunderstorms, with MVFR and areas of IFR associated with the
convection. Winds will be south to southeast this evening through
the overnight hours.

Rain and thunderstorms are expected to decrease from west to east
from late morning into the mid day on Saturday. A gradual
improvement to VFR is expected by afternoon. Winds will become
southwesterly with time on Saturday.

PREV DISCUSSION... (Issued 345 PM CDT FRI AUG 31 2018)

TONIGHT AND SATURDAY...Forecast Confidence - Medium.

A very moist airmass will push into southern Wisconsin tonight,
with precipitable water values approaching 2 inches by Saturday
morning. This is a very high value for this time of year. In
addition, the low level jet will strengthen and lean more into the
area tonight. Models are showing a wrinkle or two in the flow
tonight and tomorrow which should easily kick off storms in this
moist and unstable environment. Models have struggled quite a bit
through the day trying to pin down time and placement of storm
development tonight. Overall, models seem to be trending later in
the night and a bit farther south, though a couple solutions do
fire things late evening into early night. Could see more
development then by Saturday afternoon.

The primary concern through tomorrow will be the potential for
heavy rainfall causing additional flooding in places that have
been thoroughly soaked over the last 1-2 weeks. Expanded the Flash
Flood Watch southward due to models trending in that direction
with the heavier rains. Additionally, the expanded counties will
be more at risk for flooding based on recent rains than the
counties that were left out.

Seeing decent enough shear and lapse rates tonight into Saturday
to warrant a concern for some strong to severe storms.

Temps will be warmer than average tonight, but will be near
normal during the day Saturday. Conditions could vary from the
forecast a couple degrees in either direction based on the extent
of cloud cover.

SATURDAY NIGHT THROUGH MONDAY...Forecast Confidence - Medium.

Passing mid-level short wave may generate more scattered convection
across southern WI for a time Saturday night.  However will depend
on where outflow boundary from earlier convection sets up.  Most of
the CAMs are focusing on northern IL Saturday night but difficult to
ignore another surge of warm air advection and instability over the
area during the evening.  MUCape values of 2-4K joules in the
evening with bulk shear of 20-30 knots.  Mid-level wave shifts off
to the east later in the evening but second wave clips western CWA
later in the night.  With lingering elevated instability, will be
keeping smaller chances for convection in the late night, carrying
over into Sunday.  Most of Sunday should turn out dry as low level
jet initially weak and focused to the east.  During the day, the llj
begins to back to the southwest so need to carry chance everywhere
Will have better chances in the Sunday night and Monday periods as
llj increases in response to developing central Plains low pressure.
This will aid in increasing the threat for more widespread showers
and storms and the threat of heavy rainfall later Sunday night into
Monday. Precipitable water remains in the 1.5 to 2" range. NAEFS
return interval getting close to once in five year period valid
12Z/Mon. Ongoing Flash Flood Watch may need to be extended or
reissued for this period.

EXTENDED PERIOD...

MONDAY NIGHT THROUGH FRIDAY...Forecast Confidence - Low to Medium.

Sprawling high pressure over the eastern CONUS will amplify westward
into the central Great Lakes and MS Valley early in the period. As a
result, increasing southerly low level winds will nudge the wavering
frontal boundary northward, at least early in the week. Atmosphere
may be capped on Tuesday and Wednesday, resulting in less of a
chance of daytime convection.  Atmosphere remains unseasonably moist
with precipitable water 1.5 to 2 inches. Wednesday Night and
Thursday high pressure passing through southern Canada will move
east toward the Great Lakes.  This will nudge the front back to the
south, continuing the threat for showers and thunderstorms later in
the period.  Low level jet remains to the north or fairly weak for
the bulk of this period, so large nighttime MCS events are not
looking likely.  Best chance will be Monday night when warm front
shifts to the north across southern/central WI.  With the more humid
conditions, temperatures will remain warm and above normal for the
first week of September. A very moist airmass will push into
southern Wisconsin tonight, with precipitable water values
approaching 2 inches by Saturday morning. This is a very high value
for this time of year. In addition, the low level jet will
strengthen and lean more into the area tonight. Models are showing a
wrinkle or two in the flow tonight and tomorrow which should easily
kick off storms in this moist and unstable environment. Models have
struggled quite a bit through the day trying to pin down time and
placement of storm development tonight. Overall, models seem to be
trending later in the night and a bit farther south, though a couple
solutions do fire things late evening into early night. Could see
more development then by Saturday afternoon.

The primary concern through tomorrow will be the potential for
heavy rainfall causing additional flooding in places that have
been thoroughly soaked over the last 1-2 weeks. Expanded the Flash
Flood Watch southward due to models trending in that direction
with the heavier rains. Additionally, the expanded counties will
be more at risk for flooding based on recent rains than the
counties that were left out.

Seeing decent enough shear and lapse rates tonight into Saturday
to warrant a concern for some strong to severe storms.

Temps will be warmer than average tonight, but will be near
normal during the day Saturday. Conditions could vary from the
forecast a couple degrees in either direction based on the extent
of cloud cover.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch through Saturday evening for WIZ046-047-051-
     052-056>060-062>064.

LM...None.
&&

Update...Boxell
Tonight/Saturday and Aviation/Marine...Boxell
Saturday Night through Friday...99

Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
1113 PM CDT Fri Aug 31 2018

WIZ046-047-051-052-056>060-062>072-020415-
Marquette-Green Lake-Fond Du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
1113 PM CDT Fri Aug 31 2018

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

.DAY ONE...Tonight

Thunderstorms will develop across the region late tonight, with a
risk for marginally severe hail with a few of the stronger storms.
Heavy rain will also accompany the thunderstorms, and there will
be a risk for flooding and flash flooding, especially where soils
are already very saturated. A Flash Flood Watch is in effect for
all but the far southern and southeastern portions of the outlook
area.

Record river flooding will continue on the Baraboo River in Sauk
County. Also, high water levels causing dam gate releases will
continue to cause areas of flooding in parts of downtown Madison
and new areas of flooding in Montello in Marquette county.

There remains a Moderate Swim Risk at Lake Michigan beaches in
Sheboygan and Ozaukee Counties tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

River flooding is expected in central Wisconsin through late in
the week. Areal flooding will also continue in the downtown
Madison and Montello areas.

There are chances for thunderstorms through Friday. A few strong
or severe thunderstorms will be possible Saturday and again on
Sunday. Heavy rain and flash flooding will also be a risk. The
Flash Flood Watch continues through Saturday afternoon.

A Moderate Swim Risk at Lake Michigan beaches in Sheboygan County
will continue on Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter reports may be needed tonight through Sunday. Also, your
rainfall reports will be appreciated through the next week to
assist with areal and river flooding.

LMZ643>646-020415-
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-
1113 PM CDT Fri Aug 31 2018

This Hazardous Weather Outlook is for portions of Lake Michigan.

.DAY ONE...Tonight

Thunderstorms are likely late tonight. Hail and gusty winds will
be possible, along with frequent lightning.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

There are chances for thunderstorms through Friday.

www.weather.gov/mkx

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
805 PM CDT FRI AUG 31 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0300 PM     TORNADO          1 WSW OXFORD            43.77N 89.58W
08/28/2018                   MARQUETTE          WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE JUST SOUTHWEST OF OXFORD, WI. THE
            TORNADO HAD AN ESTIMATED PEAK WIND OF 90
            MPH, AND A PATH LENGTH OF 0.65 MILES.

0303 PM     TORNADO          1 NE ENDEAVOR           43.75N 89.43W
08/28/2018                   MARQUETTE          WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE JUST NORTHEAST OF ENDEAVOR. THE
            TORNADO HAD AN ESTIMATED PEAK WIND OF 90
            MPH, AND A TRACK LENGTH OF 1.8 MILES.

0317 PM     TORNADO          5 W MARQUETTE           43.74N 89.25W
08/28/2018                   MARQUETTE          WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE APPROXIMATELY 5 MILES WEST OF
            MARQUETTE ALONG THE MARQUETTE/GREEN LAKE
            COUNTY LINE. THE TORNADO HAD AN ESTIMATED
            PEAK WIND OF 90 MPH, WITH A PATH LENGTH OF
            3.22 MILES.

0325 PM     TORNADO          2 E MARQUETTE           43.74N 89.09W
08/28/2018                   GREEN LAKE         WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-0 RATED TORNADO
            DAMAGE EAST OF THE VILLAGE OF MARQUETTE IN
            GREEN LAKE COUNTY. THE TORNADO HAD AN
            ESTIMATED PEAK WIND OF 80 MPH, WITH A PATH
            LENGTH OF 2.09 MILES.

0358 PM     TORNADO          ALTO                    43.69N 88.79W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE BEGINNING NEAR THE TOWN OF ALTO. THE
            TORNADO HAD AN ESTIMATED PEAK WIND OF 100
            MPH, WITH A PATH LENGTH OF 2.02 MILES.

0404 PM     TORNADO          5 NE WAUPUN             43.68N 88.66W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE NORTHEAST OF WAUPUN, OR SOUTHWEST OF
            OAKFIELD. THE TORNADO HAD AN ESTIMATED PEAK
            WIND OF 94 MPH, WITH A PATH LENGTH OF 4.54
            MILES.

0408 PM     TORNADO          3 S OAKFIELD            43.64N 88.55W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-0 RATED TORNADO
            DAMAGE SOUTH OF OAKFIELD, JUST NORTH OF THE
            DODGE COUNTY LINE. THE TORNADO HAD AN
            ESTIMATED PEAK WIND OF 80 MPH, WITH A PATH
            LENGTH OF 0.14 MILES.

0409 PM     TORNADO          1 WSW SOUTH BYRON       43.64N 88.50W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE JUST SOUTH OF SOUTH BYRON. THE
            TORNADO HAD AN ESTIMATED PEAK WIND OF 100
            MPH AND A PATH LENGTH OF 0.92 MILES.

0411 PM     TORNADO          SOUTH BYRON             43.64N 88.49W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE IN SOUTH BYRON. THE TORNADO HAD AN
            ESTIMATED PEAK WIND OF 80 MPH, WITH A PATH
            LENGTH OF 0.15 MILES.

0411 PM     TORNADO          2 W BROWNSVILLE         43.62N 88.52W
08/28/2018                   DODGE              WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-2 RATED TORNADO
            DAMAGE STARTING WEST OF BROWNSVILLE IN
            EXTREME NORTHERN DODGE COUNTY. THE TORNADO
            HAD AN ESTIMATED PEAK WIND OF 125 MPH, WITH
            A PATH LENGTH OF 3.95 MILES.

0412 PM     TORNADO          BROWNSVILLE             43.61N 88.50W
08/28/2018                   DODGE              WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 TORNADO DAMAGE
            NEAR BROWNSVILLE. THE TORNADO HAD AN
            ESTIMATED PEAK WIND OF 107 MPH , WITH A PATH
            LENGTH OF 2.7 MILES.

0416 PM     TORNADO          3 E SOUTH BYRON         43.64N 88.43W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE EAST OF SOUTH BYRON. THE TORNADO HAD
            AN ESTIMATED PEAK WIND OF 90 MPH, WITH A
            PATH LENGTH OF 3.05 MILES.

0422 PM     TORNADO          3 SSE EDEN              43.66N 88.34W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-1 RATED TORNADO
            DAMAGE SOUTH OF THE VILLAGE OF EDEN. THE
            TORNADO HAD AN ESTIMATED PEAK WIND OF 90
            MPH, WITH A PATH LENGTH OF 4.48 MILES.

0430 PM     TORNADO          1 ENE DUNDEE            43.66N 88.16W
08/28/2018                   FOND DU LAC        WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-0 RATED TORNADO
            DAMAGE NEAR DUNDEE. THE TORNADO HAD AN
            ESTIMATED PEAK WIND OF 80 MPH, AND A PATH
            LENGTH OF 0.04 MILES.

0457 PM     TORNADO          5 NE OOSTBURG           43.68N 87.74W
08/28/2018                   SHEBOYGAN          WI   NWS STORM SURVEY

            A NWS STORM SURVEY FOUND EF-0 RATED TORNADO
            DAMAGE NORTHEAST OF OOTSBURG. THE TORNADO
            HAD AN ESTIMATED PEAK WIND OF 80 MPH, AND A
            PATH LENGTH OF 0.3 MILES.

&&