Special Weather Statement, NWS Milwaukee, WI

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
112 PM CDT Mon Apr 10 2017

.UPDATE...

Pneumonia front continues to move quickly southward across the
shoreline and over Lake Michigan early this afternoon. It will
move south of the state line between 2 pm and 4 pm this
afternoon. Expect a quick wind shift to the northeast, with gusty
winds lingering into early this evening.

The rest of the front has already crossed most of the northern
half of the forecast area. This will continue southward and reach
the state line by 3 to 4 pm this afternoon. Temperatures will
plummet as well behind the front, with 70s falling into the 50s,
colder near the lake. Clouds will also continue to move into the
area this afternoon.

Slight risk from SPC looks on track across the southeastern
portions of the area for this afternoon. Building mean layer CAPE
with strong deep layer shear in place, with very steep mid level
lapse rates. Convection in eastern Iowa should eventually move
northeast into southern portions of the area early this afternoon,
with more development possible to the east of there per consensus
of mesoscale models.

Approaching 500 mb vorticity maximum with upper divergence from
250 mb jet streak should help with synoptic upward vertical
motion. Low level jet may focus into northeast Illinois and far
southeast Wisconsin as well. Continued high PoPs for thunderstorms
in the southeast and parts of the south central counties.

Large hail and damaging winds are the main hazards. It will be
interesting to see how any convection develops and/or evolves with
the cold/pneumonia front moving south through the area. Areas
behind it may become more stable with respect to surface parcels,
but elevated parcels may continue to tap into steep lapse rates
aloft.

&&

.AVIATION(18Z TAFS)...

Cold front will slide south across the area by 3 to 4 pm this
afternoon, reaching areas near the lake about an hour earlier.
Winds will quickly shift to the northeast and gust to 25 knots at
times this afternoon after the front moves through near the lake,
with lower northeast gusts inland.

Periods of thunderstorms should develop and move across southern
and southeastern portions of the area this afternoon, exiting the
southeast around 7 pm this evening. Large hail and damaging winds
are possible in the strongest storms. Lower ceilings and
visibilities, down to or below alternate minimums, are expected
in any storms as well.

Scattered showers are then anticipated tonight, with winds
gradually weakening and shifting to the north and northwest. Low
ceilings in IFR category or lower are expected as well, lingering
into Tuesday.

&&

.MARINE...

Small Craft Advisory is in effect until 9 pm this evening across
the nearshore waters of Lake Michigan. Pneumonia front will
continue to push south and exit Winthrop Harbor Illinois between 2
pm and 4 pm this afternoon. Winds should quickly shift to the
northeast with gusts to 25 knots after the front moves through.
The gusty northeast winds will linger into the evening, before
weakening by later this evening. Elevated waves are expected as
well, highest toward Sheboygan.

Thunderstorms should move east across the waters between 3 pm and
7 pm this afternoon/evening. Large hail and damaging winds are
possible with the strongest storms, along with locally higher
waves.

&&

.PREV DISCUSSION... (Issued 744 AM CDT Mon Apr 10 2017)

UPDATE...

AVIATION(12Z TAFS)...Showers and tstorms will redevelop
for early afternoon and last until early evening. VFR
conditions this morning will give way to Cigs of 1-3 kft
within the storms but also after the cold frontal passage.
Cigs will then lower to 600-1500 feet this evening and overnight
as cool, moist air flows into the region on nly winds. MVFR vsbys
via light fog is possible after the cold frontal passage.
Very low vsbys, cigs, and gusty winds with tstorms.

PREV DISCUSSION... (Issued 400 AM CDT Mon Apr 10 2017)

Today and Tonight...Forecast confidence medium to high.

Sct showers and tstorms will continue to move newd across far srn
WI and ern WI through about 15z as a shortwave trough passage
occurs. Elevated CAPE up to 2000 J/KG will support the possibility
of large hail. There will be a break in the precip. from late
morning into the very early afternoon until another vorticity
maximum approaches from the sw while the cold front will shift
south from central WI. MLCAPEs will rise up to 2000 J/KG in the
southeast with lesser amounts toward wrn WI. Deep layer
unidirectional shear of 40-50 kts is expected. Tstorms will erupt
with the aforementioned forcing mechanisms with highest
concentrations of storms over sern WI. The Slight Risk of SVR
storms looks good given the CAPE, shear, and steep mid level lapse
rates. The cold front is expected to accelerate down Lake MI
enhancing the convergence for storms but also rapidly cooling the
airmass over far ern WI from middle to late afternoon. A strong
shortwave trough approaching from the west will then move across
central and srn WI tonight with continued chances of showers. Cold
advection will cool temps to 35-40F by Tue AM.

TUESDAY - Confidence...Medium
Much cooler airmass in place with surface/850 lows to our east and
low level thermal trough in place. Lingering low level troughing
and cool pool should result in a good deal of cloud cover with
this regime.

WEDNESDAY - Confidence...Medium
With a surface high shifting to our east a low level return flow
will set up ahead of the next system. Showers are expected to
remain to our north or northwest through the day. Would likely see
some increase in cloud cover during the afternoon. 925 temps will
get a boost with the renewed southerly flow so temps will get a
boost over the cool day Tuesday.

WEDNESDAY NIGHT AND THURSDAY - Confidence...Medium
Mid level shortwave energy combined with low level moisture influx
and an inverted surface trough feature will all result in high
rain chances Wednesday night with some of this lingering into
Thursday.

THURSDAY NIGHT AND FRIDAY - Confidence...Low
The GEM and ECMWF are showing a more robust solution as it relates
to precip associated with a WAA regime. The GFS is essentially dry
with this or at least holds this off into Friday night.

FRIDAY NIGHT THROUGH SATURDAY NIGHT - Confidence...Medium
There appears better consensus for a low moving into WI with an
initial warm front generating shra/tsra and then a trailing cold
front producing more shra/tsra heading into later Saturday
evening.

SUNDAY - Confidence...Low to Medium
Looks like cooler and drier wx sets up in the wake of the frontal
boundary. However the GFS is rather quick to bring the front back
into the area Sunday night while the GEM/ECMWF keep things dry
with high pressure ridging in.

AVIATION...Coming soon.

MARINE...A Small Craft Advisory is in effect until noon for
breezy sly winds and high waves. Another Small Craft Advisory may
be needed for this afternoon and evening for brisk nly winds and
high waves with a cold frontal passage.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 9 PM CDT this evening for LMZ643>646.

&&

Update...Wood
Today/Tonight and Aviation/Marine...Gehring
Tuesday THROUGH Sunday...Collar

Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
324 AM CDT Mon Apr 10 2017

WIZ046-047-051-052-056>060-062>072-110830-
Marquette-Green Lake-Fond Du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
324 AM CDT Mon Apr 10 2017

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

.DAY ONE...Today and Tonight

Approaching low pressure will bring a chance for thunderstorms
during the early morning hours and then again this afternoon.
There is a slight risk of severe thunderstorms in southeast
Wisconsin with a marginal risk in south central Wisconsin. The
better chance for severe storms will be this afternoon. The
primary hazards will be large hail and strong winds.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

There is a chance of thunderstorms Friday night through Saturday
evening.

.SPOTTER INFORMATION STATEMENT...

Spotters activation may be needed this afternoon.

LMZ643>646-110830-
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-
324 AM CDT Mon Apr 10 2017

This Hazardous Weather Outlook is for portions of Lake Michigan.

.DAY ONE...Today and Tonight

A small craft advisory is in effect until noon due to breezy
south winds and high waves.

There is a chance of thunderstorms this morning. There is a
slight risk of severe storms this afternoon.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

There is a chance of thunderstorms Friday night through Saturday
evening.

Collar
www.weather.gov/mkx

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
925 AM CDT MON APR 10 2017

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

0458 AM     HAIL             SILVER LAKE             42.55N 88.17W
04/10/2017  M0.50 INCH       KENOSHA            WI   PUBLIC

            RELAYED VIA SOCIAL MEDIA. TIME ESTIMATED
            FROM RADAR.

&&

SPM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
943 AM CDT MON APR 10 2017

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

0507 AM     HAIL             2 N STURTEVANT          42.72N 87.90W
04/10/2017  E1.00 INCH       RACINE             WI   PUBLIC

            PEA TO QUARTER SIZE. RELAYED VIA SOCIAL
            MEDIA.

&&

SPM

Special Weather Statement
National Weather Service Milwaukee/Sullivan WI
152 PM CDT MON APR 10 2017

WIZ062-067-068-101930-
Green-Lafayette-Iowa-
152 PM CDT MON APR 10 2017

...A STRONG THUNDERSTORM WILL AFFECT LAFAYETTE...NORTHWESTERN GREEN
AND SOUTHEASTERN IOWA COUNTIES...

At 151 PM CDT, a strong thunderstorm was located near Shullsburg, or
11 miles southwest of Darlington, moving northeast at 45 mph.

Pea size hail is possible with this storm.

Locations impacted include...
Mineral Point, Darlington, Shullsburg, Belmont, Benton, Argyle,
Blanchardville, Somers, Wiota, Ridgeway, New Diggings, Lamont,
Hollandale, Gratiot, Yellowstone Lake St Park, Lead Mine, Jordan
Center and Woodford.

LAT...LON 4266 9043 4304 8997 4290 8984 4286 8984
      4285 8980 4268 8965 4251 9003 4251 9043
TIME...MOT...LOC 1851Z 224DEG 38KT 4256 9029

SPM