Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
714 AM CDT Fri Aug 31 2018

.SHORT TERM...(Today and tonight)
Issued at 408 AM CDT Fri Aug 31 2018

Thunderstorms have become more numerous early this morning across
Wisconsin as a result of increasing moisture advection in the
lower levels. Not expecting much behind the main complex for the
rest of the morning, although there may be isolated to scattered
storms around until the LLJ sufficiently weakens later this
morning.

Low clouds are expanding this morning per satellite trends and it
is not entirely clear when or if they will break up some this
afternoon. Regardless, an elevated mixed layer with mid level
lapse rates exceeding 8 C/km overtop surface dew points in the
upper 60s to lower 70s will create a very unstable atmosphere by
late afternoon. Thunderstorms should develop over the ND/SD/MN
border area late this afternoon or evening as a cold front and mid
level trough arrive. There are two possible scenarios that may
play out after this time:

1.) The thunderstorms that develop across western MN advance
eastward in a somewhat organized fashion, posing a damaging wind
threat depending how organized the complex can become. The
developing LLJ this evening over Iowa would kick off additional
convection across southeast MN into southern WI and northeastern
IA, leaving a convective minimum from southwest to east central MN
and parts of west central WI. The NAM, GFS, GEM, and HRRR have
been buying into this scenario. Or...

2.) The thunderstorms that develop across western MN grow upscale
into an organized severe MCS by mid evening and track southeast
across most of the CWA, bringing an enhanced severe threat with
the potential for fairly widespread wind damage. The Hires ARW,
NMM, HREF, and ECMWF seem to be siding with this scenario.

In either case, central MN, southeastern MN, and WI stand the best
chance for thunderstorm activity and heavy rainfall...again.

.LONG TERM...(Saturday through Thursday)
Issued at 408 AM CDT Fri Aug 31 2018

Forecast confidence remains high that temperatures will average
near or above normal through Wednesday of next week. Normal values
continue to fall the first week of September with highs dropping
into the low to mid 70s, and overnight lows in the 50s.

Models continue to support an upper ridge building across the Mid-
Atlantic states through early next week. As the ridge extends
westward into the Ohio Valley, the mean flow aloft will remain
from the west-southwest, or southwest across the Upper Midwest.
This ridge also builds deeper into the mid-level of the atmosphere
leading to further southwest flow, and warm temperatures for the
first part of September. Near the surface, a weak cold front will
move through Saturday morning, and will likely stall in Iowa
before lifting northward Sunday morning. Saturday looks to be the
driest in terms of the holiday weekend. Once this front moves back
northward, an increasing chances of showers and thunderstorms
will develop. Chances of thunderstorms will remain in the forecast
through the middle of next week as several subtle short waves
ride northeast in this developing southwest flow aloft.

Very little spread in the ensembles for 85h temperatures next week,
especially across the Great Lakes, and Ohio Valley. There is more
spread in these ensembles further to the north across the Northern
Plains, and Upper Midwest. Therefore, forecast confidence is lower
for this part of the region in terms of the continued warm and
unsettled period past Wednesday of next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 715 AM CDT Fri Aug 31 2018

A few thunderstorms are ongoing at the start of the TAF period,
north of New Richmond and southeast of Mankato. Neither are
expected to impact the TAF sites. MVFR cigs are fairly widespread
across most of the area, except there remain pockets of VFR
conditions. Expecting the MVFR clouds to fill in this morning
which will likely remain in place for much of the day.
Thunderstorms should develop over west central MN late this
afternoon or this evening, possibly organizing into a line which
may impact several TAF sites late this evening.

KMSP...MVFR conditions will develop this morning and persist for
much of the day. Best chance for TS will be this evening, after
00Z.

/OUTLOOK FOR KMSP/
Sat...VFR. Wind N at 5kts.
Sun...VFR with -TSRA possible. Wind SE at 5-10 kts.
Mon...MVFR/IFR with -SHRA possible. Wind E at 10G15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

SHORT TERM...BORGHOFF
LONG TERM...JLT
AVIATION...BORGHOFF

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
326 AM CDT Fri Aug 31 2018

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
010830-
Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns-
Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa-
Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington-
Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota-
Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth-
Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk-
St. Croix-Pierce-Dunn-Pepin-Eau Claire-
326 AM CDT Fri Aug 31 2018

This Hazardous Weather Outlook is for portions of central and
southern Minnesota...and west central Wisconsin.

.DAY ONE...Today and Tonight

There is a slight risk of severe thunderstorms late this
afternoon and tonight. Large hail, damaging winds, and heavy
rainfall are possible with an expected thunderstorm complex. A
tornado cannot be ruled out either.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

There is a chance of thunderstorms Sunday through Thursday. The
probability for severe weather is low, but heavy rainfall is
possible at times.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation will likely be needed later today and
tonight.

Borghoff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
823 AM CDT FRI AUG 31 2018

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

0815 AM     HEAVY RAIN       OWATONNA                44.09N 93.22W
08/31/2018  E2.00 INCH       STEELE             MN   BROADCAST MEDIA

            ABOUT 2" OF RAIN FELL IN 1 HOUR. PHOTOS OF
            STREET FLOODING RELAYED VIA TWITTER.

&&

MKM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
827 AM CDT FRI AUG 31 2018

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

0745 AM     TSTM WND DMG     OWATONNA                44.09N 93.22W
08/31/2018                   STEELE             MN   PUBLIC

            PHOTO SHARED VIA TWITTER SHOWS A COUPLE OF
            LARGE TREE BRANCHES DOWN.

&&

MKM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1036 AM CDT FRI AUG 31 2018

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

0733 AM     HAIL             1 WSW OWATONNA          44.08N 93.24W
08/31/2018  E0.75 INCH       STEELE             MN   PUBLIC

            REPORTED VIA FACEBOOK.

&&

MKM

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1132 AM CDT FRI AUG 31 2018

WIZ024-311700-
Pierce-
1132 AM CDT FRI AUG 31 2018

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL PIERCE COUNTY...

At 1131 AM CDT, a strong thunderstorm was located over Ellsworth, or
10 miles north of Red Wing, moving northeast at 25 mph.

Winds in excess of 30 mph and nickel size hail are possible with this
storm.

Locations impacted include...
Ellsworth, El Paso, Beldenville, Martel and Esdaile.

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 4460 9248 4471 9260 4487 9238 4486 9230
      4475 9213 4473 9214
TIME...MOT...LOC 1631Z 229DEG 20KT 4470 9250

SPD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1145 AM CDT FRI AUG 31 2018

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

1140 AM     HAIL             1 S ELLSWORTH           44.73N 92.41W
08/31/2018  M1.75 INCH       PIERCE             WI   TRAINED SPOTTER

            PING PONG TO GOLF BALL SIZE HAIL, LASTED
            ABOUT 8 MINUTES.

&&

CCS

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1209 PM CDT FRI AUG 31 2018

WIZ023-024-311730-
Pierce-St. Croix-
1209 PM CDT FRI AUG 31 2018

...A STRONG THUNDERSTORM WILL AFFECT NORTH CENTRAL PIERCE AND SOUTH
CENTRAL ST. CROIX COUNTIES...

At 1209 PM CDT, a strong thunderstorm was located over Martel, or 11
miles east of River Falls, moving northeast at 20 mph.

Half inch hail is possible with this storm.

This storm will remain over mainly rural areas of north central
Pierce and south central St. Croix Counties.

LAT...LON 4481 9235 4485 9244 4493 9241 4489 9223
TIME...MOT...LOC 1709Z 210DEG 17KT 4485 9238

SPD