Alert archive / South Dakota / Tornado Watches in 2011

Tornado Watch 265

May 8, 201117 counties in Nebraska; 5 counties in North Dakota; 19 counties in South Dakota

The Storm Prediction Center issued this tornado watch at May 8, 2011, 6:13 PM CDT for 17 counties in Nebraska; 5 counties in North Dakota; 19 counties in South Dakota. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: May 8, 2011, 6:13 PM CDT (23:13 UTC)
Expired: May 9, 2011, 12:17 AM CDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 3 in
Strongest gust expected: 60 kt

All 41 counties

Burleigh County, ND, Emmons County, ND, Grant County, ND, Morton County, ND, Sioux County, ND, Antelope County, NE, Blaine County, NE, Boone County, NE, Boyd County, NE, Brown County, NE, Cherry County, NE, Garfield County, NE, Holt County, NE, Keya Paha County, NE, Knox County, NE, Loup County, NE, Madison County, NE, Pierce County, NE, Platte County, NE, Rock County, NE, Thomas County, NE, Wheeler County, NE, Bon Homme County, SD, Brule County, SD, Buffalo County, SD, Campbell County, SD, Charles Mix County, SD, Corson County, SD, Dewey County, SD, Gregory County, SD, Hughes County, SD, Hyde County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Todd County, SD, Tripp County, SD, Walworth County, SD

The radar

The Aberdeen radar (KABR), 181 km from the middle of the area, began a volume at 23:12 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 40%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 60%
One or more hailstones of 2 inches or more: 40%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
May 8, 8:08 PM CDT	Tornado Warning	ABR	Lyman	14 min
May 8, 8:20 PM CDT	Severe Thunderstorm Warning	UNR	Tripp	45 min
May 8, 8:43 PM CDT	Severe Thunderstorm Warning	ABR	Lyman	47 min
May 8, 9:00 PM CDT	Tornado Warning	ABR	Lyman	35 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 11.2 hours before the alert went out and 170 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1515 m above ground
0-6 km bulk shear: 58 kt
0-1 km storm-relative helicity: 267 m²/s²
0-3 km storm-relative helicity: 662 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

375 
WWUS20 KWNS 082313
SEL5
SPC WW 082313
NDZ000-NEZ000-SDZ000-090600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 265
NWS STORM PREDICTION CENTER NORMAN OK
615 PM CDT SUN MAY 8 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

       SOUTH CENTRAL NORTH DAKOTA
       NORTHERN NEBRASKA
       CENTRAL SOUTH DAKOTA

EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 615 PM UNTIL
100 AM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES WEST NORTHWEST OF
BISMARCK NORTH DAKOTA TO 20 MILES EAST SOUTHEAST OF BURWELL
NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO
FORM THIS EVENING ALONG THE INSTABILITY AXIS EXTENDING FROM NORTHERN
NEB INTO SOUTH CENTRAL ND.  WEAKENING INHIBITION AND WEAK LOW LEVEL
WARM ADVECTION WILL HELP INITIATION.  THOSE STORMS THAT FORM WILL BE
IN ENVIRONMENT OF FAVORABLE LOW LEVEL AND DEEP LAYER VERTICAL SHEAR
TO BECOME SLOW-MOVING SUPERCELLS CAPABLE OF VERY LARGE HAIL AND
DAMAGING WINDS.  ISOLATED TORNADOES WILL ALSO BE POSSIBLE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 27015.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 8, 5:06 PM CDT	Mesoscale Discussion	SPC	Brown, Cherry, Keya Paha, Rock	54 min

Nearby

Tornado Watches in South Dakota, 2011 Tornado Watches in Nebraska, 2011 Tornado Watches in North Dakota, 2011 Every tornado watch in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.