Alert archive / South Dakota / Tornado Watches in 2015

Tornado Watch 326

June 21, 20156 counties in South Dakota

The Storm Prediction Center issued this tornado watch at Jun 21, 2015, 4:57 PM MDT for 6 counties in South Dakota. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Jun 21, 2015, 4:57 PM MDT (22:57 UTC)
Expired: Jun 21, 2015, 9:42 PM MDT
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2.5 in
Strongest gust expected: 60 kt

Counties Butte County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Perkins County, SD, Ziebach County, SD

The radar

The Rapid City radar (KUDX), 133 km from the middle of the area, began a volume at 22:59 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: 50%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 80%
One or more hailstones of 2 inches or more: 40%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Jun 21, 5:00 PM MDT	Severe Thunderstorm Warning	UNR	Harding	60 min
Jun 21, 5:45 PM MDT	Severe Thunderstorm Warning	UNR	Harding, Perkins	60 min
Jun 21, 6:41 PM MDT	Severe Thunderstorm Warning	UNR	Harding, Perkins	64 min
Jun 21, 6:59 PM MDT	Tornado Warning	UNR	Perkins	31 min
Jun 21, 7:25 PM MDT	Tornado Warning	UNR	Perkins	35 min
Jun 21, 7:49 PM MDT	Tornado Warning	UNR	Perkins	26 min
Jun 21, 8:13 PM MDT	Tornado Warning	UNR	Perkins, Ziebach	47 min
Jun 21, 8:57 PM MDT	Tornado Warning	UNR	Ziebach	47 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

Rapid City, SD (KRAP), launched 12:00Z, 11.0 hours before the alert went out and 139 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: 1334 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: -57 m²/s²
0-3 km storm-relative helicity: -69 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.

560 
WWUS20 KWNS 212252
SEL6  
SPC WW 212252
SDZ000-220400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 326
NWS STORM PREDICTION CENTER NORMAN OK
455 PM MDT SUN JUN 21 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  NORTHWEST SOUTH DAKOTA

* EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 455 PM UNTIL
  1000 PM MDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE
  WIDESPREAD LARGE HAIL LIKELY WITH ISOLATED VERY LARGE HAIL
    EVENTS TO 2.5 INCHES IN DIAMETER POSSIBLE
  SCATTERED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

SUMMARY...ISOLATED SUPERCELL STORM OVER SOUTHEAST MT WILL TRACK INTO
WATCH AREA...WITH THE POTENTIAL OF OTHER STORMS FORMING THIS
EVENING.  VERY LARGE HAIL...DAMAGING WINDS...AND PERHAPS A TORNADO
OR TWO ARE POSSIBLE.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTHWEST OF
BUFFALO SOUTH DAKOTA TO 75 MILES SOUTHEAST OF LEMMON SOUTH
DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 323...WW 324...WW 325...

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 28035.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 20, 7:47 PM MDT	Mesoscale Discussion	SPC	Bennett, Oglala Lakota	58 min
Jun 21, 12:05 AM MDT	Mesoscale Discussion	SPC	Bennett, Custer, Fall River, Jackson, Lawrence, Mellette and 3 more	85 min
Jun 21, 2:23 PM MDT	Tornado Watch	SPC	Campbell, Corson, Dewey, McPherson	8 hr
Jun 21, 4:24 PM MDT	Mesoscale Discussion	SPC	Butte, Campbell, Corson, Dewey, Harding, Meade and 2 more	66 min

Nearby

Tornado Watches in South Dakota, 2015 Every tornado watch in 2015

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.