Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 868

May 22, 2012Cherry County, Keya Paha County, Nebraska; 27 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 22, 2012, 1:59 PM MDT for Cherry County, Keya Paha County, Nebraska; 27 counties in South Dakota. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued
May 22, 2012, 1:59 PM MDT (19:59 UTC)
Expired
May 22, 2012, 3:30 PM MDT
In force
91 min
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 29 counties

Cherry County, NE, Keya Paha County, NE, Aurora County, SD, Bennett County, SD, Brule County, SD, Buffalo County, SD, Campbell County, SD, Corson County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Gregory County, SD, Haakon County, SD, Hand County, SD, Hughes County, SD, Hyde County, SD, Jackson County, SD, Jerauld County, SD, Jones County, SD, Lyman County, SD, McPherson County, SD, Mellette County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Todd County, SD, Tripp County, SD, Walworth County, SD, Ziebach County, SD

The radar

The Aberdeen radar (KABR), 189 km from the middle of the area, began a volume at 19:55 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.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 8.0 hours before the alert went out and 156 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-pSkew-T log-p diagram, Aberdeen, SD at 12:00Z on 2012-05-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Aberdeen, SD at 12:00Z on 2012-05-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 296 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
1654 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
296 m²/s²
0-3 km storm-relative helicity
279 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.

280 
ACUS11 KWNS 221959
SWOMCD
SPC MCD 221959 
SDZ000-NEZ000-222130-

MESOSCALE DISCUSSION 0868
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT TUE MAY 22 2012

AREAS AFFECTED...FAR N-CNTRL NEB...CNTRL SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 221959Z - 222130Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT IS LIKELY
DURING THE AFTERNOON AND EVENING OVER FAR N-CNTRL NEB AND CNTRL SD.
LARGE HAIL AND DAMAGING WIND GUSTS WILL BE POSSIBLE. TRENDS WILL BE
MONITORED FOR A WW.

DISCUSSION...MESOANALYSIS AT 19Z SHOWED A ZONE OF STRENGTHENING
LOW-LEVEL CONVERGENCE ARCING S-SWWD FROM N-CNTRL SD INTO NWRN NEB.
STRONG SURFACE HEATING AND VERY STEEP LOW-LEVEL LAPSE RATES ARE
SPREADING NEWD OUT OF THE NEB PANHANDLE AND INTO PORTIONS OF CNTRL
SD...WHICH IS AIDING IN THE REDUCTION OF CINH. IN ADDITION...50S TO
NEAR 60 DEWPOINTS RESIDE ALONG/AHEAD OF THE SURFACE CONVERGENCE
ZONE. THIS MOISTURE COMBINED WITH BOUNDARY LAYER HEATING AND STEEP
MIDLEVEL LAPSE RATES IS YIELDING MLCAPE VALUES NEAR 1500 J/KG BASED
ON OBJECTIVE ANALYSIS GUIDANCE. RECENT VISIBLE SATELLITE IMAGERY
SHOWS A FEW ELEMENTS OF CUMULUS OCCURRING NEWD OUT OF WRN NEB AND
INTO S-CNTRL SD. GIVEN THIS TREND...COMBINED WITH 17Z HRRR
GUIDANCE...ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT APPEARS
PROBABLE DURING THE NEXT FEW HRS. THE FAVORABLE THERMODYNAMIC
ENVIRONMENT COLLOCATED WITH LOW-LEVEL SLYS VEERING TO 20-40 KT WLY
MIDLEVEL FLOW WILL FAVOR ORGANIZED MULTICELL CLUSTERS/LINE SEGMENTS
AND PERHAPS A SUPERCELL. THESE STORMS WILL BE CAPABLE OF PRODUCING
LARGE HAIL AND DAMAGING WIND GUSTS. TRENDS WILL CONTINUE TO BE
MONITORED FOR A POSSIBLE WW.

..GARNER/WEISS.. 05/22/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FSD...ABR...LBF...UNR...

LAT...LON   45779861 43469850 42479968 42560204 44270231 45860156
            45779861

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 22, 4:54 PM MDTSevere Thunderstorm WatchSPCBeadle, Brown, Brule, Buffalo, Campbell, Clark and 15 more7 hr
May 22, 5:11 PM MDTMesoscale DiscussionSPCButte, Harding, Lawrence, Meade, Perkins94 min

Nearby

Mesoscale Discussions in South Dakota, 2012Mesoscale Discussions in Nebraska, 2012Every mesoscale discussion in 2012

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.