Alert archive / South Dakota / Mesoscale Discussions in 2012
Mesoscale Discussion 721
The Storm Prediction Center issued this mesoscale discussion at May 5, 2012, 6:21 PM CDT for 5 counties in Nebraska; 21 counties in South Dakota. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- May 5, 2012, 6:21 PM CDT (23:21 UTC)
- Expired
- May 5, 2012, 7:45 PM CDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 95%
All 26 counties
Boyd County, NE, Brown County, NE, Keya Paha County, NE, Rock County, NE, Thomas County, NE, Aurora County, SD, Beadle County, SD, Bon Homme County, SD, Brule County, SD, Charles Mix County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Kingsbury County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Sanborn County, SD, Turner County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 148 km from the middle of the area, began a volume at 23:24 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, 11.4 hours before the alert went out and 175 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 554 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- -13 m²/s²
- 0-3 km storm-relative helicity
- 60 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
156
ACUS11 KWNS 052321
SWOMCD
SPC MCD 052321
IAZ000-MNZ000-SDZ000-NEZ000-060045-
MESOSCALE DISCUSSION 0721
NWS STORM PREDICTION CENTER NORMAN OK
0621 PM CDT SAT MAY 05 2012
AREAS AFFECTED...PARTS OF N CNTRL NEB...SERN SD...SWRN MN...NWRN IA
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 052321Z - 060045Z
PROBABILITY OF WATCH ISSUANCE...95 PERCENT
SUMMARY...SEVERE STORMS ARE EXPECTED TO RAPIDLY INCREASE IN NUMBER
AND INTENSITY EARLY THIS EVENING...WITH A RISK FOR LARGE HAIL THE
PRIMARY INITIAL THREAT THROUGH 01-03Z.
DISCUSSION...ISOLATED VIGOROUS CONVECTIVE DEVELOPMENT ALREADY
APPEARS UNDERWAY ACROSS SOUTHEASTERN SOUTH DAKOTA...NORTH OF A
FAIRLY SHARP SURFACE FRONTAL ZONE THAT HAS ADVANCED SOUTH OF BROKEN
BOW AND NORTH PLATTE...WHILE REMAINING QUASI-STATIONARY NORTH OF
NORFOLK THROUGH THE SIOUX CITY AREA...ON INTO CENTRAL IOWA. THIS IS
BEING SUPPORTED BY LOW-LEVEL WARM ADVECTION...AND LIFT OF MOIST
PARCELS TO LEVELS OF FREE CONVECTION...ABOVE THE FIRMLY ENTRENCHED
COOL/STABLE NEAR SURFACE LAYER. EVEN TO THE NORTH OF THE
FRONT...ACROSS MUCH SOUTHERN/EASTERN SOUTH DAKOTA...WARM ELEVATED
MIXED LAYER AIR HAS BEEN TENDING TO INHIBIT CONVECTIVE DEVELOPMENT.
HOWEVER...INHIBITION APPEARS LIKELY TO WEAKEN BY THE 01-03Z TIME
FRAME...IF NOT BEFORE...AIDED BY INCREASING LARGE-SCALE MID-LEVEL
FORCING DOWNSTREAM OF THE UPPER TROUGH LIFTING ACROSS THE NORTHERN
ROCKIES...PERHAPS AIDED BY RADIATIVE PROCESSES. AS THIS OCCURS...A
RAPID INCREASING IN STORM DEVELOPMENT APPEARS LIKELY IN THE PRESENCE
OF STRONG CONVECTIVE LAYER SHEAR AND MOST UNSTABLE CAPE UP TO
2000-4000 J/KG. LARGE HAIL SHOULD BE THE PRIMARY THREAT
INITIALLY...BEFORE ACTIVITY BEGINS TO CONSOLIDATE LATER THIS
EVENING.
..KERR/THOMPSON.. 05/05/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...FSD...OAX...ABR...LBF...UNR...
LAT...LON 43509963 44429835 44509750 44289650 43219635 42759849
42159953 41690083 43509963SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 9:54 PM CDT | Mesoscale Discussion | SPC | Adams, Antelope, Boone, Buffalo, Burt, Butler and 42 more | 96 min |
| May 4, 10:55 PM CDT | Mesoscale Discussion | SPC | Adams, Antelope, Boone, Buffalo, Burt, Butler and 34 more | 35 min |
| May 4, 11:00 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Boone, Buffalo, Burt, Butler, Cass and 34 more | 3 hr |
| May 5, 2:09 PM CDT | Mesoscale Discussion | SPC | Antelope, Boone, Burt, Butler, Cedar, Colfax and 22 more | 96 min |
| May 5, 3:52 PM CDT | Mesoscale Discussion | SPC | Antelope, Boone, Cedar, Cuming, Dakota, Dixon and 11 more | 83 min |
| May 5, 5:31 PM CDT | Tornado Watch | SPC | Antelope, Boone, Cedar, Custer, Dakota, Dawson and 15 more | 5 hr |
| May 5, 6:44 PM CDT | Mesoscale Discussion | SPC | Banner, Cheyenne, Kimball | 61 min |
| May 5, 6:46 PM CDT | Severe Thunderstorm Watch | SPC | Arthur, Blaine, Boyd, Brown, Cherry, Deuel and 10 more | 6 hr |
| May 5, 3:06 AM CDT | Mesoscale Discussion | SPC | Custer, Fall River, Haakon, Hughes, Hyde, Jackson and 9 more | 84 min |
| May 5, 3:19 AM CDT | Severe Thunderstorm Watch | SPC | Bennett, Buffalo, Butte, Custer, Dewey, Fall River and 17 more | 9 hr |
| May 5, 6:49 AM CDT | Severe Thunderstorm Watch | SPC | Aurora, Beadle, Bon Homme, Brookings, Brule, Charles Mix and 18 more | 7 hr |
| May 5, 9:50 AM CDT | Mesoscale Discussion | SPC | Aurora, Beadle, Brookings, Brule, Buffalo, Davison and 13 more | 55 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.