Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 1877

September 3, 20127 counties in Nebraska; 11 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Sep 3, 2012, 7:18 PM CDT for 7 counties in Nebraska; 11 counties in South Dakota. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Sep 3, 2012, 7:18 PM CDT (00:18 UTC)
Expired: Sep 3, 2012, 8:45 PM CDT
In force: 87 min
Issued by: the Storm Prediction Center

Counties Boyd County, NE, Custer County, NE, Garfield County, NE, Holt County, NE, Loup County, NE, Rock County, NE, Wheeler County, NE, Aurora County, SD, Beadle County, SD, Brule County, SD, Charles Mix County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hand County, SD, Jerauld County, SD, Sanborn County, SD, Spink County, SD

The radar

The Sioux Falls radar (KFSD), 172 km from the middle of the area, began a volume at 00:21 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 nearest sounding before it

Aberdeen, SD (KABR), launched 00:00Z, 0.3 hours before the alert went out and 177 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: 75 J/kg
Mixed-layer CIN: -103 J/kg
Mixed-layer LCL: 3125 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 152 m²/s²
0-3 km storm-relative helicity: 154 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

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

448 
ACUS11 KWNS 040019
SWOMCD
SPC MCD 040018
SDZ000-NEZ000-040145-

MESOSCALE DISCUSSION 1877
NWS STORM PREDICTION CENTER NORMAN OK
0718 PM CDT MON SEP 03 2012

AREAS AFFECTED...ERN SD THROUGH NCNTRL NEB

CONCERNING...SEVERE THUNDERSTORM WATCH 613...

VALID 040018Z - 040145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 613
CONTINUES.

SUMMARY...THREAT FOR ISOLATED STRONG TO DAMAGING WIND GUSTS AND HAIL
WILL PERSIST ANOTHER HOUR OR SO MAINLY WITH STORMS OVER ECNTRL
SD...BUT OVERALL SEVERE POTENTIAL IS BECOMING INCREASINGLY MARGINAL.

DISCUSSION...MOST STORMS THAT DEVELOPED EARLIER ALONG CONVERGENCE
TROUGH AXIS FROM CNTRL SD INTO NEB HAVE UNDERGONE A CONSIDERABLE
DECREASE IN INTENSITY AS THEY BEGIN TO MOVE EAST OF PRIMARY
INSTABILITY AXIS. THIS TREND WILL LIKELY CONTINUE AS CONVECTIVE
INHIBITION INCREASES WITH ONSET OF NOCTURNAL COOLING...ESPECIALLY
GIVEN WEAK FORCING AND ABSENCE OF A NOCTURNAL LLJ.

..DIAL.. 09/04/2012

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

ATTN...WFO...FSD...OAX...ABR...GID...LBF...

LAT...LON   41299984 43349929 45009893 45499834 45069793 43419797
            41819853 41299984

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 4, 5:08 PM CDT	Mesoscale Discussion	SPC	Antelope, Boone, Burt, Butler, Cass, Cedar and 25 more	97 min

Nearby

Mesoscale Discussions in South Dakota, 2012 Mesoscale Discussions in Nebraska, 2012 Every 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.