Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 831

May 18, 20125 counties in Nebraska; 9 counties in South Dakota; Goshen County, Niobrara County, Platte County, Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 18, 2012, 2:54 PM MDT for 5 counties in Nebraska; 9 counties in South Dakota; Goshen County, Niobrara County, Platte County, Wyoming. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: May 18, 2012, 2:54 PM MDT (20:54 UTC)
Expired: May 18, 2012, 4:30 PM MDT
In force: 96 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Box Butte County, NE, Dawes County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Bennett County, SD, Custer County, SD, Fall River County, SD, Haakon County, SD, Jackson County, SD, Jones County, SD, Oglala Lakota County, SD, Pennington County, SD, Stanley County, SD, Goshen County, WY, Niobrara County, WY, Platte County, WY

The radar

The Rapid City radar (KUDX), 72 km from the middle of the area, began a volume at 20:56 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

Rapid City, SD (KUNR), launched 12:00Z, 8.9 hours before the alert went out and 66 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: 2604 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 103 m²/s²
0-3 km storm-relative helicity: 177 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.

963 
ACUS11 KWNS 182054
SWOMCD
SPC MCD 182054 
SDZ000-NEZ000-WYZ000-182230-

MESOSCALE DISCUSSION 0831
NWS STORM PREDICTION CENTER NORMAN OK
0354 PM CDT FRI MAY 18 2012

AREAS AFFECTED...ERN WY...NWRN NEB...SWRN SD

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 182054Z - 182230Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...STORMS DEVELOPING FROM ERN WY INTO SWRN SD AND NWRN NEB
INTO THE EARLY EVENING MAY POSE A THREAT FOR ISOLATED STRONG TO
DAMAGING WIND GUSTS AND HAIL. HOWEVER...COVERAGE OF ANY SEVERE
EVENTS ARE EXPECTED TO REMAIN SPARSE...AND OVERALL THREAT DOES NOT
APPEAR TO WARRANT A WW AT THIS TIME.

DISCUSSION...QUASI-STATIONARY FRONT EXTENDS FROM ERN ND SWWD THROUGH
CNTRL AND SWRN SD INTO SERN WY. SFC DEWPOINTS HAVE MIXED INTO THE
30S SOUTH OF THIS BOUNDARY FROM SERN WY INTO EXTREME SWRN SD...BUT
ARE GENERALLY IN THE UPPER 40S TO AROUND 50F ON THE COOLER SIDE.
MLCAPE HAS INCREASE TO 500 J/KG ALONG AND JUST NORTH OF THE FRONT
WHERE TEMPERATURES HAVE WARMED INTO THE MID 80S AND DEWPOINTS ARE
HOLDING IN THE UPPER 40S. HOWEVER...FORECAST SOUNDINGS STILL
INDICATE AN INVERSION PRESENT BETWEEN 850-700 MB. STORMS WILL
CONTINUE DEVELOPING OVER THE HIGHER TERRAIN OF WY...THE BLACK HILLS
OF SD AND GENERALLY ALONG AND NORTH OF THE FRONT. OTHER HIGH BASED
ACTIVITY WILL PERSIST IN THE MORE DEEPLY MIXED BUT LOW CAPE
ENVIRONMENT SOUTH OF THE FRONT. GIVEN THE HIGH BOUNDARY LAYER
TEMPERATURE-DEWPOINT SPREADS...A FEW STORMS MAY BECOME CAPABLE OF
ISOLATED STRONG TO DAMAGING WIND GUSTS. SOME HAIL MAY ALSO BE
POSSIBLE. GIVEN THE MARGINAL THERMODYNAMIC ENVIRONMENT...OVERALL
THREAT DOES NOT APPEAR SUFFICIENT TO WARRANT A WW AT THIS TIME.

..DIAL/WEISS.. 05/18/2012

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

ATTN...WFO...ABR...LBF...UNR...CYS...

LAT...LON   45070030 43710061 42310230 41480452 42310530 43630509
            44300342 45070030

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 18, 11:05 AM MDT	Mesoscale Discussion	SPC	Sweetwater	115 min
May 18, 4:19 PM MDT	Mesoscale Discussion	SPC	Hot Springs, Johnson, Natrona, Washakie	56 min

Nearby

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