Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 834

May 18, 201211 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 18, 2012, 7:22 PM CDT for 11 counties in South Dakota. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 18, 2012, 7:22 PM CDT (00:22 UTC)
Expired: May 18, 2012, 9:45 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Brule County, SD, Buffalo County, SD, Hand County, SD, Hughes County, SD, Hyde County, SD, Jackson County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Stanley County, SD, Sully County, SD

The radar

The Aberdeen radar (KABR), 199 km from the middle of the area, began a volume at 00:25 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, 0.4 hours before the alert went out and 161 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: 180 J/kg
Mixed-layer CIN: -118 J/kg
Mixed-layer LCL: 3219 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: -2 m²/s²
0-3 km storm-relative helicity: 20 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.

355 
ACUS11 KWNS 190023
SWOMCD
SPC MCD 190022
SDZ000-190245-

MESOSCALE DISCUSSION 0834
NWS STORM PREDICTION CENTER NORMAN OK
0722 PM CDT FRI MAY 18 2012

AREAS AFFECTED...CNTRL SD

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 190022Z - 190245Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED SEVERE STORMS WILL REMAIN LIKELY...BUT COVERAGE
MAY BE TOO LOW FOR A WATCH.

DISCUSSION...A SUPERCELL IS CURRENTLY ONGOING OVER JACKSON COUNTY
SD...ON THE SURFACE FRONT. OBSERVED 00Z SOUNDINGS SHOW VERY STEEP
LAPSE RATES IN PLACE WITH MODEST SLY FLOW ALOFT. HELPING TO AUGMENT
HODOGRAPH LENGTH ARE THE NLY WINDS BEHIND THE FRONT. IN THIS
CASE...WITH DEWPOINTS IN THE MID 50S NEAR THE BOUNDARY...THE AIR IS
STILL UNSTABLE DESPITE BEING COOLER. THEREFORE...THE ENTIRE
HODOGRAPH IS EFFECTIVE...PROVIDING A FAVORABLE PROFILE FOR SEVERE
STORMS. LARGE HAIL IS LIKELY AND DAMAGING WINDS MAY ALSO OCCUR AS
THIS CELL DEVELOPS NEWD ALONG THE BOUNDARY.

OTHER ACTIVITY CONTINUES OVER NWRN NEB...BUT CURRENTLY WELL AHEAD OF
THE FRONT. IT IS POSSIBLE THAT OTHER CELLS ZIPPER SWD ALONG THE
ADVANCING COLD FRONT INTO S CNTRL OR N CNTRL NEB LATER THIS
EVENING....ALTHOUGH CIN WILL BE INCREASING.

..JEWELL/MEAD.. 05/19/2012

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

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

LAT...LON   43560091 43510164 43720179 44180152 44810067 45030017
            45039937 44759883 44309863 44039866 43749881 43629975
            43560091

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 12:51 AM CDT	Mesoscale Discussion	SPC	Beadle, Brule, Buffalo, Edmunds, Faulk, Hand and 12 more	84 min

Nearby

Mesoscale Discussions in South Dakota, 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.