Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 1476

July 16, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jul 16, 2012, 2:07 PM MDT for 4 states. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Jul 16, 2012, 2:07 PM MDT (20:07 UTC)
Expired: Jul 16, 2012, 4:00 PM MDT
In force: 113 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 23 counties

Carter County, MT, Adams County, ND, Bowman County, ND, Emmons County, ND, Grant County, ND, Hettinger County, ND, Logan County, ND, McIntosh County, ND, Sioux County, ND, Butte County, SD, Campbell County, SD, Corson County, SD, Dewey County, SD, Edmunds County, SD, Harding County, SD, McPherson County, SD, Meade County, SD, Perkins County, SD, Potter County, SD, Sully County, SD, Walworth County, SD, Ziebach County, SD, Crook County, WY

The radar

The Rapid City radar (KUDX), 148 km from the middle of the area, began a volume at 20:11 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.

Severe Thunderstorm Watch 487Jul 16, 2:55 PM MDT

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 8.1 hours before the alert went out and 155 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: 3356 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: -24 m²/s²
0-3 km storm-relative helicity: 67 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.

605 
ACUS11 KWNS 162008
SWOMCD
SPC MCD 162007
SDZ000-NDZ000-MTZ000-WYZ000-162200-

MESOSCALE DISCUSSION 1476
NWS STORM PREDICTION CENTER NORMAN OK
0307 PM CDT MON JUL 16 2012

AREAS AFFECTED...PORTIONS NRN SD...SRN ND...EXTREME SERN
MT...EXTREME NERN WY.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 162007Z - 162200Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...SVR POTENTIAL INCREASING IN CORRIDOR FROM NWRN SD/EXTREME
SERN MT DOWNSHEAR ACROSS SD/ND BORDER REGION THROUGH REMAINDER
AFTERNOON.  DAMAGING GUSTS AND OCNL HAIL ARE POSSIBLE.  20Z
CONVECTIVE OUTLOOK HAS BEEN UPGRADED CATEGORICALLY FOR THIS REGIME.

DISCUSSION...SFC MESOANALYSIS SHOWED PRIMARY LOW OVER CENTRAL SD
NEAR PIR...ALONG QUASISTATIONARY FRONT EXTENDING NEWD BETWEEN
ABR-ATY AND WSWWD OVER NRN RIM OF BLACK HILLS.  SECONDARY LOW-LEVEL
CIRCULATION WAS EVIDENT IN REFLECTIVITY IMAGERY NEAR STURGIS
SD...WITH BOUNDARY EXTENDING NWWD ACROSS DEVILS TOWER AREA OF WY TO
SWRN CARTER COUNTY SD.  VIS IMAGERY SHOWS INCREASING COVERAGE/DEPTH
OF CONVECTIVE ELEMENTS ALONG AND E OF BOUNDARY FROM SERN MT TO BLACK
HILLS...AND OTHER CONVECTION DEEPENING OVER BIGHORNS FARTHER WSW.
ENHANCED LOW-LEVEL ELY/NELY FLOW OVER W-CENTRAL/NWRN SD...AROUND NRN
PORTION OF SECONDARY CYCLONE...SHOULD CONTRIBUTE BOTH LOW-LEVEL
THETAE ADVECTION AND ENHANCEMENT TO STORM-RELATIVE INFLOW FOR ANY
SUSTAINED CONVECTION MOVING OFF BLACK HILLS OR WRN SEGMENT OF
BOUNDARY.  LAPSE RATES ALOFT ARE NOT PARTICULARLY STG...PER MORNING
UNR RAOB AND MODIFIED MODEL SOUNDINGS.  HOWEVER...PROGRESSIVELY
HIGHER THETAE WITH EWD EXTENT N OF BOUNDARY WILL CONTRIBUTE TO
MLCAPE RANGING FROM AROUND 1000 J/KG OVER NERN WY TO 3500 J/KG ALONG
CENTRAL-ERN PORTIONS ND/SD BORDER WHERE SFC MOISTURE IS GREATEST.
WELL-MIXED SUBCLOUD LAYERS WILL SUPPORT STG-SVR GUST THREAT...AND
RISK OF LARGE HAIL WILL BE ENHANCED IN ANY SUPERCELLS.  40-50 KT
EFFECTIVE SHEAR MAGNITUDES ARE EVIDENT OVER THIS CORRIDOR IN SUPPORT
OF SUPERCELL POTENTIAL.

..EDWARDS/CARBIN.. 07/16/2012

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

ATTN...WFO...ABR...BIS...UNR...BYZ...

LAT...LON   44640190 44400358 44450443 44870592 45790489 46230377
            46650125 46680054 46529951 45609893 44739999 44480118
            44640190

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 16, 2:53 PM MDT	Severe Thunderstorm Watch	SPC	Carter	7 hr
Jul 16, 5:53 PM MDT	Mesoscale Discussion	SPC	Carter, Fallon	67 min
Jul 15, 6:49 PM MDT	Mesoscale Discussion	SPC	Benson, Bottineau, Burke, Cavalier, Eddy, McHenry and 10 more	56 min
Jul 15, 9:54 PM MDT	Mesoscale Discussion	SPC	Benson, Bottineau, Burke, Cavalier, Eddy, McHenry and 10 more	66 min

Nearby

Mesoscale Discussions in South Dakota, 2012 Mesoscale Discussions in North Dakota, 2012 Mesoscale Discussions in Montana, 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.