Alert archive / South Dakota / Mesoscale Discussions in 2007

Mesoscale Discussion 910

May 28, 20077 counties in South Dakota; 4 counties in Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 28, 2007, 2:02 PM MDT for 7 counties in South Dakota; 4 counties in Wyoming. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 28, 2007, 2:02 PM MDT (20:02 UTC)
Expired: May 28, 2007, 4:30 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center

Counties Custer County, SD, Fall River County, SD, Haakon County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Ziebach County, SD, Campbell County, WY, Converse County, WY, Niobrara County, WY, Weston County, WY

The radar

The Rapid City radar (KUDX), 85 km from the middle of the area, began a volume at 20:03 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 302May 28, 3:35 PM MDT

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 8.0 hours before the alert went out and 80 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: 3389 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 112 m²/s²
0-3 km storm-relative helicity: 101 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.

000 
ACUS11 KWNS 282002
SWOMCD
SPC MCD 282002 
SDZ000-WYZ000-282230-

MESOSCALE DISCUSSION 0910
NWS STORM PREDICTION CENTER NORMAN OK
0302 PM CDT MON MAY 28 2007

AREAS AFFECTED...NERN WY...WRN SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 282002Z - 282230Z

CLUSTER OF STRONG TSTMS DEVELOPING OVER CENTRAL WY ARE EXPECTED TO
INCREASE IN INTENSITY AS THE MOVE INTO NERN WY OVER THE NEXT SEVERAL
HOURS. ADDITIONAL ISOLATED SVR TSTMS MAY OCCUR OVER THE BLACK HILLS
BEFORE 21Z...WHILE EVENTUALLY MOVING INTO THE LOWER ELEVATIONS OF
WRN SD BY 23Z...WHERE CINH CONTINUES TO WEAKEN. A WW MAY BECOME
NECESSARY OVER THE AREA LATER THIS AFTERNOON.

LATEST SFC ANALYSIS PLACES A SFC LOW OVER CENTRAL WY NEAR RIW. PER
SAT/RADAR IMAGERY A CLUSTER OF TSTMS HAVE DEVELOPED OVER CENTRAL WY
JUST AHEAD OF THIS SFC LOW IN A REGION OF MODERATE HEIGHT FALLS
AHEAD OF AN UPPER TROUGH OVER THE GREAT BASIN. ATTM...THE
ENVIRONMENT INVOF OF THIS CONVECTION WAS DRY WITH DEWPTS IN THE 30S.
HOWEVER...50-100 MILES DOWNSTREAM OF THIS ACTIVITY...AN AXIS OF
HIGHER DEWPTS /READINGS NEAR 50 F/ EXTENDED SW-NE ACROSS NERN WY.
RECENT OBJECTIVE ANALYSIS SHOWS THAT AROUND 1000 J/KG OF MLCAPE AND
LESS THAN 25 J/KG OF MLCINH EXISTS OVER MOST OF NERN WY. ADEQUATE
DEEP LAYER SHEAR/FORCING WILL EXIST AS MODERATE MID LEVEL WINDS
OVERSPREAD NELY WINDS AT THE SFC. WITH THE MODERATE INSTABILITY
EXPECTED TO SLOWLY INCREASE...AT LEAST AN ISOLATED SVR THREAT IS
EXPECTED TO DEVELOP WITH THIS ACTIVITY. FURTHER EAST...MODERATE
UPSLOPE FLOW INTO THE BLACK HILLS BEHIND A COLD FRONT ALONG WITH
WEAKENING CINH /AS THERMAL GRADIENT LAGS THE MAIN WIND SHIFT/ WILL
CONTINUE TO SUPPORT TSTM DEVELOPMENT. SIMILAR TO NERN WY...THE
MAGNITUDE OF THE VERTICAL SHEAR ALONG WITH MODERATE INSTABILITY WILL
SUPPORT AT LEAST AN ISOLATED SVR WIND/HAIL THREAT WITH THESE THE
STRONGEST TSTMS. GREATER INHIBITION OVER WRN SD /AWAY FROM THE
HIGHER TERRAIN/ WILL LIKELY KEEP THE SVR THREAT RELATIVELY CLOSE TO
THE BLACK HILLS THROUGH 23Z.

..CROSBIE.. 05/28/2007

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

ATTN...WFO...ABR...UNR...CYS...RIW...

44450437 44080653 43500667 43130659 42750623 42900507
43340283 43600184 43840131 44960124 45190186 45200231
44850314

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 28, 2:17 PM MDT	Mesoscale Discussion	SPC	Edmunds, Faulk, McPherson, Potter, Sully, Walworth	118 min
May 28, 3:35 PM MDT	Severe Thunderstorm Watch	SPC	Brown, Butte, Campbell, Corson, Custer, Dewey and 19 more	9 hr

Nearby

Mesoscale Discussions in South Dakota, 2007 Mesoscale Discussions in Wyoming, 2007 Every mesoscale discussion in 2007

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.