Alert archive / Wyoming / Mesoscale Discussions in 2012

Mesoscale Discussion 1409

July 5, 2012Carter County, Montana; Lawrence County, South Dakota; 9 counties in Wyoming

The Storm Prediction Center issued this mesoscale discussion at Jul 5, 2012, 2:40 PM MDT for Carter County, Montana; Lawrence County, South Dakota; 9 counties in Wyoming. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued: Jul 5, 2012, 2:40 PM MDT (20:40 UTC)
Expired: Jul 5, 2012, 4:15 PM MDT
In force: 95 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

Counties Carter County, MT, Lawrence County, SD, Albany County, WY, Campbell County, WY, Converse County, WY, Crook County, WY, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY, Weston County, WY

The radar

The Rapid City radar (KUDX), 199 km from the middle of the area, began a volume at 20:43 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.

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 8.7 hours before the alert went out and 192 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: 1568 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 44 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

822 
ACUS11 KWNS 052040
SWOMCD
SPC MCD 052040 
SDZ000-NEZ000-MTZ000-WYZ000-052215-

MESOSCALE DISCUSSION 1409
NWS STORM PREDICTION CENTER NORMAN OK
0340 PM CDT THU JUL 05 2012

AREAS AFFECTED...ERN WY...FAR WRN NEB...FAR WRN SD...FAR SE MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 052040Z - 052215Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...A SEVERE THREAT MAY DEVELOP AS STORMS INCREASE IN COVERAGE
ACROSS ERN WY AND FAR WRN SD. LARGE HAIL AND DAMAGING WINDS ARE
EXPECTED TO BE THE PRIMARY THREATS AND WW ISSUANCE MAY BE NEEDED
LATE THIS AFTERNOON.

DISCUSSION...THUNDERSTORMS ARE DEVELOPING FROM JUST WEST OF LARAMIE
NWD TO NEAR CASPER ALONG A ZONE OF LOW-LEVEL CONVERGENCE AND JUST TO
THE EAST OF 1005 MB SFC LOW. A NARROW CORRIDOR OF LOW-LEVEL MOISTURE
IS PRESENT TO THE EAST OF THE SFC LOW ACROSS ERN WY WHERE SFC
DEWPOINTS ARE IN THE MID 50S TO NEAR 60 F. IN RESPONSE TO SFC
HEATING...MODERATE INSTABILITY HAS DEVELOPED ALONG MOST OF THE MCD
AREA WITH MESOANALYSIS ESTIMATING MLCAPE VALUES IN THE 1000 TO 1500
J/KG RANGE. IN ADDITION...FORECAST SOUNDINGS ACROSS ERN WY SUGGEST
30 TO 40 KT OF DEEP LAYER SHEAR IS PRESENT. THIS MAY BE ENOUGH TO
SUPPORT A SEVERE THREAT WITH THE MORE INTENSE CELLS THAT REMAIN
DISCRETE AND ROTATE. INITIALLY...THE GREATEST SEVERE THREAT FOR HAIL
AND DAMAGING WIND GUSTS SHOULD BE IN THE SRN PART OF THE MCD WHERE
LAPSE RATES ARE STEEPER THAN IN AREAS TO THE NORTH. THE SEVERE
THREAT COULD INCREASE ACROSS THE NRN PART OF THE MCD AFTER A FEW
MORE HOURS WHEN LOW-LEVEL FLOW IS FORECAST TO INCREASE.

..BROYLES/THOMPSON.. 07/05/2012

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

ATTN...WFO...UNR...CYS...BYZ...RIW...

LAT...LON   45540458 45510509 45170539 44640569 43720601 43100618
            42140617 41830612 41480589 41300562 41150526 41100499
            41150442 41550403 42140388 42920380 43850375 45050360
            45400407 45540458

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 5, 4:10 PM MDT	Severe Thunderstorm Watch	SPC	Carter, Powder River	8 hr
Jul 5, 5:37 PM MDT	Mesoscale Discussion	SPC	Carter	53 min
Jul 5, 5:55 PM MDT	Tornado Watch	SPC	Carter	6 hr
Jul 5, 4:52 PM MDT	Mesoscale Discussion	SPC	Clay, Union, Yankton	53 min

Nearby

Mesoscale Discussions in Wyoming, 2012 Mesoscale Discussions in Montana, 2012 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.