Mesoscale Discussion 1502

Issued

Aug 9, 2016, 3:51 PM MDT (21:51 UTC)

Expired

Aug 9, 2016, 5:45 PM MDT

In force

114 min

Issued by

the Storm Prediction Center

Chance of a watch

80%

Counties Carter County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Bowman County, ND, Butte County, SD, Custer County, SD, Fall River County, SD, Haakon County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Crook County, WY, Niobrara County, WY, Weston County, WY

The Rapid City radar (KUDX), 141 km from the middle of the area, began a volume at 21:55 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.

• Severe Thunderstorm Watch 435Aug 9, 4:15 PM MDT

731 
ACUS11 KWNS 092151
SWOMCD
SPC MCD 092151 
SDZ000-NDZ000-NEZ000-MTZ000-WYZ000-092345-

MESOSCALE DISCUSSION 1502
NWS STORM PREDICTION CENTER NORMAN OK
0451 PM CDT TUE AUG 09 2016

AREAS AFFECTED...PARTS OF SERN MONTANA...NE WYOMING INTO SWRN NORTH
DAKOTA/WRN SOUTH DAKOTA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 092151Z - 092345Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...INITIATION OF STORMS IS UNDERWAY ACROSS PARTS OF THE
NORTHERN HIGH PLAINS...WEST THROUGH NORTHWEST OF THE BLACK HILLS
REGION...WITH AN INCREASING RISK FOR SEVERE WEATHER EXPECTED THROUGH
EARLY EVENING AS ACTIVITY INTENSIFIES AND SPREADS EASTWARD.  A WATCH
LIKELY WILL BE ISSUED SOON.

DISCUSSION...SCATTERED DISCRETE THUNDERSTORM DEVELOPMENT IS ONGOING
ACROSS PARTS OF EASTERN WYOMING INTO SOUTHEASTERN MONTANA...EAST OF
THE LARAMIE MOUNTAINS AND EAST/NORTHEAST OF THE BIG HORNS.  THIS
APPEARS LARGELY IN RESPONSE TO DIURNAL SURFACE HEATING AND WEAKENING
OF INHIBITION...NEAR A THERMAL LOW AND SURFACE TROUGHING TO THE LEE
OF THE NORTHERN ROCKIES.  IN THE PRESENCE OF STEEP MID-LEVEL LAPSE
RATES...STEEPENING LOW-LEVEL LAPSE RATES AND MOISTENING
SOUTHEASTERLY NEAR SURFACE FLOW...CAPE HAS BECOME MODERATELY LARGE
/IN EXCESS OF 2000 J PER KG/.  AND VEERING OF WINDS WITH HEIGHT
BENEATH AT LEAST MODEST /30-40+ KT AT 500 MB/ SOUTHWESTERLY
MID-LEVEL FLOW IS CONTRIBUTING TO STRONG SHEAR.  

THIS ENVIRONMENT APPEARS INCREASINGLY CONDUCIVE TO SUSTAINED
SUPERCELL STORMS OVER THE NEXT FEW HOURS...WITH STRONGER CELLS
TENDING TO EVENTUALLY PROPAGATE EASTWARD/SOUTHEASTWARD WITH A RISK
FOR SEVERE HAIL...LOCALLY STRONG SURFACE GUSTS...AND PERHAPS A
TORNADO OR TWO.  TOWARD 00-02Z...A CLUSTERING AND/OR CONSOLIDATION
OF ACTIVITY MAY COMMENCE ACROSS ACROSS PARTS OF NORTHWESTERN SOUTH
DAKOTA...WHERE LARGE-SCALE ASCENT ASSOCIATED WITH LOW-LEVEL WARM
ADVECTION AND CONVERGENCE APPEARS LIKELY TO BECOME FOCUSED.

..KERR/GUYER.. 08/09/2016

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

ATTN...WFO...BIS...UNR...CYS...BYZ...

LAT...LON   45350698 46150605 46530449 45850265 44560120 43160207
            42940324 42870448 43600514 44740563 45350698

Mesoscale Discussions in South Dakota, 2016Mesoscale Discussions in Montana, 2016Mesoscale Discussions in Wyoming, 2016Every mesoscale discussion in 2016

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.