MESO: Mesoscale Discussion 1531

ACUS11 KWNS 212222
SWOMCD
SPC MCD 212221
SDZ000-NDZ000-MTZ000-WYZ000-212315-

MESOSCALE DISCUSSION 1531
NWS STORM PREDICTION CENTER NORMAN OK
0521 PM CDT SAT JUL 21 2012

AREAS AFFECTED...ERN MT...SW ND...WRN SD...NE WY

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 212221Z - 212315Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...A SEVERE THREAT APPEARS LIKELY TO DEVELOP ACROSS ERN MT
EXTENDING SEWD INTO WRN SD EARLY THIS EVENING. LARGE HAIL AND WIND
DAMAGE WILL BE THE PRIMARY THREATS. WW ISSUANCE WILL LIKELY BE
NECESSARY OVER THE NEXT HOUR ACROSS PARTS OF THE NRN PLAINS.

DISCUSSION...THUNDERSTORMS ARE STARTING TO DEVELOP ACROSS ERN MT
ALONG THE WRN EDGE OF MODERATE INSTABILITY WHICH EXTENDS SEWD ACROSS
ERN MT INTO WRN SD. THE INSTABILITY AXIS IS LOCATED BENEATH AN
UPPER-LEVEL RIDGE WHERE LARGE-SCALE ASCENT IS NOT THAT STRONG AND
TEMPS ALOFT ARE WARM. HOWEVER...MESOANALYSIS SUGGESTS THE CAPPING
INVERSION IS WEAK ENOUGH TO ALLOW FOR CONVECTIVE INITIATION. STORMS
ARE EXPECTED TO INITIATE NEAR A LEE TROUGH EXTENDING SSEWD FROM THE
GLASGOW AREA TO NORTHWEST OF RAPID CITY ALONG WHICH LOW-LEVEL
CONVERGENCE IS ENHANCED. THE CURRENT THINKING IS THAT SCATTERED
SEVERE STORMS WILL DEVELOP EARLY THIS EVENING ACROSS WRN MT AND WRN
SD AND MOVE EWD ACROSS THE NRN PLAINS SIMILAR TO THE WRF-NSSL
SOLUTION. THE CONVECTION SHOULD POSE A THREAT FOR LARGE HAIL AND
WIND DAMAGE.

..BROYLES/CARBIN.. 07/21/2012

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

ATTN...WFO...BIS...UNR...BYZ...GGW...

LAT...LON 48490486 48990540 48990714 48480781 47320784 46650641
45710567 45130478 44720442 44270420 43930382 43770317
44270252 44940217 45750203 46480227 46880294 48490486

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