MESO: Mesoscale Discussion 1533

ACUS11 KWNS 212307
SWOMCD
SPC MCD 212306
NEZ000-SDZ000-COZ000-WYZ000-220030-

MESOSCALE DISCUSSION 1533
NWS STORM PREDICTION CENTER NORMAN OK
0606 PM CDT SAT JUL 21 2012

AREAS AFFECTED...SE WY...FAR SWRN SD...WRN NEB...NRN CO

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 212306Z - 220030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN ISOLATED SEVERE THREAT WILL PROBABLY CONTINUE EARLY
THIS EVENING ACROSS ERN WY AND MAY ALSO IMPACT WRN NEB. MARGINAL
WIND DAMAGE AND HAIL WILL LIKELY BE THE PRIMARY THREATS. DUE TO THE
ISOLATED NATURE OF SEVERE THREAT...WW ISSUANCE IS UNLIKELY ACROSS
THE CNTRL HIGH PLAINS.

DISCUSSION...SCATTERED THUNDERSTORMS ARE DEVELOPING ALONG AN AXIS OF
MODERATE INSTABILITY EXTENDING FROM NEAR RAPID CITY SWWD TO NEAR
CHEYENNE. MLCAPE VALUES ARE ESTIMATED IN THE 1000 TO 1500 J/KG RANGE
WITH 0-6 KM SHEAR OF 20 TO 25 KT WHICH SHOULD SUPPORT MULTICELL
DEVELOPMENT. IN ADDITION...SFC TEMPS ABOVE 100F WITH DEWPOINTS IN
THE 40S F ARE CREATING VERY LARGE TEMP-DEWPOINT SPREADS WHICH MAY
ENHANCE DOWNDRAFT ACCELERATION. AS THE STORMS GRADUALLY MOVE NEWD
INTO WRN NEB...ISOLATED STRONG DOWNBURSTS WILL BE POSSIBLE. IN SPITE
OF THE WARM AIR ALOFT...HAIL WILL ALSO BE POSSIBLE MAINLY WHERE THE
CONVECTION HAS ACCESS TO MODERATE INSTABILITY.

FURTHER TO THE EAST ACROSS NCNTRL NEB...CONVECTION HAS DEVELOPED
NEAR A SFC LOW TO THE EAST OF VALENTINE NEB. THIS STORM SHOULD MOVE
INTO INCREASING INSTABILITY AND MAY BE MAINTAINED FOR A FEW HOURS.
HOWEVER...WARM AIR ALOFT AND WEAK LARGE-SCALE ASCENT BENEATH A CNTRL
PLAINS UPPER-LEVEL RIDGE WILL LIKELY KEEP THE ACTIVITY VERY
ISOLATED. HAIL AND STRONG WIND GUSTS WILL LIKELY BE THE PRIMARY
THREATS.

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

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

ATTN...WFO...ABR...LBF...UNR...BOU...CYS...

LAT...LON 42170071 42449999 42919962 43239985 43660049 43880136
43540306 43350436 42640526 42160623 41530676 41080672
40320595 40320537 40580474 41190391 41980244 42170071

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