MESOSCALE DISCUSSION 1459, AREAS AFFECTED...SRN NV...NW AZ AND SE CA CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

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MESOSCALE DISCUSSION 1459 NWS STORM PREDICTION CENTER NORMAN OK 0218 PM CDT FRI JUL 13 2012 AREAS AFFECTED...SRN NV...NW AZ AND SE CA CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 131918Z - 132045Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...AN ISOLATED SEVERE THREAT MAY DEVELOP ACROSS NW AZ...SRN NV AND SE CA THIS AFTERNOON. THE PRIMARY THREATS SHOULD BE HAIL AND STRONG GUSTY WINDS. THE SEVERE THREAT SHOULD REMAIN TOO MARGINAL TO WARRANT WW ISSUANCE. DISCUSSION...SCATTERED THUNDERSTORMS HAVE DEVELOPED IN NW AZ THIS AFTERNOON ON THE ERN EDGE OF A WELL-DEFINED CORRIDOR OF LOW-LEVEL MOISTURE WHERE SFC DEWPOINTS ARE IN THE MID TO UPPER 60S F. THE MOISTURE ALONG WITH SFC HEATING HAS ALLOWED MODERATE INSTABILITY TO DEVELOP FROM NW AZ EXTENDING WWD ACROSS SRN NV INTO SE CA WHERE MLCAPE VALUES ARE ESTIMATED IN THE 1000 TO 2000 J/KG RANGE. IN ADDITION TO THE INSTABILITY...THE LAS VEGAS WSR-88D VWP SHOWS ABOUT 25 KT OF 0-6 KM SHEAR WITH UNIDIRECTIONAL WINDS BELOW 3 KM. THESE FACTORS COMBINED WITH STEEPENING LOW-LEVEL LAPSE RATES SHOULD BE FAVORABLE FOR A MARGINAL WIND DAMAGE THREAT WITH THE STRONGER CELLS THIS AFTERNOON. A HAIL THREAT MAY ALSO DEVELOP WITH CELLS THAT INITIATE IN AREAS WITH MODERATE INSTABILITY. ..BROYLES/CARBIN.. 07/13/2012