MESOSCALE DISCUSSION 1455, AREAS AFFECTED...CO...NE CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

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MESOSCALE DISCUSSION 1455 NWS STORM PREDICTION CENTER NORMAN OK 0354 PM CDT THU JUL 12 2012 AREAS AFFECTED...CO...NE CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 122054Z - 122230Z PROBABILITY OF WATCH ISSUANCE...40 PERCENT SUMMARY...SCATTERED STRONG TO SEVERE STORMS POSING A DAMAGING DOWNBURST WIND THREAT AND PERHAPS SOME HAIL TO AROUND 1 INCH IN DIAMETER APPEAR POSSIBLE ACROSS PARTS OF NEB AND EXTREME NERN CO OVER THE NEXT FEW HOURS. GREATEST SEVERE POTENTIAL IS NOT EXPECTED TO BE WIDESPREAD AND PERSIST MORE THAN A FEW HOURS BUT A WATCH IS POSSIBLE IF ACTIVITY BECOMES MORE WIDESPREAD/INTENSE. DISCUSSION...MAXIMUM IN DIURNAL HEATING CYCLE HAS CONTRIBUTED TO A FEW STORMS INITIATING ALONG PRE-FRONTAL TROUGH AXIS BISECTING NEB THIS HOUR. THIS REGION LIES BENEATH BROADLY DIFFLUENT MID/UPPER FLOW TO THE SOUTH OF A WEAK SHORT WAVE TROUGH TRANSLATING EAST ACROSS THE DAKOTAS AND WRN MN. HOT AND DEEPLY MIXED BOUNDARY LAYER AIRMASS CHARACTERIZED BY MID TO UPR 90S F TEMPERATURES AND 30-40 F TEMP/DWPT SPREADS WILL SUPPORT THE POTENTIAL FOR DAMAGING DOWNBURST WINDS BENEATH ANY OF THE STRONGER CORES. WEAK LOW LEVEL S-SWLY FLOW TOPPED BY 20-25 KT WNWLY FLOW ALOFT RESULTS IN EFFECTIVE SHEAR MAGNITUDES AT LEAST ADEQUATE FOR ORGANIZED MULTICELL STORMS AND PERHAPS EVEN A HIGH-BASED SUPERCELL NEARER THE NERN CO BORDER. MOST MODEL GUIDANCE SUGGESTS THAT GENERALLY SUBTLE/WEAK LARGE SCALE ASCENT ACROSS THE REGION WILL LIMIT GREATER STORM COVERAGE AND PERSISTENCE. AND...EXPECT A DECREASE IN SEVERE POTENTIAL GOING INTO THE EVENING AS INSTABILITY BEGINS TO WANE. HOWEVER...OVERALL STORM EVOLUTION WILL NEED TO BE MONITORED CLOSELY IN THE NEXT HOUR OR SO AND A WATCH IS POSSIBLE IF A GREATER THREAT EVOLVES ACROSS A LARGER REGION. ..CARBIN/WEISS.. 07/12/2012