MESO: Mesoscale Discussion 1455

ACUS11 KWNS 122054
SWOMCD
SPC MCD 122054
NEZ000-SDZ000-COZ000-122230-

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

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

ATTN...WFO...FSD...OAX...GID...LBF...GLD...BOU...

LAT...LON 40939914 40230142 40600226 41320204 41900030 42609926
42839879 42759765 42459712 41769745 40939914

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