MESOSCALE DISCUSSION 0527 NWS STORM PREDICTION CENTER NORMAN OK 0144 PM CDT SAT APR 14 2012 AREAS AFFECTED...CNTRL/WRN KS CONCERNING...TORNADO WATCH 165... VALID 141844Z - 141945Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 165 CONTINUES. THE THREAT FOR SIGNIFICANTLY TORNADIC SUPERCELLS IS INCREASING OVER PARTS OF SWRN KS INCLUDING THE DODGE CITY AREA. INFLOW INTO DISCRETE SUPERCELLS EVOLVING OVER MEADE AND GRAY/FORD COUNTIES IS LIKELY BECOMING SURFACE BASED PER MODIFIED RUC/OBSERVED SOUNDINGS. SBCAPE VALUES OF 2000-3000 J/KG AMIDST STRONG DEEP-LAYER SHEAR WILL SUPPORT RAPID INTENSIFICATION WITH THESE STORMS. STRONG LOW-LEVEL SHEAR -- 0-1 KM SRH OF 297 M2/S2 PER HAVILAND KS PROFILER THAT ALSO INDICATES A LARGE AMOUNT OF STREAMWISE VORTICITY CONCENTRATED IN THE LOWEST 0.5 KM AGL -- COULD SUPPORT SIGNIFICANT TORNADOES. ADDITIONAL CLUSTERS OF STORMS INCLUDING SUPERCELLS FARTHER NORTH ACROSS THE WW AREA WILL POSE MAINLY A LARGE/VERY LARGE HAIL THREAT AND PERHAPS A COUPLE OF TORNADOES BEFORE A MORE FAVORABLE THERMODYNAMIC ENVIRONMENT FOR SFC-BASED SUPERCELLS ARRIVES WITHIN A FEW HOURS.
MESOSCALE DISCUSSION 0526 NWS STORM PREDICTION CENTER NORMAN OK 0141 PM CDT SAT APR 14 2012 AREAS AFFECTED...SWRN NEB THROUGH NWRN KS CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 141841Z - 142045Z STORMS ARE EXPECTED TO DEVELOP FROM SWRN NEB THROUGH NWRN KS BY MID TO LATE THIS AFTERNOON. SUPERCELLS WITH TORNADOES AND VERY LARGE HAIL ARE EXPECTED TO BE THE MAIN THREATS. TORNADO WATCH WILL BE NEEDED BEFORE 20Z. THIS AFTERNOON A WARM FRONT EXTENDS THROUGH SRN NEB INTO SWRN NEB WHERE IT INTERSECTS A DRYLINE THAT ARCS SEWD THROUGH THE NERN TIP OF CO THEN SWD THROUGH WRN KS. LOW CLOUDS ARE DECREASING FROM THE SOUTH AS BOUNDARY LAYER MIXING DEVELOPS NWD. THIS IS CONTRIBUTING TO DESTABILIZATION IN WARM SECTOR. LATEST OBJECTIVE ANALYSIS SHOWS AN AXIS OF 500-1000 J/KG MLCAPE FROM SWRN NEB INTO NWRN KS...AND INSTABILITY WILL INCREASE FURTHER AS DIABATIC WARMING CONTINUES. BANDS OF HIGH LEVEL CIRRUS HAVE BEEN INCREASING ACROSS NERN CO INTO WRN NEB...AND THIS MAY BE INDICATIVE OF AGEOSTROPHIC FORCING WITHIN UPPER JET EXIT REGION THAT WILL BEGIN TO OVERTAKE THE DRYLINE THIS AFTERNOON. LATEST VISIBLE IMAGERY SHOWS AN AREA OF CUMULUS INCREASING IN VICINITY OF THE DRYLINE OVER WCNTRL KS. AS THE CAP WEAKENS AND THE BOUNDARY LAYER CONTINUES TO DESTABILIZE...STORMS ARE EXPECTED TO INITIATE FROM NWRN KS THROUGH SWRN NEB. EFFECTIVE DEEP SHEAR OF 50+ KT WILL SUPPORT SUPERCELLS WITH VERY LARGE HAIL AND TORNADOES LIKELY.
MESOSCALE DISCUSSION 0525 NWS STORM PREDICTION CENTER NORMAN OK 0123 PM CDT SAT APR 14 2012 AREAS AFFECTED...CNTRL/WRN OK...ERN TX/OK PANHANDLES...WRN NORTH TX CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 141823Z - 142030Z THE THREAT FOR SEVERE THUNDERSTORMS INCLUDING TORNADOES MAY INCREASE THIS AFTERNOON...AND THE ISSUANCE OF A TORNADO WATCH IS POSSIBLE. CONVECTIVE INITIATION MAY BECOME OF INCREASING CONCERN INTO MID-AFTERNOON OWING TO A FEW APPARENT MESOSCALE PROCESSES: 1. LOW-LEVEL ASCENT ALONG A N-S-ORIENTED DRYLINE FROM THE ERN TX/OK PANHANDLES ACROSS W TX THAT WILL SLOWLY MIX EWD DURING THE NEXT COUPLE OF HOURS...AND MAY AID IN STORM INITIATION. SFC WINDS HAVE SLIGHTLY VEERED WEST OF THE DRYLINE DURING THE LAST HOUR...SUGGESTING THAT THE DRYLINE MAY BE MODESTLY SHARPENING WITH AN ATTENDANT INCREASE IN LOW-LEVEL ASCENT. THE CUMULUS FIELD JUST EAST OF THE DRYLINE APPEARS TO HAVE BECOME INCREASINGLY AGITATED PER RECENT VIS SATELLITE IMAGES...WHICH COULD EVOLVE INTO DEEPENING CONVECTION. STRONG HEATING AND DEEP BOUNDARY-LAYER CIRCULATIONS JUST WEST OF THE DRYLINE WILL ALSO AID IN INITIATION. 2. A SECONDARY MOISTURE GRADIENT IS NOTED 30-50 MILES WEST OF THE DRYLINE...WITH ATTENDANT ASCENT AUGMENTED BY AN EWD-MIGRATING...SUBTLE MID-LEVEL SHORTWAVE TROUGH CROSSING THE AREA PER WATER VAPOR IMAGERY. HIGH-BASED CUMULUS IS DEVELOPING OVER THE CNTRL TX PANHANDLE WHERE THE MID-LEVEL ASCENT OVERLAYS THE SECONDARY MOISTURE GRADIENT...AND THESE FEATURES MAY FOCUS INITIATION IN THE ERN TX PANHANDLE DURING THE NEXT FEW HOURS. 3. A DIFFERENTIAL HEATING ZONE IS NOTED OVER WRN OK FROM ROGER MILLS COUNTY SWD TOWARD WILBARGER COUNTY TX. THE VERTICAL CIRCULATION WITHIN THIS ZONE OWING TO DIFFERENTIAL DIABATIC HEATING AND DIFFERENTIAL VERTICAL MIXING RATES COULD ALSO FOCUS CONVECTIVE INITIATION THIS AFTERNOON. THUNDERSTORMS MAY ERUPT ALONG THE AFOREMENTIONED FEATURES BETWEEN 1930 AND 2100Z. IF CONVECTIVE INITIATION OCCURS...STORMS WOULD RAPIDLY BECOME SEVERE. EFFECTIVE BULK SHEAR MAGNITUDES OF 45-55 KT WILL FAVOR RAPID EVOLUTION TO FAST MOVING SUPERCELL STRUCTURES. WITH 531 M2/S2 OF EFFECTIVE SRH ACCORDING TO THE 17Z NORMAN RAOB...AND A LARGE DEGREE OF STREAMWISE VORTICITY IN THE LOWEST 0.5 KM...TORNADOES...SOME STRONG...WILL BE OF CONCERN...CONTINGENT ON THE INITIATION OF STORMS. THE MORE SUBSTANTIAL THREAT FOR STRONGER TORNADOES WILL BE NORTH OF THE RED RIVER...WHERE THE ISSUANCE OF A PARTICULARLY DANGEROUS SITUATION TORNADO WATCH WILL BE POSSIBLE. THE THREAT COULD BE SOMEWHAT LOWER SOUTH OF THE RED RIVER...WHERE LOW-LEVEL SHEAR MAY NOT BE AS STRONG AND CONVECTIVE COVERAGE NOT AS GREAT. ULTIMATELY...THE ISSUANCE OF A TORNADO WATCH WILL BE CONTINGENT ON AN INCREASINGLY APPARENT UPTICK IN CONVECTION...FOR WHICH SOME UNCERTAINTY REMAINS. SATELLITE AND OBSERVATIONAL TRENDS WILL CONTINUE TO BE MONITORED...WITH A WW...OR PERHAPS MULTIPLE WATCHES...POSSIBLY BEING ISSUED BY MID-AFTERNOON.
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