ZCZC SPCSWOMCD ALL ACUS11 KWNS 171031 SPC MCD 171031 TXZ000-ARZ000-OKZ000-171200- MESOSCALE DISCUSSION 1045 NWS STORM PREDICTION CENTER NORMAN OK 0531 AM CDT WED JUN 17 2015 AREAS AFFECTED...PORTIONS OF ERN TX...ERN OK...WRN AR CONCERNING...TORNADO WATCH 306... VALID 171031Z - 171200Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 306 CONTINUES. SUMMARY...TORNADO WATCH 306 IN TEXAS WILL LIKELY BE ALLOWED TO EXPIRE ON SCHEDULE AT 1200Z. PRESENT INDICATIONS ARE THAT ADDITIONAL/DOWNSTREAM TORNADO WATCH ISSUANCE WILL BE UNLIKELY IN THE SHORT-TERM. DISCUSSION...REGIONAL VWPS SUGGEST THAT LOW-LEVEL SHEAR REMAINS RELATIVELY STRONG BENEATH 30-35 KT OF FLOW AROUND 1 KM AGL WITHIN THE ERN SEMICIRCLE OF T.D. BILL. THIS IS ESPECIALLY THE CASE IN PROXIMITY TO AND JUST N OF AN E/W-ELONGATED ZONE OF WEAK BAROCLINICITY ARCING FROM E-CNTRL TX INTO SWRN LA...OWING TO THE RELATIVELY BACKED/ELY NEAR-SFC WIND COMPONENT THAT IS ALSO ENHANCING LOW-LEVEL SRH. FURTHERMORE...RICH MOISTURE CONTINUES TO BE DRAWN NWD ACROSS E TX...WITH MIDDLE 70S SFC DEWPOINTS EXTENDING NWD FROM THE GULF COAST TOWARD THE BAROCLINIC ZONE -- ENHANCING LOW-LEVEL THETA-E AND MARGINAL BUOYANCY. A PAIR OF FEEDER BANDS ASSOCIATED WITH OCCASIONAL LIGHTNING HAVE EVOLVED INVOF WEAK CONFLUENCE AXES NEAR AND S OF THE BAROCLINIC ZONE AMIDST THE STRONG SHEAR. YET...SINGLE-SITE RADAR VELOCITY DATA HAVE INDICATED NOTHING MORE THAN WEAK...TRANSIENT CYCLONIC SHEAR ZONES...WITH LITTLE IN THE WAY OF SUSTAINED DISCRETE/SEMI-DISCRETE CELLS PER BASE REFLECTIVITY DATA. AS SUCH...DESPITE THE VERTICAL SHEAR PROFILES RESULTING IN SOME CONDITIONAL RISK FOR ONE OR TWO BRIEF TORNADOES -- SPREADING NWD INTO PARTS OF ERN OK AND WRN AR WITH TIME TODAY -- CONFIDENCE IN CONTINUATION OF SUCH POTENTIAL BEYOND THE 1200Z EXPIRATION TIME OF TORNADO WATCH 306 IS LOW. THE LACK OF A SUBSTANTIAL INFLUX OF MID-LEVEL DRY AIR -- PER WATER VAPOR LOOPS -- AND RELATED LACKING INCREASE IN POTENTIAL INSTABILITY/TORNADO-ENHANCING STORM-SCALE PROCESSES MAY BE DETRIMENTAL TOWARD THE SUPPORT OF A GREATER TORNADO RISK. AS SUCH...ADDITIONAL/DOWNSTREAM TORNADO WATCH ISSUANCE IS NOT CURRENTLY PLANNED...THOUGH COORDINATION WITH THE AFFECTED WEATHER FORECAST OFFICES ADDRESSING THIS ISSUE WILL LIKELY BE INITIATED IN THE NEXT COUPLE OF HOURS. LATER TODAY...DIURNAL HEATING OF THE MOIST BOUNDARY LAYER BETWEEN RAIN BANDS PERIPHERAL TO T.D. BILL MAY PROVE SUFFICIENT FOR SOME UPTICK IN CONVECTIVE INTENSITY AND PERHAPS A RISK FOR ONE OR TWO BRIEF TORNADOES ROUGHLY WITHIN THE NERN QUADRANT OF T.D. BILL AND VICINITY. SUCH POTENTIAL WILL BE ADDRESSED IN SUBSEQUENT MCD ISSUANCE THIS MORNING. ..COHEN/GOSS.. 06/17/2015 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LCH...SHV...TSA...HGX...FWD...OUN...EWX... LAT...LON 28889582 29169678 30579701 32709682 34239665 34709535 34069434 30569443 29429475 28889582 NNNN