MESOSCALE DISCUSSION 1702 NWS STORM PREDICTION CENTER NORMAN OK 0335 PM CDT MON AUG 12 2013 AREAS AFFECTED...PORTIONS OF ERN CO...WRN KS...SWRN NEB...SERN WY CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 122035Z - 122300Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...AN ISOLATED SVR THREAT MAY DEVELOP THIS AFTERNOON. DISCUSSION...AN ELY COMPONENT OF THE LOW-LEVEL FLOW CONTINUES TO TRANSPORT MODESTLY RICH MOISTURE INTO THE HIGH PLAINS...WITH SFC DEWPOINTS IN THE LOWER/MIDDLE 50S IN MANY AREAS JUST E OF THE ROCKY MOUNTAIN FRONT RANGE. HIGHER DEWPOINTS -- INTO THE LOWER 60S -- ARE FOUND OVER THE LOWER ELEVATIONS. UPSLOPE FLOW/TERRAIN-DRIVEN CIRCULATIONS CONTINUE SUPPORTING SCATTERED THUNDERSTORMS OVER THE CO FRONT RANGE...WITH ADDITIONAL ACTIVITY FARTHER N INTO SERN WY AND INVOF A FRONT EXTENDING SEWD FROM FAR SERN WY INTO NERN CO AND NWRN KS. VISIBLE SATELLITE DATA INDICATE FAIRLY WELL-STRUCTURED ANVILS EMANATING FROM THIS CONVECTION AND EXTENDING DOWNSHEAR/EWD...IN RESPONSE TO MODERATE HIGH-LEVEL FLOW/CONVECTIVE VENTILATION. MODERATE INSTABILITY MAY SUPPORT A FEW VIGOROUS UPDRAFTS/DOWNDRAFTS WITH SVR HAIL/WIND OCCURRING ON SPORADIC BASIS...AS CONVECTION IS FORECAST TO HAVE A TENDENCY OF SPREADING ACROSS THE LOWER ELEVATIONS INTO LATE AFTERNOON/THIS EVENING. HOWEVER...LOW/MID-LEVEL FLOW AOB 6 KM AGL IS RELATIVELY MODEST -- GENERALLY 25 KT OR LESS -- PER AREA WIND PROFILER DATA...AND THIS MAY SERVE AS A MITIGATING FACTOR FOR MORE ORGANIZED CONVECTION AND LESSEN THE OVERALL SVR THREAT. ALSO...THE LACK OF STRONGER DEEP-LAYER FORCING FOR ASCENT MAY REDUCE THE COVERAGE/MAGNITUDE OF ANY SVR POTENTIAL. ..COHEN/KERR.. 08/12/2013
Posted on: Mon, 12 Aug 2013 21:56:08 +0000
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