MESOSCALE DISCUSSION 1213, AREAS AFFECTED...PARTS OF SRN/ERN SOUTH DAKOTA INTO SRN MINNESOTA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

        MESOSCALE DISCUSSION 1213     NWS STORM PREDICTION CENTER NORMAN OK     0911 PM CDT MON JUN 18 2012          AREAS AFFECTED...PARTS OF SRN/ERN SOUTH DAKOTA INTO SRN MINNESOTA          CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE           VALID 190211Z - 190345Z          PROBABILITY OF WATCH ISSUANCE...60 PERCENT          SUMMARY...UNCERTAINTY LINGERS CONCERNING THE INITIATION OF STORM     DEVELOPMENT THIS EVENING.  BUT ONCE IT BECOMES MORE CERTAIN...A WW     WILL PROBABLY BE NEEDED.          DISCUSSION...A PLUME OF VERY WARM ELEVATED MIXED LAYER AIR...WHICH     HAS ADVECTED OFF THE PLATEAU REGION THROUGH MUCH OF THE SOUTHERN AND     CENTRAL PLAINS AND MIDDLE MISSOURI VALLEY REGION...CONTINUES TO     PROVIDE STRONG INHIBITION TO CONVECTIVE DEVELOPMENT SOUTH OF THE     SOUTHERN SOUTH DAKOTA AND SOUTHERN MINNESOTA STATE BORDERS.  THE     LOWER AND MID-LEVEL THERMAL GRADIENT IS SHARP ALONG THE NORTHERN     PERIPHERY OF THIS PLUME...WHERE CONVERGENCE AND WARM ADVECTION ARE     EXPECTED TO STRENGTHEN SUBSTANTIALLY THROUGH THE 03-06Z TIME FRAME.      GUIDANCE CONTINUES TO INDICATE THAT THIS WILL OCCUR WITH SOUTH     SOUTHWESTERLY 850 MB JET STRENGTHENING IN EXCESS OF 50 KT ACROSS THE     CENTRAL PLAINS.            THE ENVIRONMENT REMAINS RELATIVELY DRY ACROSS MUCH OF THE DAKOTAS     AND MINNESOTA...BUT HIGH MOISTURE CONTENT AIR IS PRESENT ALONG AND     SOUTH OF A REMNANT CONVECTIVELY GENERATED OR ENHANCED BOUNDARY     EXTENDING ACROSS SOUTHERN MINNESOTA AND NORTHWEST IOWA INTO NORTHERN     NEBRASKA.  THIS BOUNDARY HAS ALREADY BEGUN TO LIFT NORTHWARD THROUGH     THE MID MISSOURI VALLEY...WITH RAPID SURFACE DEW POINT INCREASES     INTO THE UPPER 60S/NEAR 70F OBSERVED OVER SOUTHEASTERN SOUTH DAKOTA     DURING THE PAST FEW HOURS.          UNCERTAINTY LINGERS CONCERNING LOCATION OF CONVECTIVE INITIATION     THIS EVENING...BUT SOME GUIDANCE HAS BEEN SUGGESTIVE THAT BOUNDARY     LAYER BASED STORM DEVELOPMENT MAY NOT BE OUT OF THE QUESTION BY     03-04Z ACROSS THE YANKTON/SIOUX FALLS AREA.  OTHERWISE...POTENTIAL     FOR VIGOROUS CONVECTION ROOTED ABOVE THE BOUNDARY LAYER APPEARS MORE     LIKELY ACROSS AREAS OF SOUTHEASTERN SOUTH DAKOTA AND SOUTHERN     MINNESOTA...A BIT FARTHER TO THE NORTHEAST.  WITH STEEP MID-LEVEL     LAPSE RATES SUPPORTING SIZABLE CAPE IN THE PRESENCE STRONG SHEAR     BENEATH 50-70 KT WESTERLY 500 MB FLOW...SEVERE STORMS...INCLUDING A     FEW SUPERCELLS APPEAR PROBABLY ONCE ACTIVITY INITIATES.          ..KERR/CARBIN.. 06/19/2012               ATTN...WFO...MPX...FSD...ABR...          LAT...LON   43399637 43019691 42979808 43449936 44109980 44659869                 45099704 45249569 44879412 44249365 43829383 43399637