Sparks, Oklahoma

regional weather discussion... rapid thunderstorm development is likely by 5 PM from near Cushing... to Norman... to Duncan... and south into Texas near Henrietta. Very large hail will be possible... along with damaging winds and isolated tornadoes. Surface analysis and radar observations just before 4 PM showed a cold front from just east of Stillwater southwestward through Oklahoma City to near Chickasha. A dry line intersected the front near Wellston... and extended southwestward through Norman to near Rush Springs... and into Texas near Henrietta. Very unstable conditions were present all along and southeast of the dry line... with cape values over 3000 in the I-35 corridor south of Oklahoma City. Mid-day upper air data indicate that the cap has weakened since this morning... and satellite images show widespread cumulus clouds continuing to become more concentrated along the front and dry line... from east of Stillwater to south and east sides of the Oklahoma City area... and into southern Oklahoma near Duncan and Waurika. All indications are that scattered thunderstorms will develop rapidly along the dry line as the cold front overtakes it... beginning between Cushing and Norman by 5 PM. Additional development is likely southward to the Red River region between Waurika and Henrietta. With highly unstable conditions present... and strong vertical wind shear... organized severe thunderstorms and supercells will be likely. Very large hail... possibly to baseball size or larger... will be the main concern along with damaging winds and isolated tornadoes.