A continued threat for severe weather and heavy rains will exist from Kansas & Oklahoma east-northeast to Pennsylvania & West Virginia. In Oklahoma, from a Altus to Anadarko to Guthrie to Owasso to Jay line south & eastward, there is a chance for severe weather. Tornadoes are more likely along the Red River, with hail being the concern further north.
Here is more on this event from the Storm Prediction Center.
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1122 am CDT Sat Apr 23 2011
Valid 231630z – 241200z
..there is a slight risk of severe thunderstorms from central Texas into the middle MS and much of the Ohio Valley…
Todays upper pattern is dominated by a long fetch of southwest flow aloft from the southwest states into the northeast. A strong middle/upper level jet over the Great Lakes region will move into Quebec…leaving much of the central/eastern states with rather weak forcing mechanisms aloft for organized convective development. Nevertheless…a surface front extending from Texas into the upper Ohio Valley will provide the focus for thunderstorms today and tonight.
Latest surface analysis shows the main surface baroclinic zone extending from northern Arkansas northeastward along the Ohio River into southern Ohio. Scattered showers and thunderstorms have been ongoing along this axis overnight…reinforcing the thermal/instability gradient. Relatively strong heating is expected south of the boundary where forecast soundings show MLCAPE values around 1500 j/kg. The combination of low level convergence along the boundary and a weak cap to its south will lead to scattered afternoon storms. Steep middle level lapse rates and effective deep-layer shear over 40 knots will promote supercell structures with large hail and damaging winds the main threats. Low level shear profiles also support some risk of tornadoes this afternoon and evening.
A cold front is sagging slowly southward across OK and northwest Arkansas. This boundary should stall by early afternoon…with strong heating and very unstable conditions developing over southeast OK/northeast Texas and portions of western Arkansas. Present indications are that storms will develop rapidly along the boundary by late afternoon and spread southeastward into Texas/Arkansas through the evening. Forecast soundings show ample moisture/cape and bulk shear values of 35-40 knots…favorable for supercells. Thermodynamic parameters support a risk of very large hail along an axis from southeast OK/north central Texas into central Arkansas this afternoon and evening.
Later tonight…low level warm advection is expected to intensify across OK where steep lapse rates and moderate elevated cape will be present. Some potential for elevated hailstorms will exist tonight across this region.