Excessive Heat Warnings remain in effect across the California'sCentral Valley and much of the Desert Southwest......A couple rounds of severe thunderstorms and heavy rainfall possibleacross portions of the Central Plains toward the Mid-Mississippi ValleyFriday and Saturday...A strong upper-level ridge associated with the ongoing heat wave over theSouthwest is forecast to reach its peak intensity today (Thursday) beforesliding off slowly toward the southern Plains during the next couple ofday...