The dryline s western dry boundary developed with the penetration of dry westerlies to low levels from aloft, and its eastern moist boundary formed with the extension upward of the moist low level southerlies. The dryline moved eastward and it decayed when the dry westerlies replaced the moist southerlies in the upper part of the dryline. Numerical short range forecast over the United States is provided by the Eta model at the National Centers for Environmental Prediction. It is shown that Eta analyzed structure of the drylne is close to the observed, except that some observed small scale vertical variations are not captured in the analysis. Conditions favoring severe storm formation seen in 3 May analyzed fields include a strong westerly wind maximum in the middle troposphere, a 500 mb trough and a negative absolute vorticity area in the upper troposphere in the vicinity of Oklahoma.
Heavy rainfall amounts werepredicted to the southeast of the observed.