I expect it to trigger widespread thunderstorm activity this afternoon and evening. It should move on to the east tomorrow leading to some drying and stabilization in its wake. Have outlooked severe in Zone 8 today because of the high instability present. The pattern will also evolve to a McCollum Type III by afternoon as flow in mid and upper levels becomes westerly. P chart of the 12 UTC sounding from Luke Air Force Base on August 19, 1994.
Wind speeds are in knots.
The small box indicates the location of Phoenix, and the Salt and Verde River Basins are outlined. Observed Weather Widespread, significant storms occurred throughout the afternoon - primarily over east half of state. There were numerous reports of heavy rains and flash floods and of wind damage and some hail. Tucson was particularly hard hit. Storms developed early as the shortwave moved eastward across the state.