An unusually strong trough is dropping south into Arizona this morning and will interact with a little moisture that has moved into the state from Mexico.
Strong southerly flow ahead of the approaching trough continues to advect moderate amounts of moisture into southern Arizona. The front continues to push south, ressulting in mosture convergence along the boundary.
A few runs develop deep convection just to the east of Phoenix. I took a look at the HRRR and it was very similar. the HRRRx was more like the WRFGFS and WRFNAM which kept deep convection farther to the northeast of Phoenix.