The top graphic is a plot of surface potential temperature (from SUNY Albany weather pages) for 20 UTC this afternoon (21 March 2011). Below that is a 20 UTC surface plot from NCAR RAP. I like to use surface theta for surface analysis in the west, since it can highlight features that are masked by varying surface station elevations. The SUNY objective analysis smears out the horizontal gradients however, and the actual front has a very strong theta gradient over a much smaller distance, i.e., the gradient between Tucson and Phoenix captures the frontal zone.
The eastern Pacific blended PW product (third graphic) indicates that a narrow plume of higher precipitatble water extends into Arizona along the frontal zone. However, the current regional radar data (bottom) indicate that, at present, the front is associated with a broad band of weak rainshowers. These may strengthen over the next couple hours as the front advances eastward across eastern Arizona.
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