There are multiple sources of uncertainty in precipitation forecasts related to landfalling tropical storms, but include (1) track and (2) the chaotic nature of convective storms. The latter can lead to large spatial and temporal variations in precipitation, even over short distances (see also the Madweather blog). Last night's NCAR ensemble, for example, produced anywhere from 1 to 4 inches of precipitation at Davis-Monthan AFB near Tucson.
Unfortunately, the moisture will not be coming to northern Utah. Did you know it's been since June 13 since we had more than 0.08" at the Salt Lake City Airport! If only Newton's apple fell a bit further from the tree.