Up to 4 inches could fall in some areas through Wednesday. Those include Flagstaff, Payson, Prescott and the Grand Canyon's South Rim. Up to 6 inches is forecast at the canyon's North Rim.
Arizona has about ten tropical systems get within a couple hundred miles of the Valley since the 1960’s.
Remnant moisture from Tropical Storm Norbert was the last major tropical system to impact the Valley with record rain in September 2014. That system left hundreds of homes flooded and cars submerged on our freeways.
Ken Waters with National Weather Service in Phoenix said this storm brought 100 to 500-year rainfall amounts over portions of Phoenix.
Norbert was a testament to how powerful these storms can be, even in the middle of the desert.
“The bigger threat is always going be if we have some heavy showers with a lot of rain all at once, we just don't have the capacity to get rid of that water fast enough,” said Waters.
Of the last ten tropical cyclones to get close to the Valley, eight of them occurred during the months of September and October making this prime time for remnants of Rosa to move into Arizona.
“It may be every 5 to 10 years we have a system like this and this one is following suit over a number of these historical storms,” said Waters.