The center of what is now Tropical Storm Rosa is currently approaching the West Coast of Baja California, and it is expected to be downgraded to a tropical depression by tomorrow morning after it traverses the Baja. It is forecast to continue to move north-northeastward across Arizona, and it will likely traverse Yavapai County on Tuesday afternoon. The storm will direct a very moist airmass across the terrain of Arizona from the South, leading to moderate to heavy rainfall tonight to tomorrow morning, especially in the more favored south-facing terrain areas. Thus, the main precipitation bands from Rosa are expected to move across Yavapai County from late tonight through tomorrow around noon. In advance of the approaching storm, the thunderstorm activity has not yet been as widespread as previously anticipated, but the storm is still on its way as expected. Right behind Rosa is an upper-air trough that will help to create strong vertical wind shear and lifting over Arizona on Wednesday - Thursday.
The main impact with this event will be scattered rain showers and thunderstorms today through Thursday, with prolonged periods of moderate to heavy rain across the Quad City area tonight to tomorrow morning. There is also a possibility of a few thunderstorms becoming severe, with larger hail, damaging winds, or isolated weak tornadoes possible, especially on Wednesday from the mid morning to the evening hours. Rainfall amounts could still be 1.5”-2.5” across the Prescott area, with local areas of heavier rainfall near south-facing mountain slopes.
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