Pinellas County, Level A evacuation areas (including me) and people in mobile homes are ordered out by 6 AM tomorrow morning:

Pinellas County is also issuing evacuations. A mandatory evacuation for residents living in mobile homes and residents living in Level A evacuation areas will go into effect on Tuesday 6 a.m. The evacuation will affect about 288,000 residents.

Sally Bishop, director of the EOC for Pinellas County, says they recommend that anyone who wants to evacuate out of the county should consider doing so Monday evening or very early Tuesday morning.
I'm guessing this is because of possible flooding. Evacuation level map here (PDF). Tool for evacuation level and shelter info here.

(via Bay News 9)