Appears that it can overwinter.  I'm sure that there are many variables (elevation, winter severity, etc.), but below is an explanation from the attached CSU fact sheet:

Early blight (Alternaria leaf spot) (Figure 5) is caused by the fungus Alternaria solani. Symptoms become prevalent during the hotter months. This disease produces brown to black, target-like spots on older leaves. If severe, the fungus also attacks stems and fruit. Affected leaves may turn yellow, then drop, leaving the fruit exposed to sunburn. Sanitation is the best control. Remove all diseased plant tissue on the ground, as the fungus overwinters on leaf debris. Do not plant tomatoes in the same place next year. Space plants farther apart to improve air circulation. Avoid overhead irrigation. If the infestation is heavy, sulfur dust may help protect new leaves from infection.

02.949_Recognizing Tomato Problems.pdf (2259KB - 18 downloads)