As workers shape a tunnel connecting the under-construction 274-bed California Pacific Medical Center campus to some medical offices on the opposite side of the street, Van Ness Avenue will close to traffic from Geary to Post for the third and final time this year. Well, final for now, anyway.

That's all weekend, 12:01 a.m. Friday to 11:59 p.m. Sunday, the Chronicle gravely warns.

No, this is not just déjà vu. The first of three planned closures was back in April, and thus there have already been two separate times that the situation has snarled traffic trying to get to and from the Golden Gate and the Marina.

So tell your Uber driver, tell your cabbie, tell everyone you love to avoid Van Ness, maybe entirely, but certainly in the area of Geary and Post. Like, at all costs. Otherwise the cost is a somewhat significant detour on Larkin, Franklin and Gough. Actually, Franklin and Gough will be pretty bad as a result of this too.

Muni and Golden Gate Transit buses as well as emergency vehicles will be granted access, of course, and sidewalks will be open to pedestrians.

Don't say you weren't warned.