When I searched, I found this price available departing PDX on Friday, December 14, returning from SFO on Monday, December 17.
This is a Basic Economy fare, which should be fine for a quick weekend trip, but if you think you'll be filling a suitcase with last minute gifts, you can get a Main Cabin seat for $157 on these same dates.
Need a room in San Francisco? Here's what's available for the above weekend dates on Hotelwatchdog.
For more weekend travel deals from your city, make sure to have a look at our new and improved Weekender search tool.