A Student Pilot reported a near miss at 2;300 FT during descent for landing at PRB with an aircraft which apparently had just departed PRB.

Narrative

Approaching PRB from the east on V248 I started my descent from 4;500. I had been listening to talk on the CTAF and established Runway 19 was being used as the active runway. This was my first flight to PRB and it was a little difficult to see the runways in the landscape; but I was confident I was on a straight track to the VOR on the field. When I had the field in sight I announced on the CTAF I was approximately six miles east and would be making left traffic for Runway 19. Immediately after that another pilot announced 'Departing 19 left turn out; departing to the south east.' I was too far to get a good visual on him and right after that two more aircraft announced intentions. My descent was taking longer than planned so I chose a heading well to the south; continued descending; and then planned to turn back to the airport. With my head on a swivel due to all the traffic around the airport I looked left and right then began my turn. When I banked right; my view panned downward and I immediately saw a second aircraft climbing from below that passed less than 100 FT directly below me. In retrospect I should have been more alert to traffic from below. This was most likely the departing aircraft although it seemed plenty of time had passed for him to have cleared the area.