That's funny!
I was asking the same question as Ramy on Saturday, and in fact almost landed at the same cropduster strip (Westlake Farms) a few hours earlier in the day, while making pretty much the same transition from around Mineral King in the Sierra Nevada towards Avenal on the west side of the San Joaquin valley. Same model glider, too.
Eighty kilometers with no lift. And how can the wind be on the nose when the shear line is in front of me?
At the time the answer was probably "not the speed you're flying".
If it was easy it wouldn't be fun.
Jim