[upflying]

Like past threads on this subject, Caltrans will close the road if R3 conditions exist.
(R3 means AWD/4WD must use chains)
If an Outback needs chains, turn around and wait for conditions to improve.

 

[upflying]

R3 is rare, the more common R2 means Sierra roads turn into parking lots so you won't be going anywhere.
The last I80 R2 Sierra crossing took me a bladder busting 4 hours to drive 40 miles.

 

[upflying]

I have heard CHP making the vehicles turn around if they don't carry chains on I-5. Just ordered Z143 from Amazon for $74 a few dollars more than Walmart but I can't find any cheaper chain to buy locally.

The only time I have seen inspections to determine if chains are in your possession are big rig truckers. In this case, Caltrans is doing the inspections, not CHP.
From a practical standpoint, CHP does not have the staffing to stop every vehicle on a major highway to see if chains are buried in the trunk somewhere.
From a common sense standpoint, such a check point would create a traffic jamb 50 miles long.
This does mean inspections might (but very unlikely) occur on sparsely traveled secondary roads in the Sierra.
CHP and Caltrans will turn you around at a chain control checkpoint if chains are not mounted on a vehicle that should have them on.