Yes.  All capital losses, even ones carried over, are first netted against "this year's" (2020 in your case) capital gains.

Only one issue: 2020 is not over yet !

I have a similar question.  Taking the facts above, assuming $80k in short term stock losses from 2018 and $80k in short term stock gains in 2020 - can the entire amount be offset in 2020?  In this case, would $0 be owed in taxes?  Also, are there limits to the amount that can be offset in any one year (i.e., what if it were $800k instead of $80k)?  Finally, are there time limits for the offset?  I.e., do the losses "expire" after a certain amount of time?  Thanks!  

Yes.  But you have to get the carryover amount from your 2019 return, not directly from 2018.

You get to first offset the loss against any gains you have each year so that can use more of it up.  Then after applying the loss to the current gains you can take a max loss of 3,000 (1,500 MFS)per year.  Turbo Tax does all the calculations for you.  Just enter the prior year carryover amount.

If you transferred your prior return it should be already filled in.

Unused capital  losses carry forward until you die or use them up whichever comes first. 

anyway if you have a carryforward loss of 80,000 and a gain this year of 80,000, your capital gain on 1040 will be zero.

Yes you may.  Capital losses may be used to offset capital gains.  If the losses exceed your gain, you can use up to $3K to offset ordinary income.  If your net losses exceed $3K, you carry carry forward.

Q. Assuming $80k in short term stock losses from 2018 and $80k in short term stock gains in 2020 - can the entire amount be offset in 2020?  In this case, would $0 be owed in taxes?  

A. Assuming there were no capital gains (long or short) to offset on your 2019 tax return; $77,000 of the $80,000 2018 loss would carry forward to 2020.  That is, you were required to "use up" $3000 of the capital loss on your 2019 return, assuming you had other income (of any type) to offset*. So. in the example,, you would have $3000 of taxable short term  capital gain on your 2020 return. 

*Technically, if your standard (or itemized) deduction is greater than your AGI, without  the capital loss, then all your capital loss is carried forward.