If today’s losses hold through tomorrow (a BIG if), the SPX weekly chart will look like it does below (or worse).
In that chart you can see the SPX has put up an incredibly bearish looking wick at important resistance.
It was at this resistance that the SPX put up a similar looking wick in May 2008 after which you know what happened.
Stepping back and looking at the chart into 2000, one can see similar wicks were put in place at the top of retracement rallies in bear markets.
If one has the desire to be short, use last week’s high of ~1343 or slightly above as a stop position – a break above this level implies the SPX will have broken back above resistance line (1).
And again, should today’s sell-off be wiped out with a rally tomorrow, all of this analysis is invalidated.
Even if it is invalidated, the reward/risk ratio of being short on a wick like this at important resistance in front of the potential for a waterfall decline in prices seems quite favorable.