From a BIG picture perspective, today's weakness has the potential to inflict some serious damage to the dominant January uptrend from 266.64 to 286.63, particularly if SPY cannot claw its way above the 20 DMA (279.66) ahead of the closing bell.
The last time SPY CLOSED beneath its 20 DMA was nearly three months ago, back on 11/09/17, but let's notice that the prior three trading weeks exhibited mostly sideways prior action, which is quite a contrast to the near-vertical ascent during the last 4 weeks.
My sense is that a close beneath the 20 DMA accompanied by a sharply down-sloping 5 DMA (282.61) represents the set up within an incomplete, larger-developing corrective period that will point towards a next target in the vicinity of the lower BBnd Line, now at 272.07. Because the 20 DMA is the mid-point of the BBnd width, and because a close beneath the mid-point line overwhelmingly skews the directional potential towards downside continuation to test the lower BBnd line, we have to consider the prospect of another 2% decline into the 272 area in the hours immediately ahead.
For the next 2-1/2 hours, all eyes on the relationship between the SPY and its 20 DMA... MJP