One can fit an odd-looking but well-channeled 5-wave advance from yesterday's low to today's high (Chart 1 blue), although a double zigzag (Chart 1 red) appears more acceptable. If the rebound turns out to be corrective, a small wave four or a large X is likely in progress. On the other hand, momentum picking up that befits a wave 3 will support a sustainable rally.
SPX filled the first gap and is retesting the breakout trend line (Chart 2) in a small degree wave [C], as chances are that this rebound takes more time and price.
Gap hunting is likely in progress. SPX fills one gap (Chart 1). Chart 2 offers tracking squiggles from the low.