As we speak, the e-SPU is pressing on key initial support at 1621, which if violated and sustained, will point to 1615, a much more important near-term support plateau.
If that is violated, then yesterday's relentless up-move is indeed in danger of becoming a 1-day wonder, and an extremely nasty, twisted, Bull Trap.
For starters, though, a decline that breaks and sustains beneath 1515 will tell us that the e-SPU has morphed into a range-bound market, between 1635-1642 on the high side, and 1600 to 1591 on the low side.
That will probably contain all of the action heading into Wednesday's FOMC announcement and Bernanke's Press Conference, at which time investors probably will react with enough force to send the index through the top or the bottom of the delineated range.
Bottom line: lots of choppy trading, swoons and rallies, fits and starts likely ahead for the rest of today, into next Wednesday afternoon.