The market went from neutral to surprisingly strong on the last day of trading April 1st. This was perhaps not so surprising if you had watched the "breakout ratio" on http://www.screenulator.com/cgi-bin/view_screen?id=breakout_ratio

Breakout ratio is a measure of underlying strength of the market, which is the number of topline breakouts to the bottom line breakouts. This unique method only available at screenulator, has consistently predicted overall direction of the market since its inception. For example see the following list:

Date, topline breakouts: bottom line breakouts

2010-4-1 50: 13 

2010-3-31 55: 11 

2010-3-30 57: 25 

2010-3-29 49: 26 

Contrast with the SPY chart:

http://www.screenulator.com/cgi-bin/view_chart?id=spy_watch_2010-4-1

The market was weak on March 31, it went down compared to March 30, but the breakout ratio improved from 57:25 to 55:11 This effectively suggested underlying strength of the market, and the next day April 1, the market went up.