If my 14 year old Daughter did fundamental analysis of the markets, she would probably say something along the lines of "Considerable time is sooooo 2014 FOMC, everybody knows that Patience is whats in style now". Sorry, just a bit of humor there. However, just as we looked at the term "considerable time" from the Fed last year is the same way we look at "patience" this year because it gives us some type of guidance as to when the Fed might start raising interest rates.
When Yellen marches up to Capitol Hill today, traders will be looking for some type of indication that "patience" might be removed from the next FOMC statement to pave the way for a possible rate hike within the next two fed meetings. If she does give some indication towards this, expect USD to strengthen across the board.
Personally, I feel her testimony today should favor USD strength. The pressure has been on the Fed for quite some time to be more hawkish in their guidance. It will be extremely difficult for Yellen to remain neutral in front of the Senate because they will be trying to pry some type of hawkish sentiment out of her today. This situation should keep the dollar strong.
When I worked on the trading desk, I always found it disheartening watching this testimony because it tends to show how ignorant politicians are when it comes to monetary policy (and that statement is not politically biased as it is aimed at both parties). If you choose to watch the testimony and place trades based on it, try looking for shorter term opportunities on breaks of consolidation as it may lead to some sustained short term moves.