GBP/USD broke out above the resistance trend line of the upward trend channel, which means that medium term prognosis for the pair will most likely remain bullish.
I think that the first serious resistance on the way up will be in the zone around 1.3800 – 1.3830.
If the limit of the channel is reached, the pair should rally at least to 1.4150.
All the levels I have listed have already been levels of support in the past and there is a large possibility for the pair to meet a resistance at them.
I also think that GBP/USD could retrace down to test the trend line breakout before the pair rebounds from it and continues moving to the upside.