Don't forget beyond about 144 hours it gets very dodgy believing what is being shown, unless you see consistent trends or output. Ensembles are the best help in this regard. For example, ECMWF's ensemble mean shows a strong Pacific jet beyond 300 hours, and then a mean ridge in the western CONUS. Although nothing solid can be gained from this, the hints are that western US troughing is favoured. Something similar is shown on the GFS ensembles. A few hints are there that w/c 22nd May could see a lower latitude sub-tropical jet causing troughing in the SW'ern US. This might be followed by a ridge before the polar front jet in the N Pacific starts to breakdown into a western US trough. But, the main thing I've learned over the years is not to be too worried about it - once out there, chase day-by-day!