It looks like the 500 mb pattern will continue to be characterized by significant blocking during the next week. Figures used here to examine the pattern are GFS model products from the 00 UTC run last evening (5 April 2012). The GFS analysis above shows the Rex Block that has been over the central US, north through central Canada. A Rex Block (as opposed to the more familiar Omega Block) is a persistent pattern with a closed low directly south of a closed (usually) anticyclone. It appears that the 500 mb cyclone that's been stuck over Oklahoma is now heading east. So what will that leave us with? The GFS ensemble average for 500 mb at 48-hours (00 UTC on the 7th) shown below forecasts that a new Rex Block will develop from off the Pacific coast north through Alaska. The central US and north Atlantic get stuck with Omega Blocks by 48-hours.
This pattern stays in place, at least in the GFS forecasts, through 120-hours (above), and is still hanging in place at day 7 (below). Thus, a seriously blocked situation for North America. During the coming week forecasted 500 mb heights reach above 5820 m over much of the south-central half of the US - so, early summer/late spring conditions will continue.
Historical note - The Rex Block was named for Commander Daniel F. Rex, Office of Naval Research. Rex studied large-scale blocking patterns under Carl-Gustaf Rossby at the University of Stockholm and received his Ph.D. in 1951.
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