The upper-level pattern over NA is set to undergo a substantial change through the short & medium range, featuring a mean western trough and eastern ridge which is in contrast to what has been the predominate composition of late.

This will alter the May temperature profile; month-to-date temp anomalies:

ncep_cfsv2_mtd_t2anom_canada

12z GFS ensembles temp anomalies for days 0-5:

gefs_t2ma_5d_noram_21

This new arrangement won’t be bereft of activity as multiple disturbances migrate NE from the western trough position. The stronger storms and heaviest precip will likely remain south of the border overall but this pattern could also spark some convection for interests here as well.

12z GEFS precip anomalies @ day 10:

gefs_tprecip_a_noram_41

The extended range could mark some re-established downstream blockiness and ridging returning to the west.

12z GFS ensembles 500mb height anomalies, days 10-15:

gefs_z500a_5d_noram_61

I’ll have a new set of Euro weeklies up tomorrow morning.

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