An incoming regime change will be marked by a strong upper-level ridge anchored over the SW USA and a trough carving into the central portion of the country. Numerous rounds of moisture may veer through the base of the mean trough position and subsequently eject on a general path impacting a wide swath of the east.
Ridging stationed to the south through parts of the US may initially nose it’s way into SW BC but that doesn’t seem like an overly prolonged affair as lower heights could return into the medium range and potentially beyond.
Meanwhile troughiness sinking through the GL will assist in delivering a sturdy SW flow to Atlantic Canada as a downstream ridge stands firm in the Atlantic, with a series of disturbances riding along the dividing line between the two in piecemeal but persistent fashion.
The transition into the extended range looks as if broader troughiness may give way to another round of possibly subdued H5 ridging through the midsection of the continent towards the late-month time period.
New Euro weeklies tomorrow evening should offer additional insight.
12z GFS ensembles 500mb height anomalies @ hour 120 / day 5:
Hour 240 / day 10:
Hour 360 / Day 15:
WPC total precip for days 1-7: