Guidance has come into better agreement regarding the medium-range development of the H5 pattern over NA as upper ridging favours the western Provinces and varied levels of restrained troughiness loiters through a portion of the east. It seems less likely now that any forceful or long-lasting eastward extension of the ridge will occur with more of a back-and-forth profile expected through that region.
Warm and largely dry conditions should control the west, with some shifting of the core of anomalous heat between the Prairies and BC through the next 10 days and possibly beyond as an upper high languishes over the southwest and central regions of the USA.
This is reflected in the continued positive phase of the PNA over the coming days:
Here’s a selection of meteograms from the latest 06z run of the GFS for locations across the west to illustrate both temps (F) and precip (inch).
Downstream in the east lower heights are set to continue in an abated state compared to the recent relatively deep central & eastern trough. The predicted axis of the trough and the subsequent ridge in the Atlantic could offer resistance for the east coast, depending on how exactly things develop.
The lowest height anomalies should still be in the far NE and up towards Greenland but a potential series of fronts and subsequent modest cool shots through the GL and into the Maritimes is on tap via this configuration, mingled in with some milder and drier conditions as well.
00z EPS 500mb height anomalies, days 1-5:
The 00z GFS ensembles prediction of the upper-level pattern farther out into the extended range, days 11-15:
The probabilistic temp outlook from the 00z NAEFS at the surface level, days 8-14:
Finally, total precip from the 06z GEFS through day 10: