The image below courtesy tropical tidbits shows the upper-level height anomalies through October 21st (according to the latest Global Forecast Ensemble System).
Notice the continuous bright orange colors over the northeastern United States indicative of an upper-level ridge of high pressure with a trough (dip in the jet stream) over the western United States.
The the following image shows the historical height anomalies associated with weak La Nina conditions in the Equatorial Pacific:
Notice the yellow and orange colors over much of eastern Canada, the Great Lakes and Northeast indicative of persistent upper-level high pressure over these areas and a strong trough of low pressure across the Gulf of Alaska.
Also of interest is the light blue (lower heights/low pressure) over the Gulf of Mexico and western Caribbean (indicative of the active tropical hurricane season we have had in this region).
Reanalysis of Sea-Surface-Temperatures during weak La Nina patterns matches up pretty well with current Sea Surface Temperature Anomalies:
As we head later into October I will be looking at some of the historic analog years (past years that match up with current global conditions) during weak La Nina Winters and will issue a Winter Forecast for the 2017-18 Season.