A timely example: Persistent Western ridge, Eastern trough next 2+ weeks
In the coming days, a remarkably persistent weather pattern will begin to develop across North America and adjacent ocean regions. Characterized by strong high pressure near the West Coast and low pressure over the Eastern Seaboard, this “quasi-stationary,” high-amplitude atmospheric wave pattern will essentially become locked in place for at least the next 2 weeks. Patterns like this have a tendency to become self-reinforcing, lasting for much longer than more typical transient weather patterns and leading to prolonged stretches of unusual weather. This particular event will be no exception: California (and much of the West Coast) will almost certainly experience an extended, multi-week warm and dry spell, while much of the East Coast shivers through repeated blasts of cold, Arctic air.
From Mountain Weather Master Joe Ramey
Here is another emergence of the “Ridiculously Resilient Ridge” that we saw in 1995-96 winter and that led to severe drought across southern California and much of the Great Basin. Dr Jennifer Francis has talked about Arctic Amplification for many years now. Her hypothesis is with less hemispherical thermal gradient (due to stronger warming at higher latitudes), the jet stream weakens and amplifies. This leads to long persisting or ‘stuck’ weather patterns. Here is a quick summary of her theory: https://www.youtube.com/watch?v=_nzwJg4Ebzo