The melt was driven by powerful, warm winds called foehn winds (that's German for hairdryer, by the way). (earther.com)
However the positive AAO generated a wind regime that moved up and over the mountains, creating anomalous foehn storms on the eastern side of the peninsula.5 As the winds descend, temperatures adiabatically rise 10 to 20 degrees or more due to changes in pressure without any additional heat as depicted in Figure 2 above. (landscapesandcycles.net)
When the Southern Annular Mode is positive, it increases the odds of foehn wind events. (earther.com)