Atmospheric circulation patterns strongly influence the timing of snow

Atmospheric circulation patterns strongly influence the timing of snow melt and vegetation green-up.  At Barrow/Utqiaġvik, Alaska, years with late snow melt are associated with a blocking high-pressure system over the Arctic basin and low-pressure over the eastern Bering Sea which tends to block the flow (transport) of warm southerly air into the higher latitudes (left panel, below).  In contrast, years with early snow melt are associated with a low-pressure system over the western Bering Sea and a high-pressure ridge over eastern Alaska which tends to facilitate the northerly transport (flow) of warm southerly air (right panel). Source of this figure is: Stone, R. S., D. C. Douglas, G. I. Belchansky, and S. D. Drobot. 2005. Polar Climate: Arctic sea ice. Pages 39-41 in D. H. Levinson, (ed.). State of the Climate in 2004. Bulletin of the American Meteorological Society 86(6), 86 p. doi:10.1175/1520-0477-86.6s.1