Snow and Ice Update

Snow cover extent has been relatively stagnant across Alaska in the past two weeks, with somewhat less than half of the state's land area under snow cover.  At valley-level across the interior, snow cover has only been established across northern and eastern areas, and temperatures were warm enough last week to eliminate snow in parts of Alaska's upper Yukon region.  Compare NSIDC snow cover estimates from the latest date and one week earlier:

Here's a chart of snow extent so far this season (heavy black line) compared to previous years in the past couple of decades.  The early October advance of snow cover across the north and east pushed snow extent above normal for the time of year, but we're now very close to normal for the date:

Fairbanks received 2 inches of snow yesterday, and the NWS expects a substantial storm from Fairbanks eastward and southward in the next few days:

Given the date on the calendar, and assuming the forecast is approximately correct, it seems likely this will represent the establishment of the permanent winter snow cover for a wide area.

The sea ice situation is more unusual, as sea ice has expanded very rapidly from the seasonal minimum on Alaska's side of the Arctic.  The NWS and NSIDC analysis maps already show only a narrow band of ice-free waters to the north of the Beaufort Sea coast, and the combined Chukchi/Beaufort ice extent is the greatest for this date since 2001 - and almost exactly equal to the 1981-2010 average.

The chart below illustrates the rapid recovery from well below normal to above-normal ice extent in the past month.  Remarkably, the ice growth from September 15 to October 17 is the greatest in the satellite era (1979-present).

On the Russian side of the basin, however, sea ice is far below normal - for example, the Kara Sea is tracking near record lows, with essentially no seasonal ice growth yet (same as last year).

The explanation for the contrast lies partly in the weather pattern: low pressure and cold on the Pacific side of the Arctic Ocean in the past month, and a positive Arctic Oscillation that has brought very warm air from the Atlantic domain into western and Arctic Russia.