Anchorage, Alaska has been experiencing prolonged fog since Halloween, causing poor visibility and slick driving conditions. According to the National Weather Service Alaska Region, this is now the second longest streak of consecutive hours with 2 miles visibility at Anchorage International since 1953, with the streak ending at 75 hours. The cause of the fog is attributed to a strong high pressure over Alaska trapping moisture near the ground, combined with a slower than average freeze-up due to unusually mild October temperatures.

Mike Brubaker writes:

It was a foggy Halloween and the conditions really have not changed. I know people are wondering when it will finally lift. It has made for some slick driving conditions, and of course poor visibility in the darkness. I am wondering if this fog spell is in any way exceptional, based on the weather records, and what causes long spells of fog like this?

National Weather Service Alaska Region Consult from Rick Thoman on behalf of:

Brian Brettschneider, this is now the second longest streak of consecutive hours with <2 miles visibility at Anchorage International (since 1953). The Streak ended at 9 am Friday when visibility went up to 2.5 miles: 75 hours. The longest was 85 hours ending December 10-14, 2009. A. strong high pressure over Alaska has trapped moisture near the ground over large parts of the state. The unusually mild October has contributed to a slower than average freeze-up, so there is more open water on rivers and lakes that add to the near-ground moisture. Thoman R. Climate Science and Services Manager, NWS NOAA.