Heat and Floods

There's an autumn chill in the air for much of Alaska this morning, but summer had a record-breaking last gasp in the eastern interior at the weekend.  Chinook flow from the south produced extraordinary downslope warming for southeastern locations, including 89°F at both Northway and Eagle on Sunday (the 90°F in the map below is a rounding error):

It's hard to overstate how anomalous this kind of heat is at this point on the calendar.  Northway, at 1700 feet above sea level, has only ever reached 89°F or higher in June, with data back to 1943.  The record highs for both July and August are 88°F, and of course the August record was set early in the month.  The previous highest temperature in the second half of August was only 84°F.

As for Eagle, with data (some gaps) back to 1902, the latest in the year for 89°F was August 15, 1982.   It also reached 90°F on August 12, 2013.

This is the second time this month with record-breaking heat for these communities: just two weeks ago, Northway saw its latest measurement of 87°F, on the 6th of the month.  Eagle was 90°F then too.

Here's the 500mb flow (as of 4pm AKDT on Sunday) that produced the downslope warming: notice the strong southwesterly winds between the major North Pacific ridge and the strong trough near the Bering Strait.

The Bering Sea trough and associated storminess has been causing havoc for the Kuskokwim Delta coast, with major flooding reported:

https://alaskapublic.org/2024/08/18/bering-sea-storm-brings-erosion-and-flooding-to-western-alaska-communities/

Two strong and very similar storms moved up the Bering Sea into the Seward Peninsula in the past several days: here are MSLP analyses from Friday morning (top) and Sunday afternoon (bottom):

Next up is the remnant circulation of Typhoon Ampil, which affected northern Japan last week.  The now-extratropical storm moved through the western Aleutians yesterday, and will near the Bering Strait late tomorrow.  Wind and flood warnings are in place for most of Alaska's west coast.