Plume of airborne glacial silt from the Copper River Valley in southcentral Alaska
GOES-18 Dust RGB images, from 1300 UTC on 20 October to 1340 UTC on 22 October [click to play animated GIF | MP4]
Strong gap winds accelerating out of the Copper River Valley — located along the coast of southcentral Alaska — were lofting fine particles of glacial silt/sand, and transporting those aerosols southward across the Gulf of Alaska during 20-22 October 2023. 10-minute GOES-18 (GOES-West) Dust Red-Green-Blue (RGB) images created using Geo2Grid (above) displayed the plume of airborne silt/dust (shades of pink) during that 48-hour period.
During the daylight hours on 21 October, GOES-18 True Color RGB images (below) showed the long plume as it curled southeastward across the Gulf of Alaska. The hazy plume of blowing silt/dust could be seen moving down the narrow Copper River Valley before emerging from the coast.
GOES-18 True Color RGB images, from 1640 UTC on 21 October to 0130 UTC on 22 October [click to play animated GIF | MP4]
Surface analyses, from 0000 UTC on 20 October to 0600 UTC on 22 October [click to play animated GIF | MP4]
The strong gap wind flow resulted from a tight coastal pressure gradient as a ridge of high pressure began building across southern Interior Alaska (above), which forced surface winds to accelerate down the Copper River Valley (located northeast and east of Cordova, as seen in the topography image below) toward the Gulf of Alaska.
Topography image centered on the Copper River Valley [click to enlarge]
Prior to sunrise on 22 October, the western edge of the plume briefly drifted across Middleton Island (PAMD), where it reduced the surface visibility to 6 miles from 1300-1500 UTC (below).
Plot of surface report data from Middleton Island [click to enlarge]