Northern lights in Oregon: tonight’s chance

Two climates on either side of the Cascades

Oregon's thresholds span less than 0.9 Kp from one corner of the state to another, which is small compared with the gap between a Pacific winter night and a high desert one. The Willamette Valley, where most Oregonians live, collects marine cloud for much of the dark season. Central and eastern Oregon sit in the rain shadow of the Cascades, where the air is drier, the towns are small and the night is dark. The NASA POWER averages show the contrast month by month: in July, Bend is at 24% cloud amount against 39% in Portland in the same month.

What a G3 night looks like here

When the Kp reaches the threshold of a town, the aurora appears low over the northern horizon, a pale glow with a green or reddish tint that a phone camera brings out. Most Oregon sightings are of that kind. Only around Kp 7.6 does the oval itself reach Portland, which happens in the rarest storms. Above a dark horizon, though, the red light from the upper part of the aurora, more than 300 km high, can stand far above the green and stay visible from much farther south, as the colors guide explains.

Timing a storm from the West Coast

Oregon has one advantage over the Midwest on storm nights: it is far to the west. A coronal mass ejection that arrives in the late evening on the East Coast arrives three hours earlier on the Pacific clock, still before midnight in Bend or Portland. SWPC writes its forecast blocks in Universal Time, and Oregon runs eight hours behind in winter, so a block forecast for 06 to 09 UT is 10 pm to 1 am Pacific standard time. The three-night forecast does the conversion and keeps only the dark hours. Plan for a long wait in the cold either way: the peak of a storm rarely lands where the forecast puts it, and the OVATION line of the tool is the better guide once it has begun.

Coast, valley or desert

Astoria, at the mouth of the Columbia, needs about Kp 6.8 and has the ocean to the west, not the north, so the northern horizon there crosses land and river. Pendleton has the lowest threshold of the state in this comparison and the flat wheat country of the Columbia Plateau around it. The Washington page covers the other side of the river, and the Idaho page the high country to the east.