NOAA Forecasts Minor Geomagnetic Storm and Friday Aurora Chance for Far Northern States

A storm-level space-weather forecast does not guarantee a northern-lights display. Still, NOAA’s Space Weather Prediction Center has identified a narrow Friday-night opportunity for observers in the far northern United States, provided the disturbance arrives near its predicted time and local skies stay dark and clear.

The strongest forecast window runs from 10 p.m. Friday to 1 a.m. Saturday Eastern time, equivalent to 7 p.m. to 10 p.m. Pacific. NOAA expects the planetary K index, or Kp, to reach 5 during that three-hour period the threshold for a minor G1 geomagnetic storm.

At G1 intensity, NOAA says aurora is commonly visible at high latitudes, with northern Michigan and Maine given as examples. Viewers farther south face longer odds unless activity exceeds the main forecast. A moderate G2 storm is possible, but it is not the expected baseline; at that level, aurora has previously been observed as far south as New York and Idaho.

Timing is the largest forecast constraint

The Kp index measures disturbance in Earth’s magnetic field on a scale from 0 to 9. Higher values generally correspond to a brighter aurora and an auroral oval that expands farther from the poles. A forecast of Kp 5 therefore creates a plausible viewing opportunity in northern states without promising a broad display across the country.

Three-hour geomagnetic forecasts can be early or late by several hours. That uncertainty is important Friday because the nominal peak does not align equally well with darkness across every U.S. time zone. The forecast period begins after nightfall in the East but overlaps the evening farther west.

NOAA’s broader viewing guidance recommends looking within one or two hours of local midnight, generally from 10 p.m. to 2 a.m. Observers should seek a dark location away from city lighting and find an unobstructed northern horizon. At lower latitudes, any display may remain low in the north rather than filling the overhead sky.

Cloud cover can end the opportunity regardless of geomagnetic strength. The University of Alaska Fairbanks’ Geophysical Institute notes that darkness and at least partially clear skies are basic requirements for seeing aurora. Sunlight and clouds remain the largest viewing obstacles, while dim displays may be easier for cameras to detect than for human eyes.

A fast solar-wind stream is driving the forecast

The expected disturbance comes from a high-speed stream of solar wind associated with a coronal hole, rather than a major eruption from the Sun. Reported solar-wind velocity rose from about 305 to roughly 422 kilometers per second, and enhanced conditions were expected from Nov. 7 through Nov. 9.

Coronal holes can send faster solar wind toward Earth and increase the transfer of energy into the planet’s magnetic environment. As NOAA explains in its aurora guidance, the visible light is produced when accelerated electrons travel along Earth’s magnetic field and collide with atoms and molecules in the upper atmosphere.

The strength of that response depends on more than wind speed. The orientation of the magnetic field carried by the solar wind influences how efficiently energy enters Earth’s magnetosphere, which is one reason a predicted storm can arrive weaker, stronger or at a different time than forecast. NOAA’s bulletin at 00:35 UTC on Nov. 7 reported that no geomagnetic storm had occurred during the preceding 24 hours and listed Kp at 3.33.

Saturday night is expected to remain below storm level, with Kp between 3 and 4. Activity could increase again Sunday, reaching roughly Kp 4.67 to 5 from 1 p.m. to 7 p.m. Eastern. Much of that interval falls in daylight for U.S. observers, reducing its viewing value. A later period from 10 p.m. Sunday to 1 a.m. Monday Eastern is forecast near Kp 4.67, just below the G1 threshold.

For Friday, northern Michigan and Maine sit within the most plausible continental U.S. viewing area under the main G1 forecast. A wider footprint depends on the less certain G2 possibility and even then, arrival time, darkness and a clear northern sky will decide whether observers see an aurora or an ordinary night.

By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.