WASHINGTON STATE — A strong Geomagnetic Storm Watch was issued Tuesday morning by NOAA’s Space Weather Prediction Center, which means there’s a chance to see the aurora borealis across western Washington Tuesday night.

The storm’s multiple eruptions of highly charged solar plasma and magnetic field, each a coronal mass ejection (CME), emitted from the sun on Sunday and arrives and impacts the Earth’s upper atmosphere tonight into tomorrow.

The result will be a chance to see the aurora Tuesday night into Wednesday across western Washington and even down into Oregon as well as eastward into the lower Midwest.

For best viewing, head out of the city, away from the lights and look north. Use the display of your phone to scan the sky, as our cellphone cameras usually can pick up the lights before our eyes.

GALLERY | Northern lights dazzle western Washington skies

Our forecast is for mostly clear skies, but still, some pockets of fog and low clouds may develop around the Puget Sound Lowlands, which may impair visibility in some neighborhoods.

An elevated geomagnetic response may also produce limited and minor effects on some technological infrastructure. Just before 11 a.m. PDT, NOAA’s SWPC reported that a shock associated with one or both of the approaching CMEs had arrived.

Geomagnetic Storm activity is expected to still be present, but weaken into Wednesday night.

What are the northern lights?

Our brilliant aurora shows begin about 93 million miles away on the surface of the sun. At times, a sunspot cluster will erupt into a complex called a “solar storm,” emitting huge bursts of energy in the form of flares and expulsions of magnetic field and plasma. These bursts are known as coronal mass ejections, or CMEs.

The CMEs pull away from the sun and hurl into space. The size, speed, and strength of a CME can vary greatly. CMEs typically arrive at Earth in three to five days, but the fastest have been found to reach our planet in as little as 15 to 18 hours!

Once here, the ejected energy and plasma, and the embedded magnetic field, interacts with our earth’s atmosphere. This disruption results in an exchange of energy from the solar wind into our earth’s magnetosphere, and is known as a ‘Geomagnetic Storm.’

How are solar storm strengths rated?

The Space Weather Prediction Center (SWPC) is part of NOAA (National Oceanic and Atmospheric Administration). The SWPC keeps track of solar flares and geomagnetic storms and has developed a scale similar to those for hurricanes and tornadoes, so as to keep tabs on these disturbances and communicate their intensity to the public.

Part of the scale is based on a ‘K’ index, sometimes called a ‘Planetary-K’ index, stylized as “Kp.” This reading quantifies the horizontal movement in the earth’s magnetic field over three-hour intervals, with 0 being totally calm (marked by green), and five or more indicating a geomagnetic storm is occurring (marked by red). The top of the scale is 9, reflecting an extreme storm.

The colors, intensity, shape, and coverage of an aurora borealis event correlate to the Kp index as such: Kp0 means we might see faint green, from Kp3 we might see some yellows, Kp4 brings pink, Kp5 brings blue and purple, and at Kp8 red becomes part of the mix. Thus, greens are common with lower Kp values, but the blues, purples, and red become visible in only more intense Geomagnetic storms.

In the severe Geomagnetic storm that occurred in May of 2024, SWPC’s planetary K-index showed that the Kp index reached between 8 and 9 in the early morning hours of May 11.

While the Kp index measures the movement in the magnetic field, the overall impacts of a geomagnetic storm, including disruptions to power grids, GPS, and communications systems, are also measured by SWPC, with the ‘G scale.’ The scale goes from G1-G5, with G1 corresponding to Kp5 and G5 to a Kp9.

G5 storms are rare. Until the massive rounds of aurora borealis in May of 2024, a G5 storm hadn’t been observed since 2003. Because severe geomagnetic storms have the potential to affect global navigation satellite systems, scientists work to understand how to improve those systems during such storms.

What do the colors mean?

Green northern lights are by far the most common. They become visible when the oxygen in the lower atmosphere gets excited by the changes in the magnetosphere.

Reds are generally only seen in the higher latitudes (think of all of those brilliant pinks and reds you’ve seen photographed in northern Europe) unless the solar storm is very intense.

Similarly, blues and purples are more rare, and only show themselves in the stronger solar storms. Blue aurora is the result of ionized nitrogen molecules.

The aurora breakout of May 2024 led to the visibility of the entire aurora spectrum in the mid-latitudes.

Spotting the aurora borealis

CMEs—and thus, the resultant “Northern Lights,” are fairly common. Social media has made that apparent, as even photographers in Western Washington (not just Norway and Finland!) are able to capture them several times a year, sharing documentation on X, YouTube, and other platforms. In order to see the aurora borealis, you’ll have the best luck if:

• You are in a remote area: avoid big city light pollution
• The weather cooperates: clear or mostly starry skies are best
• There is a new moon: full moon’s light interferes with the show
• You look north, naturally! (These are the “northern” lights!)

SkunkBayWeather.com sits on a property at the very northern reach of the Kitsap Peninsula, and its north-facing webcams capture the Northern Lights on a regular basis.

However, geomagnetic storms aren’t often strong enough such that the Northern Lights are visible all throughout the United States. The G5 level storm in 2024 resulted in an aurora observed as far south as California and Florida.

Usually at our latitude, only the fainter greens are easy to spot. During the May 2024 solar storm, many Washingtonians were amazed by the waving curtains of pinks and purples in the mix, too.

While the naked eye cannot see the full range of colors in the night sky, personal cameras, including those on mobile phones, were able to capture the brilliant colors of the aurora borealis in Iceland and Alaska, and also right here in Western Washington.

Your camera lens can pick up far more color and light than the lens of your eye, especially if it’s set up with a long exposure. This tip is often communicated by broadcasters and NWS meteorologists, so as to keep everyone’s expectations within reason.