Solar Dynamics Observatory satellite image of solar flare (NASA)

UPDATE, 3:30 p.m.: NOAA’s Space Weather Prediction Center (SWPC) just posted the following:

The R3 (Strong) Radio Blackout today at 12:49 EDT (1649 UTC) was accompanied by an earth-directed CME. Hampered by limited observations of the event, SWPC forecasters are now anticipating the passage of the [coronal mass ejection] around 1:00 a.m. EDT, Saturday, July 14. G1 (minor) Geomagnetic Storm activity is expected to then ensue through the rest of the day.

In short, NOAA is predicting minor effects from this space weather event - no major impacts on the power grid or satellites anticipated - although we remind you forecasting space weather is difficult and surprises are possible. Sky watchers in northern U.S. (and high latitudes) may have an opportunity to see aurora late Friday night into early Saturday morning.

Original post, from 2:30 p.m.: A massive sunspot region facing Earth - known as 1520 - has unleashed a large solar flare. NOAA’s Space Weather Prediction Center says the flare is rated an X1.4. This type of flare is considered “strong” and can cause a blackout of high frequency radio communication on the sunlit side of Earth for one to two hours.

It is not yet known whether the flare was accompanied by a coronal mass ejection (CME) - an outburst of particles that can trigger a geomagnetic storm on Earth and damage the electrical grid.

Joe Kunches of NOAA’s Space Weather Prediction Center in Boulder said one of the NASA satellites tasked with watching for solar weather, SOHO, was “on maneuvers” when the flare launched.

That will make the task of predicting the course of any subsequent CME more difficult.

“The home plate umpire wasn’t paying any attention,” said Kunches.

But two other NASA sun-facing satellites, STEREO A and B, were watching.

“It’s now up to the first and third base umpires to see if it crosses home plate” – meaning Earth, Kunches said.

UPDATE, 2:35 p.m.: NASA’s Goddard Space Weather Center said a CME has occurred with the flare. No additional information is yet available.

In addition to possible effects on the power grid, geomagnetic storms can disturb Earth-orbiting satellites and produce aurora - mainly at high latitudes, but into the mid-latitudes if they are strong enough

Another view of the flare (NASA)

NOAA’s Space Weather Prediction Center is closely monitoring this situation.

Related: Are we ready yet for potentially disastrous impacts of space weather?

The X-flare emitted by the gigantic sunspot region falls within the class of biggest solar flares. M-class flares are medium-sized and C-class flares are smaller.

Within each class of flares, there additional size divisions.

For example, X-flares are rated 1-20 (and higher). The present flare, an X1.4, is at the bottom of the scale. So while this is a large, strong flare, it’s not the same as an X20 flare, considered extreme.

NOAA had predicted an 15% chance of a X-class flare today - owing to emergence of the sprawling sunspot region which rotated into view on July 6.

Just how big is sunspot region 1520? blog noted:

[The sunspot] is so wide it stretches roughly 139,000 kilometers across the sun which is about 11 Earth diameters. This particular sunspot is even larger than its predecessor, AR1515, which was visible on the sun last week before it rotated around to the back side of the sun.

US News and World Report said the X-class was the sixth of the year, following one which occurred last week:

On July 6, a similarly sized flare caused no significant problems on Earth. [Today’s] flare, classified as an X1.4, was much smaller than the X5.4 flare that erupted on March 7 and caused temporary outages of military satellites.

(Note: the CME that accompanied the X-class flare last week missed Earth to the south.]

We’ll keep you posted about any new developments with this sunspot region and solar flare.

The Post’s Brian Vastag contributed to this report.