Quite an eruption has just taken place on the sun. AR 3363 just let off an M5.7 flare, peaking at 0006 UTC (July 18). This image from SDO shows ejecta leaving the blast site:
While we have seen stronger flares recently, this one is special because of its duration. The X-ray flux was greater than M5 for more than an hour, and as of writing this at 0530 UTC, it is still elevated at C6.8. Being such a strong, long duration event, the flare produced a fast and impressive CME.
Unfortunately, as the eruption took place on the west limb of the sun, the CME is not squarely Earth-directed. However, it looks likely that we will receive at least a glancing blow, possibly on July 20 or 21. It is very hard to say at this point how much we will be hit and how much geomagnetic storming will result, but anywhere from a G1 (Kp 5) to a G3 (Kp 7) could be possible.
A moderate S2 solar radiation storm in progress as a result of the M5.7 flare. This is the first S2 storm since 2017! Proton levels climbed quickly after the flare, and could stay elevated even for as long as a day or two. Here's the graph showing the storm:
The red line indicates proton levels streaming past Earth. The sudden rise just after midnight July 18 can be clearly seen. HF radio is being somewhat disrupted in the polar regions, and minor satellite corrections may be necessary.
On top of all this, a G1 geomagnetic storm is currently underway. It seems to be the combined effect of multiple weak CME impacts in the previous days, as well as a small coronal hole high speed stream. While the solar wind speed is slightly elevated at 525 km/s, the other solar wind data is pretty average. This means that the auroral oval is not especially strong, and only higher latitudes will have any chance of seeing the aurora. The latest image from the OVATION aurora forecast shows the conditions in the Northern Hemisphere:
Hopefully this will improve soon with a favourable impact from the latest CME! Updates will follow as necessary regarding the CME trajectory and any impact.
Update July 19 0400 UTC:
NOAA Space Weather Prediction Center (SWPC) has released an updated official CME tracking model. The model forecasts a glancing blow with a estimated arrival time of July 20 1500 UTC. The yellow dot in the center is the sun, the green dot to its right represents Earth, and the yellow/red line indicates the CME, with redder and darker colours standing for stronger solar wind data.
SWPC has issued a G1 (Kp 5) storm watch for July 20. G2 (Kp 6) or greater seems unlikely, but not entirely to be ruled out, especially if the Bz is oriented to the south when the CME arrives.
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