A G4 (Severe) geomagnetic storm watch is in effect for 2 June. A powerful coronal mass ejection (CME) erupted from the Sun the evening of 30 May. The CME is anticipated to arrive at Earth later on Sunday, 1 June. The CME arrival will likely lead to immediate geomagnetic disturbances with the potential for G3 (Strong) levels, and a chance for G4. Conditions will likely intensify as CME progression continues and G4 levels become more possible on Monday, 2 June. Geomagnetic storm levels will likely begin subsiding by Tuesday, 3 June, with G1-G2 (Minor-Moderate) still possible. Confidence in an Earth-arrival component to this CME is good. However, timing and intensity are more uncertain. These watches represent potential based on our best analyses. We will not know the true nature of this CME’s geomagnetic storm potential until the CME arrives at our solar wind observatories located 1 million miles from Earth. Upon arrival at those spacecraft, we will know the magnetic strength and orientation that are very important to what levels and duration of geomagnetic storm conditions are expected to occur. As always visit our website for the latest information and updates.