A warning of a geomagnetic storm was issued after three coronal mass ejections (CME) from a huge sunspot had occurred. The National Oceanic and Atmospheric Administration's Space Weather Prediction Center announced that minor geomagnetic storm monitoring is in effect for May 15 and 16.
As a result of the storm, northern parts of the US may be able to see northern lights over the Atlantic the next few nights. A prediction map showing where the Aurors can be visible can be seen below. 
CMEs come from the outer atmosphere of our sun. This is a region with extremely strong magnetic fields. When these fields close, they can suddenly eject matter in a huge explosion – a CME. This matter – sometimes a billion tons of it – is thrown into space and strikes every object it encounters.
When a CME explodes toward Earth, the solar material interacts with atoms and molecules in our atmosphere. The collisions produce polar lights.
The three CMEs responsible for the recent geomagnetic storm came from the Sunspot Group region 2741. The series began on May 10 and the material of the first two is expected to arrive on May 15 Earth on May 16.
"The site of origin for the CMEs has been associated with the disappearance of solar filaments (DSF) along the magnetically neutral line near the unipolar sunspot group, region 2741," states a NOAA statement.
A sinew is a long line of colder substances floating above the solar corona. NASA notes that these filaments can float in this way for days before disappearing. "Sometimes they also launch into space and release in a shower solar material that either rains down or escapes into space and becomes a moving cloud called coronal mass ejection or CME," the space agency noted ,
are temporary regions on the sun's surface that are darker and colder than the environment – about 4,500 degrees Celsius cooler.
According to SpaceWeather, the sunspot that gave rise to the last three CMEs seems to dissolve and is no longer capable of producing large CMEs that pose a greater risk to Earth. When the sun causes large explosions, a strong geomagnetic storm can disrupt GPS systems, satellites and power grids.
The sun is currently in a quiet phase, called the sun's minimum. The activity of the sun increases and decreases every 11 years. The solar maximum, when the activity reaches its peak, increases the number of sunspots. The next solar maximum should reach its peak around 2024.