an oval-shaped area around the magnetic poles, in which auroras might be visible. Imagine you open the tap on your sink to wash your hands. In the sink, the water usually goes around in a circle before leaving through the drain. Depending how strong and how much water comes out of the tap, that circle changes its shape and size. Something similar happens with the aurora oval. Depending on the amount and speed of particles, the oval changes shape and strength.
NOAA Space Weather Prediction Center has developed a model for the short-term forecast (30 minutes). Colors in the model show the probabilities to see auroras. Of course, it is not a viewing guarantee. Bright green is for about 30-50% and orange-red for over 80% probability. Here is the direct link for both, the Northern and Southern hemisphere.