SPACE WEATHER NOAA Forecasts Solar Flares: Probabilities for a medium-sized (M-class) or a major (X-class) solar flare during the next 24/48 hours are tabulated below. Updated at 2002 Sep 21 2200 UTC FLARE 0-24 hr 24-48 hr CLASS M 50 % 50 % CLASS X 05 % 05 %