Low stratus means a stratus cloud quite near the ground. Or other: it means fog who starts some meters above soil. It developes often below wintry inversions, when vertical air interchange is disturbed and humid air can accumulate. Below the upper limit dew point is reached and with lasting inversion low stratus can grow until touching the ground. Out of low stratus drizzle or, if temperatures are below freezing point, snow flakes are possible.