The surface model chart displays accumulated precipitation over the last model interval (usually 1, 3, or 6 hours), 1000-500MB thickness, sea-level pressure, and 10 meter wind speeds in knots. The red thickness lines indicate thickness of 540 decameters or greater; blue less than 540 decameters. 540 decameters is often roughly the boundary between precipitation that falls as snow (blue) and rain (red).