NAM model radar simulation indicates light to moderate rain over Washington, D.C. at 10 a.m. Saturday morning.

Link: Rock ‘n’ Roll Marathon closures, Metro advisories

A little wave of low pressure will zip into the region early Saturday morning. For the race’s start time at 7:30 a.m., rain may not have yet begun, but by around 9 a.m., rain is likely. The rain shouldn’t be particularly heavy, but may well fall steadily between 8:30 a.m. and 1 p.m. or so. Amounts will probably be around 0.1-0.2 inches.

It will be a chilly rain too, with temperatures in the low 40s to begin and only rising into the mid-40s by the race’s conclusion early afternoon.

Winds out of the north and northeast at around 5-10 mph shouldn’t be a major factor.

Here’s a graph showing predicted temperartures, rain, and wind from the National Weather Service during the day Saturday.

For marathon newbies, here are a couple good resources that provide tips for running in rain and cold rain:

Runner’s World: Marathon in the rain tips

New York Daily News: Expert tips for running in the rain