Timing: Light snow will overspread the area from the southwest during the morning tomorrow, increasing in intensity toward evening. The heaviest snow will fall overnight Saturday, tapering off Sunday morning.
Amount: The most likely accumulations in the immediate DC area are in the range of 5-8", although some areas of more than 8" are possible.
CapitalWeather.com chart above, photo © Kevin Ambrose
10am SAT to 2pm: Light snow overspreads the area from SW to NE. Best guess for first flake inside the beltway is around 11am.
Don't be fooled by the widespread sunshine and seasonable temperatures (low 40s) this afternoon. There is plenty of cold air available for this system, so the main risk to the forecast is that the storm will track further east and give less precipitation, rather than mixing with rain in the DC area. There is plenty of moisture available along the Gulf Coast; latest radar shows moderate to heavy rain as far east as western Alabama. Barometric pressure falls along the Louisiana and Alabama coast over the last several hours have been at rates as high as nearly 2 mb/hr, which indicates strong storm development.
The CapitalWeather.com team will be monitoring the storm's progress through the evening, including the model runs from data just now being collected, and posting an update around midnight.