For days, computer models have forecast extreme snow amounts this weekend for the D.C. area.  Given the consistency of the models and a weather pattern conducive for a blockbuster storm, human forecasters are now confident enough to predict excessive snow amounts as well.

[Blizzard watch: Severe snowstorm likely Friday through Sunday]

Generally, the amounts forecast by people are lower than those forecast by the computer.  This is likely because human forecasters understand the climatology and storm history of the region and know how improbable the computer simulations are.  So, bear in mind, the human forecasts may be a little conservative…

Forecasters

Capital Weather Gang: 12-25 inches

NBC4: 10-18″ 

FOX5: 1 foot or more

ABC7: 1 to 2 feet

WUSA9: 1 to 2 feet

National Weather Service: 18-24 inches (through 7 p.m. Saturday, additional snow possible after)

Weather.com: 12-24 inches

Dave Tolleris (WxRisk on Facebook): 12-24 inches

AccuWeather.com: 6-24 inches

Models forecasts

European model: 18-22 inches

GFS: 24-30 inches or more

All GFS ensemble members: Range of 1-3 feet

GFS ensemble mean: 18-24 inches

Canadian: 18-27 inches

NAM model: 18-24 inches through 1 a.m. Sunday

Read more from the Capital Weather Gang

How to prepare for this weekend’s high-impact winter storm

The key characteristics of Washington’s biggest snowstorms

Everything you need to know about snow in Washington, D.C.