Update, 3:40 p.m.: In case you missed it, we have offered our best bet at an accumulation forecast for the region. Follow this link: Wednesday winter storm: Rain to a little wet snow forecast inside Beltway, increasing snow amounts north and west  Original post from 10:03 a.m.  How many readers recall the March 6, 2013, the so-called “Snowquester”? After the storm, and not one of our better forecasts, I wrote: “The best forecast for Snowquester was one we could not issue with a straight face, and one most Washingtonians would have ridiculed: Rain, sleet, and/or snow likely — heavy at times — with snow accumulations of 0-14 inches.”  Right now, the best forecast for Wednesday, the busiest travel day of the year, is something along those lines for the D.C. area – although we expect to be able to narrow it down a bit more this afternoon.  Thus far, we have not yet issued a specific snowfall forecast for the simple reason too many possibilities remain on the table. But, as more information pours in this morning and early this afternoon, we’ll try to offer an initial sense at what the most likely and least likely accumulation outcomes are across the D.C. metro region.  For now, let me share with you some of the forecasts that are out there – which are understandably vague – to give you a sense of the ranges.  The National Weather Service forecast office in Sterling has a terrific Web site in which it comprehensively lays out snowfall possibilities. The only issue you might have with it is that it’s a moving target, constantly jumping around: Visit in a couple hours and it may be totally different from what it is now (we prefer a steadier approach).  For the moment, the information it presents seems reasonable. Here are the odds it assigns for different snow outcomes in Washington, D.C. (percentages are somewhat higher in our colder suburbs to the north and west):  At least one inch: 48 percent At least four inches: 38 percent At least eight inches: 25 percent At least a foot: 12 percent  Its forecast for the most likely snowfall amounts are around an inch or less near the city, 1-3 inches in our colder suburbs, and 4-6 inches in the mountains, per the map below:  But consider its high-end and low-end scenarios, shown below, are 13 inches and 0 inches, respectively.  The National Weather Service’s Weather Prediction Center in College Park has published the map below, with somewhat higher chances of significant snow compared to its sister office in Sterling. It indicates a 60-80 percent chance of a at least an inch in the D.C. metro region, and a rather hefty 40-60 percent chance of at least 4 inches.  A few other outlets have also issued forecasts – which are mostly in the 1-3 or 2-4 inch range around the District, but 3-6 inches or so to the north and west:  Early this afternoon, we’ll put out our initial ideas for amounts. Consider we’re still about 48 hours away from the first snowflakes – which can be an eternity in snow forecasting. Forecasting snow in Washington, D.C. is always challenging and this is a more complicated than usual forecast – probably the hardest since the infamous March 6, 2013 storm mentioned up top. We understand there is, literally, a lot riding on this forecast, so we are committed to taking a careful and thoughtful approach.  Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
Right now, a big range of snowfall forecasts are on the table for Wednesday. Forecast uncertainty is high, but we share with you some examples.