Twenty seven years ago, in the middle of a snowy D.C. winter, a large and disruptive winter storm barreled up the Eastern Seaboard. The system was so immense that snowfall amounts of 8″ or more spanned each of the Eastern states, save for Florida. Across the D.C. area, 10-14″ fell.
Of all the past weather patterns that are drawing comparisons to the upcoming winter storm, perhaps the period surrounding the heavy snowstorm on January 22, 1987 presents one of the closest matches. This doesn’t mean that the event will unfold in exactly the same way, but does mean that we can take a look at one of the most favorable scenarios for snow lovers.
To get right to the point, the January 1987 snowstorm occurred with many of the same features in place that will be present for the Wednesday night-Thursday period: a high pressure system over eastern Quebec, a strengthening storm along or just off the East Coast, and another low pressure center – a weaker disturbance – over the Great Lakes (see image below). The storm that would eventually “bomb out” and become a full-fledged Nor’easter had its lowest pressure at 850 mb (about 1,500 feet above the ground) track just south of the D.C. area. This type of track is usually favorable for an all snow or mostly snow event in and near the city and close-in suburbs. A large amount of lift in the atmosphere, which typically produces heavy precipitation, also helped this storm become a big snowmaker.
Compare these features to the European operational model run’s forecast from Monday morning (below). We have an intensifying surface storm along the coast, high pressure just offshore of Quebec with a second high moving into western Quebec, and a disturbance advancing into the Great Lakes. Last night’s European model run stayed consistent with the placement of these same features.
No, it’s not a perfect match, but it’s close enough to warrant further investigation. The European model (again, from Monday morning) forecast the 850 mb low pressure center to track slightly south of D.C. (see first image below), and the Mid-Atlantic is in a favored area for heavy precipitation (see the blue X on the second image below). Last night’s European model run showed a nearly identical 850 mb low position and jet stream configuration.
Okay, okay. It’s just one pattern that looks similar. Why draw this much attention to it? Well, in looking across the full spectrum of similar patterns (the 15 showing the strongest correlations, anyway), more than half (8 out of 15) have resulted in a storm producing at least 1″ of liquid equivalent precipitation across most of the D.C. Metro Area (see below). A 10:1 snow-to-liquid ratio would translate roughly to 10 inches of snow for every 1 inch of liquid. 12:1 or even 15:1 ratios could be in play, resulting in 12-15 inches of snow per 1 inch of liquid.
Snowfall totals from the January 22, 1987 storm were tightly clustered at the three area airports: 10.8″ at Reagan National, 11.1″ at Dulles International, and 12.3″ at Baltimore-Washington International Thurgood Marshall. Below, I’ve posted the snow accumulation map for the storm. Note the tremendous areal extent of 8-12″ amounts, with a sizable one foot-plus zone embedded within.
There is still some time left to fine-tune our forecast, and we will certainly consult the vast suite of model guidance and other data available to us. If there’s one thing that the January 1987 pattern match (or “analog” in meteorology lingo) and 14 other (among more) similar-looking patterns are signaling, it’s that this storm has a good chance to be a heavy snow event in the Washington, D.C. metro area and surrounding suburbs.