Incoming winter storm could mimic 1987 heavy snow event

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.

Four panel display showing, clockwise from top left, the surface pressure, 850 mb pressure, 500 mb height, and 300 mb wind speed patterns associated with the January 22, 1987 snowstorm. Two important characteristics that supported heavy snow in D.C. were the placement of the low pressure center at 850 mb (see the red L on the top right panel) just south of the city and the Mid-Atlantic's location within an area of strong lift at the jet stream level (see the red X on the bottom right panel; rapid rates of lift result in heavy precipitation). (St. Louis University's Cooperative Institute for Precipitation Systems; modified by author)

Four panel display showing, clockwise from top left, the surface pressure, 850 mb pressure, 500 mb height, and 300 mb wind speed patterns associated with the January 22, 1987 snowstorm. Two important characteristics that supported heavy snow in D.C. were the placement of the low pressure center at 850 mb (see the red L on the top right panel) just south of the city and the Mid-Atlantic’s location within an area of strong lift at the jet stream level (see the red X on the bottom right panel; rapid rates of lift result in heavy precipitation). (St. Louis University’s Cooperative Institute for Precipitation Systems; modified by author)

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.

(MDA Information Systems LLC, Weather Services; modified by author)

(MDA Information Systems LLC, Weather Services; modified by author)

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.

Both forecast graphics courtesy of MDA Information Systems LLC, Weather Services (modified by author)

Both forecast graphics courtesy of MDA Information Systems LLC, Weather Services (modified by author)

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.

The top 15 pattern matches and their associated storm's liquid equivalent precipitation amounts. Dark blue shading (first shade of blue) marks at least 0.5", while the third shade of blue (hard to see, I know!) marks at least 1". The purple shading marks at least 1.5". Only one of these storms (the top right panel) can be considered a "light" precipitation event (less than 0.25"). (Saint Louis University's Cooperative Institute for Precipitation Systems)

The top 15 pattern matches and their associated storm’s liquid equivalent precipitation amounts. Dark blue shading (first shade of blue) marks at least 0.5″, while the third shade of blue (hard to see, I know!) marks at least 1″. The purple shading marks at least 1.5″. Only one of these storms (the top right panel) can be considered a “light” precipitation event (less than 0.25″). (Saint Louis University’s Cooperative Institute for Precipitation Systems)

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.

(Saint Louis University's Cooperative Institute for Precipitation Systems)

(Saint Louis University’s Cooperative Institute for Precipitation Systems)

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.

 

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