wpostServer: http://css.washingtonpost.com/wpost2

Most Read: Local

Posted at 11:00 AM ET, 02/06/2013

D.C. snow drought: It’s worse than you think


January 27, 2011 — The remnants of D.C.’s last big snow already quite melty one day after it fell. (Kevin Ambrose)
Washington, D.C. has now gone a record 742 days without a 2 inch or greater snow event. We’ve been treated to frequent snow in the air of late, just not any of significance. A truly tormenting tease if you’re longing for snow fun.

And if we examine the winter with the last big snow (2010-11) a bit further, we find that it was not a particularly good snowfall winter either, thanks in part to a lot of very small events and one larger melty one.

So, in reality, we’re now three years removed from experiencing a snow season worth talking about. Perhaps getting that all-time record snow record (56.1 inches) in 2009-10 wasn’t a good thing?

As Jason noted on Monday, we’ve had 6 snow accumulation events (0.1”+ snow) on the winter, yet D.C.’s official snowfall total is an abysmal 1.5”.

That brings us out to an average snow event of just one-quarter inch. Dusting central.


Average snow accumulation per event equals the total of all events that included 0.1” or greater snowfall, divided by the number of those types of events in a winter. In the period since 1888-99, 94 seasons have seen six or more wintry events including snow accumulation and 32 have not. The top-two winter averages are comprised of seasons that had three or four storms. 2009-10’s 6”+ avg came from nine events. (Ian Livingston)

First, let’s start with some good news. If you take an average of the last 30 winters before this one, we can expect about 6.2 accumulating snow events per winter. With at least a handful of weeks left, we’re already there this season! Overperformer?!

Of those seasons with six or more accumulation events, this one is running well below the lowest in terms of average snow amount per event. 1988-89 was closest to our current average, averaging 0.71 inches per event for the 8 events. This biggest “storm” that winter produced 1.2 inches.

This season still has several weeks to go at the least, but even if the next event is a 4 inch snowstorm, we’d only barely get past that 1988-89 mark. A 5 inch snowstorm would catapult us past 2010-11’s similarly pathetic 0.8 inch event average — 12 accumulation events that year, with only Commutageddon being of real note.

If we’re able to hold an event average below 1 inch, it would be the first time in history we’ve had three seasons with that distinction in a row.

The lowest seasonal event averages, 0.1 inch in 1972-73 and 1997-98, both consisted of only one accumulation event. 1926-27 has the closest average to this year (so far) with 0.46 inch per event, out of five events, though the max was more than five times higher this year’s 0.4 inches at 2.2 inches.


The largest snowfall by season since the official observation location has been National Airport. Dark red bars indicate a top-20 D.C. snowstorm. 2009-10 had two such events (December 2009 not shown). The horizontal dashed line is the 5 inch snow mark, one threshold for a Winter Storm Warning in the city. (Ian Livingston)
In the years since snow has been recorded at National Airport, the smallest maximum-event total for a winter came in those tremendously snow-unfriendly times of 72-73 and 97-98, with 0.1 inch each. The highest maximum-event total for the period is the 18.7 inches that fell during the first Presidents’ Day Snowstorm of 1978-79.

Half of the National Airport winters (34 of 68, including this one) have brought what I’ll call “warning snow.” Warnings for snow begin at the 5 inch mark over a 12 hour period, though it can also be verified by 7 inches over 24 hours, or via a mix of hazardous ice and snow. Here, warning snow is a 5 inch snowstorm.

Despite our historic lack of a 2 inch or greater snowstorm, stretches such as the current one without warning snow are not uncommon.

Two others of similar or longer length occurred during the 2000s. At National, there have even been two stretches with 4 winters in a row that did not feature warning snow. One came back in the late 1940s into early 1950s.

Overall, in the last 30 winters D.C. has averaged 0.8 warning events a year, though they tend to clump and come in multiples for years that have them. Snowy 2009-10 had 4. 1960-61 leads the group since the mid-1940s with 5 such events.

Though it might seem hopeless as a snow lover, we’ve still got some prime snowstorm climatology ahead — cough Presidents’ Day 2003 — for good snow. We also can “expect” about five and a half inches on average, from tomorrow through the rest of the season.

Can we get it done before the clock runs out?

By  |  11:00 AM ET, 02/06/2013

Categories:  Latest, Local Climate

 
Read what others are saying
     

    © 2011 The Washington Post Company