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Posted at 10:30 AM ET, 04/12/2010

Is April snow in D.C. becoming more rare?

By Ian Livingston

* Sun today, chance of rain tomorrow: Full Forecast *


A rare April snow covers the Capitol Grounds. By CWG photographer Kevin Ambrose, April 7, 2007. See archived radar for that day.

Despite the early-April warmth (and maybe to spite people who consider it a four letter word) some snow lovers can't ever get enough. So before we put to bed discussion of snow chances 'til 2010-11, let's take a look at what April typically has to offer metro region snow hounds.

By the books, April provides close to nothing in the snow department. Nonetheless, snow does occasionally stick in April and an analysis of the stats tells an interesting story about its characteristics and long-term trends. One conclusion of my snow analysis is that snow of any consequence (of say, at least an 1") has always been fairly rare in the D.C. area during April. And quite interestingly, another conclusion is that April snow might be a dying breed, at least in the city itself.

Keep reading for an in-depth look at April snow stats... Do you like snow in April?


*There is some discrepancy in the public record on the 1924 storm. The National Weather Service (at Sterling) indicates either 5" (seasonal data) or 5.5" (here and here) on its Web site. For continuity across the article, and in further graphics, I have used the seasonal total of 5" rather than 5.5".

Snow has accumulated during April in Washington, D.C. 20 times since authentic records began at the start of 1888. By comparison, there have been around 150 in March and only 3 in October. Of the 20 events, one began in late March and dropped marginal additional accumulation in April. Another April event (of 1") is noted in the pre-authenticated snowfall records during the winter of 1886-1887.


Surface low pressure develops near the North Carolina coast early on April 1, 1924. Image courtesy NOAA archives.

The month's largest accumulation event occurred near the tail end of the "April-snow heyday" (keep on reading for more on this) when a brief but unusually cold air mass dropped into place ahead of a clipper-type system that eventually re-formed off the North Carolina coast early on April 1, 1924. The storm rapidly developed, heading from North Carolina to Maine by the morning of April 2, and dropped heavy spring snow across the interior northeast. Around 5" of snow fell in D.C. and other parts of the area, with some heavier amounts reported.

Seven other events greater than 1" have occurred in April. But no event since the 1924 storm has been able to surpass 1" in the city. Snow has fallen twice during the same April in only two seasons on record, 1897-1898 and 1906-1907.


*1880s includes some records through 1885.

A comparison of the past five decades and the first five decades of records (post 1880s, since data on the 1880s is quite incomplete) seems to indicate that we are either in a prolonged April snow drought or that April snow is in jeopardy of being moved from the endangered list to the extinct list here in Washington. The 1890s through the 1930s saw fourteen April events.

During the April-snow heyday, when "big" springtime snowfalls were more common, 5 events over less than a decade produced 15.3" of snow from 1915-1924. Every April from 1915 through 1918 featured an event with over 1", two of which were 3"+. By comparison, the last three accumulating snows at National -- all occurring on April 7 strangely enough -- happened in 2007, 1990 and 1972, combining for a paltry 1.2" of snow.


The "return rate", or length between accumulating events, in April has grown as the frequency of events has dropped. 14 events through 1923-24 produced an average wait between accumulating April snow of 3 years. Since 1924, the 6 events have come about once every 14 years. In today's "why is National destroying our snow records world?" it is worth pointing out (yet again) that the downward trend in event numbers showed up prior to the snowfall observation location being moved to the airport during the 1940s.

The story is a little different to the north and west, however. At Dulles (IAD), for example, the frequency of April snow is not much higher than National but it has been able to record 1" or more of total April snow 4 times going back to 1972-73 (while neither National or Baltimore-Washington have done so). April's most notable example (since IAD records began in the 1960s) of the "interior advantage" came during 1990 when IAD recorded 4" of snow compared to National's 0.2" and BWI's 0.1".


In summary, the evidence for declining April snow in Washington is compelling but perhaps inconclusive. Urbanization along with possible climate change effects on the entire globe are all likely playing a role. It is also possible the April snow heyday was a blip, an anomalous period in time when April events happened more frequently simply by chance. Any observation location is of course just one spot on a large map, and late-season events can have numerous micro-scale differences that result in variable snow patterns.

Sources include NOAA daily records, official monthly and seasonal records posted on NWS Sterling's Web site and other NOAA archives like the Daily Weather Maps project. Ian is co-author, with Kevin Ambrose, of the forthcoming "Great Blizzards and Snowstorms of Washington, D.C." The book will be available by late 2010 or early 2011.

By Ian Livingston  | April 12, 2010; 10:30 AM ET
Categories:  Local Climate, Winter Storms  
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Comments

Generally April snow is rather unwelcome; it rarely if ever sticks, and never makes roads slippery enough to cause anything to shut down. Flurries and hail are more common in April.

It's uncertain whether global warming is diminishing the frequency of late-season snows. Even this season has been somewhat unusual. During February we were cold, but the rest of the world seemed to be warmer than usual, except of course some sections of Siberia.

Posted by: Bombo47jea | April 12, 2010 10:51 AM | Report abuse

Bombo, I considered mentioning temperature trends -- or apparent trends -- for April but I'm still pretty much in the beginning stages of dealing with that info so I did not want to go down the wrong path with it. Here is a (smooshed) graph of April high temps from 1872-2009 which seems to show some general warming over the period.

Posted by: Ian-CapitalWeatherGang | April 12, 2010 11:09 AM | Report abuse

Gee, Will Senator Inhoff now not be able to build an igloo in April? Perhaps if he generated less hot air the trendmight be reversed.

Posted by: buckcameron01 | April 12, 2010 2:15 PM | Report abuse

Keep in mind that getting snow here in DC is a lot more than a function of temperature. We have to have the correct weather pattern to set up, as we had several times during the past winter.

Posted by: dcawx | April 12, 2010 9:10 PM | Report abuse

I'd suspect it has a lot to do with urbanization. Up through the 1920s, DC had a lot of empty space. It wasn't until FDR's New Deal in the 1930s that a lot of the Federal Government Bureaucracy came into being, bringing with it the increase in not only population but also concrete and roads.

Interesting post; like the stats.

Posted by: nlcaldwell | April 12, 2010 9:55 PM | Report abuse

I have a copy of the Washington, DC Monthly Meteorological Summary for April 1924. The discrepancy in the snow total for April 1 is because 0.5 inches of sleet was recorded, in addition to 5.0 inches of snow. Today, these totals would be lumped together and recorded as 5.5 inches of snow and ice.

Posted by: rodneysmall | April 13, 2010 11:09 AM | Report abuse

rodneysmall, Thanks for the info -- good to know. There are several similar discrepancies in that timeframe on daily numbers and monthly. I wonder if it's a similar issue in some cases.

Posted by: Ian-CapitalWeatherGang | April 13, 2010 11:34 AM | Report abuse

You're welcome, Ian. In looking at the early reports from the Weather Bureau, snow did not seem to be nearly the big deal it is today, and it can be difficult to determine how much snow fell on a given day, or even during a given storm. For example, I have a copy of the February 1899 Report for the Maryland and Delaware Section of the Climate and Crop Service of the Weather Bureau. That Report records 35.2 inches of snow for Washington, DC in February 1899 (still a monthly record), but does not record how much snow fell during the historic February 11-13, 1899 storm. For that, I had to rely on a December 1988 American Meteorological Society article, which mentions that Washington received 21.0 inches.

Posted by: rodneysmall | April 13, 2010 1:30 PM | Report abuse

rodneysmall, the daily data indicates: .5", 7", 12" and 1" the 11th through the 14th for 20.5. That matches LWX's list for biggest all time. The majority of the "issues" with differing data occur from the late 1910s through the 40s.. A fair number are minor, but a few are large enough to shift data over a month/season a bit... I am assuming the public info on LWX site is the correct though.

Posted by: Ian-CapitalWeatherGang | April 13, 2010 6:47 PM | Report abuse

Thanks for that information, Ian. May I ask where you obtained the daily data? I note that the February 1899 Report states that the snow ended on February 13.

Posted by: rodneysmall | April 13, 2010 8:15 PM | Report abuse

The latest I can remember seeing April snow in the D.C. area was the classic El Nino year of 1983, where a succession of strong April cold fronts brought snow showers and squalls as late as April 30, though little if any actually stuck on the ground.

Posted by: MMCarhelp | April 13, 2010 9:00 PM | Report abuse

rodneysmall, they came from a friend of a friend. From the Northeast Regional Climate Center originally. I pulled up the weather maps for 1899 and created a loop -- sort of crude, but.. I can see how it lasted early into the 14th based on those. Looks like quite a storm for sure.. phasing etc. Not to even mention the cold!

Posted by: Ian-CapitalWeatherGang | April 13, 2010 9:44 PM | Report abuse

Thanks, Ian. In looking at the February 1899 Weather Bureau Report in more detail, snow was reported to have ceased in Washington County, MD at about 7 P.M. on February 13th, and in Baltimore at 11:10 P.M. that same evening, but the Report does not specifically say what time it ceased in Washington. Did your friend rely on some other report or notes that someone took during the storm?

Posted by: rodneysmall | April 14, 2010 9:04 AM | Report abuse

Well, the info I got is the raw output so it would have come from the climate records I'd think. Doing heavy re-analysis of a storm so long ago is difficult but it does appear it would have been the type where we got the upper level energy passing through behind the main system. Maybe some additional snows on the last day (not noted in the report?). I dunno.

Posted by: Ian-CapitalWeatherGang | April 14, 2010 5:17 PM | Report abuse

I can't find any comment regarding snow on February 14th in the February 1899 Weather Bureau Report. Apparently, additional data was recorded about the storm, but it did not find its way into the Report. Do you know whether, in general, there are additional non-public climate records that meteorologists have access to?

Posted by: rodneysmall | April 14, 2010 9:50 PM | Report abuse

I'm not sure what all there is that would be non-public. The dailies are an example I suppose. Though they probably should be public... taxpayers and all! Once I finish working on what I have I will try to make them public in some fashion that is useful.

Posted by: Ian-CapitalWeatherGang | April 15, 2010 6:27 PM | Report abuse

Thanks, Ian. One thing I would be interested in is daily high and low D.C. temperature data back to 1871. The oldest daily temperature data I have is for January 1893. If you know where I can obtain older data, or if you know of someone who has a spreadsheet that has historical D.C. daily temperature data, you can e-mail me at rodney.small@gmail.com

Rodney

Posted by: rodneysmall | April 16, 2010 10:30 AM | Report abuse

The comments to this entry are closed.

 
 
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