WASHINGTON - Are you still dreaming of a white Christmas? Then sorry to say, this is not the article for you.
It’s hard to deny just how warm this December has been, but let me put it in perspective. The average (1981-2010) monthly temperature for the District of Columbia is 39.8 degrees. Since the turn of the millennium, the District has only seen six Decembers at or below this average with 2010 being the last year.
This December will mark our fifth in a row of above normal temperatures. Through the first half of the month (December 1-15th), the average temperature at Reagan National has been 50 degrees, which would be the warmest of all-time if it remains above 1984 and 1889 averages of 45.6 degrees, and there is reason to believe we just may come awfully close to that number.
Let us take a step back and look at some facts. A typical December in Washington D.C. will see the mercury break the 60-degree mark three times throughout the month. Through just the first half of this month, we have done it a total of seven times. D.C. has yet to fall to the freezing mark in December, and has only done so once through the extent of fall on November 23rd. A brief cold spell is coming for the weekend, but all indications are that this will be short cold event.
It is not winter officially yet, but it is not uncommon for the D.C. area to at least get a glimpse of snow by this point of the season. So far to this point, not even a flake has fallen in the nation’s capital. The last “white” Christmas in Washington D.C. was in 2010 on a cloudy, 36-degree day when a couple of snow flurries brought a light coating to the grassy surfaces in parts of the region. While no snow fell, Christmas Eve and Christmas Day featured over half a foot of snow still on the ground following the December 19th blizzard which brought 15 inches of fresh snow to D.C. while parts of the suburbs were buried in nearly two feet.
In an average year, the National Weather Service gives us about a 10 percent to 25 percent chance of having a white Christmas. What are the chances this year? Zero. Zilch. Nada. The culprit? You guessed it…El Niño.
El Niño has held us in its grasp through the majority of the fall. This year’s El Niño event will likely end up being categorized as the strongest ever observed. While it has weakened a bit since peaking in November, it still remains categorized as a very strong event. The strength of this El Niño is helping to power abnormally strong winds in the upper levels of the atmosphere, and these winds are disrupting the formation of what are known as high latitude blocking patterns. These are areas of upper level high pressure near the polar region, which force the cold from the polar region down into our neck of the woods. The lack of these features is generally keeping the jet stream well to the north, allowing autumn warmth to hold steady when typically we should be seeing more and more pushes of cold air.
For the weekend ahead, get the winter coat ready. Temperatures on Saturday afternoon are only expected to peak in the mid-40s, more typical for this time of year, before the majority of the region falls back into the 20s by Sunday morning.
However, Sunday will be as cold as Christmas week gets. In a similar fashion to this past weekend, the Jetstream heads northward as an area of surface high pressure pushes off the Southeast coastline. Strong southerly flow may make our first full day of winter (Tuesday, December 22nd) a 60-degree day, and there is strong model agreement that by Christmas Eve, parts of the region may in fact once again approach 70 degrees.
D.C.’s record high for Christmas day is 72 degrees from 1964, but even mid-60s would be quite the rare event. Since record keeping began in 1871, only four times has the high temperature on Christmas Day exceeded 65 degrees, most recently in 1982 (70 degrees), which was another very strong El Niño December.
Although Christmas Day is still over a week away and the high temperature may depend heavily upon whether or not there is any rain on Christmas Day (which is not certain at this point), the odds are increasing that anyone living in D.C. under the age of 32 may be looking at their warmest Christmas so far. Hopefully Santa has his t-shirt and shorts ready!