Saturday, December 12, 2015

Christmas Day weather in Memphis – What does history tell us?

Undoubtedly one of the most common questions meteorologists get during the holiday season: “Any chance of a White Christmas this year?” That is no less true here in the Mid-South where a significant snowfall at any point in the winter season can be a unique (and disruptive!) event. Fortunately, thanks to a lengthy modern weather record available for Memphis that dates back to 1875, we have a pretty good idea just how likely a White Christmas is, at least statistically speaking. As you'll see below, and probably as you were already expecting, the odds are not in snow lovers’ favor!

Before jumping ahead to our chances of a White Christmas, here are some temperature statistics for Christmas Day in Memphis, thanks to data compiled by NWS Memphis and the National Climatic Data Center. The coldest Christmas Day in 138 years of records was in 1983 as a major Arctic air outbreak was gripping much of the nation. The high in Memphis that day was a mere 16 degrees after a bone-chilling morning low of 0! No snow that day, though it was plenty cold enough to support it!

High/low temperature map Christmas morning 1983. Brutal cold dominated the nation along/east of the Rockies except south Florida.
On the flip-side, the warmest Christmas Day in the records was in 1889 where the temperature reached a balmy 76 degrees after a mild low of just 63, a month that ended up by far the warmest December in Memphis history. When you average it out over nearly 140 years of records, a seasonable Christmas Day isn't too bad - with a high temperature of 48 degrees and a low near 33 degrees and skies that average partly cloudy to partly sunny at worst.

In terms of any type of precipitation, measurable amounts (0.01” or more) have fallen on Christmas Day 36 times. The vast majority of those years featured just liquid rainfall in mainly light amounts, but one major soaker occurred in 1987 when 4.24” of rainfall was reported at Memphis, following an equally soggy Christmas Eve. Some Mid-South residents spent that Christmas dealing with flooding, the hardest hit of those in West Memphis, AR where cleanup was still underway after a destructive F3 tornado just 11 days earlier on December 14 (link). Sleet or freezing rain has been reported on Christmas Day a handful of those times, but just trace or light amounts.

Now the statistic you most want to know. Just how likely (or unlikely!) is a White Christmas in Memphis? The answer definitely lies on the “unlikely” side of the equation; in fact it’s more appropriate to label a White Christmas in Memphis as exceptionally rare. Only once in nearly 140 years of records has measurable snowfall occurred. That was in 1913 when 3.5” of the white stuff made for the sole exception to the rule we still consider today. However, there have been several other years where snowflakes have been seen in the Memphis skies on Christmas Day but with no accumulation. The most recent was in 2012, a year where Memphis just barely missed an all-out blizzard that hit parts of Arkansas on Christmas Night, with around an inch of snow falling the morning after Christmas in Memphis.

Listing of all recorded snowfalls on Christmas Day at Memphis International Airport

Officially, the National Climatic Data Center considers any city to have a “White Christmas” if at least one inch of snowfall is on the ground on Christmas morning, no matter when that snowfall occurred. Using this definition, Memphis does have a few additional years it can add to that list. Those include 1962, 1963, 1998, and 2004, in addition to the 1913 snowfall that occurred on Christmas Day. 2004 is likely the most remembered as the city had around 2” of a sleet and snow mixture covering the ground following a winter storm on December 22. Long-timers of the Memphis area may even better remember the historic Memphis snow of December 22, 1963. 10” of that 14.3” snowfall total still lay on the ground that Christmas morning!
Official "White Christmases" in Memphis, which had at least 1" of snow on the ground.

NCDC's "White Christmas" probabilities for the US (greater than 1" of snow on the ground Christmas morning)
When considering the NCDC criteria, the odds of a White Christmas in Memphis - with at least 1" of snowfall on the ground - end up at around 3.6%. Slightly better than the 0.7% odds if you only consider measurable snowfall on Christmas Day itself! Either way, clearly the odds don't fall on your side if you're looking for a White Christmas and want to spend the holiday in Memphis. Perhaps one Christmas soon we'll be able to make a new exception to the rule! Until then, average expectations for any given year would indicate a cool, but not cold, Christmas Day and at best modest chances of precipitation, which almost always falls in liquid form.

Top Image is "Graceland Christmas" by Thomas Kinkade, borrowed from artofthesouth.com.

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