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A Snowball's Chance in Hell: What Are The Odds Of A White Christmas In Miami?

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This story originally ran Dec. 21, 2012.

Once upon a time, snow fell in Miami.

Seems whenever the weather gets even moderately cold, someone somewhere in South Florida invokes Jan. 19, 1977 -- the day it snowed in Miami.

Not only did the snow make front page news in The Miami Herald, the front page about snow made The Miami Herald Front Pages book

Arnold Markowitz wrote the day's story, the beginning of which reads as follows:

Snow fell Wednesday on Miami.
Flurries of fine snow – now you see it, now you don’t – also fell in Fort Lauderdale, in West Palm Beach and in many other places where that has never happened before.
With snow came record cold and gusty winds. They will remain uncommon South Florida visitors at least through today, when highs will be in the 50s.
Beginning soon after dawn Wednesday, gray clouds of fragile, granular snow blew into Dade County on the skirts of a blustery northwest wind.
It snowed as far south as Cutler Ridge in South Dade, seldom lasting longer than a few minutes, but long enough to dust the palms with a fine, powdery coating.

OK, not exactly an occasion to trot out the sleigh. But there's a modicum of hope in that 1977 flurry -- hope for a white Christmas in Miami.

It's enough hope to get us wondering if you could put a number on how likely (or unlikely) a Miami white Christmas is.

"Less than 1 percent," said Barry Baxter, a meteorologist with the National Weather Service in Miami.

Baxter explained there are two main conditions necessary for snow: cold air and humidity. South Florida is certainly susceptible to unseasonably cold Arctic blasts in the winter.  But "whenever we get the very strong cold fronts," Baxter said, "it pulls out the very dry air, so we usually don’t have the moisture behind these fronts to produce the snow."

Baxter said a whitest Christmas scenario would be a cold front Christmas Eve and maybe some frost for Christmas morning. "You get the frost on the cars, you can scrape it off and try to make a little tiny snowman out of it."

Jeff Masters, chief meteorologist with Wunderground.com, was able to crunch some data for us. 

In an email, he wrote:

There has only been snow in Miami once in 117 years of record keeping, on January 19, 1977 (didn't really accumulate, so I'm not sure even this event qualifies as a white Christmas.)
If we assume that 1 in 117 years that a specific day in the coldest 100 days of winter will get snow, (i.e., Christmas Day), the odds work out to a White Christmas occurring about once every 12,000 years.
That's under the old climate; with global warming, the odds of extreme cold events go way down, so maybe we're talking once every 40,000 years now.
This may be counter-balanced some by the possibility that climate change may cause unusual winter circulations like we saw in the winters of 2009 - 2010 and 2010 - 2011, where the jet stream weakened and sagged far to the south, allowing cold air to spill out of the Arctic and invade Florida.
We also have to consider that once every 300 or so years, we get a climate-cooling eruption like occurred in 1815, when the eruption of Mt. Tambora in Indonesia depressed global temperatures by about 2F for a year. It's too late for an eruption to cool the climate this year and I put the odds of a white Christmas occurring in Miami this year at 1-in-20,000.

Masters noted that there's always the possibility of a nuclear war. The ensuing nuclear winter would give Miami better odds for a white Christmas. Although, that's probably not exactly what Bing Crosby was singing about.