Thursday, December 17, 2009

White Christmas update - 6 days until... snow?

Since I published my post 72 hours ago on the possibility of a white Christmas (which I pegged at less than 10%, subsequently disappointing an entire segment of the Mid-South), computer model data has started to coalesce into a possible scenario that seems viable given the weather pattern that we have been "enjoying" the past couple of weeks.

My overall thinking from that last post is essentially unchanged. And, truth be told, I am now more convinced that my statement "we will see a precip-producing low move by to our south within a couple of days of Christmas" is going to be accurate. The fun part is, it looks like the southern stream low that was anticipated around Christmas will actually affect us during the 48-60 hours leading up to Christmas Day. Why is this "fun," you ask? Think about when we typically get snow in the Mid-South... on the back side of low pressure systems or when cold air is already entrenched. In this region, cold air is typically not entrenched ahead of low pressure systems. SOOO.... low pressure moves by to our south (an optimum pattern for winter snow) a day or two before Christmas and drags the cold air in on Christmas Eve or Christmas Day! Any lingering moisture has the distinct possibility of changing to light snow!

Sounds easy, but will it work out that way? While the computer-generated data is starting to support this scenario, we're still 7-8 days out and things can definitely change. You've heard it before and you'll hear it again: the storm track and timing of the arrival of cold air behind it are crucial, as is moisture behind the departing system. For now, my Thursday forecast carries a good chance of rain Wednesday and a "chance of light rain or light snow" Christmas Eve as cold air pours in. The pattern actually holds on Christmas Day as well, so a few flurries on Christmas are not out of the realm of possibility. Therefore, my "less than 10% chance of a White Christmas" is hereby raised to 20%, given that the definition of "White Christmas" is measurable snow on the ground on Christmas Day. The possibility of seeing some sort of snow, flurries to a dusting, on Christmas Eve is a little higher than that.

Only 6 more grocery shopping days... !!!

I'll post more as conditions warrant.

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4 comments:

Hampers said...

I am dreaming of White Christmas. It might snow this Christmas. It was nice going through your blog. Keep it up the good work.

MWN/Erik said...

Thanks for your comment. Yes, we can at least "dream" a little huh? We'll see how it pans out. How does it look in the UK?

--Erik, MemphisWeather.net

Kevin said...

Erik

The link to the NOAA Climate Prediction Center on your forecast page
http://www.memphisweather.net/forecast.html
is incorrect.

You have:
http://www.cpc.ncep.noaa.gov/index.phpl

Should be:
http://www.cpc.ncep.noaa.gov/index.php

MWN/Erik said...

Thanks for catching that, Kevin. Fixed.

--Erik