A couple of days ago, I poo-poo'd the idea of a White Christmas, mainly because I'm a grinch. OK, I'm kidding. Actually, because at 5 days out, and given our history (no measurable snowfall on Christmas Day in nearly a century), I didn't want to wish-cast in some snow and then have to disappoint everyone by taking it out. It's now 48 hours closer to Christmas and the National Weather Service is jumping on board, as are local media outlets. This morning I had seen enough (from the computer models, not from every other media outlet) to persuade me to put snow chances back in the MWN forecast for Christmas.
Here's MWN's official stance as of this minute... subject to change on a whim. Two pieces of atmospheric energy will split the area Friday night and Saturday - one to the north and one to the south. Their proximity to the metro area (and relative strength) determines our precipitation chances. I now am fairly convinced that most of the daytime hours Friday will be dry. I'm sticking with a 20% chance of rain in the afternoon.
By evening, as colder air moves in, some of the rain could mix with light sleet. Again, minimal amounts are expected, if any. After midnight, the atmosphere moistens up enough to start discussing some accumulation and cold air deepens over the region. I believe we could see a round of light snow between midnight and 9am Christmas Day (Saturday). Depending on the scenario that plays out, it could be a dusting to possibly an inch in the northern areas (say Tipton Co. and north). The image below is a Memphis sounding from this morning's GFS computer model valid Christmas morning at 6:00am. It shows moisture in the lowest ~6,000 feet of the atmosphere (red and green lines nearly touching) and temperatures below freezing in the entire column (red line less than 0 Celsius).
During the day on Christmas, temperatures will remain near freezing and scattered light snow showers will be possible throughout the day. Very little if any accumulation is expected from these snow showers, maybe as much as a quarter to half inch. In all, I'd be surprised to see anyone in the metro area with more than an inch and I believe a quarter to half inch total is much more likely. I am not guaranteeing snow, but I am saying that it looks more likely than it did yesterday.
The last "White Christmas" (snow on the ground Christmas morning) in Memphis was 2004 (2" from a previous day storm). The last time measurable snow fell ON Christmas Day was 1913! Here's to opening presents with flakes falling outside!
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