The GFS, which is one of the long range computer models continues to hint at the possibility of snow though non-accumulating on the morning of Christmas Eve. So I wanted to know why the model was spitting out snow when typically it's hard to get snow when there is no moisture or lift in the snow growth zone and the answer could be icing!!! You can still get ice to form in clouds as long as the temperature within the cloud is not above -4° C and the temperature forecast at 10AM in Birmingham where moisture is 80% in the cloud is -4.2° C. I learned that frozen precipitation will be observed if the saturated cloud layer extends to the surface. In this case, it doesn't 100% so it may be tough for precipitation to reach the ground. Because there is no moisture or lift in the dendritic layer or snow growth layer it will be tough to get snowflakes and so snow grains might be possible if they even reach the ground. It's all about cloud physics!!!
What are snow grains? Precipitation of very small white and opaque grains of ice. The clouds that can produce this type of precipitation are stratus, stratocumulus and perhaps fog. They form in and fall from shallow clouds and are the cold weather equivalent to drizzle. Accumulation is usually light when it comes to snow grains because the lift in the atmosphere is usually weak. The clouds are usually made up of ice and water droplets with some supercooled droplets as well.
Here is a picture of what they look like:
CHRISTMAS EVE OVERVIEW
So with that said, I would say there is a slight chance for central and north Alabama to see some snow grains on the morning of Christmas eve. Obviously the higher elevations stand a better chance and perhaps a coating on elevated surfaces if the GFS model is correct this far out. Ground temperatures will be too warm for the snow to stick and roadways will be just wet for travelers. Not all long range models agree on this scenario. If the EURO model pans out then the chance for some wintry precipitation is pretty much zero. The EURO is slightly warmer and shows much less low level moisture than the GFS. So snow lovers, this is still a long shot for a few snow grains and don't get your hopes up for a white Christmas.
Over time, I'll be monitoring the moisture field closely and the duration of saturation. Also, if any bit of lift develops this could alter the forecast too. Overall, it will be almost impossible for dendrites aka snow flakes to form with this kind of sounding forecast but at a max drizzle or snow grains might develop where moisture extends all the way to the surface and for a long period of time.
SNOWFALL FORECAST VIA BOTH LONG RANGE MODELS:
That's the latest...
Let me know if you have any questions,
Jill Gilardi Fox 6 Meteorologist