UPDATE: Tue 21 Dec 2010 / 10:30p.m.
Newest model runs continue to suggest a lack of cold air for any significant snowfall with the Thursday-Friday precipitation event.
Sometimes enough cooling can occur within the core of the mid-level trough to overcome marginally cold air, but in general this system lacks sufficient chill for ice crystal formation in the lower cloud layer.
Therefore, unless something radically changes, I'm expecting a cold rain possibly mixing with snow before ending during the day Friday...with no accumulation.
As for rain, the potential exceeds an inch and could approach two in eastern sections. This is due to a moist atmospheric environment, over-running of a frontal surface stalled to our south, and vigorous lift provided by the upper low.
==================Earlier Tuesday post===============
Tue 21 Dec 2010 / 4:30p.m.
A mid-level trough will move our way and generate a cold rain Thursday and into part of Christmas Eve day. We talked about this Monday night, and this system looks to have ample moisture to work with.
So it could be quite soggy with ½” to 1” of rain falling between Thursday evening and Friday afternoon (discussion continues below this map). There's even a chance some of the rain could change over to a wet snow as the upper trough core passes overhead.
However, the air in the lowest few thousand feet above ground level does not look to be cold enough for snow, since most of the cold air will come after the trough has moved away. This means snow falling from higher-based clouds would melt on the way down.
Even if we were to get a period of snow, it would melt quickly and there's very little chance we'll see a white Christmas 2010 in Texoma. If the cold air air arrives sooner than expected, then this forecast would require adjustment.
So I'm saying some wet snow could fall Thursday night or Friday morning, but it probably would not accumulate beyond a light dusting, and it would melt away soon after falling.
The trough will move east by Christmas Eve night, meaning Santa can stow his umbrella during the Texoma leg of his journey. His thick red suit will come in handy against the cold though!
So my outlook for Christmas 2010 in Texoma remains the same: sunny, windy and quite cold.
The persistent cycle of blocking/unblocking/blocking to our east gave this forecast a higher than average chance of being “right” so far out.
However, 10-day forecasts in general are pretty tough to pull off. The “bust” potential is just too high because a small error two or three days out becomes a HUGE error by 10 days.
Here’s Hoping You Have A Wonderful Christmas!
Chief Meteorologist / KXII-TV