Tranquil weather will continue today and Christmas Eve with dry weather and temperatures slightly below the 30 year norms. This will mean highs in the mid 40s both day and morning lows tomorrow in the mid 20s.
The ECMWF model backed off its mega snowstorm solution last night and thus it appears the chances for a historic, major snowstorm have taken a big hit. The synoptic setup remains complicated as we see two to three different pieces of upper level energy that are forecast to interact or not interact with one another over Christmas weekend and it is the exact interaction of these system that will determine who gets what or anything and how much of it. The latest model trends have been for the northern branch of the jet stream to not really interact or phase with the southern stream system, but instead overwhelm the southern stream and thus greatly hinder the moisture inflow from the Gulf and force any low pressure development further east. This scenario would also force the low to slide ENE not N or NNE and thus we would likely see a shorter period of precipitation and also less intense rates for most areas. This scenario would result in light snow amounts on Christmas Day across TN/GA/VA and the western Carolinas, with perhaps a little more in the eastern sections of NC/VA, but no big totals for anyone.
There are still a few members of the GFS Ensemble showing a bigger event similar to what the Euro had been showing, but support for the blockbuster scenario is waning. However, I do think there is still potential for the system to track closer to the coast in perhaps a similar scenario as the 6z GFS and there is plenty of room for this track to shift one way or the other. A shift east would mean less snow for most everyone, and a shift west could greatly increase the snow potential.
Yesterday I outlined my thoughts in that I though the operational ECMWF solution was too extreme, although still in the round of possibilities, and that a further easts track with a less intense storm could materialize. That seems to be what we are heading towards. If you are looking for an idea of how I think the precip totals could look, I actually like the 6z GFS Ensemble mean which you can find on my model page at this link:
This would favor light snows on Christmas Day across the Tennessee Valley and parts of the interior southeast and Appalachian Mountains as well as North Georgia, upstate SC and western NC. Further east there is potential for increased precipitation as the storm strengthens off the southeast coast. This could bring a widespread 2-4 or 3-6 inch type snow event to areas of the piedmont of NC and southeast Virginia if my track verified. I also give credence to the 00z ECMWF solution which would be even a bit wetter for some parts.
There is as I mentioned still plenty of wiggle room with this scenario so stay tuned.
As the storm moves out colder air will pour in behind it and we will see cold mornings on both Monday and Tuesday with lows in the upper teens to low 20s and this could be colder if sufficient snow cover is on the ground. Highs will struggle into low to mid 30s on Monday and stay in the 30s on Monday in the western part of the state and struggle to get to 40 in the Triangle.
It looks like for the first time this month we will see a period of above normal weather as we head towards New Year’s Eve and into the first few days of January. This is because the NAO will slowly rise to only weakly negative levels while the EPO strengthens into a strong positive phase supplying the country with a large supply of mild Pacific air as the cold air retreats north of the border. This will mean slowly moderating temperatures through next week and we could actually be above normal by Thursday with highs in the 50s and possibly into the 60s by New Year’s Eve and Day as a storm system approaches and brings a chance for rain.
However, for cold and snow lovers don’t fret. It appears that the Ensembles of the GFS, ECMWF, and GGEM all support a brief warm up (few days) because the west based –NAO will re-intensify and we may see more ridging in the western US this time around which COULD increase storm chances as we head into early January, because this increased ridging along with the west based –NAO could force s/w’s to dive further south on average, increasing the chances of storms to form in the Gulf.
First lets worry about this upcoming storm. I will post an update this afternoon after I look at the 12z guidance. The 12z NAM is in and does not look supportive of a big event.