So far this has been the 10thcoldest start ever for December and although we will warm back close to normal over the weekend, more cold is on the way.
We will see temperatures hang in the 30s again today as most areas are getting off to a very cold start with many locations this morning. We will start to see a gradual warm-up tomorrow, and by Saturday we may actually crack 50 again. At the same time, a strong storm system will form in the Tennessee Valley and quickly strengthen as upper level energy dives in and carves out a monster trough over the eastern US. This storm could have a surface pressure in the mid 980s and will be a very strong storm. Model data is nearly unanimous in showing this storm either lifting up the NC piedmont or moving west of the area up the Appalachian Mountains. I am not concerned at the moment for any p-type issues as the precipitation begins; I think we will all start as rain. The track of the low and the strength of the low does however make me worry about the possibility of severe storms especially over the eastern sections of the state. The atmosphere will be very dynamic and if we get enough low level instability, severe storms and tornadoes could be a problem Sunday over coastal sections.
We will also see very strong winds with this storm as the pressure gradient becomes very intense. There will be a very strong push of cold, arctic air behind the storm Sunday evening and temperatures will fall very quickly once the front pushes through. Snow will likely kick up by Sunday evening in the NC Mountains and we could see a prolonged northwest flow snow event for those areas. There is a small chance that the precip could end as snow east of the mountains Sunday evening and night, but it would be very inconsequential and as of now is not likely.
Very cold air will blast in and Monday will likely see our high occur at midnight and it will struggle to get out of the 20s for most areas on Monday with a cold, strong blustery northwest wind all day. The very cold weather will stick around through mid-week before we see some moderation later in the week. As of now it looks to be a dry week, but I am watching for any indication of an overrunning setup for next weekend. The 6z GFS and ECMWF hint at this by day 10.
The overall weather pattern will feature a strong 500mb low over New England, a strong west-based –NAO block over Greenland, and a very strong –AO, as the hemispheric weather pattern becomes very disturbed and amplified, which is not very typical for a strong La Nina winter. When you get a very strong –AO, you want to see where the coldest air in the world goes and it looks like initially it may go to Europe. It will likely be colder than normal in a good part of the US in the 11-15 day period, particularly the mid-Atlantic and southeast, but major arctic cold may stay at bay. However, there are plenty of warning signs showing up including a 1055-1060mb high shown by the models in far northern Canada. All and all it looks like temperatures will be colder than normal through the whole month of December.