Sunday(3/16): We reached 42 degrees (15 degrees below average).
Monday(3/17): We reached 28 degrees (30 degrees below average).
Tuesday(3/18): We reached 39 degrees (19 degrees below average).
Today we'll be in the mid to upper 40s, which will be about 10 degrees below average. There has been a large 'wedge' of cold air over Central Virginia for a large part of this week. The meteorological term for this is COLD AIR DAMMING (CAD).
This dome of cold air is usually initialized when high pressure establishes itself over the Great Lakes and brings with it cold arctic air. Its clockwise flow brings air down the eastern seaboard and pits it against the Appalachians.
Below is a profile view, also known as a cross section. Imagine you are standing in Georgia looking north. To the left you see the Appalachians, to the right you see the Atlantic ocean. The cold air is wedged between the two:
(Image courtesy of the Washington Post)
Here's what our temperatures were this morning at 10AM on Wed 3/19/2014:
Check out the colder air over the Eastern Seaboard! The Ohio River Valley is feeling the temperatures that we would normally be feeling if CAD never took place. We have been seeing this all week, and it can be a headache for forecasters. You can also see this at higher altitudes. This next image is the temperatures at about a mile above sea level at 8am on Tue 3/18/2014:
(Image courtesy of Accuweather)
CAD keeps us colder than everyone else, and when enough moisture is provided (like a cold front moving over the Appalachians) we can see lots of snow or wintry precipitation. The half foot of snow we got at the beginning of the week was a result of the CAD interacting with a surface low that tracked up the coast and provided enough moisture for the precipitation.
Thanks for checking this out, and feel free to email me with any questions or thoughts!