After the rainfall for many parts of the southeastern US, we can look forward to a change back to more wintry conditions. A very strong Arctic front will pass through the area and move down through the peninsula of Florida tomorrow night into Friday morning. We’ll see an area of light rain develop just ahead of the front, and that precipitation will transition to light snow for areas in northern Alabama, Georgia, Tennessee, northern South Carolina and central and western North Carolina tomorrow afternoon through Friday morning. Some areas(especially higher elevations) should see accumulating snowfall. Light dustings might even accumulate into north central Alabama, and Georgia. Along with the snowfall, we can expect very windy and very cold conditions beginning tomorrow afternoon and gradually moving from northwest to southeast, eventually covering the SE US. Attached is a map from the NAM(North American Mesoscale) computer model which shows the light rain and snow(behind blue freezing line at 850mb, 5000ft) at 7pm tomorrow night. High temperatures for Friday will be in the 30’s and 40’s down into south Georgia, Alabama, South Carolina, Tennessee and North Carolina(20’s in the mountains), and dropping into the 50’s into central Florida. Frost and freeze conditions could reach into north central Florida by Saturday and Sunday mornings. Temperatures should moderate some on Saturday and Sunday, but still remain quite cold. Another clipper type low pressure system should drop down into the Kentucky, East Tennessee and North Carolina areas on Sunday, bringing another chance of flurries and snowshowers.
Next week, the high pressure area bringing us the cold/cool air, will slowly move off of the Atlantic coast. However, as it does, another cold front will move in and the combination of flow around the departing high pressure system and the uplift/moisture from the incoming cold front will bring overrunning into Mississippi, Alabama, Tennessee, and eventually Georgia and the Carolinas, for late Monday night through Tuesday night. As this moisture moves in and the high pressure departs, easterly to northeasterly flow will set up in the favored CAD(cold air damming) areas of the Appalachians, from North Central North Carolina down to NE Georgia. IF the moisture arrives early on Tuesday, the evaporational cooling could lead to freezing rain for these areas, until warm air advection turns the freezing rain to plain rain by Tuesday afternoon. In some insituational CAD scenarios such as this it is extremely hard to scour out the low level cold, and significant icing develops. One other thing to consider is that the computer models often underestimate temperatures related to low level, cold, dense arctic air that funnels down the eastern slopes of the Appalachians. It’s more likely this will just be a very cold rain for these areas, following a brief period of sleet. For the rest of the Southern US outside of the CAD areas, look for a cool rainy Tuesday. After this cool to cold conditions for the remainder of next week.
The longer range looks like we may see a return to milder conditions, as we get into a zonal flow where mild Pacific air flows into our area from January 20-27. I’ll update more on that in the next update. Keep in mind an upper level low pressure system could impact us at any time between now and the end of February, which could bring surprise snowfall. We’ve seen these pop up several times this Fall into Winter. It appears another Stratospheric warming event is taking place in the Arctic regions(upper level temps warm and press lower level cold south), so we should see very cold temperatures the last few days of January and into February.
NAM model depiction for tomorrow night at 7PM. The green area represents light rain transitioning to light snow. Note the blue 5000ft freezing line(credit to Raleighwx.net).
DGEX(extended NAM) model(credit to Raleighwx.net) for 1pm on Tuesday. Green is moderate rain(possibly freezing rain in NC, NE GA, and NW SC). Top map shows temperatures. Notice the 30’s in NC, upstate SC and NE Georgia. This is what an insituational CAD, or cold air damming event looks like. Notice the warmer temperatures all around. The cold air is funneling down into these areas along the east slope of the Appalachians. Typically, these temps will be overstated by a few degrees, considering Arctic air is located to the NE: