Big warm up in store for the week before Christmas

The first half of December definitely felt a lot like Christmas, with daytime highs running as low as 10 degrees above average.

But for the week leading up to Christmas, we will see thermometers climb into the low 60s, which is 10 degrees above average!

Why the thermal swing? The answer lies with the polar jet, which levels off and retreats northward towards the Great Lakes. As a result, warm and humid air is able to transport back into the Tennessee Valley, and the region basks in the mild air mass.

That’s not to say that Christmas will be abnormally warm: Medium range forecast models indicate that a big dip in the jet returns the weekend before Christmas, sending the region back into a cold air regime. It may not be cold enough to snow, but it will feel festively cool enough for the winter holiday.