FIRST COMES THE RAIN

There's a lot of rain in the Southern U.S. and much of it is heading our way. It's a sure bet to hit us Tuesday afternoon and night. Only the details of exact timing and rain amounts are in question. It looks like a nice, cold, soaking rain-just the type to help ease the drought. But it also doesn't look heavy enough to cause a flood threat.

And here's what one of our computer models is showing for 8 p.m. Tuesday (around the peak of the event):

The yellow and reddish colors represent heavier rain, so I expect at least a brief period of downpours.

The area in blue is snow, and you'll notice some of it is dark blue. That represents heavy snow, but it's mostly confined to the northern part of Pa. So, the Poconos could see accumulating snow, perhaps even several inches. Just a bit farther south, and at lower elevations, it should be just about all rain.

THE ARCTIC BLAST

I first had the dramatic drop in temperatures in my forecast from last Tuesday, Nov. 29th. That was Day 10 of our 10-Day forecast. The next day, I had a forecast high of only 39 degrees for Friday, Dec. 9th  — a full 10 degrees below normal. See, we can sometimes be precise in a forecast even TEN days in advance. That's why we are the only ones to do a 10-day forecast every day.

Here is what the Arctic air mass looks like tonight. The coldest air has just moved down into Montana from western Canada, with temperatures near zero:

By the time the arctic air gets here on Friday, it won't be as severe. Here are the temperatures predicted by one model for first thing Saturday morning:

Those are low temperatures in the 20s. But the wind at the time will probably make it feel like the teens. That's quite a change from our mild November.

The unseasonably cold weather should last through the weekend, but it won't be long-lasting….this time. Here's the forecast from the "Best of the Best" that I've described in the past: Ensembles of the European model (the model is run 51 times, and the results averaged):

Those blue and purple colors represent temperatures way below normal on December 15th. It sure looks like December is going to turn out to be a much different type of month than November.

Glenn "Hurricane" Schwartz
NBC10 Philadelphia