Trouble late Tuesday ... and beyond

Another round of stormy weather is headed for the Carolinas later Tuesday, and the computers hint at more trouble -- possibly of the frozen variety -- late next week and about two weeks from now.

Some rapid and major changes in our weather will take place over the next 24 hours.

A flash flood watch already is in effect for Tuesday and Tuesday night for Burke, Caldwell, McDowell, Rutherford, Watauga and Wilkes counties in the Charlotte region. Additional watches and warnings are likely Tuesday.

Today, we're locked in a chilly pattern, governed by high pressure off the East Coast. But the seeds of change are visible. The cloud cover that thickened overnight is a telltale sign of the moisture surging into the Carolinas from the Gulf of Mexico.

By later today, low pressure will move eastward from the Arkansas-Texas area. Rain gradually will spread into the Carolinas, falling mostly in the mountains initially but reaching the foothills and Piedmont by later this afternoon.

It will be a chilly rain at first, with temperatures staying in the 40s today and dewpoint readings also in the 40s.

But a warm front on the east side of the low pressure system will move northward Tuesday, crossing the Charlotte area sometime in the morning. That will push our temperatures into the 60s, and the dewpoint temperatures will follow suit.

The Carolinas will be in the warm, unstable southeast side of the low pressure system by Tuesday afternoon and night, and that's where severe weather takes place.

Chris Horne, of the National Weather Service's office in Greer, S.C., says strong thunderstorms and heavy rain are forecast across the Carolinas, with the most likely area for severe weather being in the Piedmont.

"Some degree of thunderstorm wind damage threat -- perhaps even a tornado -- should exist into the night," Horne said.

These likely will be those sneaky severe storms -- the kind we experience in the Southeast during the winter. They move extremely fast, sometimes at 50 mph, and often have little or no lightning to herald their arrival.

And looking ahead? This part of the discussion is based on some GFS computer model projections for Dec. 8-9 and again Dec. 13. The GFS is one of several computer models used by meteorologists for long-range forecasts.

First, an important caveat ... long-range computer model forecasts often don't pan out. The science of meteorology has a tough enough time predicting 24 or 48 hours ahead. Forecasts such as these -- 192 to 264 hours in advance -- are iffy.

But the computers show a pattern of low pressure systems forming over the Southwest and moving across the Southeast and up the East Coast. This is exactly the pattern predicted by a number of long-range forecasters for the winter.

The big questions are: 1. Which path will the storms follow? 2. How much cold air will be in place in the Carolinas?

The storm path is important. If the Charlotte region remains on the north and west side of the storm's center, we're more likely to see cold rain or frozen precipitation. The GFS model has been waffling on the storm expected to affect our area Dec. 8-9, predicting a chance of frozen precipitation one time, then making it a rainy forecast the next. These models are updated a couple times each day.

However, the Dec. 13 storm system has been predicted consistently to remain east of the Charlotte area, putting us at a risk of something frozen.

I mention these GFS forecasts not to sound an alert about an upcoming ice storm. I think the computer models will change a bunch of times between now and then. In fact, the storm might never develop.

But I introduce the topic now, because we'll be dealing with it a lot this winter. Let's see how these long-range forecasts fare.