Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: TUESDAY, February 15, 1994                   TAG: 9402150107
SECTION: VIRGINIA                    PAGE: B1   EDITION: METRO 
SOURCE: CATHRYN McCUE STAFF WRITER
DATELINE:                                 LENGTH: Medium

RULE: DON'T BET ON WEATHER ICE STORMS MAY HOLD OFF, OR MAYBE NOT

And we probably won't get hit next week.

But McIntosh, chief of the National Weather Service station in Roanoke, draws the line on making predictions past then.

A professional meteorologist for some 30 years, McIntosh knows better than to attempt to divine what the weather gods hold in store.

"Let's face it. Winter's got a long way to go," he said Monday.

Fancy computers and historical trends help meteorologists peer into the future, but the reception is fuzzy.

For instance, the long-range forecast through April shows below-average temperatures and above-average rainfall for our area.

"You're not dealing with a great deal of certainty there," McIntosh notes.

That information comes from weather centers in Washington, D.C., and Charleston, W.Va. McIntosh takes that as a guide and develops five-day outlooks for the region.

On Monday, he leafed through a folder of computer-drawn maps covered with wavy lines and numbers to illustrate what happened here last week. In the second-story office at the old airport terminal, two other meteorologists answered phones, tore off the constant printouts of weather updates, and read the weather from a row of computers, some with blinking colored blobs to show systems and fronts.

Two huge windows lined one wall, the drapes closed. "Afraid we might see something we didn't forecast," McIntosh joked.

For us, the Appalachian Mountains figure prominently in what does or doesn't fall from the sky onto our heads.

Virginia is situated between the cold, dry weather systems that move across the north and the Great Lakes, and the warmer, wetter systems that sweep up from the Gulf of Mexico.

When these two systems collide, we get dumped on.

This is what happened last week - and McIntosh saw it coming Thursday and began alerting airport, highway and other officials.

Picture the Appalachians as a giant fence running diagonally from mid-Pennsylvania, along the Virginia-West Virginia border and into Tennessee and North Carolina.

As the high-pressure system in the north rounds the top of the mountain chain, the arctic winds swirl clockwise down into Virginia, and run smack into that geologic barrier.

"That cold air's like syrup. It doesn't want to move out," said Donato Cacciapaglia, also at the Roanoke weather station. So there it sits, banked against the Blue Ridge.

From the south comes a low-pressure system, moving counter-clockwise. As its tendrils encounter the dense cold-air mass, they sweep up and over the mountains. The warm air rises; droplets form and then fall through the cold syrup.

A recipe for freezing rain. Sleet. Disaster.

As bad as it was - perhaps the worst ice storm in 20 years - it could have been worse, McIntosh said. The Roanoke Valley got three to four inches of sleet - tiny bits of ice that pile up like slush on the ground.

Had it been five degrees colder, the sleet would have frozen on contact. "At that depth, it'd been chaos," he said - like a giant hockey rink.

Because of its position on the mountainous fence between these two competing weather systems, Southwestern Virginia is no stranger to ice storms.

But storms of this severity are rare, so meteorologists are loathe to be specific when asked when, where, and how much.

A final word: Be prepared.