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Nasty weather gets caught in valleys

| Sunday, March 17, 2013, 12:11 a.m.
Eric Felack
The valleys along the Route 28 Expressway, like this one south of the Pittsburgh Mills mall, can trap cold air, causing roadways to remain frozen longer than surrounding areas.
Valley News Dispatch
Deep valleys along the Route 28 expressway, such as this one seen from the Bakerstown Road overpass in Tarentum, can hold cold air, making the pavement colder than other areas of the highway.
Valley News Dispatch
Higher elevations, with few surrounding hills for protection, are more prone to severe winter weather because they have nothing to block northwestern winds from blowing through. One such area surrounds the Pittsburgh Mills mall in Frazer.

Turns out, you're not crazy after all.

If you're one of the thousands of Valley commuters who use the Route 28 expressway between Springdale and Tarentum and who swear the road and weather conditions there are worse than nearby areas, you're probably right.

Route 28, and other roadways in the region, have a number of peaks and pockets that may experience more severe weather known as “microclimates” that can create havoc for motorists.

Continually problematic, the ridges on Tarentum hill, along Route 28 near the Tarentum and Pittsburgh Mills exits, become slippery faster during snow and freezing rain, because the respective valleys of those hills are colder, many times trapping severe weather.

During serious snowstorms, it is not unusual to see at least a few snow-stalled vehicles flanking the roadsides there.

According to state police at Kittanning, there are accidents in those areas during winter storms, but the accident numbers are not high when compared to other parts of the roadway.

The number of reportable accidents from the Springdale exit (12) to Tarentum's exit (14) are dwarfed by the higher numbers close to Pittsburgh, according to Sgt. Darren Burford of state police at Kittanning.

Any motorist driving that section of Route 28 is aware of road conditions during winter storms, especially salt truck drivers.

“There are always priority areas,” said Rich Staub, 56, of Plum, a PennDOT equipment operator who covers the Allegheny County portion of Route 28.

The ridges and the hollows of Route 28 are among the priorities, as is the Highland Park Bridge, which has the added treachery of being located above not just a body of river, but a dam that creates even more moisture and air movement.

In those areas, PennDOT will overlap driver routes so the more troublesome spots are hit with salt more frequently.

“The level landscape by the (Pittsburgh Mills) mall, where there's no hills stopping the wind, the wind is able to come through and make the road colder,” Staub said.

Low-lying areas, such as in Tarentum where Bull Creek runs under Route 28, holds the cold weather, according to Staub. His salt truck has documented some hollows of Route 28 registering 3 degrees colder than other parts of the highway. PennDOT salt trucks are equipped with thermometers measuring the air temperature as well as the road temperature.

Bernie Salsbery, road foreman for Frazer, said, “I have a friend who works for Cheswick and they won't get a flake there, but I'll have an inch or two inches up on the hill above the mall.”

That's not news to Kay Don Yute, 75, who has lived along Yutes Run Road in Frazer, near the mall, since 1957.

“It could be raining in Harwick and you go up Yutes Run Road and it will be all snow because of the high altitude,” he said.

According to Yute, his property sits about 1,310 feet above sea level, which is on the high side.

The topography of the Appalachian Plateau that surrounds Pittsburgh is generally 1,100 feet above sea level, according to Albert D. Kollar, president of the Pittsburgh Geological Society. The highest areas in Allegheny County are about 1,400 feet.

There are other high points near Route 28, including a hill in Harrison reported at 1,355 feet, according to John Harper, retired chief of the Pennsylvania Geological Survey's Oil, Gas, and Subsurface Geological Services office in Pittsburgh.

The prevailing winds and the terrain of Route 28 can make for some microclimates that can create slick spots in the roads, according to Stephen Cropper, chief meteorologist for WPXI television, a news partner of the Valley News Dispatch.

“Our terrain lends itself to microclimates,” said Cropper.

A microclimate is anywhere you see a change in the weather within a short distance.

For Route 28, Cropper said that because the prevailing winds are from the northwest, “we get a large amount of winter-type weather. With that wind, you get two distinct facts with the terrain: The open area, the ridge area is more exposed, they are going to get more winter weather than the sheltered valleys.”

Then the valleys have their own weather scenario: The temperature is typically colder; the air is heavier and sinks, according to Cropper.

The terrain and topography of southwestern Pennsylvania naturally sets up microclimates that can change even within the same day.

“I think folks who have lived here long understand that if you drive five or six miles, you can have a completely different weather pattern,” Cropper said.

But when forecasting the weather, local meteorologists have to play to all of those weather possibilities, especially when it comes to dangerous winter storms, which are among the most difficult weather patterns to forecast, according to Cropper.

“It only takes a few seconds for someone to encounter something that could be deadly,” he said.

Mary Ann Thomas is a staff writer for Trib Total Media.

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