Winter can be the most challenging season for truckers. Blizzards, ice storms and deep freezes can slow them down for days, delaying deliveries as well as potentially damaging equipment and freight. The following are patterns that cause extreme winter weather, catching the attention of forecasters.
Lake-effect snow machine
Lake-effect snowfall downwind of the Great Lakes is a common occurrence from late fall through the heart of winter.
The pattern features a sharp, persistent southward plunge of the jet stream over the eastern U.S., aided by low pressure over or near Hudson Bay. Repeated rounds of cold air spill over the relatively warmer waters of the Great Lakes, producing heavy lake-effect snowfall that can persist for several days.
The heaviest lake-effect snowfalls usually occur downwind of the lakes in places like Michigan’s Upper Peninsula; Chicago; Cleveland; Erie, Pennsylvania; and Buffalo, New York. One of the most extreme lake-effect snowfalls on record slammed Redfield, New York, about 40 miles northeast of Syracuse. The town was slammed with almost 12 feet of accumulation from Feb. 3-12, 2007.
One of the most extreme winter weather patterns for the West Coast is the atmospheric river, a narrow plume of moisture that extends from the tropics or subtropics of the Pacific to the coasts of Washington, Oregon and/or California. Storm systems can tap into atmospheric rivers as they plow inland, flooding valleys and dumping several feet of snow in the Cascades, Sierra Nevada and Southern California mountains. Atmospheric rivers develop periodically from fall through early spring, and their intensities can vary from weak to exceptionally strong.
A total of 40 atmospheric river events were documented last season from October 2019 through March 2020. According to the Center for Western Weather and Water Extremes (CW3E), seven of those events were classified as strong. During a high-impact atmospheric river event in January 2017, high elevations in the Lake Tahoe region were slammed with more than 10 feet of snow over a week’s time. More than 2 feet of rainfall flooded low elevations in California.
Ice, ice baby
Major ice storms are among the highest-impact winter weather events for trucking and supply chains. They bring traffic and lives to a standstill for days or weeks, and knock out electricity to widespread areas.
(Image: The Weather Channel)
The typical setup features Canadian Arctic air at ground level that flows into the U.S. Meanwhile, moist air aloft from the Gulf of Mexico overruns the cold air below and rainfall begins. The rain freezes on contact with the ground, in addition to trees, power lines and other elevated surfaces. The result is a large swath of freezing rain and icy conditions that can extend for hundreds of miles.
A major ice storm hit parts of Oklahoma, Kansas and Texas in late October. It produced ice buildup of more than a half-inch, cutting power to more than 400,000 customers. The storm damaged or destroyed more than 1,300 power poles, 1,050 crossarms and 194 transformers.
Forecasters look to Alaska, Canada’s Arctic region and even Siberia for signs of bitterly cold and dry air masses during the heart of winter. When these air masses reach the U.S., they often produce extreme, record-breaking cold snaps.
The frigid air is typically dislodged from these regions when the jet stream bulges northward over western North America. This forces a southward plunge of the jet stream across the central and eastern United States, ushering in subfreezing and sometimes subzero temperatures for several days.
Freight such as beverages and other liquids, chemicals, pharmaceuticals and produce can become damaged if they get too cold. It’s extremely important for drivers to follow protect-from-freeze (PFF) protocols, especially if they have to park for several hours in areas of extreme cold. Also, all drivers should use ample amounts of diesel additive to prevent fuel gelling.
Meteorologists monitor an index called the North Atlantic Oscillation (NAO) when examining the potential for a blockbuster East Coast winter storm, often called nor’easters. The index oscillates between a positive and negative phase to various degrees.
(Image: The Weather Channel)
When the NAO slips into a deeply negative state, the jet stream will dip southward over the eastern United States where it can lock in for a long period of time. This is due to what meteorologists call atmospheric blocking by high pressure near Greenland. The blocking allows intensifying snowstorms to crawl up the Eastern Seaboard rather than move out to sea.
In March 2018 the NAO slipped into a negative phase for about three weeks. Four nor’easters produced blizzard conditions and coastal flooding in portions of the mid-Atlantic and Northeast, stopping truckers and supply chains in their tracks.