WASHINGTON - On Jan. 26, 2011, a moderate snowfall blindsided the Washington area.
The storm wasn't meteorologically unusual or noteworthy. The center deepened at a normal mid-winter rate. Spatially and temporally, it was concentrated and fleeting.
It produced about 5 to 10 inches of snow, no more than an average season's highest single-storm total. But its effects were crippling. The metro area's transportation network was brought to its knees.
Although the federal government was criticized for sending its employees home early during the height of the storm and despite Washington's perceived inept winter weather driving, the coup de grace for the disastrous afternoon commute was the timing and, more importantly, the rate of snowfall.
The storm moved rapidly through central Virginia into the Washington metro area during the early to middle afternoon hours. Heavy sleet quickly changed to snow. The snowfall rates exceeded 2 to 3 inches per hour.
Traffic slowed as highway volume increased and visibility lowered. Then there were accidents. Traffic slowed further. All the while, snow was quickly piling up. Snowfall rates approached 3 inches per hour. Long traffic backups became frozen in place as drivers were shrouded in a thick blanket snow. The plows were unable to clear the snow and the roads were clogged with stranded motorists and abandoned cars.
The storm was the culmination of many factors that paralyzed the region's road network. But the snowfall rate is what transformed the routes with a single bottleneck into one giant parking lot entombed in ice.
A recent example of this phenomenon (on a smaller scale) played out Sunday on Interstate 270.
The snow was heavier than expected northwest of Washington, particularly in Frederick and Washington counties in Maryland where more than 6 inches fell in a short period of time.
A few motorists spun-out at the onset of the snow. Some vehicles slid off the roadway. Passersby stopped to assist those in need of help.
A few minor crashes led to a dramatic slowing of traffic during a short period of very intense snowfall. The skip lines on I-270 disappeared and it wasn't long before two nearly 10-mile-long backups in both the north and south lanes were buried under several inches of snow. Some motorists were stuck for longer than two hours on what would otherwise be a 15-minute drive.
On Tuesday, a quick-hitting round of winter weather is expected to strike Washington during the heart of the morning rush hour. As in 2011, the National Weather Service has offered advance notice. Whether Washingtonians have learned from the mistakes made three winters ago will become apparent soon, perhaps by noon tomorrow.
Morning commuters should plan for the potential of a significant disruption to travel. Those who have the luxury of being flexible should consider revising their morning plans. Unnecessary travel should be postponed until the afternoon when the weather is expected to improve.
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