The mix-up, some say, may have kept the blizzard of 2016 from breaking into the region’s top three snowstorms on record, based on accumulations. It has also brought into focus the mechanics of how snow depth is counted and has prompted the National Weather Service to announce it will look into the procedures used at the airport.
Mark Richards, senior weather observer at National, stood by the accuracy of the reading Sunday, saying his team did the best it could under tough conditions. But he acknowledged that the team had to abandon the standard measuring process when they lost the tool typically used to tally totals, called a snow board.
“We would like it to be as accurate as possible,” Richards said. “… But it’s an inexact science. Everyone has to understand that measuring snow in a blizzard is a tough thing to do.”
Susan Buchanan, a National Weather Service spokeswoman, said Sunday that the agency would assemble a team Monday to conduct a “comprehensive assessment of how snow measurements are taken” at National and other locations. She said the agency would make suggestions after its review.
The National Weather Service has clear guidelines on how to measure snowfall for one simple reason: Snowstorms have a huge effect on the economy, life and property. They cost millions of dollars. How much snow falls may determine whether additional relief is sent into a location after a major storm.
The timeline of snowfall on Saturday suggests something was askew at National.
At 8 p.m. Saturday, 17.8 inches of snow had been recorded there. Although snow continued to fall until midnight, that was the final measurement that the airport submitted to the National Weather Service.
The measurement reflects a 0.3-inch increase in the three hours between 5 and 8 p.m., during which time light to moderate snowfall was being reported at the airport. It also reflects no additional snow accumulation in the four hours after 8 p.m. Significantly higher preliminary snowfall totals were reported at the region’s two other airports. Dulles International recorded 29.3 inches, while Thurgood Marshall-BWI Airport recorded 29.2 inches. Teams at both of those airports used snow boards.
Still, Richards, who has been monitoring weather at National for 30 years, said the totals were not that far off from areas in nearby Arlington and Alexandria. Near National, a weather observer trained by the National Weather Service reported 19.4 inches one mile northwest of the airport in the Crystal City neighborhood. At the White House, approximately 3.5 miles north, 22 inches were recorded.
Many residents question why Washington’s official weather records are measured at an airport on the river in Virginia, which may not be representative of the weather in the city.
“People use National Airport as the weather centerpiece of the entire region, but it’s the warmest location in the entire region,” said Bob Leffler, a retired National Weather Service climatologist . “It’s just not a good site.”
The blizzard was the snowiest storm on record at BWI, surpassing the 26.8 inches measured on Feb. 16-18, 2003. It was the second-snowiest storm on record at Dulles, coming in just behind Feb. 5-6, 2010, when “Snowmageddon” overtook the region.
The National Weather Service requires that snow be measured with a snow board, which can be little more than a piece of plywood painted white. The board should be placed on the ground before the storm starts in a location that will be undisturbed by drifting. When the storm starts, snow should be measured every six hours, and then the board should be swiped clear.
But once the storm got going Friday night, the board was buried and the observer could no longer locate the board. Instead, he took multiple snow depth measurements and averaged them. This is what was reported to the National Weather Service; it wasn’t snowfall, but rather snow depth.
“Snow boards are the standard to use — when you can use them.” Richards said. “Snow boards are just not effective in a storm that has very strong winds its just going to blow off.”
But without the use of a snow board, the measurement is questionable. Jim Lee, the meteorologist in charge at the National Weather Service in Sterling, Va., said he agrees that if the snow hasn’t been measured by the guidelines, the totals are “perishable.”
Leffler, also the author of the Weather Service snow measurement guidelines, said that depending on the density of the snow, the loss of the snow board may have kept the total 10 or even 20 percent too low. That adjustment would push National’s total past 20 inches.
It also cannot be compared with the region’s other airports.
“I can tell you with 100 percent certainty” that the measurements were performed by the guidelines at Dulles, Lee said. He said he knows this because his office is responsible for those measurements, and they used a snow board and swiped it every six hours.
Jason Samenow contributed to this report.