After a series of busted snow forecasts last winter, the National Weather Service's Baltimore/Washington forecast office is adjusting its forecasts in the months ahead to better communicate snowfall uncertainty.
Efforts to do so began last year when the forecasters released maps showing bands where various accumulations are likely -- say, an inch or less south of Baltimore, 2-4 inches for the city, and 4-6 inches for the northern and western suburbs. On top of that, forecasters will provide a storm's overall minimum and maximum snowfall potential (i.e., a bust or a blowout) and will give probabilities, in percentages, that snowfall will reach certain benchmarks.
So instead of hearing a best guess of 2-4 inches, you might instead see something like this:
2-4 inches forecast for Baltimore, but be prepared for anything from a trace to 8 inches. Chance of 2" or more: 70 percent. Chance of 4 inches or more: 30 percent. Chance of 8 inches or more: 5 percent.
Storms like one that approached the region March 6 illustrate the art of snow forecasting in this region -- and the frustration some snow lovers feel when the forecasts are wrong. The storm had the potential to dump as much as a foot of wet, heavy snow, causing concerns of power outages and collapsed roofs. But it ended up bringing only rain and gusty winds here.
"Last winter really brought out why this is such an important thing and why this is going to be so good," said Chris Strong, warning coordination meteorologist at the weather service's office in Sterling, Va. Transportation departments and emergency management officials use the weather service's date to inform their preparations, he added.
The problem often lies in a hard-to-pin-down rain/snow line that can shift because of warm ocean air and slight movements in storm track.
"It's not unique to here, but we certainly have a lot of trouble with it here because of the proximity to the ocean," Strong said.
The meteorologists often communicate that information in forecast discussions, sometimes jargon-filled summaries of weather conditions that rarely trickle down in detail to the average person getting their weather forecasts from smartphone apps or TV meteorologists. The added detail in snow forecasts could help ensure appropriate preparation for possible snow storms -- and keep expectations in check.
"There's a lot that goes into it. It's complicated," said Steve Zubrick, science and operations officer at the Sterling office. "We're trying to just acknowledge that there's a range of possibilities."