WDBJ7 Winter Weather Preview: A delight or another disappointing winter?
ROANOKE, Va. (WDBJ) - Love it or hate it, the winter season is approaching. In fact, some of our mountain communities have already spotted the first snowflakes of the season.
Last year was a complete disappointment for snow lovers with many areas never getting more than an inch for the entire season. Will this year be a boom or a bust?
LAST YEAR’S WIMPY WINTER
We saw one of the lowest snowfall totals in history last year in Roanoke. We had a few systems bring snow, but only one system had enough measurable snow totaling 1.6 inches in Roanoke. Only three other Winters have had lower amounts with a trace of snow recorded in both 1918 and 1919. The highest amounts of snow usually fall in the months of December, January, and February. We do see snow in March and April, but those totals are usually light, unless you recall the Blizzard of 1993.
Here’s how last year’s totals (right) compared to the 30-year average (middle).
|REPORTING SITE||30-YEAR AVERAGE SNOWFALL||LAST WINTER’S TOTAL|
LA NINA LINGERS - AND COULD BE STRONGER
One of the larger influences on our winter weather here in Virginia, and across much of the United States, is the El Niño-Southern Oscillation (ENSO). When the trade winds over the Eastern Pacific strengthen and the sea surface temperatures cool, La Niña develops. NOAA’s forecasters estimate a 95% La Niña will last through this winter and it could get stronger.
When La Niña develops, often the polar jet stream is kept farther to the north over the Pacific NW which leads to cooler and wetter conditions there and quite the opposite for the south. La Niña this year is expected to be a strong one so its influence will likely be significant to our overall weather pattern.
In the past, La Niña winters have not been very fruitful for snow with each nearly each season seeing below average snowfall. In fact, precipitation alone during these winters has been below average. While we could see large snow events in a La Niña winter like we did with the Blizzard of 1996, odds for an active season are low.
La Nina isn’t the only factor which influences the atmospheric conditions. We look at things such as the extent of Arctic sea ice which has been at a minimum this year. This can feed in colder air at times.
Snow cover in Siberia can also play a role. If extensive snow pack occurs, it can actually create an atmospheric warming event as it reflects the sun’s heat off the snow and back into the atmosphere. This can weaken the “polar vortex” or knock loose the colder air at the North Pole, sending it dropping into the lower latitudes. Should it enter at the same time a storm is developing, we could have a slam dunk storm. That happened during the winter of 1996 with a blizzard the struck the area in one of the biggest snows on record during a La Nina year.
Coming up with snowfall totals for a winter forecast is mostly scientific, but there is still a lot of guesswork involved when trying to predict long-range patterns. Even seasoned meteorologists looking at the same data, you’ll still have some disagreements. Given the fact last year was such a bust and there has only been a few other times we’ve had back-to-back winter snow droughts, we are expecting much more than last year. At the same time, a La Nina pattern will likely hold down snowfall amounts just below the 30-year average.
Here’s a look at the region-by-region snowfall forecast.
In Danville, the winter season hasn’t disappointed the past several years. The winter of 2018-19 brought 15″ of snow to Danville. 21″ of snow fell in the 2017-18 winter. Compare that to the 15″ in Roanoke that same year. Danville and Southside is one of the few locations where we’re forecasting above average snowfall.
WHEN CAN WE EXPECT THE FIRST SNOW?
While each year can be drastically different, on average, the first flakes of the season fall in December with the first inch or more of snow coming in early January. However, you may remember the big storm on December 9-10, 2018 that dumped over a foot of snow even before the first day of winter.
Just for fun, we put together our predictions on when we believe the first 1″ of snow will occur.
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