Without any obvious large-scale patterns influencing the weather, Colorado seems to have returned to a normal winter storm pattern, with wave after wave of Pacific moisture rolling onshore and delivering a steady series of snowstorms across the Northern Rockies.
“The westerlies across the Pacific are strong now and are driving repeated storms into the western mountains. It has not, however, been far enough south to produce snow and rain for the southwest USA, including southwest Colorado,” said state climatologist Dr. Roger Pielke.
Thursday’s storm snarled holiday traffic but also delivered a fresh blast of new snow at all local areas, with 6 inches at Copper Mountain, five at A-Basin, 3 at Breckenridge and 2 inches at Keystone, as of the 2 p.m.
Just across the Divide, Loveland picked up 9 inches for the highest storm total of the day.
Breckenridge weather watcher Rick Bly hasn’t compiled the month-end totals for Breckenridge but December is sure to wind up as the third month in a row with above-average precipitation, the first time that’s happened in quite some time.
As of Thursday morning, snowfall for the month was about 40 percent above average, Bly said. And there’s more snow on the way, with the forecast calling for waves of moisture to roll in every few days, at least through early next week.
“It’s a very progressive, active Pacific Ocean,” said Colorado Avalanche Information Center forecaster Scott Toepfer, indicating that another storm is due Saturday night, with another system ringing in the New Year with fresh powder Monday night into Tuesday. Toepfer said it looks like the jet stream could drop a little further south with that system, bringing heavier snows to the Northern Mountains along with a good blast for the San Juans, where precipitation has been lagging a little bit.
The snowpack at Red Mountain Pass is at about 84 percent of normal, Toepfer said.In general, the southern mountains have been drier than average this season, especially compared with the past few years.
“It’s just the luck of the draw where the storm track decided to stroll this year,” Toepfer said, explaining that the jet stream has just stayed that tad to the north, which means the San Juans haven’t seen the southwest flows coming in from Southern California. The recent series of storms has been originating in the central Pacific rather than the Gulf of Alaska, which means the temperatures have been slightly warmer than average for this time of year.
Looking at large-scale satellite images, Toepfer said there’s a zonal flow beginning in China and Russia and extending all the way across the Pacific before ridging and troughing as it hits the West Coast.
“In that kind of flow, the storms move in fast and move out fast, and there’s not a lot of time for dry slots to form in between,” he said.
The current weather pattern comes close, but doesn’t quite meet the definition of a Pineapple Express, when copious subtropical moisture from near Hawaii hooks up with the Polar jet stream for what can be exceptionally heavy snows. But should the present pattern shift just a little, with storms coming in slightly colder, conditions could resemble the winter of 1983, “when we were tunneling down Main Street (in Breckenridge) to get our mail,” Toepfer said.