You know it’s a strange season when parts of south Texas and Florida area seeing more snow than Fort Collins.
Fort Collins hasn’t seen measurable snow in 35 days. You can blame the abnormally long streak and recent short-sleeve weather on a familiar atmospheric phenomenon that has been unusually stubborn: a high-pressure ridge crouching over the western third of the United States.
That ridge might finally leave us for the eastern Pacific Ocean this weekend, which could mean cooler weather and a dash of snow.
The ridge is nothing new for the Western states. It’s the reason late summer and early fall are often warm and dry in Fort Collins. Like a giant dome stationed over Colorado, the ridge fends off cold fronts and moisture and usually clears out by early October, said National Weather Service meteorologist Todd Dankers.
Except this year it won’t budge.
“That’s what’s abnormal,” Dankers said. “Normally, you’re seeing more active weather as we move into winter patterns.”
The ridge has kept Fort Collins pretty much snow-free since Nov. 7, the last time the city got measurable snow. We’ve had three measurable snows this fall, but two of them were in October. In all, we’ve received less than half the normal amount of snow between Oct. 1 and Dec. 11 — 6.2 inches compared with a normal amount of 15.4 inches, according to 1981-2010 averages from the Colorado Climate Center’s weather station at Colorado State University.
The ridge is also the culprit of this month’s surprisingly warm highs. Through Dec. 12, nine days of December have seen high temperatures of 55 F or more. Normal highs for early December are in the lower 40s, like what we saw for a spell last week.
November was Fort Collins’ sixth-warmest on record. Highs regularly defied historic normals by 10 to 20 degrees, reaching a peak of 77 degrees Nov. 27.
Why isn’t the ridge moving? It’s hard to say, Dankers said.
It’s similarly hard to say whether La Nina, or the cooling of waters in the equatorial Pacific, has anything to do with recent conditions. Dankers added that La Nina is still developing and is “rather weak right now.” Forecasters have predicted that La Nina would bring drier-than-usual conditions to Northern Colorado this year.
Recent weather aligns with seasonal predictions for late fall and early winter.
This weekend and next week could be a different story, though, Dankers said.
Forecasters predict the high-pressure ridge will move by early next week, allowing cooler Canadian air to flow down to the Rockies. The absence of the ridge means snow storms could pass over the area, and the first chance of snow comes Saturday night into Sunday morning.
There could be more snow where that came from if the ridge makes itself at home over the eastern Pacific, Dankers said.
The move would be a welcome development for California, where dryness influenced by the same ridge has contributed to widespread wildfires this month. Same goes for Colorado’s mountain snowpack, which has taken a serious hit because of recent dryness.
As of Tuesday, 10 snowpack monitoring sites hit record lows for this time of year, according to the Colorado Climate Center. Another six locations had the second-lowest snowpack levels ever recorded this time of year.
Several of those records and near-records are in the Colorado River and South Platte River basins. On Tuesday, snowpack in the South Platte and Colorado river basins sat at 76 percent and 62 percent of the averages for this time of year, respectively, according to data from the Natural Resources Conservation Service.
Snowpack is crucial for Northern Colorado’s rivers and water supply.
Fall 2017 measurable snow in Fort Collins
Oct. 9: 1.5 inches
Oct. 30: 0.1 inches
Nov. 7: 4.6 inches
Source: Colorado Climate Center