The first snows that fell at and above treeline earlier this week have disappeared on all but the highest north faces. Cold nights and warm dry days under high pressure are left in the wake of the first storm system. The first hard frosts have triggered the leaves to stop producing chlorophyll, changing their color from green to yellow and red. This change is right on schedule with the average peak in color during the third week in September.
A weak, broad closed area of low pressure slowly moved across the State last week, cooling the atmosphere with days and nights of steady rains. Precipitation totaled from 2-4in. over parts of Central Colorado. During the week the snow level decreased, as winterlike air touched elevations from 14,000′ down to nearly 12,000′ Sunday night. Today we found a couple inches of snow above 13k’ during a Labor Day hike.
Lower down the Aspen leaves are turning a shade of green only seen on dime sized new leaves in Spring and full sized healthy green leaves showing a hint of yellow during the last days of Summer.
The first major warmup of the season came during the second week in April. The dry chinook winds descended off the mountains and warmed temperatures in the city to nearly 80 degrees. Small hints of Spring were appearing as a few of the flowering trees were beginning to show their colors.
To the west, in the high valleys, temperatures were in the 60s for the first time since late October.
Above treeline, there was a patchwork of conditions depending on aspect and elevation. On Friday a strong west wind above 12000′ kept the surface of very high S faces cool due to evaporational cooling, while the sun kept them soft and skiable.
Loveland’s 5am snow report was a big goose egg. By 6 the moist westerly flow had picked up and snow was falling. Convective showers moved through during the day adding snow the the already softening surface. At about 3pm a piece of convective energy passed right over the western edge of Clear Creek County dumping nearly 4 inches in just over an hour. Here’s a short point-of-view of the last run of my day. Enjoy!
During the past two days, relatively warm moisture laden air was carried by a 140kt jet stream from the Pacific Ocean north of Hawaii inland across the Sierras and through the Great Basin. The snowfall that resulted began falling in temperatures that were 20 degrees warmer than average for late-January and was wet and dense. The falling snow dried out as the temperature gradually dropped throughout the day creating “right-side up” powder. Many people that have skied this perfect snow also call it “hero” snow!