1:15 PM, Thursday, May 21, 2015
For those wondering about the frequent occurrence of clouds and precipitation since the middle of April, the general weather pattern will stay in place into next week, but not every day should be completely overcast. A very persistent atmospheric “trof” in the Southwest has resulted in a storm track from the Southwest to the central plains, with the Front Range region receiving rain and snow with each disturbance that moves through. The storms bring upper level Pacific moisture and draw lots of low-level moisture from the Gulf of Mexico.
The next storm in the sequence will impact the Colorado/Wyoming region this evening through Friday midday (ending from south-to-north on Friday). Almost all areas should get some moderate rain (and moderate amounts of snow above 11,000 feet). There may be a few heavier showers or thundershowers mixed in. Given the wet ground, watch for some minor flooding in localities with the heavier showers.
Much of western Colorado has seen sunny intervals yesterday and today. There is a good chance for some breaks in the overcast Friday afternoon (late afternoon up toward Wyoming) through early afternoon Saturday. But given the moist, unstable conditions, there will likely be redevelopment of clouds and some showers or thundershowers late in the day. Temperatures will probably warm above 60 on Friday and Saturday along the urban corridor, but stay below the average which is around 70.
Saturday night into Sunday may see the coverage of clouds and showers increase as the next atmospheric disturbance moves up from the southwest. It’s too early for high forecast confidence, but most indications currently suggest another lull in activity on Memorial Day before some late-day thundershowers develop.
Many parts of the south-central and Southwest U.S. have had an unusually wet 5 weeks. Some stations in Oklahoma are at the 20-inch mark. Here in Colorado there are some May monthly totals exceeding 10 inches (around Colorado Springs and in northern Weld County). Boulder is up to 6.38″ for the month, and 10.35 inches since April 16th. In the last 65 years there have been three similar periods in Boulder (all centered on May) that were just a little wetter: 1969 (10.74″), 1978 (10.38″) and 1995 (11.36″). And then there is 2013 when 18.17 inches fell in September alone, most of it in 8 days.
On March 16th this year Denver was 81 degrees and Boulder was 80 degrees, both records. That is still the warmest that we have been this year.