After all of the snow and cool weather across Colorado for most of 2019, warmer weather finally returned in time for Colorado’s hottest month of the year.
Will July’s relatively dry and warm weather — Denver, Colorado Springs and Grand Junction all ran over a degree above average in July — continue into August? Early indications are that the rain may return and cooler temperatures along with it.
places most of Colorado as having better-than-average chances of experiencing a wetter-than-average August. Computer models have been hinting at a surge of precipitation to move into Colorado and the Southwest in recent weeks, giving forecasters an extra indication that August could be more active in the Southwest.
“Enhanced odds for above-normal precipitation, albeit with limited probabilities, across the northern and central Great Plains, northern and central Rockies, Missouri River Valley, and much of mainland Alaska are based largely on dynamical model guidance,” in his 30-day assessment earlier in July.
Monsoon moisture, however, is tricky to forecast, especially over a longer-term period like a monthly outlook. Monsoonal showers and storms tend to be hyper-local and hit-or-miss in nature. For example, during the deadly flash flood in Lakewood earlier in July, Denver International Airport barely recorded any rainfall (0.01 inches), a relatively common occurrence in a monsoon-driven storm.
Typically, wetter summertime weather equals generally cooler weather. Cloud cover and the cooling process of evaporation usually combine to limit temperatures during the peak heating hours. Each of Denver’s top-five wettest Augusts on record (1979, 1951, 2008, 1923 and 1991) also each finished with below average temperatures for the month. So if extra moisture is in the forecast, cooler weather may well accompany it.
For the first half of August, there are indications it may be wetter and cooler. places virtually all of Colorado in both the wetter and cooler probability zones. A surge of monsoonal moisture could be responsible for a stormy and potentially cooler spell, and other local meteorologists are picking up on this possibility as well.
Rainfall looks below average (first image) for the next week, but above average during the following week (second image)… Monsoon influence may finally make its presence felt here in during August. We'll see…
— Brian Bledsoe 🐊 (@BrianBledsoe)
Awaiting the seasonal wind flow (monsoon) to kick in enough to bring CO widespread wet weather. Today is a good indication: humidity has increased over Mexico, northern Gulf of CA, and AZ (red shades). It'll take about a week for the humidity to bring much impact to the state.
— Matt Makens, Makens Weather (@MattMakens)
As alluded to above, the monsoon’s moisture has mainly been trapped in northern Mexico and far southern Arizona and New Mexico so far this summer. The monsoon — the annual reversal of winds that helps draw up moisture to the desert Southwest each summer and early fall — is normally approaching peak season by late July and early August. That mostly hasn’t happened yet, though within the last week some surges of monsoonal moisture have started to work deeper into the Four Corners region.
The lack of recent rainfall means that moisture is starting to be needed again in parts of the state, mainly thanks to the slow start to the monsoon season. In particular, southern Colorado, which often feels the brunt of the annual monsoon, is starting to need the rain. Grand Junction, Alamosa, Durango and Colorado Springs are all running below average on rainfall so far this summer.
While it’s not a huge issue yet — Colorado is still fully and officially drought-free — a wet August could help keep wildfires in check for the remainder of the summer and into early fall.
And if early indications are anything to go off of, it’s looking at least promising that meaningful moisture will re-soak Colorado this August.
