DArcyS, you've got the right idea here. The important thing to remember about the North American Monsoon in the US is that it is not so much a "season" as it is a highly variable weather pattern that sometimes or frequently occurs during that season; this is especially true in Colorado, which is on the northern fringe of the northern fringe of the NAM. Globally, the monsoon is the northward shift of the high pressure subtropical ridge, which can result in a complete reversal of prevailing winds in places like India. Locally, the northern fringes of a monsoon pattern will depend on where the nearest subtropical high is and how it interacts with other patterns like the jet stream. Our "typical" monsoon pattern in CO, based on the "typical" location of the high, shifts the winds from easterly to southerly or southeasterly.DArcyS wrote: ↑Wed Jul 14, 2021 7:48 pm Initially I was wondering about snow in relation to the monsoon. If there's a strong monsoon flow, I would "guess" the odds for snow go down, since snow in the summer probably requires a strong cold front from the north. But how does the monsoon interact with northerly fronts? I don't know, I'm not a meteorologist, I don't have access to past weather data, so I can really only "guess."
This map (https://earth.nullschool.net/#2021/06/2 ... ,46.48,895) shows the wind pattern and temperature at the 500 mb level (~18,700 ft) around the time of the snow dusting that spurred this thread. The subtropical high is blocked all the way up over the Pacific Northwest (making it hot and dry there), the winds are totally reversed over eastern Oregon and NorCal, and the jet stream is wrapped around the high (bringing cold, northerly winds south to CO). This is a monsoon pattern, but definitely not our (or anybody's) typical one.
Gambling with weather is dangerous, but I'll buy a drink for anyone who can dig through the historic data on that website and find me an example of late summer snow caused by a typical CO monsoon pattern (that is, southerly or southeasterly winds). Based on the fundamentals, such a scenario should be near enough impossible to call it impossible (at least as far as a physicist is concerned ).