6 AM MDT, Thursday, September 9, 2021
As if the smoky haze isn’t enough, the high temperatures Thursday and Friday are likely to be near or at record levels. The records for Denver and Boulder both 94 today, and for Friday they are 93 in Denver and 94 in Boulder. The next chance for showers does not get here until Saturday, and then it’s only a very small chance.
For some historical perspective, last year we were experiencing an unusually early occurrence of snow and freezing temperatures on the 8th and 9th of September!
6 AM MDT, Wednesday, September 1, 2021
Moisture from what was once Hurricane Nora in the Pacific has resulted in some locally heavy rain in the desert Southwest. Some more locally heavy rain and flash flooding is possible today in western Colorado, particularly in the San Juans. For the Front Range, the chance for significant rain is smaller. It should be cooler, with some showers or thunderstorms around, but many parts of the Front Range could get through the next couple days without any significant rain that really soaks into the soil.
The good news is that the prevailing southwesterly winds should help lower the smoke concentration in the air for a day or two. The bad news is that the prevailing wind should become more westerly again by Friday, and there is still a lot of smoke being pumped into the atmosphere to our west in California.
For August, the Boulder climate station had 0.68 inches of rain, which is only 40% of the 30-year average. It is the 13th August in a row that is drier than average. No other month has had such a consistent anomaly, either dry or wet. Although there were some local areas that got a heavy thunderstorm during August, the major climate stations in Cheyenne, Boulder, Denver, and Colorado Springs had a drier and hotter August than average.
6 AM MDT, Saturday, August 28, 2021
Have you heard of Hurricane Nora? The weather headlines this weekend will be dominated by Hurricane Ida heading for Louisiana. But the lesser-known Hurricane Nora, on the Pacific Coast of Mexico, may be the one to have some influence on the weather in Colorado. An envelope of tropical moisture associated with the remnants of Nora are forecast to move north into Arizona and New Mexico by September 1st, and possible into Colorado and Wyoming during the period of September 2nd to 4th. That would increase the chances for widespread rain, but more on that in a few days.
Smoke: When prevailing winds are from the southwest, our smoke levels decrease because there is very little wildfire in the Southwest. But today the wind is more from the west, and some of the worst wildfire is to our west in central California. Smoke is already on the increase from Salt Lake to Cheyenne this morning, and that trend is likely to overspread the Denver-Boulder area today. A cold front this evening may help diffuse that smoke a little tonight and tomorrow, but the risk of occasional smoky skies will be with us for a few days.
Cold front: A cold front this evening will make Sunday a cooler day, but hot weather (90 in the lower elevations) is likely to return Monday and Tuesday. There may be some areas of low clouds and maybe some localized showers or drizzle tonight or Sunday morning, but widespread significant rain is not expected. Many areas will probably remain dry.
7:30 AM MDT, Wednesday, August 4, 2021
The stretch of days with moisture in the air is coming to an end as a drier atmosphere will work its way across the region today and stick around through at least the end of the week.
I hope you had a chance to breathe deep this morning. There is still a lot of smoke across the northern Rockies that extends east from major fires in the northwestern United States and southwestern Canada. As the flow across Colorado becomes more northwesterly today, we may see a return to smoky skies. 90-degree days will also make a comeback this week.
5:45 AM MDT, Friday July 30, 2021
A plume of moisture associated with the southwest monsoon has been immediately to our west and is expected to move over the Front Range region later today and into the weekend. In addition, a cold front by this evening should result in some easterly or northeasterly upslope flow in the low levels. All of that means that the chance for showers and thunderstorms ramps up later today. There is a chance for showers to redevelop in parts of the area into the late night or early morning.
Over the weekend expect cooler temperatures than recent days with a better chance than the usual 20%-30% climatology for showers and thunderstorms.
6:45 AM MDT, Wednesday, July 28, 2021
Temperatures in many low-elevation areas are likely to reach the 95-100 range this afternoon and Thursday afternoon. Friday will likely continue the heat wave, but with a small chance of afternoon thunderstorms re-entering the scene, and slightly less hot temperatures. The weekend is expected to bring cooler weather with a much better chance for showers and thunderstorms across the Front Range region.
What is the monsoon?
The Southwest monsoon (sometimes called the North American monsoon or the Mexican monsoon) is not responsible for all summer rain, but it can have a major influence during mid summer. It occurs when numerous thunderstorms along the Mexican Sierra pump lots of tropical Pacific moisture into the atmosphere. By mid July some of the moisture works its way into the American Southwest where it enhances the chances for showers and thunderstorms. In some years that moisture brings one or more periods of enhanced shower/thunderstorm activity to Colorado and Wyoming.
The monsoon has been active in the Southwest (including southern Colorado) this month. This weekend we may see it expand through Colorado and into Wyoming, at least for a day or two. Although there are exceptions, monsoon thunderstorms are not typically known for severe hail or tornadoes. But under certain conditions they can produce heavy rain.
6 AM MDT, Friday, July 23, 2021
It has been a while since I’ve posted, and that’ s because we have been in a typical (and not very interesting) July pattern with a small percentage of the Front Range receiving a late day thundershower and low elevation temperatures reaching into the 90s.
I don’t have any big changes to report, but there is a small change today and Saturday that may increase the chance for a late day thunderstorm, and the extra clouds will probably keep some portions of the Front Range a little below 90. The flash flood watch currently in the foothills is mostly to keep us aware that if a thunderstorm moves across an area recently burned by wildfire, there could be very rapid and dangerous runoff. Thunderstorms are likely to become more scarce again by Monday, along with low elevation temperatures rising back into the 90s.
You may have noticed that smoke haze from western fires is mostly gone. Don’t get too used to that. The fires are still there, it’s just that the wind direction is steering it more to the north of the Front Range region. I’m dreading its return sometime next week.
1PM MDT, Thursday, July 1, 2021
There is plenty of moisture in the atmosphere today, so numerous showers and thunderstorms this afternoon means that just about everyone will hear thunder and get at least a sprinkle. A few locations are likely to experience heavy rain for an hour or two. Be alert for local flooding.
The weekend looks warm with a scattering of afternoon thunderstorms. The chance for rain is less than today, but it might still be good to have a plan B for your outdoor activity.
In the longer range, we may be heading for a hotter, drier period by the middle of next week.
5 AM MDT, Thursday, June 24, 2021
A cool stretch begins today, but really kicks in tomorrow and should last through the weekend. An increased chance for afternoon and evening thunderstorms will accompany the cooler weather.
Today will still be warm, but cooler than yesterday, with more clouds and thunderstorms scattered around in the afternoon and evening. Then for Friday through Sunday the afternoon, maximum temperatures could remain below 80 in the lower elevations of eastern Colorado and southeastern Wyoming. It is very likely that measurable rain will occur at least once at all locations this afternoon through Saturday night, and many areas could see measurable rain more than once. A few spots could even experience a strong thunderstorm.
Although western Colorado won’t cool off as much, less hot weather and small chance for thunderstorms will occur there as well.
9 AM, Saturday, June 19, 2021
As the Little River Band once sang, “time for a cool change.” That change is coming, but it won’t last long.
Today is likely to be another hot day (but not record hot) with a considerable amount of clouds around and some locations getting an afternoon thunderstorm. Sunday will be warm at first, but the cold front may move into southeastern Wyoming and northern Colorado before evening, and then south through eastern Colorado during the evening. There may be a few thunderstorms around during the afternoon, and then a period of low clouds and some areas of drizzle or light rain Sunday night or early Monday. Monday’s high temperatures in the lower elevation may struggle to reach 75. But drier and hotter weather should be back by midweek.
The solstice occurs Sunday, June 20th, at 9:32 PM MDT. That will be just in time for the start of our 36-hour cool spell.
Western Colorado, where the drought persists, will not see much cooler weather or rain from this cold front.