If you can believe it, Friday’s high temperatures was only in the 70’s across the lower elevations. What a gorgeous day! However, the brief cooldown will quickly be replaced by yet another heatwave in Front Range Colorado. This one will be stronger and longer than the last. Let’s discuss just how hot it will get, our concerns about new wildfires, and when the heatwave may finally relax.
Key Highlights from This Post:
- A developing stagnant ridge of high pressure will facilitate a resurgence of the heatwave lasting well into next week
- High temperatures in the 90’s to low 100’s likely through at least Wednesday across the Denver-Boulder area
- One aspect of the forecast will help to take the edge off the heat, but not much
- Almost no rainfall is expected during the heatwave, but high-based thunderstorms are a concern to spark new wildfires
- The heatwave will likely relax towards the end of next week
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W
ithin the last week or so we’ve gotten our first taste of persistent summer heat across the Front Range. Even worse, within the last few days, the inaugural bouts of smoke from the inevitable wildfires burning across the drought-stricken western United States have inundated the area. Fires burning in New Mexico, Arizona, Utah and even south of the border in Mexico have contributed to haze and smoke this week in Denver and Boulder. Alongside the drop in visibility and air quality, the sunsets have been stunning several days this week.
The smoky sun setting behind the Denver skyline on June 8, 2021.
A frontal passage late Thursday night ushered in a much more comfortable airmass to most of Colorado for Friday, with some areas sitting 20 degrees colder this afternoon compared to yesterday.
Don’t get too comfortable, though. The reprieve from the heat will be short-lived, something we’ve been talking about all week long. The strongest ridge of high pressure yet in 2021 is poised to develop in the coming days bringing a rapid return of the scorching heat to the Southwest. The ridge axis will slowly slither northward up the spine of the Rockies this weekend, before exploding even further into Canada by early next week. Notice in the 500mb height forecast animation below that this potent ridge begins in Mexico. As it intensifies, the center ends up directly over the Four Corners region early next week. By late Wednesday, the ridge starts to flatten out a little possibly signaling the end (or at least a relaxation) of the impending heatwave. More on this later. Between now and then though, 90’s and even some triple-digit temperatures will be rampant across parts of Colorado.
The one thing that will help the eastern half of the state evade the worst of this heatwave is the positioning of the high pressure center. Model consensus keeps the core of the high closer to the Four Corners region, and maybe even along the Utah/Arizona border. As shown below, this positioning will actually allow for weak northwest flow across the Front Range. This slight northerly component for our winds aloft will help to take the edge off the heatwave when its maximized around the early to middle part of next week.
The below graphic shows forecast temperatures at the 700mb level (near 10,000 feet elevation) which is a good proxy for overall airmass temperatures this time of year (and separates out the day and night cycles). As you can see, the warmest core of the airmass on Tuesday is clustered very closely around the Four Corners with the Front Range area certainty warm, but not the warmest.
So what does this all boil down to (pun intended!)? Well, don’t get the wrong impression. The Front Range is not going to dodge this heatwave. Not by a long shot. The ridge is too strong, too broad, and too persistent. While we’re not expecting any all-time temperature records to be shattered, one or more daily record highs will be on the chopping block as temperatures soar into the upper 90’s next week. Boulder’s record high temperatures during this stretch are shown below in red. The record high on June 16th (Wednesday) seemingly stands as the front-runner to get wrecked. The other days are less likely to eclipse their respective record values, but it’s not out of the question. This type of heatwave will wear on all of us from its duration, more so than shock us with its crippling intensity.
A look at the latest GFS ensemble temperature forecast for the next 10 days is daunting! It’s clear that Denver and Boulder are both staring down the barrel of a long-duration heat event.
Another consequence of this pattern will be persistent dry weather, particularly for western and northern Colorado. Very little if any subtropical moisture will wrap around the high pressure and make it into northeast Colorado. The southern mountains stand a slightly better chance at seeing some spotty storm activity under the ridge. However, with a dry lower atmosphere and landscape blanketed by heat and drought-stressed vegetation, any storms that pop-up will do more harm than help, at least while the heatwave is ongoing. Cloud to ground lightning strikes from largely dry thunderstorms could certainty spark new wildfires given the factors at play here. With this very stagnant and swirling pattern, you can bet that smoke from all the existing and new fires will be recirculated throughout Colorado during the heatwave. If you haven’t checked out our Wildfire Smoke Forecast page, there’s no better time than the present!
Right now it looks like a bulk of the next five days will be hot, dry, and sunny in the Denver Metro area. We wouldn’t place any bets on rainfall at this point, but we are including isolated storm chances both Sunday and Wednesday. Consider yourself lucky if you see a single raindrop in the extended!
Now the more burning question (pun intended!): when will this heatwave break? The GFS model has us believing we could see temperatures drop back into the 80’s perhaps as early as Thursday of next week as the ridge begins to flatten out and “cooler” air sinks southward into Colorado. The Euro model is less optimistic predicting that temperatures might fall into the 80’s by next Friday. There is excellent overall ensemble support for the flattening of the ridge, so we are onboard with these projections. We’re just not sure right now when the relaxation will happen. Will it be Thursday, Friday or Saturday? And when it does happen, will we actually see temperatures drop below 90°F for any meaningful amount of time?
Stay cool! Your best option to beat the heat, as usual around these parts, is to go up in elevation. Have a good weekend!
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Help support our team of Front Range weather bloggers by joining BoulderCAST Premium. We talk Boulder and Denver weather every single day. Sign up now to get access to our daily forecast discussions each morning, complete six-day skiing and hiking forecasts powered by machine learning, first-class access to all our Colorado-centric high-resolution weather graphics, bonus storm updates and much more! Or not, we just appreciate your readership!
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