Even for mid-summer standards, it’s been an exceptionally hot start to July across Colorado and the Front Range.
Including Thursday, Denver hit 90 degrees or above in eight of July’s first nine days, and was running more than four degrees above average so far this month. Statewide, temperatures were generally running a few degrees above average, especially across eastern and southern parts of Colorado.
And this is likely just the start of a prolonged, long-lived period of searing heat for both Colorado and along the Front Range.
Temperatures are expected to stay in the 90s and 100s across Colorado’s lower elevations through the weekend and into early next week, potentially threatening daily records, even during what’s typically the hottest time of the year. But what stands out about this heat isn’t necessarily the individual daily temperatures themselves. Rather, it’s the longevity of the heat wave that makes this a more unusual event.
Denver’s longest 90-degree streak on record is a 24-day streak back in 2012, according to data from the National Weather Service in Boulder. There have only been 10 different 90-plus streaks of two weeks or longer in Denver’s recorded history, and this current heat wave could well snap that stretch.
For context, Denver’s average high for this time of the year is 89 degrees. And a similar story is in place across much of the rest of the state as well, though temperatures have been slightly cooler as compared to normal in the mountains.
The Climate Prediction Center (CPC) 6-10 and 8-14 day outlooks show temperatures staying well above average throughout Colorado (though with a hotter lean to the southern and eastern portions of the state) into the middle to even end part of the month.
The primary driver behind this long-lived heat wave is a persistent weather pattern. A deep ridge of high pressure remains anchored over the southwestern U.S., driving in sinking air that warms and dries as it falls. Over a prolonged time period, that same ridge leads to more hot and dry air, while simultaneously blocking any chances of meaningful precipitation.
The jet stream is far to Colorado’s north, meaning there aren’t any significant steering currents that could really alter the current pattern. In other words, there’s nothing really that can push along the current stagnant pattern, leaving it in place over the long term.
That ridge of high pressure is driving an exceptionally dry air layer from the middle and upper levels of the atmosphere and down towards the surface. That was recorded in Wednesday morning’s sampling of the atmosphere from a weather balloon launched by the National Weather Service, which recorded a record dry air mass sitting over the Front Range.
That could all have temperatures running well above average through the end of the month. Buckle up: the current heat wave isn’t going anywhere anytime soon.
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