As of Monday morning, thick smoke from numerous large wildfires blankets the Front Range and this will remain the case through much of the week ahead. There will be some improvement in the smoke as monsoonal moisture returns in the coming days alongside late-day storm chances. Let’s run through the weather of the next ten days or so for the Denver Metro area.
This week’s highlights include:
- Thick smoke from numerous large wildfires burning across the west will blanket the Front Range early in the week
- Monsoonal flow will return somewhat as the week progresses leading to rain chances each and every day!
- High temperatures will be near or above normal through the week in the upper 80’s to middle 90’s
- The extended forecast for NEXT week has another strong ridge developing with hot temperatures and monsoon moisture shifting away from our area
DISCLAIMER: This weekly outlook forecast is created Monday morning and covers the entire upcoming week. Accuracy will decrease as the week progresses as this post is NOT updated. To receive daily updated forecasts from our team, subscribe to BoulderCAST Premium.
A blanket of smoke!
The focus for the early part of the week will be the thick smoke present across Colorado which has advected into the region over the weekend. The GOES-East visible satellite animation below shows the plethora of smoke that was present across the area yesterday as it made progress towards the Front Range from the north and west.
Visible satellite animation showing the smoke heading towards Colorado on Sunday, July 11th.
The source of the smoke are numerous large fires burning across many western states and parts of Canada. The Morgan Creek Fire north of Steamboat ignited last Friday and is also a contributor with close to 2000 acres burned already. There are now 55 large wildfires actively burning across the United States, 48 of which are in the Rockies and Pacific Northwest.
Source: National Interagency Fire Center
We begin the week with the highest smoke concentrations we’ve yet seen in 2021 as that blob of smoke shown in the prior satellite animation settles in across most of Colorado. Last night’s sunset was actually disappointing, despite cloud-free skies and thick smoke which are generally a recipe for a “blood red” sunset display. The smoke to the west of town was so thick Sunday evening that the sun completely disappeared with no vivid colors at all (unless you consider milky gray vivid).
Sunset photo taken Sunday night, 7/11/21. Ugly!
Our smoke forecast animation below shows moderate to high smoke concentrations remaining across the region through Tuesday, with signs of some slight improvement possible for Wednesday. While we don’t expect a full resolution of the smoke pollution this week, there are some changes to the weather pattern ahead that will allow for some improvement. More on that in a minute.
HRRR total column smoke forecast animation spanning from Monday morning into Tuesday night
We hate to say it, but we’re definitely in for a long and smoky summer and autumn across the Front Range (which was expected). There is too much drought and too many fires upstream from us to expect otherwise. While there may be temporary improvement from time to time, at minimum a light concentration of background smoke is likely here to stay.
Back to the forecast! For Monday, the Front Range will largely remain dry for one more day as thick smoke sits over the area. Expect mostly sunny conditions, but with smoke clearly visible causing hazy, milky skies. High temperatures are forecast to rise into the lower to middle 90’s. On Sunday the models overdid temperatures,likely underestimating the net cooling effect of the thick smoke. This may be an issue again on Monday, but overall most areas should land between 90 and 95°F across the lower elevations. NowCAST puts Boulder at 93°F.
There is an ever-so-slight chance of a weak shower or storm forming across the Foothills Monday afternoon into early evening. However, given the smoke, these will be extremely isolated and may not actually form as the models are indicating. We put the chance of rain at just 5% for the area on Monday, mainly in the Foothills.
Monsoon moisture slowly rebuilds
This year’s monsoon season for the southwestern United States officially began on July 2nd, the day which Tucson, Arizona had its third consecutive day with daily average dew points at or above 54°F.
The monsoon has been somewhat active across southern Arizona so far, but this has not fully translated to eastern Colorado yet due to less than ideal atmospheric conditions…mainly a broad area of high pressure that has persisted near or just west of the Four Corners. As the week progresses, this high pressure center will finally weaken and slide slowly off to the southwest, as seen in the animation below. With this high pressure exiting, monsoonal flow will become slightly stronger into the Front Range with each passing day this week. Precipitable water values begin around 0.75″ on Monday, but increase to around 1.0″ on Tuesday and then upwards of 1.25″ Wednesday and beyond.
GFS ensemble 500 mb height anomaly forecast animation for Monday through Friday
At the same time the subtropical moisture returns, a series of shortwave systems will scoot across the northern Rockies helping to aid in afternoon storm development. The main wave will pass by Tuesday and Wednesday, but additional shortwaves Thursday and Friday look possible as well. This will spell out elevated late-day storm chances the rest of the week with the potential for heavy downpours. The GFS ensemble precipitation plumes show the daily threat of late-day spotty storms this week, with Wednesday perhaps shaping up to be the most active for our area.
Despite the heavy downpour potential this week, the flash flooding threat appears to be low outside of the burn scars with steering winds generally remaining at 15 to 25 MPH out of the west and northwest. Scattered thunderstorms will be around Tuesday through Friday, with borderline widespread storms possible on Wednesday. For temperatures, generally upper 80’s to lower 90’s will be the norm through the week which is just a few degrees above normal for this time of year.
Looking further into the extended forecast, model ensembles agree that a high-amplitude ridge will build back across the Four Corners or Rockies late in the weekend and persist much of next week.
This pattern will seed the return of another heatwave for the Great Basin, California, and northern Rockies. Though less certain, it should support warmer than normal temperatures here in the Front Range, too. Also, monsoonal flow will be strengthened but suppressed to the south and west leading to drier weather for us. The Climate Prediction Center has our area in the “dry” bullseye of their outlook for July 17th (Saturday) through July 21st (next Wednesday). This extended forecast is obviously bad news, and that’s not even considering that wildfire smoke will certainly be pooling in the center of the high parked across Colorado.
Source: Climate Prediction Center
As we head into the middle to latter part of July, monsoon season for Colorado will be reaching its climatological peak. The coming weeks would normally offer the best chance for western Colorado to see some drought improvement, but also come with the threat of lightning to spark new fires. Monsoon season can be a double-edged sword when drought is widespread, such as is the case now. Precipitation chances typically begin to wane during the back half of summer as the flow of subtropical moisture begins to shut down.
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Forecast Specifics:
Monday: Mostly sunny and smoky with a slight chance of a late-day shower or storm, mainly across the higher terrain. Highs in the lower 90’s across the Plains with upper 70’s in the Foothills.
Tuesday: More clouds with scattered afternoon and evening thunderstorms. Smoke remains thick aloft. Temperatures in the middle 90’s across the Plains with lower 80’s in the Foothills.
Wednesday: Mostly cloudy with numerous showers and thunderstorms in the late-day. Cooler with highs in the middle to upper 80’s across the Plains and middle 70’s in the Foothills.
Thursday: Increasing clouds with scattered afternoon and evening thunderstorms. Highs climb back towards 90 degrees on the Plains with middle 70’s in the Foothills.
Friday: Increasing clouds with widely scattered late-day thunderstorms. Temperatures in the lower 90’s on the Plains and in the upper 70’s in the Foothills.
Mountains: It will be a stormy week in the Mountains with daily chances of afternoon and evening thunderstorms. Chances will be lowest on Monday statewide, but increase considerably Tuesday and beyond with monsoonal moisture returning to the state. As always, plan any Mountain activities with dangerous late-day lightning in mind! Smoke will also be widespread early in the week for sure, and likely late in the week as well. Not only will this create poor air quality for mountain activities, it will limit the views. This may not be the best week to summit any peaks!
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