With the exception of a weak cool front around midweek, it’s all about a high pressure ridge that will keep us warmer than average and dry with virtually no clouds until the weekend. We are also keeping an eye on the wildfire smoke over the Pacific Northwest and discuss when it may return.
This week’s highlights include:
- Temperatures above average through the week in the 80’s to near 90
- Weak cold front Wednesday potentially brings down some wildfire smoke
- Very dry week with little in the way of clouds
- Watching a weekend storm system to cool us down into the 70’s early next week
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.
Keeping an eye on the wildfire smoke
Yesterday the wildfire smoke and haze was quite evident on satellite imagery. Below shows the visible satellite image from yesterday afternoon. With high pressure in control over Utah, the smoke and haze was rotating around the high, over California, Oregon, Washington, Idaho, Montana, Wyoming, and the Dakotas. The smoke is a little difficult to see, but is visible as a light grey color that appears milky (highlighted in the yellow boxes). Note over Colorado the state is quite sharp and well-defined, indicative of more “clear” conditions and better air quality.
That's a lot of smoke circulating around the high pressure across the West! Eventually it will get back to Colorado later this week. For now, though, air quality remains surprisingly good! #COwx #Smoke #CAwx pic.twitter.com/XzaHVoaLdY
— BoulderCAST Weather (@BoulderCAST) September 13, 2020
As we go into the week, the high pressure will largely remain in place. However, a weak cold front will slide down into the state late tomorrow night into early Wednesday. That should allow the smoke over Montana (below) to unfortunately build back into the Front Range. Time will tell whether it sticks around for the latter part of the week and upcoming weekend. There is poised to be a developing system on Friday and the weekend, which could additionally bring in smoke from California. Regardless, today and tomorrow should experience good air quality with any smoke across the area being high up in the atmosphere with clear surface conditions.
Ridge dominates much of the week
As mentioned briefly a bit earlier, we’ve got no snow for you this week as a ridge of high pressure will largely control the weather pattern over Colorado for this last full week of summer. As of this afternoon, its position will be over the state (below). This will keep us in that warm and dry pattern, with temperatures above average in the 80’s to the lower 90’s.
Soon-to-be Hurricane Sally over the Gulf of Mexico is projected to make landfall near eastern Louisiana on Tuesday. This would be the second hurricane already this season that has impacted that state.
Very dry air is quite visible in the below precipitable water forecast for tomorrow under the ridge of high pressure. This dry air extends from California, eastward into Colorado (brown areas). Moist air is confined to the Gulf of Mexico connected with Sally and a mid-level trough over the Midwest. Given this dry stretch this week, we will see little in the way of clouds. In fact, we would not be surprised if the week has a prolonged stretch of crystal clear blue skies! Some clouds will likely approach late Friday and over the weekend with an aforementioned system, but we will be very sunny before that. Temperature-wise, highs today and tomorrow should be a tad warmer than Sunday, between 87 and 89°F as the airmass warms ever-so-slightly under the ridge.
Weak cool front midweek
On Wednesday, a weak cold front slides south out of the Dakotas and brings in light northeasterly surface winds and a somewhat cooler airmass. It should be enough to reduce afternoon highs to the middle 80’s. There are some differences between the GFS and the Euro guidance on the strength of this front. The Euro is a bit stronger with the cold air pushing south so this will be something to monitor. All-in-all, it should be a nice day with little in the way of clouds thanks to persistent dry air. The main factor will be some haze and smoke discussed previously.
Weekend system brings warmth back to end week
After the front moves through Wednesday, a gradual warming pattern should take over once again Thursday and Friday. However, if the Euro verifies in its colder solution with the midweek front, temperatures may stay in the middle 80’s Thursday and Friday. We are hedging that the warm air should build back in given a developing system moving onshore late Thursday/Friday (below left). This should help bring in southerly winds once again for the latter part of the week, ushering in above average temperatures in the upper 80’s to near 90 by the end of the work week (below right). The record high for Denver and Boulder on Friday is 93 degrees. The trough that moves onshore Friday will track up into Montana by the weekend. The current track is not too favorable for precipitation on the Plains, but it should increase clouds and a chance of unsettled weather over the High Country.
Forecast Specifics:
Monday: Sunny and warm with highs near 87 on the Plains and middle 70’s in the Foothills.
Tuesday: Sunny and warm with highs in the upper 80’s on the Plains and upper 70’s in the Foothills.
Wednesday: Sunny and dry with middle 80’s on the Plains and middle 70’s in the Foothills.
Thursday: Mostly sunny with mid to upper 80’s on the Plains and mid to upper 70’s in the Foothills.
Friday: Sunny skies becoming partly cloudy with highs in the middle to upper 80’s on the Plains and middle 70’s in the Foothills.
Weekend: Warm with temperatures in the middle 80’s to near 90 degrees with increasing clouds and a slight chance of rain/storms by Sunday.
High Country: A very quiet week across the higher terrain this week – a great time to play hookie from work and highs some 13ers or 14ers! Sunny skies will prevail most of the week, with your typical afternoon diurnal fair weather clouds on the ridge tops. Breezy conditions approach late in the week, with a chance of unsettled weather over the weekend. Check our SummitCAST page for daily updated forecasts for more than 120 mountain hiking destinations across Colorado. Here’s a look at the Longs Peak forecast to begin the week:
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