This week will feature a rollercoaster ride in temperatures from heat to more seasonal temperatures to even below normal conditions. The best chance of storms will be early in the week with flash flooding possible in the burn scars. Drier weather follows in the extended, however. Which days will be our hottest and coldest in the days ahead? Read on to find out!
This week’s highlights include:
- Toasty again on Monday in the 90’s
- Best chances of storms is on Monday with potential flash flooding in the burn scars
- A few cold fronts will cool us off during the week
- Near-record heat possible on Thursday
- Smoke concentrations will remain low through the week
- Monsoon season should be active in the Desert Southwest this month, but not necessarily for Colorado
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.
90’s continue, storms most likely through Tuesday
We hope you had a great Fourth of July holiday, however you may have celebrated! The heat and 90’s will continue early this week across the Front Range. Below shows the current weather pattern across the nation today. Tropical Storm Elsa is affecting Cuba, poised to move northward toward western Florida in the coming days and eventually move east-northeast into the Carolinas late in the week. A frontal boundary currently resides over the southern United States as well. As for us, a trough of low pressure is located over north-central Wyoming. With a trough axis extending south into central Colorado. This weak trough will aid development of showers and storms Monday afternoon and evening.
Temperatures will top out in the lower 90’s on Monday. Clouds will increase in the afternoon as storms fire across the higher terrain and make their way towards the Plains. Coverage should be more widespread today compared with Sunday, with a 40-50% chance of storms by evening. The National Weather Service has issued Flash Flood Watches across the higher terrain with the potential for heavy downpours, mainly in burn scar areas. Pea-sized hail could accompany any storms as well which will taper off after sunset.
This same, aforementioned trough axis will send a welcomed cold front into the area tomorrow afternoon (below left), with temperatures dropping back into the lower 80’s. Upslope flow will ensue in the afternoon on Tuesday.
While the main lift with the cold front will be across southeastern Colorado, instability will remain over the Denver Metro too with post-frontal upslope forcing to focus redevelopment of afternoon/early evening showers storms Tuesday. We think the favored region will be in the Foothills and south of Denver where lift is greatest. All in all, Tuesday will have just a 20% chance of storms to go with those cooler temperatures.
Heat returns Wednesday & Thursday
On Wednesday, the trough is forecast to move eastward and will be replaced by a dome of high pressure from the west. This ridge will shift east, lowering moisture content as well as increasing surface temperatures with warm air advection from Utah. Our 700 mb temperatures aloft (below left) will exceed 20°C on Thursday which is about 3 to 4 standardized anomalies above normal for early July (below right)! Our Wednesday will be sunny and dry as a result. Temperatures should rebound then back close to 90 degrees.
Thursday will by far be the hottest day of the week as temperatures approach record territory. You’ll notice that the GFS ensemble forecast shows a potential forecast high of 99°F for the area that day. Thus, expect a very hot Thursday with highs potentially near the century mark. For context, the record high for Boulder is 100°F set in 1989.
However, some clouds will likely be in place at high-levels Thursday as moisture increases under the broad westerly flow aloft from the Pacific and and with weak troughs tracking across the Pacific Northwest into Montana (below). A 10% chance of storms is warranted Thursday but overall it looks fairly dry for Front Range Colorado. The trough over the Pacific Northwest Thursday is forecast to push a cold front through some time Friday afternoon or evening, ushering in cooler weather for the upcoming weekend. That will lead to a chance of storms on Friday as well. Although, the chance of storms Thursday and Friday are much lower than earlier in the week, due in large part to drier air and downslope flow as inhibiting factors.
It is also worth noting that smoke levels will be reduced this week due to a shift in the location of the largest active fires. With the exception of three wildfires burning in close proximity to one another in northern California, most of the major smoke-producers right now are north of the border in Canada. Thus, we’re not going to see any major upticks in smoke unless we get another Canadian airmass moving in. In the smoke forecast below, the central and eastern half of the United States has thicker smoke then our area. This is because that cooler and smoke-laden Canadian air is setup there.
There will be a low background concentration of smoke through the week, but nothing like what we saw last month under those stagnant high pressure patterns. Our smoke forecast through Tuesday night is shown below.
Finally, last week the Climate Prediction Center released an updated monthly outlook for July. Front Range Colorado is forecast to have slightly elevated odds for a warmer than normal July with equal chances for above, below and near-normal precipitation. This is a slight adjustment from the warm and dry seasonal outlook they issued about eight weeks ago. Long-range model guidance does suggest an active monsoon pattern for Arizona and New Mexico during much of July, but not necessarily for our state. We’ll have to wait and see how the month shakes out, but things are looking mildly better than original expectations, especially for southern Colorado.
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Forecast Specifics:
Monday: Mostly sunny and warm, then increasing clouds with scattered showers and thunderstorms in the late afternoon and evening hours. Storms will produce heavy downpours and could cause flooding in the burn scars. Highs in the lower 90’s on the Plains and lower 80’s in the Foothills.
Tuesday: Cooler with partly cloudy skies with isolated to widely scattered afternoon/evening storms, mainly in the Foothills and across the Palmer Divide. Highs in the lower 80’s on the Plains and lower 70’s in the Foothills.
Wednesday: Sunny and warmer with temperatures near the lower 90’s on the Plains and lower 80’s in the Foothills.
Thursday: Just a slight chance of storms. Otherwise, very hot & partly cloudy with mid to upper 90’s on the Plains and middle 80’s in the Foothills.
Friday: A slight chance of storms with highs in the lower 90’s on the Plains and lower 80’s in the Foothills.
Mountains: Monday and Tuesday will be stormy with afternoon/evening showers and storms. Drier weather takes hold on Wednesday, Thursday, and Friday, although a 10-30% chance of storms exists toward the latter part of the week.
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