Thunderstorms and smoke will be on the increase through the week, with temperatures remaining near normal across the Front Range.
Quiet Monday
Following in the footsteps of this past weekend, this week begins with calm conditions remaining across the state of Colorado. A cut-off low pressure system has developed across southeast Colorado and will slowly move northeastward over the next few days. The ridge, while still centered near Las Vegas, has eroded and weakened significantly.
GFS 500 mb height anomaly map for Monday afternoon
It’s fairly trivial to pick out the upper-low in the GOES-16 water vapor animation below:
GOES-16 wator vapor animation for Monday morning showing the low spinning in southeast Colorado.
A few days ago, there was some concern that this low pressure system may push closer to the Denver Metro area. That, however, is no longer expected. A long fetch of moisture-deprived air is indicated for northeast Colorado today. Areas further south and east in Kansas, Oklahoma, and Texas will catch the brunt of the lift and rainfall
GFS precipitable water anomaly map for Monday. Dry air is wrapping into eastern Colorado on the back-side of the low.
This dry air will bring sunshine and temperatures in the mid to upper 80’s across the Metro area for Monday. Isolated thunderstorms can be expected in the Mountains.
Chances for storms the rest of the week
Though there is a very dry airmass in place on Monday, subtropical moisture remains widespread further upstream across Utah, Nevada, and California, including the remnants of Hurricane John (see above). This moisture will slowly infiltrate our region as the week progresses in the mid-levels of the atmosphere as winds turn more northwesterly. Unfortunately, this air will also be laden with smoke.
GFS 500 mb map for Wednesday morning. Northwest flow will bring moisture to our region, along with increased smoke Tuesday through Friday.
The HRRR-Smoke model forecast below is for Monday night. Notice how much smoke resides to our north and west, and the tight gradient across our region. This smoke will be moving back into the Metro area for most of the week.
HRRR-SMOKE total smoke forecast for Monday evening
The incoming moisture will be limited, but it will be enough to see daily thunderstorms return to the forecast. Isolated storms will be possible Tuesday and Wednesday. CAPE values are forecast to exceed 1500 J/kg on Wednesday east of Denver. Shear will be elevated given the southerly surface flow and moderate northwesterly winds aloft. This setup typically favors large hail and strong winds. The Denver Metro should largely be in the clear from severe weather on Wednesday, though. The threat will be further east.
GFS CAPE and shear forecast for Wednesday afternoon
Right now the best chances for afternoon and evening storms appear to be Thursday and Friday, when precipitable water values could get close to 1.2″ in Denver and Boulder.
GFS precipitable water forecast for Friday
These days in particular will need to be monitored for the potential for flash flooding as winds relax below 10 mph at the 500 mb level. It’s too early to pinpoint specific locations, or even to say if this flash flooding threat will materialize, but we will continue to monitor the situation and provide updates if needed.
GFS ensemble precipitation plumes for the time period of Monday through Friday.
What about those temperatures? Generally our highs through the week will be in the 80’s. The coolest day on paper looks to be Tuesday thanks to cooler air aloft moving into eastern Colorado Monday night associated with the low in Kansas. This cooler air will mix down to the surface and likely knock a few degrees off our temperatures heading into Tuesday.
GFS 700mb temperature map showing the low to the east and cooler air working into northeast Colorado on Tuesday.
The airmass in general will be warming through the week, but with added cloud cover and storm chances, we’re not expecting temperatures to respond too much. Models are actually trying to push temperatures into the lower 90’s Wednesday through Friday, but given the thickening smoke, this seems unlikely in my opinion. Mid to upper 80’s will be the norm through Friday.
A stronger trough will move across the northern Rockies over the upcoming weekend. This will help keep rain in the forecast and may also bring a cold front through sometime Saturday.
Forecast Specifics:
*THICK SMOKE AND POOR AIR QUALITY WILL BE PRESENT ALL WEEK*
Monday: Mostly sunny, dry, and pleasant. Highs in the upper 80’s across the Plains and mid 70’s in the Foothills.
Tuesday: Partly to mostly cloudy with isolated showers and thunderstorms in the afternoon and evening, mainly across the higher elevations. High temperatures in the low to middle 80’s for the Plains with lower 70’s in the Foothills.
Wednesday: Morning sunshine, then increasing clouds with widely scattered afternoon and evening thunderstorms, mainly south of Denver. Some storms east of Denver could produce large hail and strong winds. High temperatures in the upper 80’s across the Plains with mid 70’s in the Foothills.
Thursday: Morning sunshine, then partly cloudy with scattered afternoon and evening thunderstorms. Some storms could produce heavy rainfall. Expect highs in the mid to upper 80’s for the Plains and in the mid 70’s in the Foothills.
Friday: Increasing clouds with scattered afternoon and evening thunderstorms. Some storms could produce heavy rainfall. Look for highs in the mid to upper 80’s for the Plains with middle 70’s in the Foothills.
Weekend Outlook: Lingering subtropical moisture will continue to rest across the state of Colorado through the weekend. There will also be a Pacific trough moving across the northern Rockies during the day Saturday. We thus expect scattered storm coverage to continue through Saturday, with Sunday cooler (and probably still stormy) behind a cold front.
High Country: Scattered showers and storms will be across the Mountains each day this week and upcoming weekend. Storm chances look to be in the 20-50% range through the week, with slight wet favoritism towards southern Colorado. Check out our SummitCAST page for twice daily updated forecasts for more than 120 Colorado mountain destinations!
DISCLAIMER: This weekly outlook forecast was 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, subscribe to BoulderCAST Premium.
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