Area Forecast Discussion

KEY MESSAGES

- Storm coverage and intensity increases on Wednesday and Thursday as monsoonal moisture moves into the region. Storms from today onward will be capable of producing locally heavy rainfall and thus a low threat of flash flooding.

- Storm coverage expected to decrease again by Friday into this upcoming weekend, although mountain areas should see at least scattered storm coverage each afternoon and evening.

- Temperatures will rise back into the upper 90's to lower 100's over northeast Colorado for the weekend.

DISCUSSION /Through Tuesday/

Issued at 110 PM MDT Tue Jul 21 2026

Smoke from fires in Canada and the West Coast pivoted into our area this morning behind a weak cold front. This smoke has mostly dispersed as of the early afternoon. Current satellite and radar shows clouds and some pockets of light rain across northern Larimer and Weld counties. Even behind the cold front, the hot stretch for Northeast Colorado will continue with another day of 90's forecast in Denver- making this 19 out of 21 days this month at or above 90 F. Highs today across the plains will be slightly "cooler" than yesterday, but still in the low to mid 90s.

The high pressure has elongated compared to yesterday, putting us more on the periphery, and opening the door for scattered showers and thunderstorms. These will favor the northern foothills and mountains including the Cameron Peak and Alexander Mountain burn scars today. It is still uncertain whether or not the Urban Corridor and plains will receive any rainfall today, but any storms that form would likely be associated with outflow boundaries from storms to the north. The latest CAMs are not particularly excited about this potential.

The pattern shift towards monsoonal moisture will be in full effect by Wednesday and Thursday. The high pressure will shift off to the south over TX and NM and it is becoming increasingly likely that a shortwave will move through on Thursday. Low level southeast flow will advect more moisture to the region, so dewpoints should generally remain in the 50s for much of the week. Dewpoints could even briefly reach the low 60s on Thursday as seen in recent model guidance.

We still expect PWATs to be 150-200% of normal for Wednesday with even a slight increase in PWATs on Thursday (approaching climatological record high daily values). Storm motion could be slow on Wednesday given weak flow aloft, but will increase on Thursday with the arrival of the aforementioned shortwave. This should slightly increase rain coverage. Each afternoon, convection will start in the high country and spread into the plains by late afternoon to early evening. Rainfall totals will generally be around 0.25 to 0.75 inches with some isolated totals of 1.00 to perhaps 2.00 inches by Thursday evening. The burn scars in our area will need to be monitored, but rainfall rates should stay below flash flood guidance across the area. The only exception would be if we get training of storms. Given increased clouds and rainfall, high temperatures will "cool" into the upper 80s to low 90s for both days.

The heat starts its return to the area on Friday and then increases on Saturday and Sunday as the high pressure expands and shifts to be centered near the Four Corners region. Scattered showers and thunderstorms will remain possible on Friday, but likely will stay confined to the mountains. We have continued to nudge highs up into the upper 90s to near 100 for both Saturday and Sunday, thus record highs could be in play. A Heat Advisory could also be needed as we get closer to the weekend.

Ensemble guidance continues to depict warm temperatures with highs just below 100 degrees for much of next week across the plains. The ECMWF does try to shift the high pressure and bring some more rain to the area by mid-week, but confidence remains low on this solution at this time.

AVIATION /00Z TAFS through 00Z Thursday/

Issued at 541 PM MDT Tue Jul 21 2026

VFR through the TAF period. Southeasterly flow this afternoon is expected to eventually turn towards drainage later tonight. However, this may be briefly interrupted by outflow from a cluster of SHRA/TSRA that models develop to the northwest of the terminals. There is at least a conditional threat of some brief SHRA and outflow winds (likely out of the north) after 03z tonight... with the highest chance at DEN where a TEMPO was added for some north winds after 05z.

Tomorrow looks to feature more moisture, with limited capping by the afternoon hours, and it's probable that convective coverage will be far greater across the Denver metro compared to today. This could be in a broad period anywhere after about 20-21z, with showers potentially lingering at late as 06z Wednesday night. Have opted for a long PROB30 to cover this potential for now but this will likely need to be refined later.

BOU WATCHES / WARNINGS / ADVISORIES

None.