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484 FXUS65 KBOU 200512 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1112 PM MDT Sun Jul 19 2026 .KEY MESSAGES... - Hot weather continues through Monday, with highs pushing near 100F over the I-25 Corridor and adjacent plains. A Heat Advisory remains in effect for the Denver Metro/I-25 corridor through 9 PM Monday. - Scattered afternoon/early evening storms in the mountains expected Monday, with the plains remaining dry. - Arrival of monsoonal moisture still getting delayed slightly, but once it arrives it should last into late next week. Storms from Tuesday or Wednesday onward will be capable of producing locally heavy rainfall. - Only a slight cooling trend forecast this week with the arrival of better moisture. && .DISCUSSION /Through Sunday/... Issued at 309 PM MDT Sun Jul 19 2026 Heat and hints of monsoonal moisture have allowed scattered thunderstorms to develop over the Northern Mountains this afternoon, and satellite imagery also shows cumulus cloud cover increasing over the Front Range. Shower activity will diminish near sunset this evening. Across the low elevations, temperatures have had no trouble climbing into the upper 90s. The forecast remains on track for tomorrow being the hottest day of the week (and perhaps a contender for hottest day of the year), with essentially all model guidance suggesting Denver will hit 100F in the afternoon. These high temperatures are supported by a slight eastward shift of the upper-level ridge axis. Additionally, the mid- level core of the airmass accompanying this ridge will be centered right over the state of Colorado Monday afternoon, with 700mb temperatures nearing 20C, which exceeds the 95th percentile of climatology. Temperatures will generally trend "cooler" Tuesday through Saturday, though still hot (closer to average for the time of year), reaching the low to mid 90s each day at the low elevations. The mountains will also see high temperatures near average (70s-80s) with a better chance of experiencing some heat relief with isolated storms as monsoonal moisture increases throughout the week. We expect afternoon showers and thunderstorms over the high terrain to become more scattered in nature Monday and Tuesday as the upper- level ridge drifts southeast. However, model guidance has continued to delay the arrival of the highly anticipated monsoonal moisture with the brunt of the moisture now arriving late Wednesday into Thursday. Nevertheless, each day will have a slightly different setup regarding moisture and forcing mechanisms, especially over the Denver metro and eastern plains. A cold front will bring a northerly push of moisture to the eastern Colorado plains Tuesday morning which, combined with weak southeasterly flow, could aid in the development of a few showers over the foothills and Palmer Divide in the late afternoon and evening. More substantial moisture arrives on Wednesday as another northerly push of moisture arrives from the northern intermountain west region and southerly flow strengthens, advecting moisture from the central plains. Model guidance has also been suggesting the development of a lee cyclone north of the Denver metro area, which would also help channel moisture farther west into the I-25 corridor, the foothills, and the Northern Mountains. Uncertainty remains regarding the fine details of how the rainfall later this week will play out. However, it is worth mentioning that long- range ensembles continue to suggest precipitable water (PW) over the Denver metro area reaching or even exceeding values of 1.4" Wednesday and Thursday, which is about double the climatology for this time of year (0.7-0.8"). A shortwave trough passage on Thursday could provide additional lift for shower activity over the mountains and northern plains. Given the weak flow aloft and and slow storm motions in place, we will continue to watch how flash flood potential evolves through the week. && .AVIATION /06Z TAFS through 06Z Tuesday/... Issued at 1108 PM MDT Sun Jul 19 2026 Winds will remain from the south overnight except at BJC which will become light WNW by 07z. On Mon, light and variable winds in the morning will become east by 18z and then more ESE by 23Z. Outflow boundaries from tstms over the higher terrain may move across by 01z which could lead to a 20-30 percent chc of tstms thru 04z. Thus have included a Prob30 for this scenario. && .BOU WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 9 PM MDT Monday for COZ038>040-043. && $$ DISCUSSION...AA AVIATION...RPK