National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
129 FXUS65 KBOU 200527 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1127 PM MDT Mon Oct 19 2026 .KEY MESSAGES... - Mild and mostly dry conditions to start the week. - Isolated light rain and snow showers possible over the mountains Monday and Tuesday afternoon. - A more organized system by late Wednesday, with rain showers becoming more numerous over the mountains. && .DISCUSSION /Through Monday/... Issued at 246 PM MDT Mon Oct 19 2026 Current observations show temperatures in the 50s and 60s, and mostly sunny skies east of the Continental Divide. A few showers have developed over western Colorado and parts of Park County, although these should be short-lived. Decreasing cloud cover over the mountains and clear skies for the plains late tonight will give way to one more chilly morning (though still above average) with morning lows in the upper 30s to low 40s across the low elevations, and 30s for the mountains. Tomorrow, a shortwave will continue to drift through the area and allow for a few light showers over the high terrain once again in the afternoon. For the plains and Denver metro, 70-degree afternoon highs make a return with a few patches of mid level clouds and perhaps some virga. Surface winds are expected to generally remain light at all levels through at least tomorrow evening due to the weak pressure gradient and light southwest flow aloft. The synoptic pattern becomes more amplified on Wednesday as an upper level ridge builds over just east of our area and a strong cutoff low approaches the California coast. A subtropical jet ahead of this cutoff low will strengthen southwesterly flow aloft and begin advecting Pacific moisture towards the Four Corners Wednesday evening into Thursday. This increase in moisture will allow rain showers to become more numerous over the mountains Wednesday evening, although the heaviest rain should remain well outside of our CWA, over southwest Colorado. In terms of rainfall amounts, a trace up to 0.25" of QPF seems reasonable for the mountains, with the Denver metro and plains remaining dry. The airmass appears to be too warm for any tangible snow accumulations, with perhaps only some dustings above 12,000 ft. It is worth noting that moisture transport with this system is quite impressive. Long-range ensemble means show precipitable water (PW) values reaching the 0.60" to 0.90" range, which is well above then 90th percentile and even the daily maximum of climatology for this time of year. However, with such limited instability around (in comparison to peak monsoon season), we expect the bulk of the rainfall to be orographic in nature, coming to fruition over areas where southwesterly flow is a favorable upslope orientation (i.e. primarily southwest Colorado). With so much high terrain blocking the bulk of this plume of Pacific moisture, high clouds may be all that the foothills, Denver metro, and plains get out of this system. Regarding temperatures, there is pretty good agreement in temperatures staying warmer than seasonable through at least Saturday, with the Denver metro and plains potentially reaching the mid to upper 70s Wednesday through Friday. A cold front is still expected to push through the area on Saturday, cooling temperatures down to near-average for the weekend. && .AVIATION /06Z TAFS through 06Z Wednesday/... Issued at 1124 PM MDT Mon Oct 19 2026 VFR conditions thru the period. Winds will remain S/SSW overnight with light and variable winds at BJC. On Tue, light and variable winds in the morning will become light north by 19z and then switch to more light ENE/E by 23z or 00z. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...AA AVIATION...RPK