National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
081 FXUS65 KBOU 230713 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1213 AM MST Mon Feb 23 2026 .KEY MESSAGES... - Another big warm-up for the upcoming work week starts today. - Strong winds expected along the Front Range and foothills on Tuesday. - Snow chances return to the mountains mid-week. - Potential for multiple days of elevated to critical fire weather conditions in the plains through the week. && .DISCUSSION /Through Sunday/... Issued at 1153 PM MST Sun Feb 22 2026 It`ll be another active week across the forecast area, with winter conditions and high winds expected in the mountains, and strong winds with multiple days of potential elevated to critical fire weather conditions across the lower elevations. On Monday, we`ll kick off the week with mild and dry conditions across the forecast area, underneath a broad upper-level ridge. Temperatures are forecast to take a significant jump upwards from Sunday`s, with afternoon highs climbing into the low to mid 60s along the urban corridor and plains. This will put us roughly 8 to 20 degrees above normal across the entire forecast area. It`ll be dry out there, with minimum relative humidity values dropping between 10-15% across the majority of the plains in the afternoon, though winds are expected to remain fairly light with a loose pressure gradient in place, so while elevated fire weather conditions are expected across the lower elevations, no critical fire weather conditions are anticipated. Overnight, above-normal temperatures will remain across the forecast area. Flow aloft will begin to increase as a near 80kt, northwest to southeast positioned 500 mb jet sets up over Wyoming. This will influence how Tuesday plays out, as it will put northern Colorado in the subsident right exit region. Tuesday- As discussed in the previous AFD, there are key ingredients that can really "make or break" what happens with a mountain wave, which can be the determination of how far down the foothills the strongest winds make it. For Tuesday, there is high confidence that winds are gonna be blowing across the mountains, but still some uncertainties on how far east they will push. By early Tuesday morning, the latest guidance shows things have stayed consistent with winds at ridgetop near 80 kts and within 30 degrees of normal (~290 degrees), lapse rates ranging between 3-6C/km, and the aforementioned jet over Wyoming. Forecast soundings still show nothing more than a hint of an inversion just above ridgetop, which would be a good indicator that winds would lean more towards staying anchored to the higher foothills, rather than being reflected all the way down to their base. Additionally, moisture in the mountains has been known to be a deterrent of mountain wave amplification in the past, and with Pacific moisture expected to increase (forecast soundings show a deep moisture profile west of the Divide by 18-21Z) across the mountains through the day, this could have an impact on winds on the lee side of the Front Range (will they diminish sooner than currently forecast?). All of this being said, strong winds are expected to increase across the Front Range Mountains through the early morning Tuesday, reaching high wind criteria along the Mummy Range down to the Indian Peaks by roughly 8AM before spreading east into our typical windy spots like Jamestown and Sugarloaf in the afternoon, with a fairly tight gradient of lighter wind speeds across the lower foothills. Latest hi-res guidance shows the strongest gusts reaching between 70-75kts (80-85mph) throughout the afternoon, before decreasing and retreating back up the slopes through the evening. Considered expanding the watch to include eastern Larimer County, but winds are shy of high wind criteria over most of the eastern portion of zone 38, however, expect the strongest winds to reach high wind criteria in the typical windy spots from Wellington north to the Wyoming border. The northern tier of the plains (generally southern Morgan county northward) will see breezy conditions coinciding with marginal relative humidity values (14-20%). This would bring a few hours of near critical to critical fire weather conditions where the RH is at its lowest. Will let the day shift decide on fire weather highlights, but suspect portions of Weld and Morgan Counties to reach criteria long enough to warrant a highlight. Winter conditions are expected to develop over the northern mountains by Tuesday afternoon as Pacific moisture starts to make its way into the high country ahead of the next shortwave progged to move across the Rockies on Wednesday. With the aforementioned strong winds, blowing snow will make for difficult travel conditions for a few days. Strong winds will continue Wednesday, becoming more widespread across the lower elevations, but decreasing over the mountains. Fortunately, relative humidities should generally remain above 20% where gusty winds (35-55mph) are forecast over much of the plains, keeping critical fire weather conditions at bay. As more of the hi- res models come into play, we will need to continue to monitor for the potential some channels of stronger winds reaching high wind criteria, make their way across the northern plains Wednesday afternoon behind a passing cold front. The latest RRFS shows gusts between 55-60 mph coming off the Cheyenne Ridge as the front passes, but these winds are not expected to persist for an extended period of time, and this is just one model solution. As the front slides south across the forecast area, there will be a shot at light precipitation falling across the lower elevations, though ensembles and operational models have yet to agree on this, and anything that falls would not be significant (maybe a few hundredths). PoPs were lowered across the plains to account for the remaining uncertainty. At least we should get a decent little dose of new snow to add onto our lacking snowpack, with the current forecast bringing around 5-10 inches to the Front Range Mountains, and slightly higher amounts to the Park Range. Snow will continue across the mountains, with strong winds keeping blowing snow and hazardous travel conditions in place into Thursday morning. Beyond the quick-hitting mountain snow, the rest of the long-term period will shift focus back to fire weather conditions developing across the lower elevations to end the week. && .AVIATION /06Z TAFS through 06Z Tuesday/... Issued at 1036 PM MST Sun Feb 22 2026 VFR conditions through the TAF period. Drainage winds overnight should turn to a weak west-northwesterly direction during the afternoon Monday, before returning to drainage again Monday evening. No ceiling or visibility concerns at this time. && .BOU WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Tuesday morning through Tuesday afternoon for COZ033>035. && $$ DISCUSSION...9 AVIATION...Hiris