National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
724 FXUS65 KBOU 131104 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 504 AM MDT Fri Mar 13 2026 .KEY MESSAGES... - Gusty west winds, strongest Saturday, and warm/dry weather will sustain critical fire weather conditions for the plains/I-25 corridor through Saturday. - A cold front Saturday night will bring sub-freezing wind chills Sunday, with strong north winds and light snow to the lower elevations. Difficult travel expected in the mountains Saturday night into Sunday morning due to snow and blowing snow. - Rapid warming begins Monday into Tuesday, potentially culminating in record-breaking temperatures mid to late next week. && .DISCUSSION /Through Thursday/... Issued at 1148 PM MDT Thu Mar 12 2026 The strongest winds have largely retreated into the high foothills and leeside slopes, although breezy conditions are lingering across the urban corridor and most notably in the Fort Collins area, where gusts as of 1030 PM continue to register in the 50-65 mph range. There should be a gradual reduction in speeds through the night for the lower elevations, but they`ll remain hefty or even strengthen slightly for the higher elevations with gusts exceeding 70-80 mph at times. The westerly downslope flow won`t fully die down overnight for the urban corridor either, resulting in mild overnight lows that may not drop below 45-50F in the warmest locations near the base of the foothills. A little different over in our northeast plains, where a backdoor cold front which is creeping into the state will provide for some sub-freezing lows from roughly Fort Morgan eastward. This front`s impact on temperatures Friday should be limited, with a deeply mixed profile leading to a quick emergence of breezy west winds beginning late morning and continuing through the afternoon. Peak wind strength will not be comparable to Thursday in the absence of any mountain wave activity, but widespread gusts 30-45 mph (strongest along our northern tier of counties) will nonetheless promote critical fire weather conditions for the lower elevations as temperatures creep into the 70`s and humidity dips into the mid teens. The higher terrain will see a reduction in peak winds during the afternoon, but some gusts 55-65 mph can be expected to continue. Zonal flow aloft is set to strengthen Saturday as a shortwave begins to dig south towards Colorado. With additional low-level warming (highs will push into the mid 70`s for the plains), we`ll have another day of efficient mixing, which inevitably means more (and stronger) winds. Daytime gusts for most areas will be 10-15 mph stronger than Friday, and be relative widespread and persistent. It will also be both the warmest and driest day of this stretch of higher fire danger, so critical fire weather conditions are a sure bet. As far as the Chinook winds are concerned, cross- sections and forecast soundings are largely unsupportive of true mountain wave development, lacking a well-defined critical or stable layer. A surge of stronger winds off the foothills spreading into the urban corridor is still favored for the mid afternoon through mid evening period, with gusts roughly 40-55 mph (and some decay with eastward displacement into the plains), but driven mostly by brute force as pre-frontal winds peak in strength. By early Saturday evening, a strong cold front will push into our area and progress south into the overnight hours. Increasing mid- level moisture will impinge on the high country starting Saturday evening leading to development of snow showers, spreading north to south through the night. Snowfall will be boosted by healthy orographic and jet-induced lift, as well as robust frontogenesis, and mountain travel will become quite difficult across our mountains. Blowing snow and significant visibility reductions will be an additional concern that could snarl traffic even into the Sunday morning timeframe as snowfall tapers. Winter Weather Advisories have been issued as a result. The lower elevations won`t be entirely left out, with a quick burst of banded snow showers increasingly likely for the overnight and early morning hours as temperatures take a nosedive. Despite Saturday`s warm temperatures, the much colder airmass behind the front should allow for accumulation on roads, although with limited moisture and the quick- hitting nature of this system, amounts for most areas won`t be too impressive (mostly 1" or less north of the Denver metro and for the plains). That said, localized higher amounts of 2-3" are certainly possible contingent on localized banding, and brief northerly upslope flow would favor areas to the south of Denver, including the Palmer Divide, for the highest accumulations. Snow will diminish rather quickly Sunday as subsident flow takes hold, with wind becoming the main story yet again. Post-frontal north winds will gust 45-60 mph for much of the lower elevations well into the afternoon, strongest in the rural plains, and will make for cold wind chills through the day. Our hectic stretch of weather looks to subside Monday as the trough exits to our east and high pressure begins to expand over the Western CONUS. This expansion will be steady and produce a rapid warming trend through Tuesday, when 70`s looks to make a return. That trend will slow the rest of the week, but certainly not cease, with continued warming expected. Ensemble guidance indicates considerable amplification of the high pressure as it migrates closer to the Intermountain West, and confidence continues to rise in a prolonged period of highly anomalous March heat that is poised to threaten records. && .AVIATION /12Z TAFS through 12Z Saturday/... Issued at 452 AM MDT Fri Mar 13 2026 Winds at DIA have been a nightmare all night as they have remained from the west and gusty at times. To complicate things even further, there is a cool front just to the NE and E of DIA which has been slowly trying to move westward. If the westerlies weaken, then may see a brief wind shift to the east before things mix out later this morning. Along and to the east of this front, smoke from fires over Nebraska has been moving westward across the plains overnight. Visibility on some sensors has dropped down to 1-3 miles. At this point, I believe there is only a 10 percent chance of visbility restrictions this morning at DIA if the cool front were to move across. Don`t think the cool front will affect APA or BJC. Winds have been gusting all night at BJC from the WNW so winds may just stay gusty from the west or WNW all morning. By 16z should see decent mixing occur with winds mainly from the west at APA and DIA. By 19z, winds at all of the airports should be WNW with gusts from 30 to 35 mph thru the aftn. For tonight, winds should decrease by 01z and become more SW or SSW by 05z. Finally, VFR conditions are expected thru the period except for a 10% chance of lower visbility at DIA thru 15z due to smoke behind the cool front. && .FIRE WEATHER... Issued at 1148 PM MDT Thu Mar 12 2026 Critical fire weather conditions will become widespread for the lower elevations this afternoon as deep mixing allows for west winds 15-25 mph and gusts 25-40 mph (strongest near the WY/NE state line) to surface. Humidity will hover between 12 and 18%, generally driest for the Denver metro and southern plains. Gusty winds will subside quickly in the evening and retreat into the foothills and mountains, however downslope flow will keep overnight humidity recoveries low (25-35%) along the base of the foothills and portions of the Denver metro. West winds are set to strengthen Saturday ahead of an approaching storm system, with sustained speeds 20-30 mp and gusts 35-50 mph expected to be widespread. Saturday will also be the warmest and driest day of this period of enhanced fire danger, with highs into the mid 70`s and potential for humidity to locally lower into the single digits in the plains, contributing to heightened fire weather concerns. A window of stronger gusts for areas along and west of I-25 is possible starting mid-afternoon with gusts up to 55 mph at times. Saturday evening, a potent cold front will descend south and bring a shift in prevailing winds (becoming north). These winds will be strong and will continue well into Sunday, with gusts 40-60 mph for the lower elevations. However, the front will be accompanied by notably higher humidity as well as some light snow through Sunday morning. After the brief cooler conditions on Sunday, much warmer and drier conditions are expected to return quickly and build through the week, with periods of elevated to near-critical fire weather conditions possible as early as Tuesday depending on exact winds as well as fuel susceptibility. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 PM Saturday to 8 AM MDT Sunday for COZ031-033-034. High Wind Warning until noon MDT today for COZ033>036. Red Flag Warning from 11 AM this morning to 8 PM MDT this evening for COZ238>251. Red Flag Warning from 11 AM to 9 PM MDT Saturday for COZ238>251. && $$ DISCUSSION...BRQ AVIATION...RPK FIRE WEATHER...BRQ