National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
849 FXUS65 KBOU 211751 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1051 AM MST Sun Dec 21 2025 .KEY MESSAGES... - A little warmer today with winds picking up across the higher elevations by the afternoon or evening. - Elevated to near critical fire conditions across portions of the foothills Monday afternoon due to gusty winds. - A few record highs possible on Monday across the I-25 Corridor - Warm and dry Monday through Wednesday. Some hints of a more wintry pattern in the mountains in the latter half of the week? && .UPDATE... Issued at 226 AM MST Sun Dec 21 2025 Zonal flow aloft will remain over the area thru tonight. Cross- barrier flow will increase to above 60 kts tonight, however, cross-sections show only a weak mtn wave at this point. Will likely see a few gusts up to 70 mph above 10000 feet and possibly over the higher foothills by late evening which will continue overnight. Not sure about overall coverage and with most gusts staying blo 70 mph will not issue a high wind watch. && .DISCUSSION /Through Saturday/... Issued at 137 PM MST Sat Dec 20 2025 This morning`s backdoor cold front was a little more robust than most guidance had advertised. The post-frontal stratus also helped keep a deep inversion in place from 800-700mb (as noted from ACARS soundings) and unsurprisingly temperatures have been cooler than thought. Still, most locations were in the 50s earlier in the morning and so our daily high temperatures and our afternoon "high" temps will be pretty different. Across the mountains, we continue to see one dominant band of snow stretching across the northern tier of counties in our CWA. Indeed, SNOTEL data confirms that a majority of the accumulating snow with this event has been in the Park Range and northern Front Range. Eventually we may see a secondary band try to develop further south, but most if not all of the winter impacts will be north of I-70. A little bit of moisture lingers over the mountains into tomorrow but most of the accumulating snow will end by around midnight tonight. The flow aloft is expected to weaken a bit as we slowly start to see a ridge build to our south. Drier air and slightly moderating mid-level temperatures should allow temperatures to warm up into the 50s to low 60s across the plains. We will see the weather pattern across the country transition from a westerly zonal flow to ridging over the south central and southeast part of the country early next week. As the upper level high builds northward, flow aloft across Colorado weakens. Flow aloft also turns southwesterly over the Rockies and across the western states as the ridge builds northward and an upper level trough forms off the Pacific Northwest and British Columbia coast. This will set up a very wet pattern for California. For Colorado, the first part of the week will be mild and dry as the flow aloft weakens and transitions to the southwest. Temperatures will be well above normal with record highs possible on Monday. These very warm temperatures continue through Christmas with only a slight (5-10F degree) cool down on Tuesday. The chance for snow returns to the mountains late Wednesday and continues the rest of the week and into next weekend as Pacific moisture finally reaches Colorado. Southwest flow aloft tends to favor the west and more so the southwest mountains of Colorado. The mountains of Grand and Summit Counties tend to be shadowed by the mountains to the west, thus lighter snowfall amounts are to be expected here than across western Colorado. The Gore and Park Mountains in north central Colorado can see better snow under this southwest flow. For the foothills and plains, the westerly downslope flow will result in continued dry conditions. Winds will be gusty at times in the mountains and foothills, however the threat for strong/high winds looks very low at this time. && .AVIATION /18Z TAFS through 18Z Monday/... Issued at 1038 AM MST Sun Dec 21 2025 VFR through the TAF period. Winds are expected to remain out of the south with light speeds. Varying amounts of mid/high cloud cover will persist through Monday but no ceiling or visibility concerns are anticipated. && .FIRE WEATHER... Issued at 229 AM MST Sun Dec 21 2025 Elevated fire to near critical fire conditions will develop over portions of the foothills by late Monday morning and continue thru the aftn. Gusty west winds from 50 to 60 mph may occur at times mainly above 7000 feet. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...RPK DISCUSSION...Hiris/12 AVIATION...Hiris FIRE WEATHER...RPK