National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
230 FXUS65 KBOU 100505 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1105 PM MDT Wed Sep 9 2026 .KEY MESSAGES... - Mainly dry through Friday with warmer temperatures for Thursday and Friday. - Return to more unsettled pattern and cooler weather favored for next weekend with a chance of thunderstorms each afternoon. && .DISCUSSION /Through Wednesday/... Issued at 1251 PM MDT Wed Sep 9 2026 A quiet day is expected across the forecast area today behind this early morning`s cold front. Dare we say that fall is trying to make itself known, despite a few more 90 degree days lurking in our forecast? For today, temperatures will be at or slightly below normal across the plains with the cooler air mass in place. The cooler air won`t pack enough of a punch to make it to our mountain valleys, where afternoon high temps will still remain about five to ten degrees above normal. As evident on water vapor imagery, much drier air will be in place across the forecast area, as westerly flow aloft will keep the monsoonal moisture plume flowing into southeastern Colorado, on the periphery of our southern most counties. CAMs show storms developing along a cold front in southeastern Colorado tonight. A few may manage to move north into southern Lincoln County late tonight. With PW values around 1-1.5", any storms that do move into the area will be capable of some heavy rainfall. Warm and dry conditions are expected on Thursday as flow aloft turns more northwesterly, and 700 mb temps warm a few degrees. This will translate to a few degrees of warming at the surface, bringing afternoon high temps back to above normal across the forecast area. Relative humidities will drop into the single digits in our high mountain valleys and there will be some patchy elevated to near critical fire weather conditions, mainly for North Park and some localized areas along the Continental Divide. Mid-level moisture will start to work its way back into the area on Friday as a shortwave moves across the northern Rockies and flow aloft becomes more westerly, once again. There may be enough moisture in place for some high-based showers in the afternoon/evening, but instability looks lacking for anything substantial at this time. Folks across the plains have a good shot at ending their work week with temperatures at or around the 90 degree mark before another cold front slides south across Colorado Friday night that will bring Saturday`s high temps back closer to normal. The northern tier will remain active through the weekend, with a more pronounced shortwave expected to move into the Pacific Northwest on Saturday and traverse the northern Rockies on Sunday. This will turn flow aloft slightly more southwesterly through the day on Saturday and allow us to tap back into some mid-level Pacific moisture. Afternoon showers and storm activity will increase, with isolated to scattered showers/storms possible each afternoon. One more summerlike warmup is expected on Sunday, with afternoon highs warming into the low to mid 90s along the urban corridor. Another cold front will push south Sunday night cooling things back down to near normal temperatures for Monday. The forecast high for Denver International Airport is 93 degrees on Sunday, which would put us within a few degrees of the record high for this day (96 is the current September 13th record, last set in 2018). Looking at ensembles, this may end up being one of, if not the last 90 degree day of the season, as there is a definite trend of cooler temperatures (sub 90 degrees) present in the latest ensemble outputs (though there is certainly plenty of time for this to change!). && .AVIATION /06Z TAFS through 06Z Friday/... Issued at 1103 PM MDT Wed Sep 9 2026 VFR conditions will continue. Light SE winds will become southerly by 08z and then turn more SSW by 12z. By 18z, winds will become SE and then shift to southerly by 03z Thu evening. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...9 AVIATION...RPK