501 FXUS65 KBOU 260722 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 122 AM MDT Sat Apr 26 2025 .KEY MESSAGES... - Cooler today with light rain showers/drizzle. - Warm Sunday with critical fire weather conditions in the afternoon. - Seasonal conditions next week with opportunities for afternoon showers/thunderstorms most days, especially in the high country. && .UPDATE... Issued at 820 PM MDT Fri Apr 25 2025 A Denver Cyclone has allowed for some interesting weather across the forecast area this evening. NNE winds along its northern edge have kept persistent drizzle across the northern plains and urban corridor due to its upslope component. Fog has started to thicken in the past hour or so and is expected to spread across portions of the plains throughout tonight. We have gone ahead and issued a Dense Fog Advisory for the eastern plains and areas along the northern border until 10 AM Saturday morning, and increased PoPs in areas where drizzle has persisted for this evening update. && .SHORT TERM /Through Saturday/... Issued at 212 PM MDT Fri Apr 25 2025 Stratus remains firmly in place this afternoon across the lower elevations, keeping temperatures cool and in the 40`s outside of areas of partial clearing around the Palmer Divide and southern metro where they`ve climbed into the 50`s as anticipated. Modest instability should fuel a few afternoon showers generally over the Continental Divide, but any weak cells will lose steam as they attempt roll off the higher terrain and enter a more stable environment through this evening. Thus, main potential east of the Front Range is for some decaying rain showers. Tonight, patchy fog may redevelop on the backside of a surface cyclone. A Denver cyclone setup Saturday will bring enhanced southerly flow across most of the plains, with better clearing of low-level stratus through the morning. This will allow for warmer temperatures and some destabilization by the afternoon, with showers and a few weak thunderstorms developing mostly east of the I-25 corridor. That said, the eastern plains will remain capped through a good portion of the day, limiting downstream convective growth. && .LONG TERM /Saturday night through Friday/... Issued at 212 PM MDT Fri Apr 25 2025 Strong pre-frontal southerly flow will develop on Sunday in advance of an approaching upper-level trough. Robust warm advection will push temperatures into the upper 70`s to low 80`s east of the Rockies, and a dry airmass west of a dryline near the Kansas/Nebraska state line will keep humidity near and below 15% for most of the lower elevations in the afternoon. Critical fire weather conditions are thus expected to develop, with fire danger largely dictated by fuel susceptibility, which is currently quite variable over the plains. Nonetheless, wind gusts in excess of 30-40 mph will be widespread for the plains and Park County, so a Fire Weather Watch has been issued. As for the aforementioned dryline, there`s potential for it to extend as far west as Sedgwick/Phillips Counties and allow for some afternoon thunderstorms in our northeast corner later in the day. A more moist airmass will be in place Monday following the front, with higher chances for precipitation region-wide, moderately cooler temperatures, and breezy northerly winds. We look to remain within a slightly cooler pattern through much of the week, with oscillations between largely zonal flow aloft and a few potential dipping waves. Ensembles indicate plenty of model divergence still, so the forecast maintains near daily chances for some afternoon convection, especially for the high country, with Wednesday currently appearing to be the most favorable for more widespread precipitation. && .AVIATION /06Z TAFS through 06Z Sunday/... Issued at 1253 AM MDT Sat Apr 26 2025 Nighttime microphysics satellite shows that the low clouds over DEN and APA are rapidly thinning and clearing is just off to the southeast. The majority of the night will be spent with ceilings around 500 feet but brief periods of 100 feet ceilings or 1/2 SM fog will be possible. In addition, there may be a period when the clearing pushes over the two terminals and VFR conditions occur. There is a different story unfolding at BJC as that terminal will have LIFR conditions throughout the night. The trickiest part of the forecast will be whether fog develops between 10-13Z at DEN and APA. With winds expected to be from the NW, it is likely 1/2 SM or 1/4 SM fog develops over DEN. There is a lower chance that APA sees fog since the clearing and southerly winds may allow for VFR conditions to continue. The low clouds may transition to fog at BJC from around 09-13Z. Southerly winds will be quick to clear out clouds and any fog at DEN and APA this morning. Gusts to 30-35kts possible throughout the late morning and afternoon. The chance for thunderstorms seemed low enough (20%) that the TEMPO group was removed from the TAF. Regardless, a shower or storm cannot be ruled out and outflow winds could impact wind speeds and direction. && .BOU WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Sunday morning through Sunday evening for COZ214-240>247-249. Dense Fog Advisory until 10 AM MDT this morning for COZ038-042- 046>051. && $$ UPDATE...Bonner SHORT TERM...Rodriguez LONG TERM...Rodriguez AVIATION...Danielson