615 FXUS65 KBOU 010000 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 600 PM MDT Sat May 31 2025 .KEY MESSAGES. - Scattered afternoon showers and thunderstorms continue through Sunday (mainly over the higher terrain). - Warmer weather makes a return through the weekend, with highs back into the low 80s for most of the plains. - Wetter pattern returns early next week (Mon-Wed), along with a return to below normal temperatures. Snowmelt plus rainfall will lead to high flows on mountain streams. && .DISCUSSION /Through Saturday/... Issued at 251 PM MDT Sat May 31 2025 Weak convection has begun over the mountains and should increase through the late afternoon. There`s still potential for a few cells to move southeast off the mountains, though the environment at lower elevations is less favorable than yesterday. The current forecast seems to have a decent handle on this, though we did increase the cloud cover overnight for lingering mid level clouds. Sunday`s environment isn`t much different, although a Denver cyclone boundary could help get a bit more storm activity going south of Denver in the mid to late afternoon. Temperatures will be 4 to 8 degrees warmer. Denver will likely be near 90, but probably just short of that mark. The model handling of the Monday/Tuesday system is not that bad, though the resultant QPF still varies. One model trend is to move the synoptic scale lift steadily eastward and bring an end to the significant precipitation earlier on Thursday. Some model runs had slowed the departure over the plains resulting in larger rain amounts. Now the consensus is that the rain in the mountains will mostly be Monday afternoon and Monday night, and on the plains 4 to 6 hours later. This reduces the forecast rain amounts a bit. Most models are still in the 0.5 to 1.5 inch range for the mountains, and 0.75 to 2 inches for the plains. The NBM is in the middle of these ranges overall and seems adequate. There are some runs with lighter amounts, and a few outliers that have twice that. It seems unrealistic to have that much over a large area, but there is potential for embedded thunderstorms or a mesoscale focus that lasts a few hours. The most likely chance for intense rain would be with convection Monday afternoon and evening. See below for hydro impacts. There`s pretty good agreement on keeping a cool moist environment with another shortwave late Wednesday. Amounts should be much lighter overall, but PoPs will still be high and there could be some localized heavy showers. There`s a drying and warming trend after that, with Thursday as the transition day. NBM guidance is on the warm edge of the envelope, but this is probably OK, with temperatures back around 80 in Denver Friday and Saturday. With drying aloft but probably less and the surface, this looks like a fairly typical June pattern and there could be some threat of all kinds of severe weather and burn area flooding by the end of the week, though there`s nothing that looks like a particular threat. Just a fairly normal early June pattern. && .AVIATION /00Z TAFS through 00Z Monday/... Issued at 541 PM MDT Sat May 31 2025 VFR conditions expected through the TAF period. Light winds will turn drainage by 05/06Z and then turn more W/NW mid-morning. Chances for thunderstorms increase by 21Z (more 22Z/23Z for DIA and APA) with the possibility of strong VRB outflows gusting up to 35 kts at times. There is a chance that storms could stay north and south of DIA tomorrow, but even then gusty outflows remain possible. Storms will move out of the area around 01Z/02Z and winds should return to drainage. && .HYDROLOGY... Issued at 251 PM MDT Sat May 31 2025 Forecast temperatures, snowmelt, and rainfall will be enough to cause rises on streams in the mountains, and minor flooding could result late Monday and Tuesday in areas that get heavier rainfall. In areas east of the mountains and burn areas, the threat is lower, but there could be enough rainfall to cause localized minor flooding. Larger rivers should be able to handle the most likely rain and snowmelt, though they will be running high. There is a small chance of rain that is heavier than expected on a scale of a county or two, that could produce flooding on one of the larger rivers. At this time, this appears to be a low probability (10 percent or less). && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Gimmestad AVIATION...Ideker HYDROLOGY...Gimmestad