National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
722 FXUS65 KBOU 012043 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 243 PM MDT Wed Apr 1 2026 .KEY MESSAGES... - Mountain snow will continue through this evening, with travel impacts for higher passes during heavier snow. - Numerous rain showers are expected on the plains this afternoon and evening. Isolated thunderstorm or two possible. - A brief warm up Thursday, with potential for locally critical fire weather conditions. - Windy and cooler Friday with another round of snow for the mountains. Plains look to be dry (80% confidence). - Dry and warming trend expected over the weekend and into next week. && .DISCUSSION /Through Wednesday/... Issued at 236 PM MDT Wed Apr 1 2026 Forecast remains generally on track, with current radar showing ongoing mountain snow showers and developing scattered light rain showers on the plains. The upper level shortwave is currently entering western Colorado, as evident on water vapor satellite imagery. It will continue trekking east this afternoon/evening, with colder air being advected into the mountains. This will result in mountain valleys likely seeing a transition from rain/snow mix to all snow later today, with better snow-to-liquid ratios for the high terrain. However, this will still be wet and heavy snow as SLRs are only expected to reach up to around 13:1. Additional accumulations of 2-8" is expected across most of the mountains, with localized higher amounts likely for Park Range, as that area has more favorable moisture content and synoptic lift. For the plains, lee-cyclogenesis is still favored to develop over southeastern Colorado this afternoon with the arrival of the upper level shortwave. This will help bring a round of more widespread rain showers through this evening. Overall, precipitation will be light. However, with hi-res guidance continuing to show instability building this afternoon, and ACARS soundings showing abundant moisture being advected into the plains (current PWAT values of ~0.54", which is above the climatological 90th percentile for this time of the year), thunderstorms and briefly moderate to heavy rainfall is expected at times. Ensemble guidance still in agreement of QPF amounts generally ranging between 0.05-0.25", with localized higher amounts up to 0.50" under the heavier showers. However, there is a low chance (~30%) of QPF amounts higher than 0.50", particularly for the northeastern plains. Precipitation should gradually end across the forecast area overnight tonight, as subsidence increases aloft. Flat ridging on Thursday will bring warm, dry, and breezy conditions for the mountains and plains. Ensemble guidance is still in agreement of temperatures rising back up tot the low 70s across the plains. However, downslope winds could aid in compressional heating and raise temperatures slightly higher than forecasted. Gusty southwest winds (up to 35-40 mph at times) along the southern and eastern plains will promote elevated-to-briefly-critical fire weather conditions. However, these conditions will be heavily dependent on the precipitation (amount and location) this afternoon. Have decided to keep Fire Weather Watch as is, as Lincoln County and the eastern portions of Elbert county are still expected to receive minimal rainfall amounts, and will allow the next forecast package to see if there is a need to upgrade, expand, or cancel the watch. The next system is progged to arrive Thursday night, with a 500-mb closed low trekking just north of Colorado. This will bring another round of mountain snow through Friday, particularly for our northern mountains, as the best QG lift, mid-level frontogenesis, and upper level jet line up. As of right now, snowfall amounts are not impressive, but next few forecast packages may warrant a Winter Weather Advisory if guidance continues to trend towards higher QPF amounts. For the plains, a dry but strong cold front will traverse the region overnight, bringing wind gusts up to 40-50 mph at times through Friday afternoon. Combined with marginal relative humidity values, this could bring another round of elevated fire weather conditions. However, relative humidities still look to be marginal, hovering around 15-20%. Dry and warming conditions are expected through the weekend and early next week as weak ridging aloft dominates the weather pattern. Ensemble guidance is in good agreement of temperatures reaching up in the 60s each day through Monday, with the heat peaking mid-week with temperatures in low 70s. Daily elevated fire weather concerns are possible for South Park and portions of the plains, however relatively weak winds will be the limiting factor. && .AVIATION /18Z TAFS through 18Z Thursday/... Issued at 1151 AM MDT Wed Apr 1 2026 Showers have started to develop and move off of the foothills early this afternoon. Coverage will be spotty for the next couple of hours, before coverage increases for the late afternoon and early evening. Rain showers are expected in and around all TAF sites from around 20Z to 3Z give or take an hour. Isolated thunderstorms will be possible this afternoon, but confidence in location and coverage is too low to include in a prevailing group at this time. Showers are expected to move off to the east away from our TAF sites between 2Z and 4Z, with potential to linger a bit longer at DIA. Ceilings will start to scatter out as the showers move out of the area, with a low chance for patchy low clouds overnight. Winds will generally be on the lighter side today, with speeds mainly less than 11kts. The exception to this will be occasional wind gusts around 25kts from nearby showers or thunderstorms. Skies will be mostly clear for tomorrow morning and early afternoon, with winds increasing out of the southwest around 14kts for DIA starting around 20 or 21Z. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 9 PM MDT this evening for COZ031- 033-034. Fire Weather Watch from Thursday afternoon through Thursday evening for COZ246-247. && $$ DISCUSSION...MAI AVIATION...AP