National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
720 FXUS65 KBOU 030554 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1154 PM MDT Sat May 2 2026 .KEY MESSAGES... - Above average temperatures and dry conditions expected for Sunday. - Unsettled weather returns Monday night through Wednesday with increasing chances for rain showers and some snow for the plains. - Significant snowfall accumulations are possible (70% chance) in the mountains Monday night through Wednesday. Chances are increasing for accumulating snow along the I-25 corridor Tuesday evening into Wednesday. && .DISCUSSION /Through Saturday/... Issued at 1150 PM MDT Sat May 2 2026 An upper level ridge will continue to influence our weather for one more full day. Temperatures on Sunday morning will be near average in the mid to upper 40s. Sunday will be another above average day with highs in the mid to upper 70s for the plains with a low (20-30%) chance for light mountain snow and increasing mid to high level cloud cover by late afternoon. Monday will also feature mid to high level cloud cover and high temperatures in the 70s. Monday afternoon will bring the first signs of this system to our region. High-based showers and virga are possible (30-40%) on the plains as well as light mountain snow. Model soundings show DCAPE values as high as 800 to 1000 J/kg, so any shower could produce some gusty outflow winds. An upper level low will be located over California on Monday afternoon and moving east throughout the week. Meanwhile, the jet stream will be moving south out of Canada with at least a piece of it moving through CO/WY on Tuesday night and Wednesday. Model consensus places us in the left exit region of this jet by Wednesday morning. Models/ensemble clustering have come into better agreement over the last 36 hours, increasing the likelihood of these two features phasing together, which would put our forecast area in a favorable position for lift, frontogenesis, and thus for measurable precipitation. As a cold front approaches and moves through the forecast area on Monday night, winds will become gustier and precipitation will become more widespread with rain for the plains and snow for the mountains initially. A second surge of cold air is expected on Tuesday into Tuesday night. Thus, high temperatures on Tuesday and Wednesday could range from the mid 30s to mid 40s for the Urban Corridor and plains given increased cloud cover and precipitation chances. Temperatures on Tuesday night could fall anywhere between the upper 20s and low 30s. Have continued to nudge temperatures down for Tuesday AM through Wednesday PM. As of now, projected snow levels will be around 7500 feet on Tuesday morning and drop to or a little below 5500 feet by late Tuesday night. A subtle trend in forecast temperatures in either direction could make a substantial difference in snow levels and thus potential snow accumulations for the lower elevations. Precipitation will last into the day on Wednesday before coming to a close by Wednesday afternoon and evening. As of now, we are confident that the heaviest snowfall (8 to 13 inches) would be for the mountains making travel difficult for Tuesday through Thursday morning. There is increasing confidence in several inches of snow accumulation and some travel impacts for the foothills and Palmer Divide. Upslope flow for the Palmer Divide would be favorable for localized higher accumulations as compared to the rest of the I-25 corridor. Finally, the Denver metro and adjacent plains will start as rain on Monday night and Tuesday, but could see a switchover to snow on Tuesday night leading to at least some snow accumulations on grassy surfaces of a trace to 2 inches. Of note, nearly 90% of ensemble members now show at least a trace of snow for the Denver metro and a 70% chance of at least one inch of snow accumulation. While confidence has increased that the Urban Corridor and adjacent plains could see some accumulation, exact snowfall amounts remain uncertain. Overall, total QPF amounts of 0.5" to 1" are expected at this time with isolated higher amounts, especially for the mountains, foothills, and the Palmer Divide. Regardless of ptype, this system is much needed given that the majority of the area is currently in extreme to exceptional drought. Headlines could be needed within the next 24 to 48 hours. Finally, model guidance is in good agreement of temperatures returning back to the 70s late week as upper level ridging starts to build back in. && .AVIATION /06Z TAFS through 06Z Monday/... Issued at 1116 PM MDT Sat May 2 2026 VFR conditions will prevail for all terminals through the TAF period. Robust SW drainage flow of 08-12 kts will continue through early to mid morning Sun (W for KBJC), then begin to rotate clockwise starting near 15Z and becoming N/NW by around 17Z, +/- 2 hours. Wind direction is more uncertain for late afternoon and early evening, but will eventually return to drainage overnight. There will be an increase in mid-level cloud cover mid-afternoon as SCT cumulus develops. ISO virga is not out of the question, but moisture will be highly limited and thus the outflow wind potential doens`t appear high enough to warrant a PROB30 group at this time. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...MV AVIATION...BRQ