National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
441 FXUS65 KBOU 162248 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 448 PM MDT Thu Jul 16 2026 .KEY MESSAGES... - Hot weather continues with the heat now expected to last through Monday. The highest temperatures will occur Sunday and Monday with a Heat Advisory for the urban corridor possible. - Scattered afternoon/early evening storms in the mountains expected through Sunday with the plains remaining dry. - Significant monsoonal moisture and cooler temperatures will arrive on Tuesday of next week. The thunderstorms that develop will be capable of producing locally heavy rainfall. && .DISCUSSION /Through Thursday/... Issued at 1200 PM MDT Thu Jul 16 2026 Water vapor imagery shows a very weak shortwave trough over northeast Colorado moving southwestward with plenty of dry air aloft. At the surface, there are warm temperatures and decently high moisture values given the warmth. With very steep lapse rates and most-unstable CAPE approaching 1,000 j/kg over the mountains, widespread thunderstorms are expected in Park County with scattered coverage in Grand and Summit Counties. Some storms could have nickel size hail in South and Middle Parks. In addition, multiple rounds of storms could lead to rainfall totals around an inch in Park County. Otherwise, some isolated showers or storms could develop in the southern foothills. It is unlikely but possible that a storm or two moves onto the adjacent plains in the southwest Denver metro which could produce some wind gusts up to 35 mph this evening. Slightly warmer temperatures aloft with less moisture will lead to an increase in surface temperatures by a degree or two on Friday with less coverage of showers and storms over the mountains. A ridge of high pressure aloft will strengthen on Saturday and Sunday and place itself directly over Colorado. 500 mb heights will increase to around 594 dm over our CWA on Saturday and up to 596 dm on Sunday. High temperatures will increase as a result and highs will be 96-98 in the downtown areas of Denver, Fort Collins, and Greeley on Saturday. The warmest day of the 7-day forecast appears to be Sunday as highs in the downtown areas of those three cities will be between 99-101. The latest HeatRisk forecast value for Sunday shows most of the urban areas will have a value of 3. If models continue to show this level of heat tomorrow, a Heat Advisory may be issued for the urban corridor for Sunday. One of the bigger forecast changes over the past 24 hours is the delay in the arrival of the monsoonal moisture and cooler temperatures. The ECMWF ensembles now have a much tighter range of forecast high values with the 25th percentile in Denver of 97. This is likely due to a slight shift with the center of the upper level ridge to the northwest throughout the forecast runs. If this trend continues, it is possible that high temperatures will be around 100 degrees again in urban areas with a HeatRisk value at 3 on Monday. That means, a Heat Advisory will again be considered for Monday. Showers and storms will increase in coverage over the higher terrain on Monday as more monsoonal moisture makes its way northward. But it is not until Tuesday that the plains will begin to see better coverage of showers and storms. With the upper level ridge shifting to the south, there will be light westerly flow aloft which will allow storms to move off the higher terrain and onto lower elevations. The storms Tuesday night and into Wednesday will have ample moisture and moderate instability. It does look like the first couple of days that this monsoonal moisture arrives will have a flash flooding concern due to heavy rainfall. && .AVIATION /00Z TAFS through 00Z Saturday/... Issued at 444 PM MDT Thu Jul 16 2026 VFR conditions will prevail for all terminals through the TAF period. ESE winds will continue to persist at the terminals through early this evening with gusts generally in the 19-25 kt range. Latest guidance has accelerated the rotation to southerly drainage flow this evening, so the TAFs reflect this quicker transition. Ongoing convection across Park County could induce some sw-erly outflows after ~01Z, with corresponding impacts to KAPA in the form of occasional gusts 25-30 kts, however confidence is low. This potential is notably lower for the other two terminals. Tomorrow, expect very similar diurnal wind patterns with development of robust E/ESE flow by early afternoon. An isolated high-based shower and associated outflow wouldn`t be out of the question later in the day, but neither confidence nor projected coverage are high enough to warrant any explicit inclusion in the TAFs. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Danielson AVIATION...BRQ