National Weather Service Forecast Discussion |
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066 FXUS65 KBOU 040618 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1218 AM MDT Tue Aug 4 2026 .KEY MESSAGES... - Elevated to critical fire weather conditions likely across the high mountain valleys through the next few days. - Cooler today and Wednesday before temperatures gradually warm back to the triple digits by next weekend. && .DISCUSSION /Through Monday/... Issued at 132 PM MDT Mon Aug 3 2026 As expected, it`s hot across the I-25 corridor and plains this afternoon. Temperatures have already eclipsed 100F at several locations, with places like KDEN not too far behind (currently 99F). These temperatures are rather impressive, especially given the lingering haze/smoke across the plains along with some scattered mid-level cloud cover. We probably have another couple degrees of warming this afternoon, with highs generally hitting the 100-103F range across the I-25 corridor. What remains to be seen is how many showers are able to develop this afternoon. ACARS soundings and SPC Mesoanalysis show very meager instability, but DCAPE currently sits at about 1800 J/kg. It also seems possible (probable) that the HRRR is overdoing the amount of convection this afternoon, just based on satellite trends to start the afternoon. We still expected isolated to widely scattered showers, which would likely produce more wind (gusts up to 50 mph) than rain. Meanwhile, a strong cold front is still on track to arrive later this afternoon. The front looks to be moving through Cheyenne at the moment, with notable pressure rises across eastern Wyoming. This is expected to reach the Denver metro by about 5-6PM today, which should provide substantial relief from the heat... while also advecting some near surface smoke into the area for the evening hours. While smoke will persist through most of Tuesday, we will at least see much cooler temperatures for the plains... with highs in the mid/upper 70s. Temperatures will warm back into the low to mid 80s by Wednesday. The higher elevations won`t feel the effects of the cold front, and will instead have to contend with fire weather concerns over the next few days, as zonal flow aloft begins to strengthen. A Red Flag Warning has been issued for North Park and Middle Park on Tuesday and additional highlights may be needed for Wednesday and Thursday. Our brief cooldown will quickly be replaced by hotter and drier conditions as the upper ridge once again strengthens over the Four Corners region late this week into the upcoming weekend. With mid-level temperatures once again approaching 20-22C this would likely lead to highs approaching 100F on Saturday and Sunday. The position of the upper ridge would also limit any chance of monsoon moisture making a return until at least early next week. && .AVIATION /06Z TAFS through 06Z Wednesday/... Issued at 1145 PM MDT Mon Aug 3 2026 Current satellite and observations show stratus are quickly developing along the Front Range late tonight from persistent upslope flow. Latest KBDU METAR shows cloud base are around 6,000`AGL and approaching KBJC (already in the vicinity). With upslope expected to remain in place overnight, continued moistening of the lower levels should keep stratus developing and spread eastward across the other two TAF sites within the next hour. Latest guidance shows CIG should remain between 3,000` to 5,000` AGL before gradually scattering out after 12Z, but there is still a low chance (10-15%) that we see a few hours of CIG as low as 2,000` AGL, with KBJC having the best chances for this outcome. Smoke is expected to remain in the area through the TAF period, keeping potential for slant range visibility concerns, though there may be a few hours of clearer skies throughout the day. Winds are expected to maintain a NE to easterly component through the day today. Low confidence in winds late tonight as latest hi- res guidance shows drainage winds will struggle to settle in as a cyclone forms near the TAF sites. Depending on where the cyclone forms will determine wind speeds and direction as well as where a potential shear zone forms. && .FIRE WEATHER... Issued at 132 PM MDT Mon Aug 3 2026 Observations early this afternoon show some spotty elevated fire weather conditions across the high mountain valleys, where humidity has fallen to around 15-20% with a few gusts of 20-25 mph. We may eventually see some elevated fire weather conditions across the plains as winds increase this evening ahead of a fairly strong cold front. While the cold front will limit fire danger across the plains for the next couple of days, the front doesn`t look to be deep enough to provide much relief for the higher elevations. Zonal flow is expected to develop on Tuesday, and with deep mixing... it looks likely that North Park and Middle Park will see deep enough mixing to support a few hours of Red Flag conditions during the afternoon and early evening hours. The flow aloft is expected to turn a little bit more northwesterly by Wednesday and Thursday, with 700-500mb winds also weakening slightly. Most guidance still supports at least elevated fire weather conditions across most of the high mountain valleys... and additional highlights may be needed later this week. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 1 PM to 7 PM MDT Tuesday for COZ211-213. && $$ DISCUSSION...Hiris AVIATION...9 FIRE WEATHER...Hiris