


Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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263 FXUS65 KBOU 131735 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1135 AM MDT Sun Jul 13 2025 .KEY MESSAGES... - Warmer with isolated showers and thunderstorms across the high country this afternoon. Similar pattern again for Monday. - Afternoon showers/thunderstorms to continue most days for the upcoming week. Best chance of rain across the plains comes Wednesday. - High temperatures to linger in the 90s across the plains through mid-week. && .DISCUSSION /Through Saturday/... Issued at 224 PM MDT Sat Jul 12 2025 This morning`s (Saturday) low clouds have finally scattered out across the forecast area and a Denver Cyclone has developed. Current satellite imagery shows some cumulus starting to build along the higher terrain, with a few weak reflectivity returns starting to show in northern Park/western Jefferson Counties where surface heating has been greatest so far today. With enough instability in place as shown by the 500 to 1000 J/kg of MLCAPE shown in the SPC Meso Analysis, these cumulus are expected to transition into scattered showers and storms by early this afternoon. With a prominent cap in place across the lower elevations as portrayed in the latest ACARS sounding, these showers and storms won`t have much luck of persisting onto the lower elevations where CAPE is far more robust. However, with WNW to NNW steering flow in place, storms that form will have potential to move along the higher terrain where the cap is already broken, and we could see an isolated threat for severe hail and some gusty outflows through the early evening. With the cyclone in place, there is a chance that the convergence zone could aid in breaking the cap along the Palmer Divide and slightly north onto the adjacent plains where the more robust CAPE will be in play, but have kept the greatest PoPs south and west of the urban corridor where guidance continues to portray things staying along and south of I-70 in the mountains and foothills. Light NNW flow aloft will persist into Sunday as the ridge over the southwest remains in place. Instability will increase over the mountains as forecast soundings show SBCAPE reaching 700-800 J/kg and mid-level lapse rates steepening to 9+C/km by the afternoon. This will promote scattered afternoon and evening convection, with showers and storms expected to remain anchored to the higher terrain. Temperatures will return to the 90s across the lower elevations on Sunday and persist there through the first half of the week. Models are fairly consistent for the first half of the week, keeping pulses of afternoon mountain convection each day, becoming more widespread by Tuesday. Some discrepancies with timing of a shortwave trough entering the Pacific Northwest on Tuesday are evident between the ensembles, with the GFS supporting a cooldown on Tuesday/Wednesday, whereas the ECM ens keeps an extra day of 90F+ for the plains, seeing a cooldown for Wednesday/Thursday instead. The NBM seemed like a reasonable solution based on the differences, so little changes were made past Monday for this package. While the timing may be off, the signal is in place that a brief cooldown will occur by mid-week. Past that, ensembles show that the 90s will return and look to stick around across the plains through at least the last week of July. && .AVIATION /18Z TAFS through 18Z Monday/... Issued at 955 AM MDT Sun Jul 13 2025 VFR conditions expected through the TAF period. Winds are expected to continue to make their way to the east through the afternoon before making their way to the southeast this evening. Guidance suggests a few hours of gusty S/SE winds (15 to 25 kt) at KDEN/KAPA late tonight (5Z to 8Z), so winds were increased slightly to account for this. It`s worth mentioning that some hi- res guidance has been inconsistent between runs this morning leading to some uncertainties and lowered confidence for this evening`s forecast. Guidance hints at potential for dissipating showers and thunderstorms to drop 35 to 45 kt microbursts across all TAF sites as they move off the higher terrain. At this point, confidence is too low to include in the TAF (~20%), but this will be monitored closely as the day progresses and introduced into the TAF if confidence increases. For tomorrow, drainage looks to hold on through the morning before returning to the southeast for the afternoon at KDEN/KAPA. KBJC is expected to keep light and VRB winds through the early morning, turning towards the NE late morning. Have introduced a PROB30 for afternoon high-based convection potentially bringing strong outflows and microbursts late afternoon. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Bonner AVIATION...Bonner