Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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010 FXUS65 KBOU 251705 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1105 AM MDT Tue Jun 25 2024 .KEY MESSAGES... - Continued Hot today with a Heat Advisory for the Denver Metro. - Isolated high-based showers and thunderstorms this afternoon into the early evening with gusty winds. - Slightly milder with increased chances for thunderstorms Wednesday and Thursday. A few could be strong to severe. && .UPDATE... Issued at 1105 AM MDT Tue Jun 25 2024 Temperatures this morning are running anywhere from 2-8 degrees cooler across the I-25 corridor. Granted, it`s still going to be hot across the entire area below 7,000 ft (> 90 degF), and the current forecast highs still look well on track. We will leave the Heat Advisory in place for metro Denver and at risk populations, given temperatures at 11 AM are already at or above 90 degrees, on their way to 97-100 degrees. Unlike yesterday when clouds and gust fronts provided relief, today`s convection should be weaker and with less coverage than on Monday, which will keep temperatures hot well into the early evening hours, especially across Denver. Larimer, Boulder, and Weld Counties will likely see some relief in the form of clouds and cool-ish outflows by late afternoon. && .SHORT TERM /Through tonight/... Issued at 307 AM MDT Tue Jun 25 2024 Upper level high centered over the Central and Southern Rockies will bring another very warm to hot day to the area. Highs over northeast Colorado are expected to reach the mid to upper 90s. Winds turn northerly by early afternoon, however the airmass with these north winds won`t be much cooler, not at first anyways. Far northeast Colorado, may see highs a couple of degrees cooler today. A slight decrease in moisture and instability will lead to fewer showers and thunderstorms. By mid afternoon, we should see isolated showers and storms over the higher terrain. This activity then drifts eastward through mid evening. Any rainfall reaching the ground is expected to be brief and light. Wind gusts to 40 mph will be common with the showers and storms. The showers/storms dissipate this evening as the airmass stabilizes. && .LONG TERM /Wednesday through Monday/... Issued at 307 AM MDT Tue Jun 25 2024 The upper-level ridge will begin to show signs of deflation Wednesday with slight cooling underneath. Fairly abundant mid-level moisture will also be cycling clockwise into Colorado from the Desert SW, pushing Precipitable Water (PW) values to 2-3 standard deviations above normal later in the day. At the same time, a weak and quasi-stationary boundary looks to hover over the plains, with dewpoints likely breaking into the 60`s for the northeast plains come the evening hours. Despite the comparatively cooler temperatures, we`ll still be notably warm with high temperatures that should climb into the lower to mid 90`s for the majority of our lower elevations. Certainly sufficient to promote MLCAPE values in excess of 1,000 J/Kg, mainly east of I-25. Of all the days in the long-term forecast period, Wednesday looks like the one with the most favorable bulk shear, enough to support some stronger storms, some of which could become severe along and east of I-25 in the late afternoon and evening, as well as produce locally heavy rainfall. Flow aloft becomes more zonal Thursday. We`ll see a gradual reduction in moisture, but PW values near or slightly above 1" still seem plausible for most of the plains and urban corridor. Temperatures will hold relatively steady and remain above average, helped by development of weak downslope flow. Instability should be slightly tapered relative to Wednesday, with the more favorable parameter space located in the eastern plains. Storm motions also look to pick up Thursday, closer to 20-30kt, which will help reduce the threat of flash flooding for the burn scars. Nonetheless, at least scattered thunderstorms appear a fair solution for most areas in the afternoon. A cold front associated with an upper-level shortwave will traverse the region Friday, bringing modestly milder temperatures but also slightly drier conditions. Afternoon thunderstorm coverage looks to be somewhat reduced, with more isolated convection over the plains, and higher storm potential over the higher terrain. The weak downslope flow in place Friday is progged to dissipate by Saturday and allow for temperatures to relax a little farther, as highs descend closer to the mid 80`s for the plains. A few afternoon thunderstorms can be expected again, most numerous in the mountains, and with moisture on the rise, some of the stronger storms could produce heavier rain. With the ridge aloft pushing east of the region starting Sunday, warm southeast surface flow will become more robust and help advect more substantial low-level moisture into northeast Colorado, with some guidance hinting at development of a dryline in the plains. Hotter temperatures look slated to return as well, climbing back into the 90`s. Isolated to scattered thunderstorms can be expected again for much of the region. && .AVIATION /18Z TAFS through 18Z Wednesday/... Issued at 1105 AM MDT Tue Jun 25 2024 VFR through Wednesday and with hot temperatures both this afternoon and Wednesday afternoon. There shouldn`t be any showers at the terminals this afternoon, but one or two wind shifts with gusty winds are expected. For now, the most likely wind shift looks to be west, northwest, or north given where some weak convection should be ongoing this afternoon. We will continue to handle the potential wind shifts with a TEMPO group for VRB gusts to 30 kts. Tonight will be a normal drainage wind night (SSW at APA and DEN 8-12 kts; WSW at BJC 5-9 kts). On Wednesday, winds should shift to the ESE and maybe gust over 20 kts from midday until storms gets going and move of the mountains. Thunderstorm coverage will be much more than that past couple of days. Those storms may directly impact the terminals, but it`s about a 40 percent chance of a storm going overhead. It`s almost a guarantee that several gust fronts will move across the terminals with a wind shift and gusty winds to 35 kts. && .HYDROLOGY... Issued at 307 AM MDT Tue Jun 25 2024 Increased subtropical moisture will be present Wednesday and Thursday, boosting the potential for heavy rainfall from any afternoon thunderstorms for all areas, including mountains and plains. Storm motions will be slightly faster Thursday, helping to taper the threat of flash flooding. Isolated to scattered afternoon thunderstorms will continue beyond Thursday, but moisture will generally be more limited, thereby reducing the potential for heavier rainfall. && .BOU WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 9 PM MDT this evening for COZ040. && $$ UPDATE...Schlatter SHORT TERM...Meier LONG TERM...Rodriguez AVIATION...Schlatter HYDROLOGY...Rodriguez