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563 FXUS65 KBOU 241147 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 547 AM MDT Sat May 24 2025 .KEY MESSAGES... - A conditional severe threat today across most of the plains and I-25 corridor. - Higher shower and storm coverage through the Memorial Day Weekend, along with cool temperatures. - Gradual warming next week with more typical shower/storm coverage each afternoon and evening. && .UPDATE... Issued at 325 AM MDT Sat May 24 2025 Forecast for today regarding severe thunderstorms across the urban corridor and eastern plains has not become any more clear over the past 12 hours. A cyclone has formed bringing northwest to west winds to a good part of the Denver area keeping the low clouds from moving in. Models show this cyclone staying in place, but varying in strength through the morning and this could limit the amount of low clouds. If this were to occur, chances for strong to severe thunderstorms would be fairly high with a moist and unstable airmass in place. For areas north of Denver, low clouds have formed. One change for today...even though the easterly push last evening did spill a little over the Continental Divide, there`s not enough of an easterly push to keep moisture in place. Drier air will mix out of the low level moisture by this afternoon. Precipitable water values fall below a quarter inch so it will be very dry. Therefore, removed the mentioned of showers and thunderstorms for today and tonight west of the Continental Divide. && .SHORT TERM /Through Saturday/... Issued at 302 PM MDT Fri May 23 2025 For the most part, things continue to progress as expected this afternoon. Across the metro, it`s been a little slower to warm up, with the near-surface inversion just a touch stronger than guidance had suggested. Temperatures have made it into the upper 70s/low 80s so far, and high temperatures are still expected to make it into the low/mid 80s for most locations later this afternoon (high so far at DEN is 82F). Meanwhile, the more interesting part of the forecast will unfold over the next few hours. Convection has already developed across Elbert county, where SPC Mesoanalysis suggests the inversion/cap has eroded better than anticipated. With guidance not handling this well, it`s difficult to say how this will evolve as it drifts towards the better moisture/instability axis, but at least a marginal severe threat exists along/south of I-70 into Lincoln county this afternoon and evening. The convection north of Cheyenne still looks to be the main show this afternoon. Guidance has been remarkably consistent, with a dominant supercell or two eventually emerging from the currently disorganized TS, which then turn right and drop southeastward into the northeast corner of Colorado. Though there remains some modest capping in the region, continued daytime heating along with some surface moisture convergence should continue to erode what little cap remains. In general, the parameter space is largely favorable for severe convection, with MLCAPE exceeding 2000 J/kg along with ample deep layer shear. There may be some brief potential for a tornado or two, with some sort of boundary noted on KFTG radar near STK-AKO. As we move onto tonight, deep boundary layer moisture is expected to advect into the region as east-southeasterly flow strengthens (potentially aided by convective outflow across eastern Colorado). While this will increase surface dew points into the upper 40s/low 50s across the Denver metro, it will also lead to widespread stratus... making tomorrow`s forecast difficult. We`ll almost certainly start the forecast period socked in stratus across most of the lower elevations. Guidance, like just about every other time we have this setup, provides a large range of solutions but little in the way of any clear signal. There are generally two schools of thought here, depending on your perspective. The first would be that the continued southeasterly surface flow eventually forces some stratus breakout by mid/late morning, leading to widespread destabilization across the I-25 corridor and adjacent plains by midday. Guidance in this camp paints quite a favorable setup across most of the metro and plains, with good CAPE/bulk shear profiles and curved hodographs. If this were the case, scattered supercells would be a favored storm type with hail as the primary threat. On the other hand, a deeper stratus deck that doesn`t manage to burn off would lead to significant capping (12z NAMnest solution) with a few weak thunderstorms across the lower elevations. As is normally the case, we`ll likely have a better idea by tomorrow morning. Temperatures will be cooler than today either way, but should reach the upper 60s to low 70s. && .LONG TERM /Saturday night through Friday/... Issued at 302 PM MDT Fri May 23 2025 Cooler weather will prevail for Sunday and Memorial Day as an upper trough continues to slowly move eastward towards the CWA. Sunday looks to be the coolest day of the week, as a thicker stratus deck is likely to form Saturday night (especially if additional moisture/precip is added from convection). There`s enough forcing to support widespread showers and a few storms in the afternoon with skinny CAPE profiles across the lower elevations. The overall pattern doesn`t change significantly Monday, with temperatures again in the 60s and additional chances for afternoon showers/storms. We probably won`t have a good handle on any timing/severity of storms for another day or two, so those with outdoor activities planned should continue to check back for further updates. Model solutions gradually diverge into next week, though most ensemble guidance would suggest at least chances for showers/storms during the afternoon/evening hours... not all that atypical for late May in Colorado. A gradual warming trend is expected through the week, with potentially warmer weather looming as we get to next weekend with hints of a larger ridge developing in that timeframe. && .AVIATION /12Z TAFS through 12Z Sunday/... Issued at 546 AM MDT Sat May 24 2025 Low clouds have spread across the Denver area. A Denver cyclone produced a slight west wind component across much of the Denver area and made the low cloud development slow going. The cyclone slowly washes out over the next few hours with an east to northeast wind expected to take over by 18Z. This is expected to keep low clouds with ceilings of 500 to 1500 feet in place through at least late morning 16-18Z. We start to see the low clouds scattered and lift 18-21Z, at APA first. Though we likely keep a ceiling of 2500-5000 feet most/all of the day. The partial clearing will lead to warming and increase the instability. Best time frame for thunderstorms will be 20-02Z, and most numerous across the southern parts of Denver, towards APA. For tonight and Sunday morning, low clouds and fog set in around or shortly after 06Z Sunday with ceilings less than 1000 feet. Wind direction will should play a big role if we end up with fog or localized downslope flow leads to just low ceilings. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Meier SHORT TERM...Hiris LONG TERM...Hiris AVIATION...Meier