Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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536 FXUS65 KBOU 281604 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1004 AM MDT Tue May 28 2024 .KEY MESSAGES... - Scattered late afternoon/evening storms today, mainly over the Front Range and Palmer Divide. - Higher afternoon thunderstorm potential on Wednesday, when a few severe storms will be possible, mainly for the rural plains. - Slightly cooler Thursday behind a cold front, with isolated to scattered afternoon showers/storms each day through at least Saturday. - Drier/warmer conditions favored as we near early next week, but details become more murky Sunday onwards. && .UPDATE... Issued at 1000 AM MDT Tue May 28 2024 GOES-16 Day Cloud Phase displays a few clouds building in South Park and the southern foothills. The forecast package remains on track of scattered showers and storms occurring late afternoon through this evening. Small adjustments to increase the PoPs along the Palmer Divide and Lincoln county as CAMs continue to favor these areas for storm development through this evening. && .SHORT TERM /Through tonight/... Issued at 319 AM MDT Tue May 28 2024 Southeasterly low level flow is developing over the plains, with a broad swirl northeast of Denver producing north winds into the city. That feature will probably wash out or drop southward as the day progresses, with winds becoming more easterly in Denver. This will bring increased low level moisture. Slight warming aloft means it will still take most of the day to reach the convective temperature of around 80 at lower elevations. We`ll eventually have scattered storms mainly over the east slopes of the Front Range in the afternoon, moving east of the mountains into the early evening. The storms are most likely to survive over the higher terrain south of Denver, though an isolated storm or two over the northeast plains is possible given the increased moisture. There`s not a lot of shear and CAPEs in the areas we expect storms will likely be 400-800 J/kg, so gusty winds might be the main feature of the storms. With light winds aloft, some clouds will likely linger much of the night and there may also be some stratus/fog developing in eastern border areas towards morning. && .LONG TERM /Wednesday through Monday/... Issued at 319 AM MDT Tue May 28 2024 The ridge axis nudges east on Wednesday as a trough deepens over the Northern Rockies, and also allows for development of some lee troughing east of the Front Range. Low-level southeasterly flow will increase ahead of the approaching front, bringing with it some modest moisture advection as well as slightly warmer temperatures, which should climb into the 80`s for most of the lower elevations. Lapse rates will steepen with the arrival of colder air aloft, with mixed-layer CAPE in the range of 1,000-1,500 J/Kg looking reasonable for a good portion of our rural plains. These ingredients should lead to scattered convection initially developing in the high country near midday/early afternoon, then pushing eastward into the plains through the rest of the afternoon and evening. Drier air near the surface along the urban corridor will likely limit the coverage and intensity of any afternoon convection, with storms gathering strength as they move east where both moisture and instability will be most favorable east of a weak dryline. Potential exists for some to become severe, especially across the eastern plains, with wind and hail the primary threat, particularly as they become better organized. A cold front will drop south into northeastern Colorado Thursday, pushing through most of our CWA in the morning, ushering in modestly cooler temperatures and also tapering the convective potential somewhat in the afternoon. If it`s a little slower than anticipated it could provide a boost to afternoon thunderstorm potential mainly for southern portions of our forecast area in and around the Palmer Divide. Severe threat should not be as high as Wednesday`s, however. By Friday, upper-level flow becomes increasingly zonal as troughing remains confined well to our north into Canada, and this remains the case through at least Saturday. Thus, isolated to scattered afternoon showers and thunderstorms, albeit generally not of high intensity, appear reasonable for both days. The high country should see the greater coverage, with precipitation chances lowering slightly area-wide on Saturday under more subsident flow and drier near-surface conditions, which will also result in some modest warming and lower elevations highs rebounding into the 80`s. Solutions start to diverge more considerably come Sunday and Monday with regard to the upper-level pattern. The EC ensemble suite is on the dry side, keeping predominantly zonal and subsident flow in place, while GFS ensembles still provide more opportunity for a shortwave trough and front to sustain at least a slight chance of some afternoon showers and storms. Overall the trend seems to be towards the drier solutions however, so our forecast leans in that direction, along with above-normal temperatures for the period. && .AVIATION /06Z TAFS through 06Z Wednesday/... Issued at 1250 AM MDT Tue May 28 2024 VFR through Tuesday. Light winds are expected, except for possible thunderstorm outflows up to 25 knots after 21z. This is more likely (40% chance) for KAPA and KBJC with a 20% chance for KDEN. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...AD SHORT TERM...Gimmestad LONG TERM...Rodriguez AVIATION...Gimmestad