Area Forecast Discussion
Issued by NWS
Issued by NWS
585 FXUS64 KLUB 190521 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 1221 AM CDT Tue Aug 19 2025 ...New SHORT TERM, LONG TERM, AVIATION... .KEY MESSAGES... Issued at 1220 AM CDT Tue Aug 19 2025 - Isolated thunderstorms are expected this afternoon, and some may be capable of producing localized flash flooding and strong winds. - Storm chances will increase quickly tonight, with the flash flooding potential lasting into the nighttime hours. - Showers and storms are forecast to linger into Wednesday, with a drying trend to follow through this weekend. && .SHORT TERM... (Today and tonight) Issued at 1220 AM CDT Tue Aug 19 2025 02Z upper air analysis depicts an amplifying subtropical ridge that continues to slowly retrograde westward, which has caused the advection of monsoonal moisture to cease and the once-formidable plume to collapse. A 250 mb jet streak of 30-35 kt was observed by the 19/00Z objectively analyzed UA charts, specifically WFOs AMA and MAF, with the 250 mb anticyclone centered over Lowland Deserts of New Mexico and far northern Chihuahua. The mid-level tranche of the ridge has also shifted farther westward and is beginning to align with the 250 mb anticyclonic vortex, but it is still broad and expands across most of the Lower 48, although the circulation over the Great Plains is better defined compared to 24 hours ago. Farther north and west, a semi-progressive pattern is present over the 49th parallel, with an intense shortwave trough digging into the Pacific Northwest. The westward translation of the subtropical ridge has forced the broadly cyclonic flow farther north, resulting in an positive feedback of the ageostrophic component of the flow, as the southern-stream 250 mb jet streak is beginning to phase with the shortwave trough emerging over the Pacific Northwest. A convectively- augmented vorticity lobe was analyzed on water-vapor imagery over NW KS, which has enhanced the magnitude of high-level divergence along the leading edge of the 250 mb jet streak as it arcs around the apex of the amplifying ridge. The net result of this synoptic-scale state will contribute in the maintenance of thunderstorm chances across portions of the CWA through the predawn hours Tuesday, especially as the low-level jet, albeit weak, remains backed. Lightning potential will gradually wane by sunrise, and strong gusts are not expected due to cells being elevated atop the decoupled boundary-layer. At the surface, a convectively-reinforced trough was analyzed along the edge of the Mescalero Escarpment, where three-hourly pressure tendencies were +3 millibars, as observed by WTM data. This surface trough connects to a lee cyclone rotating in southeastern CO, and the CWA remains within a weakening, southerly fetch; and the gradient wind field is not as contaminated from storms as it was this time last night. Farther north, the convectively-reinforced, synoptic cold front was located along the 40th parallel, and was continuing to move southward into KS. (This front is expected to move into the CWA by Wednesday morning, and is of importance to the incoming storm chances Tuesday night.) Winds will become light and variable by sunrise, followed by a transition to the southeast as a weak surface high rotates into Upper Red River Valley. Temperatures will be slightly cooler than Monday, though still hot, as the core of the subtropical ridge begins to stall over the southern Rocky Mountains and geopotential height tendencies maintain neutrality over the CWA despite its amplification. Convective temperatures will be reached by 20-21Z, similar to the last few days, with highs rising into the middle 90s area-wide. However, lingering cloud debris in the mid-levels and convective overturning from multiple days of scattered-to-numerous storms may act to temper the coverage of storms across the CWA Tuesday afternoon. Isolated storms are forecast to develop Tuesday afternoon, with the remnant outflow boundaries serving as the foci for surface-based development. The gradual strengthening of the 250 mb winds will maintain the southerly propagation component, and although coverage of storms should be limited, a rogue strong-to-severe-caliber wind gust and brief, heavy rainfall will accompany cells that can organize. Meanwhile, the convectively-reinforced cold front is forecast to near the OK/KS state line before dusk Tuesday, with the front moving into the CWA late Tuesday night into early Wednesday morning. PoP chances are forecast to increase area-wide during this time, with an expectation for scattered storms to move southward across the CWA, perhaps in a loosely-organized MCS. Outflow-related theta deficits along the leading edge of the cold front, beneath a belt of 25-30 kt 500-200 mb flow, will accelerate the progression of the front, especially on the Caprock, ultimately tempering the extent of the flash flood risk during the overnight hours. However, efficient rainfall, as observed over the last few days, may warrant a localized flash flooding risk with the organized cells. Sincavage && .LONG TERM... (Wednesday through Monday) Issued at 1220 AM CDT Tue Aug 19 2025 Showers and storms will be ongoing across portions of the CWA Wednesday morning, as the cold front is forecast to move south of the CWA shortly after sunrise. Significant adjustments to the NBM PoPs have been made with this cycle, with removal of PoPs across the northern zones Wednesday afternoon. A few showers and storms may linger across the southern half of the CWA Wednesday afternoon before the mid-level vorticity lobe finally exits into the Permian Basin. Locally heavy rainfall and isolated instances of flash flooding will be the primary hazard, as the passage of the cold front, combined with the effects of convective overturning, delay the rate of mixing and maintain a nearly moist-adiabatic profile within the boundary-layer. High temperatures for Wednesday were also cooled a few degrees to align with this thinking. Additional tweaks to the PoPs may be necessary in the subsequent forecast cycles, especially as mesoscale guidance hones in on the timing of the front and the state of the post-frontal airmass. Global NWP guidance is in agreement with the amplification of the subtropical ridge over the Four Corners region by Thursday. Fortunately, as mentioned in prior forecasts, geopotential height tendencies will remain nearly neutral over W TX, which will keep temperatures near seasonal norms for the rest of the week and into the weekend. Deep-layer flow is also forecast to become increasingly confluent, maintaining large-scale subsidence, and a dry forecast is reflected through the weekend. Sincavage && .AVIATION... (06Z TAFS) Issued at 1220 AM CDT Tue Aug 19 2025 Continued VFR with an outside chance of TS by Tuesday afternoon until much better chances emerge soon after 06Z/Wed at all terminals. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...09 LONG TERM....09 AVIATION...93