Area Forecast Discussion
Issued by NWS
Issued by NWS
340 FXUS64 KLUB 291814 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 114 PM CDT Fri Aug 29 2025 ...New KEY MESSAGES, SHORT TERM, LONG TERM, AVIATION... .KEY MESSAGES... Updated at 114 PM CDT Fri Aug 29 2025 - Thunderstorms, some severe, are expected to move across the forecast area this evening and into Saturday morning, with flash flooding possible. - Chances for storms, some severe, return Saturday afternoon, and will increase quickly late Saturday night into Sunday morning. - A greater risk for flash flooding exists Saturday night and into Sunday morning across the entire forecast area. && .SHORT TERM... (This evening through Saturday) Issued at 114 PM CDT Fri Aug 29 2025 Synoptic surveillance this early afternoon reveals an anticyclonic wave break nearing its completion over northern Canada, causing the longwave troughing over the northeastern U.S. to begin pivoting northeastward towards the Canadian Maritimes. Farther west, a train of vorticity lobes were analyzed on water-vapor imagery over the Pacific Northwest and into the northern Great Plains, with another lesser-defined vorticity lobe rotating over the Slot Canyon Region of UT. The subtropical ridge has started its gradual shift eastward, with the anticyclonic vortex remaining nearly aligned through 200 mb, per the 29/12Z objectively analyzed UA charts. The 250 mb jet streak was analyzed between 50-70 kt, depending on the RAOB, with its core arcing over the central Rocky Mountains and its leading edge nosing into the southern Great Plains. Geopotential height tendencies have become slightly negative across the central and northern Great Plains in response to the anticyclonic wave break and the train of PV anomalies that have since propagated eastward into the Lower 48. Dampening of the subtropical ridge is expected throughout the short-term period as a shortwave trough digging into the central Rocky Mountains impinges on its amplitude and the center of the ridge shifts eastward over the Edwards Plateau. Low-level stratus continues to gradually erode, with the thick stratus and billow field transitioning into shallow cloud streets across along a line from CVN-LBB-SNK. A shallow, northwestward-propagating gravity wave, generated by the collapsed thunderstorms from this past morning over the Permian Basin, has accelerated the erosion of the billow field across the southwestern periphery of the cloud deck. At the surface, the cold front that moved through the CWA yesterday has become quasi-stationary. It is located along the lee of the southern Rocky Mountains, bending eastward across the northern TX Big Bend and extends all the way into Central TX between the I-10 and I-20 corridors. The CWA is within a broad fetch of moist, upslope flow, with post-frontal winds prevailing out of the northeast on mesonet and METAR data. Despite the differential mixing that is underway, dewpoints ranged between 65-69 degrees from southwest-to-northeast across the CWA, indicating that there has actually been a positive feedback with respect to the moistening of the boundary-layer compared to this time yesterday. The post-frontal surface high was weak, with an ill-defined center analyzed on mesonet and METAR data in far southern KS and northwestern OK. Winds are expected to gradually veer eastward throughout the afternoon hours, as the surface high disperses and transitions into return flow in response to the pressure falls associated with cyclogenesis along the lee of the Rocky Mountains. High temperatures will also range from the lower 80s across the far southeastern TX PH to the middle-upper 80s onto the Caprock, to near 90 degrees in the southern South and Rolling Plains. Thunderstorm chances are expected to increase quickly by sunset for locales near the NM state line, with chances increasing farther east across the rest of the Caprock and into the Rolling Plains after dark. A series of shortwave perturbations rotating through the apex of the deamplifying ridge will generate diurnally-driven storms across the higher terrain of NM this afternoon, with gradual upscale growth into a loosely-organized line expected as it approaches the NM/TX state line. The well-mixed boundary-layer beneath cloud base will facilitate the potential for strong-to-severe-caliber wind gusts in excess of 60 mph, but this risk should be localized through the late-evening as outflow-related theta deficits cause cold pools to accelerate ahead of the primary cores towards 05Z/midnight CDT tonight. Blended TPW (Total Precipitable Water) from GOES-19 indicates a plume of 1.50-1.75" PWATs advecting over the CWA, which also matches the 12Z RAOB from WFO MAF and recent mesoscale analysis. The combination of the mesoscale analysis and satellite estimates, in addition to the 12Z RAOB, indicates that PWATs are at or exceeding the 99th percentile over the CWA when interpolating the sounding climatology from WFOs AMA and MAF. Therefore, the loosely- organized line(s) of storms will be capable of producing efficient rainfall, with rain rates between 1-2 inches per hour expected with the strongest storms. However, the initial eastward propagation of the system will be at around 25 kt, before a southeastward turn occurs as the complex propagates along the thickness gradient, keeping flash flooding localized as the potential for back-building is counteracted by downshear Corfidi vectors transitioning to the northwest to near 30 kt after dark. The lack of mid-level support tonight should curb the potential for rear-inflow jet development, with outflow eventually accelerating ahead of the broken line of storms by early Saturday morning. The complex of storms is forecast to exit the CWA near or after sunrise, with lingering showers and storms possible above the stabilized, decoupled boundary-layer. Any lingering convection will be elevated, with a brief lull in showers and storms expected by the late-morning hours Saturday. NBM PoPs were removed almost completely during this time (30/15-18Z, or 10 AM-1 PM CDT), with low-level stratus thickening beneath residual anvil debris aloft. The surface pattern should be convectively-contaminated, with gradient winds forecast to restore to the southeast by the early afternoon hours from the leeward pressure falls occurring in eastern NM beneath the next incoming shortwave trough. Differential diabatic heating will allow temperatures to warm into middle 80s, and temperatures were adjusted slightly downward due to potential delays in surface heating. Regardless, high-resolution guidance has converged on the prospect for isolated-to-scattered storms to develop during the afternoon hours Saturday across portions of the CWA. Lingering outflow boundaries would serve as the focus for initiation, especially if there is a lingering MCV. NBM PoPs were lowered for the afternoon hours and capped at 50-percent, as coverage is expected to remain in check until Saturday night. With little change in the airmass expected, similar hazards compared to Friday will accompany storms during the afternoon, with low-end, severe wind gusts possible in addition to locally heavy rainfall. Sincavage && .LONG TERM... (Saturday night through next Thursday) Issued at 114 PM CDT Fri Aug 29 2025 A heavy rain event is expected Saturday night and into Sunday morning across a large portion of the CWA. In the mid/upper-levels, a well-defined shortwave trough will dig into the central Rocky Mountains and eject over the north-central Great Plains. Farther south, the center of the subtropical ridge is forecast to be over Central TX, with the corresponding jet streaks rounding the apex of the ridge becoming dampened into a quasi-zonal state following the emergence of the shortwave trough. The right-entrance region to the 250 mb jet streak will shift southward over the CWA accordingly, while the belt of strengthening mid-level flow veers to the northwest. Intense, high-level divergence atop a plume of moderate CAPE near 2,000 J/kg for most-unstable parcels; and deep-layer hodographs becoming more-elongated than Friday night as mid-level flow increases to near 30 kt suggests the potential development of a forward-propagating MCS to surge south-southeastward along the thickness gradient. A better risk for flash flooding exists Saturday night into Sunday morning, especially after the predecessor rainfall event the night before. Anomalously high PWAT content, still at or in exceedance of the 99th percentile, amidst MUCAPE values near 2,000 J/kg, will enhance the potential for rain rates potentially in excess of 2"/hr with stronger cells. The mitigating factor for a more-substantial flash flooding risk will be the forward speed of the MCS, which is forecast to be at around 30 kt to the southeast. The severe wind threat remains a bit unclear, at least during the hours leading towards sunrise, but 50+ mph gusts will be possible early on in the event as the MCS moves into the CWA late Saturday night (possibly near midnight/crossing into early Sunday morning). Eventually, outflow should accelerate ahead of the MCS and end the threat for severe-caliber gusts. Total QPF continues to vary, but there is high confidence in multiple swaths of heavy rainfall occurring across the CWA during the late night hours Saturday into Sunday morning. The issuance of a Flood Watch has been deferred to subsequent packages. Conditions are forecast to improve by late Sunday morning, with most of the CWA clearing out by the afternoon hours as a post-MCS high builds into the region beneath increasing confluence aloft. PoPs were removed for most of the CWA, but a couple of late-day showers and storms will be possible towards sunset, with minimal concerns for flash flooding and/or strong gusts. A drying and warming trend is now forecast for the first half of next week as the subtropical ridge amplifies over the Rocky Mountains. Global NWP guidance continues to advertise a longwave trough digging into the eastern half of the nation by mid-week, with flow aloft shifting to the northwest through the end of the week. Renewed storm chances are forecast each day through the end of the period. Sincavage && .AVIATION... (18Z TAFS) Issued at 114 PM CDT Fri Aug 29 2025 Clouds lift this afternoon to MVFR/VFR. Storms are expected late this evening with IFR conditions likely. There are some confidence issues with flight category changes overnight related to the propagation of the thunderstorms, but things will eventually clear up Saturday morning in time for most arrivals in the afternoon. ANB/GRF && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...09 LONG TERM....09 AVIATION...99/26