Area Forecast Discussion
Issued by NWS
Issued by NWS
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828 FXUS64 KLUB 110525 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 1225 AM CDT Sat May 11 2024 ...New AVIATION... .SHORT TERM... (This evening through Saturday) Issued at 236 PM CDT Fri May 10 2024 Surface ridging anchored from eastern CO through northern OK was maintaining cool E-NE winds across the region this afternoon. Aloft, a ridge axis around 700 mb was bisecting the CWA from N-S and is scheduled to drift east tonight ahead of a shortwave trough in SW flow. Well to our southeast and beyond the influence of this ridge across the Big Country to the Hill Country, radar and satellite showed a smattering of elevated thunderstorms at 2 PM which have been poorly handled by most models. Fortunately, this activity will not pose a threat to our area. After a gradual downturn in clouds later this evening owing to subsidence well ahead of the aforementioned upper impulse, moist isentropic ascent will amplify after midnight resulting in PWATs rising to around 1 inch which is nearly double that of normal. This moistening theme will carry through the day on Saturday with likely PoPs favoring all but our far southeast TX Panhandle counties and the northern Rolling Plains where deeper drying in the low levels looks to take its toll on measurable rain. The NAM seems too eager to overturn this dry layer through the day, so will favor a blend of the HREF mean and NBM which keeps the heaviest rainfall of 1/3" to 1/2" across the southern half of the forecast area. Elevated CAPE remains generally low but still sufficient for some thunder at times. High temps are still tricky as some of the coolest guidance from yesterday`s models have since eased somewhat which raises confidence in the slightly "milder" NBM values. && .LONG TERM... (Saturday night through next Thursday) Issued at 236 PM CDT Fri May 10 2024 An opening, positively-tilted trough is forecast to emerge over the western Great Plains on Saturday night as an elongated 250 mb jet streak continues to translate over the CWA within the split-flow regime encompassing the Lower 48. Geopotential height falls will be dampened by the deamplification of the trough as it ejects over the south-central Great Plains heading into Sunday morning, which will temper the magnitude of mid-level cooling while west-southwesterly flow aloft maintains the advection of an anemic, elevated CAPE profile with most-unstable parcel trajectories yielding <=1,000 J/kg of MUCAPE amidst moist-adiabatic lapse rates. WAA-induced showers and thunderstorms will, therefore, be ongoing at the start of the period; however, the overall QPF footprint should be light with only a few locales experience brief downpours/thunderstorms on Sunday morning. At the surface, weak cyclogenesis will occur near the vicinity of the OK PH/northern TX PH beneath the opening circulation in the mid-levels while a quasi-stationary front should be anchored along the edge of the Mescalero Escarpment. The position of the stalled front beneath the base of the shortwave trough, and presence of the thermally indirect circulation aloft, will result in renewed frontogenesis with the quasi-stationary front transitioning into a cold front and moving eastward onto the Caprock during the afternoon hours on Sunday. Elongation of hodographs aloft with LFCs rooted above a deep, moistened boundary-layer, will facilitate an increase in the coverage of showers and thunderstorms across portions of the Caprock and into the Rolling Plains as moist, isentropic ascent continues to overspread the CWA. Marginally-severe hail (near quarter size) should accompany the best-organized cells as the magnitude of the deep- and cloud-layer shear vectors support weak, mid-level rotation; and as wet-bulb zero heights lower to near 8.0 kft AGL from the weak, geopotential height falls. Locally heavy rainfall will accompany the stronger cells, although the potential for flash flooding is low due to the expectation of storm motion being governed via advection versus propagation. (Mean wind storm motion vectors are forecast to be near 40-45 kt.) The base of the positively-tilted trough will pass east of the CWA by Sunday night, with thunderstorm chances ending from west-to-east accordingly. A weakening cold front will move southward across the entire CWA following the passage of the trough; however, despite the presence of northwesterly flow at the surface through mid-levels, the boundary-layer should become well-mixed on Monday afternoon with little in the way of CAA post-FROPA as temperatures warm into the upper 70s and lower 80s area-wide. A low-amplitude, shortwave ridge is then forecast to shift over the CWA on Tuesday ahead of another amplifying trough to the west. Global NWP guidance is in agreement with the split-flow pattern beginning to phase by mid-week as the broad, positively-tilted trough ejects over the southern Rocky Mountains. This will facilitate the evolution of cross-boundary shear vectors across West Texas by the middle of the week amidst the presence of return flow and a dryline positioned in the vicinity of the CWA. The potential for severe thunderstorms is set to return during this D6/D7 window. Sincavage && .AVIATION... (06Z TAFS) Issued at 1215 AM CDT Sat May 11 2024 Light winds and VFR conditions will persist through mid-morning. Showers will begin thereafter, beginning at KLBB and KPVW before moving north and east over KCDS. MVFR CIGs are expected from mid-afternoon onwards at KLBB and KPVW. Confidence was not high enough to prevail MVFR at KCDS, however periods of lower CIGs are certainly possible there as well. Embedded thuderstorms are possible at all sites, although limited coverage did not merit their mention in the TAFs. Drizzly MVFR will continue into the evening. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...93 LONG TERM....09 AVIATION...19