Area Forecast Discussion
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Issued by NWS
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932 FXUS64 KLUB 272334 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 634 PM CDT Mon May 27 2024 ...New AVIATION... .SHORT TERM... (This evening through Tuesday) Issued at 242 PM CDT Mon May 27 2024 500 mb short wave ridging will drift eastward across the southern High Plains during the short term period, but its strength will not be sufficient to negatively affect thunderstorm potential. The more interesting setup comes below 500 mb with the 700 mb ridge displaced to the east over Oklahoma and North Texas with southwesterly flow over the forecast area. Shifting to the surface and low levels, a persistent lee trough across eastern New Mexico and a weak cold front sagging southward through the Panhandle will continue to promote an easterly low level component that will and subsequent moisture advection. Dew point temperatures by 12Z Tuesday should be above 50F New Mexico state line near 60F along I27 corridor and perhaps pushing 70F eastern counties. Two periods for thunderstorm development must be considered. The first is during the early morning hours tomorrow when mid level moisture advection and isentropic lift will likely initiate elevated convection in the vicinity of the Red River but probably east of the forecast area. Could see some of that development end up as far west as the Childress area, but keeping a small slight chance mention there looks adequate at this time. Focus then shifts to afternoon convective initiation. There remain some variables that need to be sorted to finalize specifics of the forecast, i.e., southwestward penetration (if any) of convective outflow into the forecast area and how much that destabilizes the air mass behind it and the eastward push to the dryline during the day Tuesday. In general, there does not appear much forcing in the mid levels, although there is some hint of a modest jet streak at 700 mb that may be enough to mix the dryline more than 30-60 miles into the forecast area from New Mexico, but given the richness of moisture and the lack of dynamism to the pattern will pull thunderstorm chances all the way back to the New Mexico state line. Progged MLCAPE values of 2000-4000 J/kg and effective bulk shear values in excess of 40 kts support the idea of supercellular structure even before looking at hodographs (which then also support that idea). SPC upgrade to enhanced risk mainly for very large hail and destructive hail for roughly the southeastern quarter of the forecast area looks on track with further refinements possible once the mesoscale details mentioned above become clearer. && .LONG TERM... (Tuesday night through next Sunday) Issued at 242 PM CDT Mon May 27 2024 Scattered-to-widespread, severe-caliber convection will be ongoing across portions of the Caprock and into the Rolling Plains on Wednesday evening. By this point, a mixed-mode of thunderstorms, including supercells and congealing, multi-cellular clusters, are expected to be the primary storm mode as strong theta perturbations continue to accelerate upscale growth into an organized MCS. The potential for significant gusts (i.e., >=75 mph) will accompany the MCS as strengthening inflow-layer theta-e advection will be surmounted by a reservoir of extreme instability with most-unstable parcel trajectories yielding >4,000 J/kg of CAPE. It is possible that meso-beta-scale convective vortices develop in proximity to the strong rear-inflow jet(s), which would accentuate the potential for wind-damage in addition to wind-driven hail events, after dark as the MCS moves southeastward across portions of the Rolling Plains. Flash flooding will occur from very heavy rain rates; however, the potential for a prolonged flooding event is very low owing to the anti-parallel Corfidi vectors relative to the MCS movement with a downshear component in excess of 40 kt. The vorticity lobe aloft should be convectively augmented in response to the MCS, with the potential for a mesoscale high to develop and result in locally strong wind gusts following steep pressure rises in the wake of the MCS across portions of the South and Rolling Plains. This would, in turn, cause an increase in forward-speed of the system as it is currently forecast to exit the CWA near or after midnight CDT (29/05Z) with the cold front quick to follow as it begins to stall in the Permian Basin by Wednesday morning. A low-amplitude, shortwave ridge is forecast to shift over the CWA on Wednesday as a high-level, split-flow pattern remains intact across the Lower 48 where a pseudo-Omega Block develops along the Medicine Line/49th parallel. This progressive wave train will modulate the amplitude and position of the 594 dam ridge centered over central Mexico, resulting in quasi-zonal flow to persist over West Texas during this time. At the surface, the quasi-stationary front should be located in the Permian Basin and bend northwestward into New Mexico where it should be dammed along the lee of the Rocky Mountains. Post-frontal, east-northeasterly flow will be ongoing beneath a thick, low-level stratus deck which will inhibit diabatic heating. Mild temperatures are expected, and PoPs were lowered substantially area-wide for Wednesday afternoon as the post-frontal airmass will also be convectively overturned. The lack of surface and low-level convergence, restricted diabatic heating, and the passage of the shortwave ridge overhead and attenuated mid-level flow should dampen the development of convection on Wednesday afternoon. Further lowering of PoPs may be required in forthcoming prognostications as confidence increases in the timing of the dry period. By Wednesday evening, the quasi-stationary front draped across the Permian Basin should undergo warm-frontogenesis ahead of the approach of a low-amplitude, shortwave trough pivoting over the Four Corners region. Gradual cooling of the mid-levels and forced ascent along the passage of the warm front may generate an overnight round of showers and thunderstorms as the 700 mb trough arrives, and the already-moist boundary-layer will result in low stratus expanding westward towards the TX/NM state line as the low-level jet strengthens to around 30 kt. As the shortwave trough emerges over the southern Rocky Mountains, the associated cross-barrier flow will generate a lee cyclone at around 998 mb in eastern New Mexico, with a sharpening dryline extending southward near the TX/NM state line. Guidance continues to indicate the potential for a well-defined thermal axis to develop ahead of the dryline/moist axis, both of which would serve as a foci for explosive thunderstorm development on Thursday, especially near the triple point; however, the exact positions of these mesoscale boundaries remains unclear. Therefore, the blended PoPs have been maintained with the best chances for severe-caliber convection occurring with eastward extent from the TX/NM state line. Significant-severe thunderstorms will be possible on Thursday afternoon and evening, with point and area-averaged forecast soundings indicating mixed-layer CAPE between 2,500-3,500 J/kg and most-unstable parcels yielding over 4,000 J/kg; and these estimates appear to be accurate given the lack of a synoptic-scale front aloft eroding the EML entirely. The combination of the strong-extreme instability, in addition to the cross-boundary shear vectors and effective shear magnitudes near 40 kt, indicates an environment favorable for supercells and the potential for tornadoes. Upscale growth into a larger-scale complex is possible as relatively straight hodographs aloft would favor storm-splitting and destructive interference, and with the poleward advection of precipitable water (PWAT) content exceeding the 99th percentile (e.g., forecast PWAT values between 1.40-1.60"), the potential for flash flooding will exist once again on Thursday night across portions of the South Plains and into the Rolling Plains. Sounding climatology from WFO AMA and MAF for Thursday evening (31/00Z) indicate PWAT values of 1.28" and 1.45" for the 99th percentile, respectively. Timing of the convective episode(s) on Thursday will continue to be refined in the coming days. Quasi-zonal flow is forecast to persist by the end of the week and into next weekend as the Omega Block across southern Canada meanders eastward, which will maintain cross-boundary shear vectors in the presence of the dryline in the vicinity of West Texas. The blended PoPs were accepted with the potential for strong-to-severe-caliber convection to last through the end of the period for portions of the CWA. Sincavage && .AVIATION... (00Z TAFS) Issued at 629 PM CDT Mon May 27 2024 Southeasterly low level winds may bring low CIGS back into the KCDS terminal early Tuesday morning but the chances of this are highly uncertain at the moment. Chances of these potential low CIGS affecting KLBB and KPVW are even lower. An approaching upper level storm system may bring scattered thunderstorms to all terminals mid- afternoon on Tuesday with greatest chances at KCDS. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...07 LONG TERM....09 AVIATION...01