Area Forecast Discussion
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Issued by NWS
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973 FXUS64 KLUB 170516 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 1216 AM CDT Mon Jun 17 2024 ...New AVIATION... .SHORT TERM... (This evening through Monday) Issued at 214 PM CDT Sun Jun 16 2024 A much quieter evening and overnight are in the offing following last night`s impressive heat burst south of Lubbock. Anticyclonic flow has since overspread the area within a shortwave ridge that lingers overnight. In spite of this ridging, strong heating and deep mixing along a developing dryline in far eastern NM could be enough to breach a healthy EML by peak heating. However, weak steering flow and a narrow W-E axis of lower CIN should keep any storms confined to near the TX-NM border. Addressed this poor coverage and conditional precip scenario with a 10% PoP until 10 PM. Southerly winds will remain quite breezy tonight and on Monday as lee cyclogenesis holds steady across eastern CO under stronger southwest flow. Tonight`s shortwave ridge will have departed by daybreak ahead of modest height falls and weakly cyclonic SW flow. This pattern looks more supportive for isolated storms late Monday afternoon near a dryline setting up along the TX-NM border. The main caveat is we`ll have a stronger cap tomorrow running about 1C warmer than today at 700 mb. Considering highs tomorrow should eclipse today`s temps and that most CAMs depict CIN eroding to near zero along the dryline by peak heating, NBM`s silent PoPs were traded for a sliver of 20s across our far western zones. Limited background forcing should keep storms very spotty with enough directional shear supportive of supercells - likely high based given deep and dry sub- cloud layers. && .LONG TERM... (Monday night through next Saturday) Issued at 214 PM CDT Sun Jun 16 2024 At the beginning of the period, isolated to perhaps widely-scattered thunderstorms may be ongoing across portions of the western South Plains. In the mid/upper-levels, an amplifying, positively-tilted trough will encompass the western U.S. interior with the primary shortwave trough digging into the northern Great Basin where a cyclonically-curved, 250 mb jet streak near 100 kt rounds its base. Farther south, coupling of another, more-zonal 250 mb jet streak branching over the Desert Southwest and northern Mexico will nose into western Texas, resulting in a corridor of difluent flow aloft as a shortwave perturbation ejects overhead after 18/00Z. At the surface, backed, southeasterly flow is expected to be present as a 984-986 mb cyclone in eastern Colorado drives an isallobaric response across the dry and moist sectors, with the dryline stalled near the TX/NM state line. Minimal MLCINH, confluent flow, and localized areas of convergence in vicinity of the dryline should result in the formation of a few multi-cellular thunderstorms. The presence of the cross-boundary shear vectors and moderately long hodographs aloft will favor supercell wind profiles for right-moving storms. Inverted-V profiles and LCLs rooted near 700 mb will result in the potential for localized wind-damage, with gusts in excess of 60 mph expected with multi-cells that merge and transition into a supercell or two. Warm-cloud depths approaching 13 kft AGL should temper the risk for severe-caliber hail, and torrential rainfall will accompany organized storms given the high volume of adiabatic liquid water content beneath the freezing level. Localized flooding may occur due to the slow storm motion at around 10-15 kt for cells that achieve discrete propagation. The potential for thunderstorms will wane after dark as surface-based inflow trajectories become undercut from diabatic stabilization/increasing MLCINH. Slight chance PoPs (10-15 percent) have been maintained for all locations along and west of the I-27/HWY-87 corridors through tomorrow night as the spatiotemporal coverage of cells should be limited due to weak, large-scale forcing for ascent aloft. Breezy, muggy, and warm conditions will prevail area-wide heading into the morning hours Tuesday as the lee cyclone rotates towards western Kansas beneath the amplified troughing aloft. Low stratus fields may develop as the backed, low-level jet strengthens to near 30-35 kt amidst and a clear sky (less any residual anvil debris) causes the boundary-layer to reach its saturation point. Advection fog is not expected to form, however. Hot, dry, and breezy conditions continue to be forecast for Tuesday as the airmass remains capped beneath the slight increase in geopotential heights as the northern-stream shortwave trough ejects into southern Manitoba and the subtropical ridge over the eastern U.S. expands with latitude. The orientation of these features will maintain the broadly cyclonic flow over the region, with the coupling of the 250 mb jet streaks upstream of the CWA beginning to phase and eject northeastward into the central Great Plains by Wednesday. Southerly flow will be intact on Wednesday; however, it is forecast to dampen in magnitude to around 10-15 mph as cessation of lee cyclogenesis occurs to the north of the CWA. It is counterintuitive to have cooler temperatures forecast beneath slightly positive geopotential height tendencies, but this is the case for Wednesday as 850 mb temperatures cool via adiabatic expansion from the easterly fetch along the northern periphery of a tropical disturbance moving northwestward out of the Gulf of Mexico. To the north of the CWA, a cold front is forecast to stall in the vicinity of the OK/TX PH region, and further progression to the south should be retarded by the presence of the barotropic airmass eclipsing the CWA. Presence of this stalling front to the north may lead to the first of potentially multiple rounds of showers and thunderstorms for the latter half of the forecast period, with low PoPs expanding across the CWA heading into Thursday morning. The best potential appears to be across the extreme southwestern TX PH nearest the stalled front as moist, isentropic ascent increases amidst the near-easterly flow at the surface-to-mid-levels. The forecast becomes particularly complex by Thursday/D5 as global NWP guidance remains bifurcated on the track of the tropical disturbance rotating out of the Gulf of Mexico, with a spread on the order of 200+ miles. This significant spread among the global NWP guidance suites should continue until a closed circulation develops with this disturbance. PoPs have increased by about 10 percent for Thursday compared to the previous prognostications, and have been maintained given the uncertainty involved with the track of the aforementioned tropical system, the position and longitudinal extent of the amplified ridge over the eastern U.S., and the position of the entrance region to the 250 mb jet streak over the Rocky Mountains. There is also a 20 degree spread in temperatures among the guidance as well, and the trend towards the cooler side of the envelope is being maintained owing to the expectation of easterly flow lasting through at least Thursday night. Temperatures on Thursday may hover in the upper 70s area-wide. On the other hand, NAEFS and ENS guidance continues to indicate precipitable water (PWAT) content of two to potentially three standard deviations above normal advecting into portions of the CWA on Thursday, and forecast PWAT values remain within or exceed the 99th percentile based off sounding climatology from WFO MAF. Heavy rain remains a possibility on Thursday into Friday given the open fetch of anomalously high moisture content advecting northwestward from the Gulf of Mexico, but where the heaviest rainfall occurs remains nebulous. The blended PoPs have been accepted with cool and cloudy conditions forecast through the end of the week. After internal coordination, the Marginal Risk for Excessive Rainfall from WPC on Thursday/D5 has been expanded across the central and southern portions of the CWA. Sincavage && .AVIATION... (06Z TAFS) Issued at 1213 AM CDT Mon Jun 17 2024 South to southeasterly winds will remain breezy through the entire TAF period. There is a very low chance of low CIGS early this morning but chances are too low to mention in the TAF. Isolated thunderstorms will also be possible late this afternoon into the early evening but coverage will be too low to mention in the TAF at the moment. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...93 LONG TERM....09 AVIATION...01