581 FXUS64 KLUB 191719 AAB AFDLUB Area Forecast Discussion...UPDATED National Weather Service Lubbock TX 1219 PM CDT Sun Jul 19 2020 .AVIATION... VFR conditions in place at all three TAF sites and will remain VFR through this forecast. Thunderstorms are expected to develop well west of KLBB and KPVW terminals and should remain away from all TAF sites. Will monitor through the afternoon but do not anticipate needing to add TS to KLBB/KPVW. Jordan && .PREV DISCUSSION... /issued 231 AM CDT Sun Jul 19 2020/ SHORT TERM... GOES-East low-level water vapor imagery depicts a surface trough anchored across the Texas Panhandle region/eastern New Mexico, extending southwestward into the Chihuahuan Desert and Gulf of California. This elongated fetch of moisture has been present for the last several days and will serve as a focus for more chances of convection late Sunday afternoon and evening across the western areas of the southern Texas Panhandle and the western South Plains. Current observations from the West Texas Mesonet indicate gradual moisture return with a plume of 55-59 deg F dew points streaming poleward across the Caprock and low Rolling Plains. The velocity azimuthal data from the KLBB WSR-88D detects very-low-level winds up to 700 ft AGL out of the south at around 20-30 knots, which correspondingly elongates the low-level moisture transport vectors and is therefore advecting a plume of 1.10-1.20" precipitable water content across West Texas. Later this afternoon, surface winds should begin to back to the southeast in response to gradual, weak pressure falls across eastern New Mexico and western Texas as a lee cyclone over the TX/OK Panhandle region deepens to around 1008 mb by this evening. The backing of the surface flow, similar to what was observed yesterday, will enhance low-level surface confluence and convergence, augmenting the potential for thunderstorm development along the Raton Mesa and eastern New Mexico. Today is also a great case of how there are discrepancies in the high-resolution convective-allowing numerical guidance, but this is where physical meteorological analysis comes into play. The 19/00Z RAOBs from ABQ and AMA sampled a few (although weak) mid-level subsidence layers coupled with westerly winds. These subsidence layers will continue to advect eastward towards the forecast area throughout the remainder of the morning and into the afternoon hours today, which will result in warming of the mid-levels across the forecast area, and therefore eroding the stoutness of the EML and weakening L57 lapse rates to near 6.6-7.0 deg C/km by tonight across the western South Plains. Vigorous low-level mixing is expected to occur owing to strong heating, but even with MLCAPE ~1,000 J/kg and MUCAPE ~2,000 J/kg, the presence of mid-level subsidence should act to inhibit more robust, deep convection as it progresses into the northwestern South Plains later tonight. Thunderstorms are expected to develop along the surface trough in eastern and northeastern New Mexico, and slowly progress to the southeast at around 10 kt. Single and perhaps a few multi-cellular clusters will be possible, with the main convective hazards being sub-severe winds and locally heavy rainfall. The "shelf life" of storms is not forecast to be particularly long, especially as updrafts move into an area with mid-level subsidence. Storms should begin to collapse near or after midnight CDT (20/05Z), with blowing dust a strong possibility due to the propagating outflows thereafter. To end this informative discussion, the high temperatures on the Caprock tomorrow will be in the lower 90s--a welcomed sight after an 11-day stretch of temperatures at or above 100 degrees! Sincavage LONG TERM... Not much in the way of change to the forecast this morning. An upper level ridge that spans the southern tier of the CONUS will have a weakness over the southern High Plains that will translate to a modest decrease in temperatures across the forecast area through Wednesday. This weakness may allow diurnally driven thunderstorms that form across eastern New Mexico and the western Panhandle to push some to the east and southeast during the late afternoon and evening hours with rain chances focused across the northwestern third of the forecast area. By Thursday the upper ridge will begin to strengthen some with a modest uptick in temperatures and rain chances getting pushed back into New Mexico with only slight chances of nighttime thunderstorms edging into the far western parts of the forecast area. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 14/14/14