061 FXUS64 KLUB 021926 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 226 PM CDT Fri Jul 2 2021 .SHORT TERM... Synoptic analysis this afternoon reveals a continued dynamic upper flow pattern over much of North America, with a large trough centered over the eastern Great Lakes and low-amplitude troughing over the northwestern CONUS. West Texas remains under northwesterly flow aloft with a rather high-amplitude ridge axis over the northern Great Plains and an upper high over the Desert Southwest. Water vapor imagery depicts robust mid and upper level moisture rotating around the periphery of the high, with 12z AMA and MAF soundings sampling PWATs of 1.44" and 1.42", respectively. At the surface, the frontal boundary which entered the CWA early this morning has begun to wash out as it stalls across southern portions of the CWA. Overall, the synoptic pattern will not change significantly throughout the Short Term period, with the upper high only forecast to shift very slightly westward. Consequently, upper steering flow and shear will remain weak, meaning that convection currently observed over eastern New Mexico will have a hard time organizing and is unlikely to make it into the CWA this evening. Therefore, precipitation chances this afternoon into tomorrow will rely on whether convection can initiate locally. Hi-res guidance seems to want to develop additional convection this afternoon, mainly within our southern tier of counties. With the stalled frontal boundary and the abundant moisture in place, this is certainly plausible. But, with a rather elongated and weak CAPE profile and a lack of any obvious upper level impulses upstream, precipitation this afternoon and evening will likely be in the form of scattered showers with perhaps a few embedded thunderstorms. Again, given the abundant moisture present, locally heavy rain will be the main concern. Will keep PoPs in the chance category as overall shower coverage remains uncertain. Tonight into Saturday will be a similar setup as this afternoon, with the stalled boundary situated roughly near or just south of our southern CWA border. Chances for showers and and a few thunderstorms will therefore persist, with the best chances across the southern South Plains and southern Rolling Plains. At this time, it appears that precipitation will remain scattered, as West Texas will be underneath the outer edge of the upper high and there still does not appear to be any notable inbound upper impulses. Considerable cloudiness should also keep temperatures below average, helping to limit instability. However, it should be noted that with the surface boundary in place, only subtle upper impulses would be necessary to enhance convection. Furthermore, since guidance can have trouble resolving these features, there is a chance that precip could be more widespread than currently forecast. However, at this time confidence in widespread coverage of precip is low. As such, mainly chance PoPs were retained through the period. Given the moisture and the forecasted elongated CAPE profiles, however, heavy rain and efficient rainfall are possible within the showers and thunderstorms that do form. /DWK .LONG TERM... The mid/upper-level ridge will continue to expand over the southern and southwestern CONUS this weekend, with the axis centering across the Intermountain West and through the Four Corners region as it amplifies to around 594 dam by Sunday. A strong mid-level shortwave perturbation is forecast to rotate about the ridge top, with a small tranche of the shortwave splitting off and rotating southward along the eastern periphery of the ridge, crossing the 35th parallel late Sunday. The airmass across the CWA will also be similar to the last several days as the quasi-stationary front all but dissipates by this time, with the boundary-layer characterized by lower 100 mb mean mixing ratios around 14-16 g/kg and precipitable water (PWAT) content near the 99th percentile as per 05/00Z sounding climatology from the AMA RAOB site. Northwesterly 250-500 mb flow will result in sufficient cold air advection aloft, enough to enlarge the size and depth of the EML with MUCAPE values around 2,500 J/kg, surmounted by increasing southeasterly low- level flow as a surface trough develops across the western High Plains. Increasing convergence in vicinity of the surface trough late Sunday as the aforementioned shortwave trough arrives, combined with strong, diabatic surface heating as temperatures climb into the upper 80s, should result in the initiation of thunderstorms near the Raton Mesa, southeastern Colorado, and the northwestern Texas and Oklahoma Panhandles. Multi-cellular convection is expected to be the initial storm mode, though as precipitation-loading increases from weak mid-level storm-relative winds and high PWAT content, convective clusters may very well become cold-pool-driven with the possibility of a few bows developing as cells surge southeastward into the CWA near sunset Sunday. The primary hazard of concern is the potential for localized flash flooding, especially given the recent, soaking rainfall over the last week across the forecast area. As of today (July 2nd), NASA SPoRT 0-40 cm soil moisture content has reached the 99th percentile across nearly half of the CWA, particularly in the extreme southern Texas Panhandle and northern South Plains. West Texas Mesonet data also indicates a broad area of water content near 0.50" at a depth of 5-20 cm this afternoon as well, confirming the satellite estimates. Negligible drying is expected between now and Sunday night, and the potential for excessive runoff will be exacerbated by high rain rates per hour within the deepest cores. Though, a more significant flash flood threat should be offset by the fast storm motions (current prognosis of around 330/40 kt). Nevertheless, a heavy rain event is forecast across portions of the extreme southern Texas Panhandle, and the northern South and Rolling Plains, where a swath of 1-3" of rain with locally higher amounts will be possible. A few localized wet-microburst situations will be possible as well, with strong gusts around 50-60 mph in the most intense cores or if a rear-inflow jet becomes well-established. Additional chances for precipitation exist into the middle of next week, though uncertainty exists as to when and where convection may occur owing to limited predictability. However, with poleward flow persisting over the CWA, any shortwave troughs that rotate along the downstream portion of the ridge axis may result in the potential for convection before the mid/upper-level high shifts back to the east and centers over the southern CONUS, eroding chances for rain by the end of next week. Sincavage && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 30/09